Table of Contents generated with DocToc
- Chapter 6: Completion, old and new
- 6.1: Completion and expansion
- 6.2: Configuring completion using shell options
- 6.3: Getting started with new completion
- 6.4: How the shell finds the right completions
- 6.5: Configuring completion using styles
- 6.6: Command widgets
- 6.7: Matching control and controlling where things are inserted
- 6.8: Tutorial
- 6.9: Writing new completion functions and widgets
- 6.9.1: Loading completion functions:
compdef
- 6.9.2: Adding a set of completions:
compadd
- 6.9.3: Functions for generating filenames, etc.
- 6.9.4: The
zsh/parameter
module - 6.9.5: Special completion parameters and
compset
- 6.9.6: Fancier completion: using the tags and styles mechanism
- 6.9.7: Getting the work done for you: handling arguments etc.
- 6.9.8: More completion utility functions
- 6.9.1: Loading completion functions:
- 6.10: Finally
Chapter 6: Completion, old and new
Completion of command arguments is something zsh is particularly good
at. The simplest case is that you hit <TAB>
, and the shell guesses
what has to go there and fills it in for you:
% ls
myfile theirfile yourfile
% cat t<TAB>
expands the command line to
% cat theirfile
and you only had to type the initial letter, then TAB
.
In the early days when this feature appeared in the C shell, only
filenames could be completed; there were no clever tricks to help you if
the name was ambiguous, it simply printed the unambiguous part and
beeped so that you had to decide what to do next. You could also list
possible completions; for some reason this became attached to the ^D
key in csh, which in later shells with Emacs-like bindings also deletes
the next character, so that history has endowed zsh, like other shells,
with the slightly odd combined behaviour:
% cat yx
Now move the cursor back one character onto the x and hit ^D twice and
you see: yourfile
. That doesn't work if you use vi-like bindings, or,
obviously, if you've rebound ^D
.
Next, it became possible to complete other items such as names of users,
commands or hosts. Then zsh weighed in with menu completion, so you
could keep on blindly hitting <TAB>
until the right answer appeared,
and never had to type an extra character yourself.
The next development was tcsh's, and then zsh's, programmable completion
system; you could give instructions to the shell that in certain
contexts, only certain items should be completed; for example, after
cd
, you would only want directories. In tcsh, there was a command
called complete
; each `complete ...
' statement defined the
completion for the arguments of a particular command, such as cd
; the
equivalent in zsh is compctl
, which was inspired by complete
but is
different in virtually every significant detail. There is a perl script
lete2ctl
in the Misc
directory of the shell distribution to help you
convert from the tcsh to the zsh formats. You put a whole series of
compctl
commands into .zshrc
, and everything else is done by the
shell.
Zsh's system has become more and more sophisticated, and in version
3.1.6 a new completion system appeared which is supposed to do
everything for you: you simply call a function, compinit
, from an
initialization file, after which zsh knows, for example, that gunzip
should be followed by files ending in .gz
. The new system is based on
shell functions, an added bonus since they are extremely flexible and
you already know the syntax. However, given the complexity it's quite
difficult to get started writing your own completions now, and hard
enough to know what to do to change the settings the way you like. The
rest of the chapter should help.
I shall concentrate on the new completion system, which seems destined to take over completely from the old one eventually, now that the 3.1 release series has become the 4.0 production release. The old compctl command is still available, and old completion definitions will remain working in future versions of zsh --- in fact, on most operating systems which support dynamically linked libraries the old completion system is in a different file, which the shell loads when necessary, so there's very little overhead for this.
The big difference in the new system is that, instead of everything
being set up once and for all when the shell starts, various bits of
shell code are called after you hit <TAB>
, to generate the completions
there and then. There's enough new in the shell that all those
unmemorable options to compctl
(`-f
' for files `-v
' for
variables and so on) can be replaced by commands that produce the list
of completions directly; the key command in this case is called
`compadd
', which is passed this list and decides what to use to
complete the word on the command line. So the simplest possible form of
new completion looks roughly like this:
# tell the shell that the function mycompletion can do completion
# when called by the widget name my-completion-widget, and that
# it behaves like the existing widget complete-word
zle -C my-completion-widget .complete-word mycompletion
# define a key that calls the completion widget
bindkey '^x^i' my-completion-widget
# define the function that will be called
mycompletion() {
# add a list of completions
compadd alpha bravo charlie delta
}
That's very roughly what the completion system is doing, except that the
function is called _main_complete
and calls a lot of other functions
to do its dirty work based on the context where completion was called
(all the things that compctl
used to do), and the widgets are just the
old completion widgets (`expand-or-complete
' etc.) redefined and
still bound to all the original keys. But, in case you hadn't guessed,
there's more to it than that.
Here's a plan for the sections of this chapter.
- A broad description of completion and expansion, applying equally to old and new completion.
- How to configure completion using shell options. Most of this
section applies to old completion, too, although I won't explicitly
flag up any differences. After this, I shall leave the
compctl
world behind. - How to start up new completion.
- The basics of how the new completion system works.
- How to configure it using the new `
zstyle
' builtin. - Separate commands which do something other than the usual completion system, as well as some other editing widgets that have to do with completion.
- Matching control, a powerful way of deciding such things as whether to complete case-insensitively, to allow insertion of extra parts of words before punctuation characters, or to ignore certain characters in the word on the command line.
- How to write your own completion functions; you won't need to have too solid an understanding of all the foregoing just to do simple completions, but I will gradually introduce the full baroque splendour of how to make tags and styles work in your own functions, and how to make completion do the work of handling command arguments and options.
- Ends the chapter gracefully, on the old `beginning, middle, end' principle.
6.1: Completion and expansion
More things than just completion happen when you hit tab. The first
thing that zsh tries to do is expand the line. Expansion was covered in
a previous chapter: basically all the things described there are
possible candidates for expanding in-line by the editor. In other words,
history substitutions with bangs, the various expansions using `$
' or
backquote, and filename generation (globbing) can all take place, with
the result replacing what was there on the command line:
% echo $PWD<TAB>
-> echo /home/pws/zsh/projects/zshguide
% echo `print $ZSH_VERSION`<TAB>
-> echo 3.1.7
% echo !!<TAB>
-> echo echo 3.1.7
% echo ~/.z*<TAB>
-> echo /home/pws/.zcompdump /home/pws/.zlogout
/home/pws/.zshenv /home/pws/.zshrc
Note that the `~
' also gets expanded in this case.
This is often a good time to remember the `undo' key, `^_
' or
`^Xu
'; typing this will restore what was there before the expansion
if you don't like the result. Many keyboards have a quirk that what's
described as `^_
' should be typed as control with slash, which you'd
write `^/
' except unfortunately that does something else; this is not
zsh's fault. There's another half-exception, namely filename generation:
paths like `~/file
' don't get expanded, because you usually know what
they refer to and it's usually convenient to leave them for use in
completion. However, the `=cmdname
' form does get expanded, unless
you have NO_EQUALS
set.
In fact, deciding whether expansion or completion takes place can
sometimes be tricky, since things that would be expanded if they were
complete, may need to be completed first; for example $PAT
should
probably be completed to $PATH
, but it's quite possible there is a
parameter $PAT
too. You can decide which, if you prefer. First, the
commands expand-word
, bound to `^X*
', and the corresponding command
for listing what would be expanded, list-expand
, bound to `^Xg
', do
expansion only --- all possible forms except alias expansion, including
turning `~/file
' into a full path.
From the other point of view, you can use commands other than
expand-or-complete
, the one bound by default to <TAB>
, to perform
only completion. The basic command for this is complete-word
, which is
not bound by default. It is quite sensible to bind this to `^I
' (i.e.
<TAB>
) if you are happy to use the separate commands for expansion,
i.e.
# Now tab does only completion, not expansion
bindkey '^i' complete-word
Furthermore, if you do this and use the new completion system, then as
we shall see there is a way of making the completion system perform
expansion --- see the description of the _expand
completer below. In
this case you have much more control over what forms of expansion are
tried, and at what point, but you have to make sure you use
complete-word
, not expand-or-complete
, else the standard expansion
system will take over.
There's a close relative of expand-or-complete
,
expand-or-complete-prefix
, not bound by default. The only difference
is that it will ignore everything under and to the right of the cursor
when completing. It's as if there was a space where the cursor was, with
everything to be ignored shifted to the right (guess how it's
implemented). Use this if you habitually type new words in the line
before other words, and expect them to complete or expand on their own
even before you've typed the space after them. Some other shells work
this way all the time. To be more explicit:
% ls
filename1
% ls filex
Move the cursor to the x
and hit tab. With expand-or-complete
nothing happens; it's trying to complete a file called `filex
' ---
or, with the option COMPLETE_IN_WORD
set, it's trying to find a file
whose name starts with `file
' and ends with `x
'. If you do
bindkey '^i' expand-or-complete-prefix
and try the same experiment, you will find the whole thing is completed
to `filename1x
', so that the `x
' was ignored, but not removed.
One possible trap is that the listing commands, both
delete-char-or-list
, bound by default to `^D
' in emacs mode, and
list-options
, bound by default to `^D
' in vi insert mode and the
basic command for listing completions as it doesn't have the
delete-character behaviour, do not show possible expansions, so with the
default bindings you can use `^D
' to list, then hit <TAB>
and find
that the line has been completely rewritten by some expansion. Using
complete-word
instead of expand-or-complete
will of course fix this.
If you know how to write new editor widgets (chapter
4), you can make up a function which tries
list-expand
, and if that fails tries list-options
.
There are four completion commands I haven't mentioned yet: three are
menu-complete
, menu-expand-or-complete
and reverse-menu-complete
,
which perform menu completion, where you can cycle through all possible
completions by hitting the same key. The first two correspond to
complete-word
and expand-or-complete
respectively, while the third
has no real equivalent as it takes you backwards through a completion
list. The effect of the third can't be reached just by setting options
for menu completion, so it's a useful one to bind separately. I have it
bound to `\M-\C-i
', i.e. tab with the Meta key pressed down, but it's
not bound by default.
The fourth is menu-select
, which performs an enhanced form of menu
completion called `menu selection' which I'll describe below when I
talk about options. You have to make sure the zsh/complist
module is
loaded to use this zle command. If you use the style, zsh should be able
to load this automatically when needed, as long as you have dynamic
loading, which you probably do these days.
6.2: Configuring completion using shell options
There are two main ways of altering the behaviour of completion without writing or rewriting shell functions: shell options, as introduced in chapter 2, and styles, as introduced above. I shall first discuss the shell options, although as you will see some of these refer to the styles mechanism. Setting shell options affects every single completion, unless special care has been taken (using a corresponding style for the context, or setting an option locally) to avoid that.
In addition to the options which directly affect the completion system,
completion is sensitive to various other options which describe shell
behaviour. For example, if the option MAGIC_EQUAL_SUBST
is set, so
that arguments of all commands looking like `foo=~/file
' have the
`~
' expanded as if it was at the start of an argument, then the
default completion for arguments of commands not specially handled will
try to complete filenames after the `=
'.
Needless to say, if you write completion functions you will need to
worry about a lot of other options which can affect shell syntax. The
main starting point for completion chosen by context (everything except
the commands for particular completions bound separately to keystrokes)
is the function _main_complete
, which includes the effect of the
following lines to make sure that at least the basic options are set up
within completion functions:
setopt glob bareglobqual nullglob rcexpandparam extendedglob unset
unsetopt markdirs globsubst shwordsplit shglob ksharrays cshnullglob
unsetopt allexport aliases errexit octalzeroes
but that by no means exhausts the possibilities. Actually, it doesn't
include those lines: the options to set are stored in the array
$_comp_options
, with NO_
in front if they are to be turned off. You
can modify this if you find you need to (and maybe tell the maintainers,
too).
By the way, if you are wondering whether you can re-use the function
_main_complete
, by binding it to a different key with slightly
different completion definitions, look instead at the description of the
_generic
command widget below. It's just a front-end to
_main_complete
which allows you to have a different set of styles in
effect.
6.2.1: Ambiguous completions
The largest group of options deals with what happens when a completion is ambiguous, in other words there is more than one possible completion. The seven relevant options are as follows, as copied from the FAQ; many different combinations are possible:
- with
NO_BEEP
set, that annoying beep goes away, - with
NO_LIST_BEEP
, beeping is only turned off for ambiguous completions, - with
AUTO_LIST
set, when the completion is ambiguous you get a list without having to type^D
, - with
BASH_AUTO_LIST
set, the list only happens the second time you hit tab on an ambiguous completion, - with
LIST_AMBIGUOUS
, this is modified so that nothing is listed if there is an unambiguous prefix or suffix to be inserted --- this can be combined withBASH_AUTO_LIST
, so that where both are applicable you need to hit tab three times for a listing, - with
REC_EXACT
, if the string on the command line exactly matches one of the possible completions, it is accepted, even if there is another completion (i.e. that string with something else added) that also matches, - with
MENU_COMPLETE
set, one completion is always inserted completely, then when you hit TAB it changes to the next, and so on until you get back to where you started, - with
AUTO_MENU
, you only get the menu behaviour when you hit TAB again on the ambiguous completion.
6.2.2: ALWAYS_LAST_PROMPT
The option ALWAYS_LAST_PROMPT
is set by default, and has been since an
earlier 3.1 release of zsh; after listing a completion, the cursor is
taken back to the line it was on before, instead of reprinting it
underneath. The downside of this is that the listing will be obscured
when you execute the command or produce a different listing, so you may
want to unset the option. ALWAYS_LAST_PROMPT
behaviour is required for
menu selection to work, which is why I mention it now instead of in the
ragbag below.
When you're writing your own editor functions which invoke completion,
you can actually cancel the effect of this with the widget
end-of-list
, which you would call as zle end-of-list
(it's a normal
editing function, not a completion function). You can also bind it to a
key to use to preserve the existing completion list. On the other hand,
if you want to control the behaviour within a completion function, i.e.
to decide whether completion will try to return to the prompt above the
list, you can manipulate it with the last_prompt
element of the
$compstate
associative array, so for example:
compstate[last_prompt]=''
will turn off the behaviour for the completion in progress. $compstate
is the place to turn if you find yourself wanting to control completion
behaviour in this much detail; see the zshcompwid
manual page.
6.2.3: Menu completion and menu selection
The most significant matter decided by the options above is whether or
not you are using menu completion. If you are not, you will need to type
the next character explicitly when completion is ambiguous; if you are,
you just need to keep hitting tab until the completion you want appears.
In the second case, of course, this works best if there are not too many
possibilities. Use of AUTO_MENU
or binding the menu-complete
widget
to a separate key-stroke gives you something of both worlds.
A new variant of menu completion appeared in 3.1.6; in fact, it deserves
the name menu completion rather more than the original form, but since
that name was taken it is called `menu selection'. This allows you to
move the cursor around the list of completions to select one. It is
implemented by a separate module, zsh/complist
; you can make sure this
is loaded by putting `zmodload -i zsh/complist
' in .zshrc
, although
it should be loaded automatically when the style menu
is set as below.
For it to be useful, you need two other things. The first is
ALWAYS_LAST_PROMPT
behaviour; this is suppressed if the whole
completion list won't appear on the screen, since there's no line on the
screen to go back to. However, menu selection does still work, by
allowing you to scroll the list up and down. The second thing is that
you need to start menu completion in any of the usual ways; menu
selection is an addition to menu completion, not a replacement.
Now you should set the following style:
zstyle ':completion:*' menu select=<NUM>
If an ambiguous completion produces at least <NUM>
possibilities, menu
selection is started. You can understand this best by trying it. One of
the completions in the list, initially the top-leftmost, is highlighted
and inserted into the line. By moving the cursor in the obvious
directions (with wraparound at the edges), you change both the value
highlighted and the value inserted into the line. When you have the
value you want, hit return, which removes the list and leaves the
inserted value. Hitting ^G
(the editor function send-break
) aborts
menu selection, removes the list and restores the command line.
Internally, zsh actually uses the parameter $MENUSELECT
to supply the
number and hence start menu selection. However, this is always
initialised from the style as defined above, so you shouldn't set
$MENUSELECT
directly (unless you are using compctl
, which will
happily use menu selection). As with other styles, you can specify
different values for different contexts; the default
tag is checked if
the current context does not produce a value for the style with whatever
the current tag is. Note that the menu
style also allows you to
control whether menu completion is started at all, with or without
selection; in other words, it is a style corresponding to the
MENU_COMPLETE
option.
There is one other additional feature when using menu selection. The zle
command accept-and-infer-next-history
has a different meaning here; it
accepts a completion, and then tries to complete again using menu
selection. This is very useful with directory hierarchies, and in
combination with undo
gives you a simple file browser. You need to
bind it in the special keymap menuselect
; for example, I use
bindkey -M menuselect '^o' accept-and-infer-next-history
because the behaviour reminds me of what is usually bound to ^O
in
emacs modes, namely accept-line-and-down-history
. Binding it like this
has no effect on ^O
in the normal keymaps. Try it out by entering menu
selection on a set of files including directories, and typing ^O
on
one of the directories. You should immediately have the contents of that
directory presented for the next selection, while undo
is smart enough
not only to remove that selection but return to completion on the parent
directory.
You can choose the manner in which the currently selected value in the
completion list is highlighted using exactly the same mechanism as for
specifying colours for particular types of matches; see the description
of the list-colors
style below.
6.2.4: Other ways of changing completion behaviour
COMPLETE_ALIASES
If you set an alias such as
alias pu=pushd
then the alias `pu
' will be expanded when the completion system is
looking for the name of the command, so that it will instead find the
command name `pushd
'. This is quite useful to avoid having to define
extra completions for all your aliases. However, it's possible you may
want to define something different for the alias than for the command it
expands to. In that case, you will need to set COMPLETE_ALIASES
, and
to make arrangements for completing after every alias which does not
already match the name of a command. Hence `alias zcat="myzcat -dc"
'
will work with the option set, even if you haven't told the system about
`myzcat
', while `alias myzcat="gzip -dc"
' will not work unless you
do define a completion for myzcat: here `compdef _gzip myzcat
' would
probably be good enough. Without the option set, it would be the other
way around: the first alias would not work without the extra compdef
,
but the second would.
AUTO_REMOVE_SLASH
This option is turned on by default. If you complete a directory name
and a slash is added --- which it usually is, both to tell you that you
have completed a directory and to allow you to complete files inside it
without adding a `/
' by hand --- and the next thing you type is not
something which would insert or complete part of a file in that
directory, then the slash is removed. Hence:
% rmdir my<TAB>
-> rmdir mydir/
% rmdir mydir/<RETURN>
-> `rmdir mydir' executed
This example shows why this behaviour was added: some versions of
`rmdir
' baulk at having the slash after the directory name. On the
other hand, if you continued typing after the slash, or hit tab again to
complete inside mydir
, then the slash would remain.
This is at worst harmless under most circumstances. However, you can
unset the option AUTO_REMOVE_SLASH
if you don't like that behaviour.
One thing that may cause slight confusion, although it is the same as
with other suffixes (i.e. bits which get added automatically but aren't
part of the value being completed), is that the slash is added straight
away if the value is being inserted by menu completion. This might cause
you to think wrongly that the completion is finished, and hence is
unique when in fact it isn't.
Note that some forms of completion have this type of behaviour built in,
not necessarily with a slash, when completing lists of arguments. For
example, enter `typeset ZSH_V<TAB>
' and you will see
`ZSH_VERSION=
' appear, in case you want to assign something to the
parameter; hitting space, which is not a possible value, makes the
`=
' disappear. This is not controlled by the AUTO_REMOVE_SLASH
option, which applies only to directories inserted by the standard
filename completion system.
AUTO_PARAM_SLASH
, AUTO_PARAM_KEYS
These options come into effect when completing expressions with
parameter substitutions. If AUTO_PARAM_SLASH
is set, then any
parameter expression whose value is the name of a directory will have a
slash appended when completed, just as if the value itself had been
inserted by the completion system.
The behaviour for AUTO_PARAM_KEYS
is a bit more complicated. Try this:
print ${ZSH_V<TAB>
You will find that you get the complete word `${ZSH_VERSION}
', with
the closing brace and (assuming there are no other matching parameters)
a space afterwards. However, often after you have completed a parameter
in this fashion you want to type something immediately after it, such as
a subscript. With AUTO_PARAM_KEYS
, if you type something at this point
which seems likely to have to go after the parameter name, it will
immediately be put there without you having to delete the intervening
characters --- try it with `[
', for example. Note that this only
happens if the parameter name and any extra bits were added by
completion; if you type everything by hand, typing `[
' will not have
this magic effect.
COMPLETE_IN_WORD
If this is set, completion always takes place at the cursor position in
the word. For example if you typed `Mafile
', went back over the
`f
', and hit tab, the shell would complete `Makefile
', instead of
its usual behaviour of going to the end of the word and trying to find a
completion there, i.e. something matching `Mafile*
'. Some sorts of
new completion (such as filename completion) seem to implement this
behaviour regardless of the option setting; some other features (such as
the `_prefix
' completer described below) require it, so it's a good
thing to set and get used to, unless you really need to complete only at
the end of the word.
ALWAYS_TO_END
If this is set, the cursor is always moved to the end of the word after it is completed, even if completion took place in the middle. This also happens with menu completion.
6.2.5: Changing the way completions are displayed
LIST_TYPES
This is like the -F
option to ls
; files which appear in the
completion listing have a trailing `/
' for a directory, `*
' for a
regular file executable by the current process, `@
' for a link,
`|
' for a named pipe, `%
' for a character device and `#
' for a
block device. This option is on by default.
Note that the identifiers only appear if the completion system knows
that the item is supposed to be a file. This is automatic if the usual
filename completion commands are used. There is also an option -f
to
the builtin compadd
if you write your own completion function and want
to tell the shell that the values may be existing files to apply
LIST_TYPES
to (though no harm is caused if no such files exist).
LIST_PACKED
, LIST_ROWS_FIRST
These affect the arrangement of the completion listing. With
LIST_PACKED
, completion lists are made as compact as possible by
varying the widths of the columns, instead of formatting them into a
completely regular grid. With LIST_ROWS_FIRST
, the listing order is
changed so that adjacent items appear along rows instead of down
columns, rather like ls
's -x
option.
It is possible to alter both these for particular contexts using the
styles list-packed
and list-rows-first
. The styles in such cases
always override the option; the option setting is used if no
corresponding style is found.
Note also the discussion of completion groups later on: it is possible to have different types of completion appear in separate lists, which may then be formatted differently using these tag-sensitive styles.
6.3: Getting started with new completion
Before I go into any detail about new completion, here's how to set it
up so that you can try it out. As I said above, the basic objects that
do completions are shell functions. These are all autoloaded, so the
shell needs to know where to find them via the $fpath
array. If the
shell was installed properly, and nothing in the initialization files
has removed the required bits from $fpath
, this should happen
automatically. It's even possible your system sets up completion for you
(Mandrake Linux 6.1 is the first system known to do this out of the
box), in which case type `which compdef
' and you should see a
complete shell function --- actually the one which allows you to define
additional completion functions. Then you can skip the next paragraph.
If you want to load completion, try this at the command line:
autoload -U compinit
compinit
which should work silently. If not, you need to ask your system
administrator what has happened to the completion functions or find them
yourself, and then add all the required directories to your $fpath
.
Either they will all be in one big directory, or in a set of
subdirectories with the names AIX
, BSD
, Base
, Debian
, Redhat
,
Unix
, X
and Zsh
; in the second case, all the directories need to
be in $fpath
. When this works, you can add the same lines, including
any modification of $fpath
you needed, to your .zshrc
.
You can now see if it's actually working. Type `cd
', then ^D
,
and you should be presented with a list of directories only, no regular
files. If you have $cdpath
set, you may see directories that don't
appear with ls
. As this suggests, the completion system is supplied
with completions for many common (and some quite abstruse) commands.
Indeed, the idea is that for most users completion just works without
intervention most of the time. If you think it should when it doesn't,
it may be a bug or an oversight, and you should report it.
Another example on the theme of `it just works':
tar xzf archive.tar.gz ^D
will look inside the gzipped tar archive --- assuming the GNU version of
tar
, for which the `z
' in the first set of arguments reports that
the archive has been compressed with gzip --- and give you a list of
files or directories you can extract. This is done in a very similar way
to normal file completion; although there are differences, you can do
completion down to any directory depth within the archive. (At this
point, you're supposed to be impressed.)
The completion system knows about more than just commands and their
arguments, it also understands some of the shell syntax. For example,
there's an associative array called $_comps
which stores the names of
commands as keys and the names of completion functions as the
corresponding values. Try typing:
print ${_comps[
and then ^D
. You'll probably get a message asking if you really want
to see all the possible completions, i.e. the keys for $_comps
; if you
say `y
' you'll see a list. If you insert any of those keys, then
close the braces so you have e.g. `${_comps[mozilla]}
' and hit
return, you'll see the completion function which handles that command;
in this case (at the time of writing) it's _webbrowser
. This is one
way of finding out what function is handling a particular command. If
there is no entry --- i.e. the `print ${_comps[mycmd]}
' gives you a
blank line --- then the command is not handled specially and will simply
use whatever function is defined for the `-default-
' context, usually
_default
. Usually this will just try to complete file names. You can
customize _default
, if you like.
Apart from -default-
, some other of those keys for _comps
also look
like -this-
: they are special contexts, places other than the
arguments of a command. We were using the context called -subscript-
;
you'll find that the function in this case is called _subscript
. Many
completion functions have names which are simply an underscore followed
by the command or context name, minus any hyphens. If you want a taster
of how a completion function looks, try `which _subscript
'; you may
well find there are a lot of other commands in there that you don't know
yet.
It's important to remember that the function found in this way is at the root of how a completion is performed. No amount of fiddling with options or styles --- the stuff I'm going to be talking about for the next few sections --- will change that; if you want to change the basic completion, you will just have to write your own function.
By the way, you may have old-style completions you want to mix-in --- or
maybe you specifically don't want to mix them in so that you can make
sure everything is working with the new format. By default, the new
completion system will first try to find a specific new-style
completion, and if it can't it will try to find a compctl
-defined
completion for the command in question. If all that fails, it will try
the usual new-style default completion, probably just filename
completion. Note that specific new-style completions take precedence,
which is fair enough, since if you've added them you almost certainly
don't want to go back and use the old form. However, if you don't ever
want to try old-style completion, you can put the following incantation
in your .zshrc
:
zstyle ':completion:*' use-compctl false
For now, that's just black magic, but later I will explain the `style' mechanism in more detail and you will see that this fits in with the normal way of turning things off in new-style completion.
6.4: How the shell finds the right completions
6.4.1: Contexts
The examples above show that the completion system is highly context-sensitive, so it's important to know how these contexts are described. This system evolved gradually, but everything I say applies to all versions of zsh with the major version 4.
state we are at in completion, and is given as a sort of colon-separated
path, starting with the least specific part. There's an easy way of
finding out what context you are in: at the point where you want to
complete something, instead type `^Xh
', and it will tell you. In the
case of the $_comps
example, you will find,
:completion::complete:-subscript-::
plus a list of so-called `tags' and completion functions, which I'll talk about later. The full form is:
:completion:<func>:<completer>:<command>:<argument>:<tag>
where the elements may be missing if they are not set, but the colons
will always be there to make pattern matching easier. Here's what the
bits of the context mean after the :completion:
part, which is common
to the whole completion system.
- <func>
is the name of a function from which completion is called --- this is blank if it was started from the standard completion system, and only appears in a few special cases, listed in section six of this chapter. - <completer>
is called `complete
' in this case: this refers to the fact that the completion system can do more than just simple completion; for example, it can do a more controlled form of expansion (as I mentioned), spelling correction, and completing words with spelling mistakes. I'll introduce the other completers later; `complete
' is the simplest one, which just does basic completion. - <command>
is the name of a command or other similar context as described above, here `-subscript-
'. - <argument>
is most useful when<command>
is the name of a real command; it describes where in the arguments to that command we are. You'll see how it works in a moment. Many of the simpler completions don't use this; only the ones with complicated option and argument combinations. You just have to find out with^Xh
if you need to know. - <tag>
describes the type of a completion, essentially a way of discriminating between the different things which can be completed at the same point on the command line.
Now look at the context for a more normal command-argument completion,
e.g. after cd
; here you'll see the context
`:completion::complete:cd::
'. Here the command-name part of the
context is a real command.
For something more complicated, try after `cvs add
' (it doesn't
matter for this if you don't have the cvs
command). You'll see a long
and repetitive list of tags, for two possible contexts,
:completion::complete:cvs:argument-rest:
:completion::complete:cvs-add:argument-rest:
The reason you have both is that the `add
' is not only an argument to
cvs
, as the first context would suggest, it's also a subcommand in its
own right, with its own arguments, and that's what the second context is
for. The first context implies there might be more subcommands after
`add
' and its arguments which are completely separate from them ---
though in fact CVS doesn't work that way, so that form won't give you
any completions here.
In both, `argument-rest
' shows that completion is looking for another
argument, the `rest
' indicating that it is the list of arguments at
the end of the line; if position were important (see `cvs import
' for
an example), the context would contain `argument-1
', or whatever. The
`cvs-add
' shows how subcommands are handled, by separating with a
hyphen instead of a colon, so as not to confuse the different bits of
the context.
Apart from arguments to commands and subcommands, arguments to options
are another frequent possibility; for an example of this, try typing
^Xh
after `dvips -o
' and you will see the context
`:completion::complete:dvips:option-o-1:
'; this shows you are
completing the first argument to dvips
's -o
option, (it only takes
one argument) which happens to be the name of a file for output.
6.4.2: Tags
Now on to the other matter to do with contexts, tags. Let's go back and
look at the output from the ^Xh
help test after the cd
command in
full:
tags in context :completion::complete:cd::
local-directories path-directories (_alternative _cd)
Unlike the contexts considered so far, which tell you how completion
arrived at the point it did, the tags describe the things it can
complete here. In this case, there are three: directory-stack
refers
to entries such as `+1
'; the directory stack is the set of
directories defined by using the pushd
command, which you can see by
using the dirs
command. Next, local-directories
refers to
subdirectories of the current working directory, while
path-directories
refers to any directories found by searching the
$cdpath
array. Each of the possible completions which the system
offers belongs to one of those classes.
In parentheses, you see the names of the functions which were called to
generate the completions; these are what you need to change or replace
if you want to alter the basic completion behaviour. Calling functions
appear on the right and called functions on the left, so that in this
case the function `_cd
' was the function first called to handle
arguments for the cd
command, fitting the usual convention. Some
standard completion functions have been filtered out of this list --- it
wouldn't help you to know it had been through _main_complete
and
_complete
, for example.
Maybe it's already obvious that having the system treat different types
of completion in different ways is useful, but here's an example, which
gives you a preview of the `styles' mechanism, discussed later. Styles
are a sort of glorified shell parameter; they are defined with the
zstyle
command, using a style name and possible values which may be an
array; you can always define a style as an array, but some styles may
simply use it as a string, joining together the arguments you gave it
with spaces. You can also use the zstyle
command, with different
arguments, to retrieve their value, which is what the completion system
itself does; there's no actual overlap with parameters and their values,
so they don't get in the way of normal shell programming.
Where styles differ from parameters is that they can take different
values in different contexts. The first argument to the zstyle
command
gives a context; when you define a style, this argument is actually a
pattern which will be matched against the current context to see if the
style applies. The rule for finding out what applies is: exact string
matches are preferred before patterns, and longer patterns are preferred
before shorter patterns. Here's that example:
zstyle ':completion:*:cd:*' tag-order local-directories \
path-directories
From the discussion of contexts above, the pattern will match any time
an argument to the cd
command is being completed. The style being set
is called tag-order
, and the values are the two tags valid for
directories in cd
.
The tag-order
style determines the order in which tags are tried. The
value given above means that first local-directories
will be
completed; only if none can be completed will path-directories
be
tried. You can enter the command and try this; if you don't have
$cdpath
set up you can assign `cdpath=(~)
', which will allow `cd foo
' to change to a directory `~/foo
' and allow completion of
directories accordingly. Go to a directory other than ~
; completion
for cd
will only show subdirectories of where you are, not those of
~
, unless you type a string which is the prefix of a directory under
~
but not your current directory. For example,
% cdpath=(~)
% ls -F ~
foo/ bar/
% ls -F
rod/ stick/
# Without that tag-order zstyle command, you would get...
% cd ^D
bar/ foo/ rod/ stick/
% zstyle ':completion:*:cd:*' tag-order local-directories \
path-directories
# now you just get the local directories, if there are any...
% cd ^D
rod/ stick/
There's more you can do with the tag-order
style: if you put the tags
into the same word by quoting, for example "local-directories path-directories"
, then they would be tried at the same time, which in
this case gives you the effect of the default. In fact, since it's too
much work to know what tags are going to be available for every single
possible completion, the default when there is no appropriate
tag-order
is simply to try all the tags available in the context at
once; this was of course what was originally happening for completion
after cd
.
Even if there is a tag-order
specification, any tags not specified
will usually be tried all together at the end, so you could actually
have missed out path-directories
from the end of the original example
and the effect would have been the same. If you don't want that to
happen, you can specify a `-
' somewhere in the list of tags, which is
not used as a tag but tells completion that only the tags in the list
should be tried, not any others that may be available. Also, if you
don't want a particular tag to be shown you can include `!tagname
' in
the values, and all the others but this will be included. For example,
you may have noticed that when completing in command position you are
offered parameters to set as well as commands etc.:
Completing external command
tex texhash texi2pdf text2sf
texconfig texi2dvi texindex textmode
texdoc texi2dvi4a2ps texlinks texutil
texexec texi2html texshow texview
Completing parameter
TEXINPUTS texinputs
(I haven't told you how to produce those descriptions, or how to make
the completions for different tags appear separately, but I will --- see
the descriptions of the `format
' and `group-name
' styles below.)
If you set
zstyle ':completion:*:-command-:*' tag-order '!parameters'
then the last two lines will disappear from the completion. Of course, your completion list probably looks completely different from mine anyway. By the way, one good thing about styles is that it doesn't matter whether they're defined before or after completion is loaded, since styles are stored and retrieved by another part of the shell.
To exclude more than one tag name, you need to include the names in the
same word. For example, to exclude both parameters and reserved words
the value would be '!parameters reserved-words'
, and not
'!parameters' '!reserved-words'
, which would try completion once with
parameters excluded, then again with reserved words excluded.
Furthermore, tags can actually be patterns, or more precisely any word
in one of the arguments to tag-order
may contain a pattern, which will
then be tried against all the valid tags to see if it matches. It's
sometimes even useful to use `*
' to match all tags, if you are
specifying a special form of one of the tags --- maybe using a label, as
described next --- in the same word. See the manual for all the tag
names understood by the supplied functions.
The tag-order
style allows you to give tags `labels', which are a
sort of alias, instructing the completion system to use a tag under a
different name. You arrange this by giving the tag followed by a colon,
followed by the label. The label can also have a hyphen in front, which
means that the original tag name should be put in front when the label
is looked up; this is really just a way of making the names look neater.
The upshot is that by using contexts with the label name in, rather than
the tag name, you can arrange for special behaviour. Furthermore, you
can give an alternative description for the labelled tag; these show up
with the format
style which I'll describe below (and which I
personally find very useful). You put the description after another
colon, with any spaces quoted. It would look like this:
zstyle ':completion:*:aliens:*' tag-order \
'frooble:-funny:funny\ frooble' frooble
which is used when you're completing for the command aliens
, which
presumably has completions tagged as `frooble
' (if not, you're very
weird). Then completion will first look up styles for that tag under the
name frooble-funny
, and if it finds completions using those styles it
will list them with a description (if you are using format
) of `funny
frooble'. Otherwise, it will look up the styles for the tag under its
usual name and try completion again. It's presumably obvious that if you
don't have different styles for the two labels of the tag, you get the
same completions each time.
Rather than overload you with information on tags by giving examples of
how to use tag labels now, I'll reserve this for the description of the
ignored-patterns
style below, which is one neat use for labels. In
fact, it's the one for which it was invented; there are probably lots of
other ones we haven't thought of yet.
One important note about tag-order
which I may not have made as
explicit as I should have: it doesn't change which tags are actually
valid in that completion. Just putting a tag name into the list doesn't
mean that tag name will be used; that's determined entirely by the
completion functions for a particular context. The tag-order
style
simply alters the order in which the tags which are valid are
examined. Come back and read this paragraph again when you can't work
out why tag-order
isn't doing what you want.
Note that the rule for testing patterns means that you can always
specify a catch-all worst case by `zstyle "*" style ...
', which will
always be tried last --- not just in completion, in fact, since other
parts of the shell use the styles mechanism, and without the
`:completion:
' at the start of the context this style definition will
be picked up there, too.
Styles like tag-order
are the most important case where tags are used
on their own. In other cases, they can be added to the end of the
context; this is useful for styles which can give different results for
different sets of completions, in particular styles that determine how
the list of completions is displayed, or how a completion is to be
inserted into the command line. The tag is the final element, so is not
followed by a colon. A full context then looks something like
`:completion::complete:cd::path-directories
'. Later, you'll see some
styles which can usefully be different for different tag contexts.
Remember, however, that the tags part of the context, like other parts,
may be empty if the completion system hasn't figured out what it should
be yet.
6.5: Configuring completion using styles
You now know how to define a style for a particular context, using
zstyle <context> <style> <value...>
and some of the cases where it's useful. Before introducing other
styles, here's some more detailed information. I already said that
styles could take an array value, i.e. a set of values at the end of the
zstyle
command corresponding to the array elements, and you've already
seen one case (tag-order
) where that is useful. Many styles only use
one value, however. There is a particularly common case, where you
simply want to turn a value on or off, i.e. a boolean value. In this
case, you can use any of `true
', `yes
', `on
' or `1
' for on
and `false
', `no
', `off
' or `0
' for off. You define all
styles the same way; only when they're used is it decided whether they
should be a scalar, an array, or a boolean, nor is the name of a style
checked to see if it is valid, since the shell doesn't know what styles
might later be looked up. The same obviously goes for contexts.
You can list existing styles (not individually, only as a complete list)
using either `zstyle
' or `zstyle -L
'. In the second case, they are
output as the set of zstyle
commands which would regenerate the styles
currently defined. This is also useful with grep
, since you can easily
check all possible contexts for a particular style.
The most powerful way of using zstyle
is with the option -e
. This
says that the words you supply are to be evaluated as if as arguments to
eval
. This should set the array $reply
to the words to be used. So
zstyle '*' days 'Monday Tuesday'
and
zstyle -e '*' days 'reply=(Monday Tuesday)'
are equivalent --- but the intention, of course, is that in the second case the argument can return a different value each time so that the style can vary. It will usually be evaluated in the heat of completion, hence picking up all the editing parameters; so for example
zstyle -e ':completion:*' mystyles 'reply=(${NUMERIC:-0})'
will make the style return a non-zero integer (possibly indicating
true
) if you entered a non-zero prefix argument to the command, as
described in chapter 4. However, the argument can
contain any zsh code whatsoever, not just a simple assignment. Remember
to quote it to prevent it from being turned into something else when the
zstyle
command line is run.
Finally, you can delete a context for a style or a list of styles by
zstyle -d [ <context-pattern> [ <style> ] ] ...
--- note that although the first argument is a pattern, in this case it
is treated exactly, so if you give the pattern `:completion:*:cd:*
',
only values given with exactly that pattern will be deleted, not other
values whose context begins with `:completion:
' and contains
`:cd:
'. The pattern and the style are optional when deleting; if
omitted, all styles for the context, or all styles of any sort, are
deleted. The completion system has its own defaults, but these are
builtin, so anything you specify takes precedence.
By the way, I did mention in passing in chapter 4
that you could use styles in just the same way in ordinary zle widgets
(the ones created with `zle -N
'), but you probably forgot about that
straight away. All the instructions about defining styles and using them
in your own functions from this chapter apply to zle functions. The only
difference is that in that case the convention for contexts is that the
context is set to `:zle:
widget-name' for executing the widget
widget-name.
The rest of this section describes some useful styles. It's up to you to
experiment with contexts if you want the style's values to be different
in different places, or just use `*
' if you don't care.
6.5.1: Specifying completers and their options
`Completers' are the behind-the-scenes functions that decide what sort
of completion is being done. You set what completers to use with the
`completer
' style, which takes an array of completers to try in
order. For example,
zstyle ':completion:*' completer _complete _correct _approximate
specifies that first normal completion will be tried (`_complete
'),
then spelling correction (`_correct
'), and finally approximate
completion (`_approximate
'), which is essentially the combined effect
of the previous two, i.e. complete the word typed but allow for spelling
mistakes. All completers set the context, so inside _complete
you will
usually find `:completion::complete:...
', inside correction
`:completion::correct:..
', and so on.
There's a labelling feature for completers, rather like the one for tags described, but not illustrated in detail, above. You can put a completer in a list like this:
zstyle ':completion:*' completer ... _complete:comp-label ...
which calls the completer _complete
, but pretends its name is
comp-label
when looking things up in styles, so you can try completers
more than once with different features enabled. As with tags, you can
write it like `_complete:-label
', and the normal name will be
prepended to get the name `complete-label
' --- just a shortcut, it
doesn't introduce anything new. I'll defer an example until you know
what the completers do.
Here is a more detailed description of the existing completers; they are all functions, so you can simply copy and modify one to make your own completer.
_complete
This is the basic completion behaviour, which we've been assuming up to
now. Its major use is simply to check the context --- here meaning
whether we are completing a normal command argument or one of the
special `-context-
' places --- and call the appropriate completion
function. It's possible to trick it by setting the parameter
`compcontext
' which will be used instead of the one generated
automatically; this can be useful if you write your own completion
commands for special cases. If you do this, you should make the
parameter local to your function.
_approximate
This does approximate completion: it's actually written as a wrapper for
the _complete
completer, so it does all the things that does, but it
also sets up the system to allow completions with misspellings.
Typically, you would want to try to complete without misspellings first,
so this completer usually appears after _complete
in the completers
style.
The main means of control is via the max-errors
style. You can set
this to the maximum number of errors to allow. An error is defined as
described in the manual for approximate pattern matching: a character
missing such as `rhythm
' / `rhytm
', an extra character such as
`rhythm
' / `rhythms
', an incorrect character such as `rhythm
' /
`rhxthm
', or a pair of characters transposed such as `rhythm
'
`rhyhtm
' each count as one error. Approximation will first try to
find a match or matches with one error, then two errors, and so on, up
to and including the value of max-errors
; the set of matches with the
lowest number of errors is chosen, so that even if you set max-errors
large, matches with a lower number of errors will always be preferred.
The real problems with setting a large max-errors
are that it will be
slower, and is more likely to generate matches completely unlike what
you want --- with typing errors, two or three are probably the most you
need. Otherwise, there's always Mavis Beacon. Hence:
% zstyle ':completion:*' max-errors 2
# just for the sake of example...
% zstyle ':completion:*' completer _approximate
% ls
ashes sackcloth
% echo siccl<TAB>
-> echo sackcloth
% echo zicc<TAB>
<Beep.>
because `s[i/a]c[k]cloth
' is only two errors, while
`[z/s][i/a]c[k]cloth
' would be three, so doesn't complete.
There's another way to give a maximum number of errors, using the
numeric prefix specified with ESC-<digit>
in Emacs mode, directly with
number keys in vi command mode, or with universal-argument
. To enable
this, you have to include the string numeric
as one of the values for
max-errors
--- hence this can actually be an array, e.g.
zstyle ':completion:*:approximate:*' max-errors 2 numeric
allows up to two errors automatically, but you can specify a higher
maximum by giving a prefix to the completion command. So to continue the
example above, enter the new zstyle
and:
% echo zicc<ESC-3><TAB>
-> echo sackcloth
because we've allowed three errors. You can start to see the problems
with allowing too many errors: if you had the file `zucchini
', that
would be only one error away, and would be found and inserted before
`sackcloth
' was even considered.
Note that the context is examined straightaway in the completer, so at
this stage it is simply `:completion::approximate:::
'; no more
detailed contextual information is available, so it is not possible to
specify different max-errors
for different commands or tags.
The final possibility as a value for the style is `not-numeric
': that
means if any numeric prefix is given, approximation will not be done at
all. In the last example, completion would have to find a file beginning
`zicc
'.
Other minor styles also control approximation. The style original
, if
true means the original value is always treated as a possible
completion, even if it doesn't match anything and even if nothing else
matched. Completing the original and the corrections use different tags,
unimaginatively called original
and corrections
, so you can organise
this with the tag-order
style.
Because the completions in this case usually don't match what's already
on the command line, and may well not match each other, menu completion
is entered straight away for you to pick a completion. You can arrange
that this doesn't happen if there is an unambiguous piece at the start
to insert first by setting the boolean style insert-unambiguous
.
Those last two styles (original
and insert-unambiguous
) are looked
up quite early on, when the context for generating corrections is being
set up, so that only the context up to the completer name is available.
The completer name will be followed by a hyphen and the number of errors
currently being accepted. So for trying approximation with one error the
context is `:completion::approximate-1:::
'; if that fails and the
system needs to look for completion with two errors, the context will be
`:completion::approximate-2:::
', and so on; the same happens with
correction and `correct-1
', etc., for the completer described next.
_correct
This is very similar to _approximate
, except that the context is
`:completion::correct:*
' (or `:completion::correct-<num>:*
' when
generating corrections, as described immediately above) and it won't
perform completion, just spelling correction, so extra characters which
the completer has to add at the end of the word on the line now count as
extra errors instead of completing in the ordinary way: zicc
is
woefully far from sackcloth
, seven errors, but ziccloth
only counts
three again. The _correct
completer is controlled in just the same way
as _approximate
.
There is a separate command which only does correction and nothing else,
usually bound to `^Xc
', so if you are happy using that you don't need
to include _correct
in the list of completers. If you do include it,
and you also have _approximate
, _correct
should come earlier;
_approximate
is bound to generate all the matches _correct
does, and
probably more. Like other separate completion commands, it has its own
context, here beginning `:completion:correct-word:
', so it's easy to
make this command behave differently from the normal completers.
Old-timers will remember that there is another form of spelling
correction built into the shell, called with `ESC-$
' or `ESC-s
'.
This only corrects filenames and doesn't understand anything about the
new completion mechanism; the only reason for using it is that it may
well be faster. However, if you use the CORRECT
or CORRECT_ALL
shell
options, you will be using the old filename correction mechanism; it's
not yet possible to alter this.
_expand
This actually performs expansion, not completion; the difference was
explained at the start of the chapter. If you use it, you should bind
tab to complete-word
, not expand-or-complete
, since otherwise
expansion will be performed before the completion mechanism is started
up. As expansion should still usually be attempted before completion,
this completer should appear before _complete
and its relatives in the
list of values for the completers
style.
The reason for using this completer instead of normal expansion is that
you can control which expansions are performed using styles in the
`:completion:*:expand:*
' context. Here are the relevant styles:
glob
expands glob expressions, in other words does filename generation using wildcards.substitute
expands expressions including and active `$
' or backquotes.
But remember that you need
bindkey '^i' complete-word
when using this completer as otherwise the built-in expansion mechanism
which is run by the normal binding expand-or-complete
will take over.
You can also control how expansions are inserted. The tags for adding
expansions are original
(presumably self-explanatory),
all-expansions
, which refers to adding a single string containing all
the possible expansions (the default, just like the editor function
expand-word
), and expansions
, which refers to the results added one
by one. By changing the order in which the tags are tried, as described
for the tag-order
style above, you can decide how this happens. For
example,
zstyle ':completion:*' completer _expand _complete
zstyle ':completion::expand:*' tag-order expansions
sets up for performing glob expansion via completion, with the
expansions being presented one by one (usually via menu completion,
since there is no common prefix). Altering expansions
to
all-expansions
would insert the list, as done by the normal expansion
mechanism, while altering it to `expansions original
' would keep the
one-at-a-time entry but also present the original string as a
possibility. You can even have all three, i.e. the entire list as a
single string becomes just one of the set of possibilities.
There is also a sort
style, which determines whether the expansions
generated will be sorted in the way completions usually are, or left
just as the shell produced them from the expansion (for example,
expansion of an array parameter would produce the elements in order). If
it is true
, they will always be sorted, if false
or unset never, and
if it is menu
they will be sorted for the expansions
tag, but not
for the all-expansions
tag which will be a single string of the values
in the original order.
There is a slight problem when you try just to generate glob
expansions, without substitute
. In fact, it doesn't take much thought
to see that an expression like `$PWD/*.c
' doesn't mean anything if
substitute
is inactive; it must be active to make sense of such
expressions. However, this is annoying if there are no matches: you end
up being offered a completion with the expanded $PWD
, but `*.c
'
still tacked on the end, which isn't what you want. If you use _expand
mainly for globbing, you might therefore want to set the style
subst-globs-only
to true: if a completion just expands the parameters,
and globbing does nothing, then the expansion is rejected and the line
left untouched.
The _expand
completer will also use the styles
accept-exact
applies to words beginning with a `$
' or `~
'. Suppose there is a parameter `$foo
' and a parameter `$foobar
' and you have `$foo
' on the line. Normally the completion system will perform completion at this point. However, withaccept-exact
set, `$foo
' will be expanded since it matches a parameter.add-space
means add a space after the expansion, as with a successful completion --- although directories are given a `/
' instead. For finer control, it can be set to the wordfile
, which means the space is only added if the expanded word matches a file that already exists (the idea being that, if it doesn't, you may want to complete further). Bothtrue
andfile
may be combined withsubst
, which prevents the adding of a space after expanding a substitution of the form `${...}
' or `$(...)
'.keep_prefix
also addresses the question of whether a `~
' or `$
' should be expanded. If set, the prefix will be retained, so expanding `~/f*
' to `~/foo
' doesn't turn the `~
' into `/home/pws
'. The default is the value `changed
', which is a half-way house beenfalse
andtrue
: it means that if there was no other change in the word, i.e. no other possible expansion was found, the `~
' or `$
' will be expanded. If the effect of this style is that the expansion is the same as the unexpanded word, the next completer in the list after_expand
will be tried.suffix
is similar tokeep_prefix
. The `suffix' referred to is something after an expression beginning `~
' or `$
' that wouldn't be part of that expansion. If this style is set, and such a suffix exists, the expansion is not performed. So, for example, `~pw<TAB>
' can be expanded to `~pws
', but `~pw/
' is not eligible for expansion; likewise `$fo
' and `$fo/
'. This style defaults totrue
--- so if you want_expand
always to expand such expressions, you will need to set it tofalse
yourself.
An easier way of getting the sort of control over expansion which the
_expand
completer provides is with the _expand_word
function,
usually bound to \C-xe
, which does all the things described above
without getting mixed up with the other completers. In this case the
context string starts `:completion:expand-word
', so you can have
different styles for this than for the _expand
completer.
Setting different priorities for expansion is one good use for completer labels, for example
zstyle ':completion:*' completer _expand:-glob _expand:-subst
zstyle ':completion:*:expand-glob:*' glob yes
zstyle ':completion:*:expand-subst:*' substitute yes
is the basic set up to make _expand
try glob completions and failing
that do substitutions, presenting the results as an expansion. You would
almost certainly want to add details to help this along.
_history
This completes words from the shell's history, in other words everything
you typed or had completed or expanded on previous lines. There are
three styles that affect it, sort
and remove-all-dups
; they are
described for the command widget _history_complete_word
below. That
widget essentially performs the work of this completer as a special
keystroke.
_prefix
Strictly, this completer doesn't do completion itself, and should hence
be in the group below starting with _match
. However, it seems to do
completion... Let me explain.
Many shells including zsh have the facility to complete only the word
before the cursor, which zsh completion jargon refers to as the
`prefix'. I explained this above when I talked about
expand-or-complete-prefix
; when you use that instead of the normal
completion functions, the word as it's finally completed looks like
`<prefix><completion><suffix>
' where the completion has changed
`<prefix>
' to `<prefix><completion>
', ignoring <suffix>
throughout.
The _prefix
completer lets you do this as part of normal completion.
What happens is that the completers are evaluated as normal, from left
to right, until a completion is found. If _prefix
is reached,
completion is then attempted just on the prefix. So if your completers
are `_complete _prefix
', the shell will first try completion on the
whole word, prefix and suffix, then just on the prefix. Only the first
`real' completer (_complete
, _approximate
, _correct
, _expand
,
_history
) is used.
You can try prefix completion more than once simply by including
_prefix
more than once in the list of completers; the second time, it
will try the second `real' completer in the list; so if they are
`_complete _prefix _correct _prefix
', you will get first ordinary
completion, then the same for the prefix only, then ordinary correction,
then the same for the prefix only. You can move either of the _prefix
completers to the point in the sequence where you want the prefix-only
version to be tried.
The _prefix
completer will re-look up the completer
style. This
means that you can use a non-default set of completers for use just with
_prefix
. Here, as described in the manual, is how to force _prefix
only to be used as a last resort, and only with normal completion:
zstyle ':completion:::::' completer _complete \
<other-completers> _prefix
zstyle ':completion::prefix:::' completer _complete
The full contexts are shown, just to emphasise the form; as always, you
can use wildcards if you don't care. In a case like this, you can use
only _prefix
as the completer, and completion including the suffix
would never be tried; you then have to make sure you have the
completer
style for the prefix
context, however, or no completion at
all will be done.
The completer labelling trick is again useful here: you can call
_prefix
more than once, wherever you choose in your list of
completers, and force it to look up in a different context each time.
zstyle ':completion:*' completer _complete _prefix:-complete \
_approximate _prefix:-approximate
zstyle ':completion:*:prefix-complete:*' completer _complete
zstyle ':completion:*:prefix-approximate:*' completer _approximate
This tries ordinary completion, then the same for the prefix only, then
approximation, then the same for the prefix only. As mentioned in the
previous paragraph, it is perfectly legitimate to leave out the raw
_complete
and _approximate
completers and just use the forms with
the _prefix
prefix.
One gotcha with the _prefix
completer: you have to make sure the
option COMPLETE_IN_WORD
is set. That may sound counter-intuitive:
after all, _prefix
forces completion not to complete inside a word.
The point is that without that option, completion is only ever tried at
the end of the word, so when you type <TAB>
in the middle of
<prefix><suffix>
, the cursor is moved to after the end of the suffix
before the completion system has a chance to see what's there, and hence
the whole thing is regarded as a prefix, with no suffix.
There's one more style used with _prefix
: `add-space
'. This makes
_prefix
add a real, live space when it completes the prefix, instead
of just pretending there was one there, hence separating the completed
word from the original suffix; otherwise it would simply leave the
resulting word all joined together, as expand-or-complete-prefix
usually does.
_ignored
Like _prefix
this is a bit of a hybrid, mopping up after completions
which have already been generated. It allows you to have completions
which have already been rejected by the style `ignored-patterns
'.
I'll describe that below, but it's effect is very simple: for the
context given, the list of patterns you specify are matched against
possible completions, and any that match are removed from the list. The
_ignored
completer allows you to retrieve those removed completions
later in your completer list, in case nothing else matched.
This is used by the $fignore
mechanism --- a list of suffixes of files
not normally to be completed --- which is actually built on top of
ignored-patterns
, so if you use that in the way familiar to current
zsh users, where the ignored matches are shown if there are no unignored
matches, you need the _ignored
completer in your completer list.
One slightly annoying feature with _ignored
is if there is only a
single possible completion, since it will then be unconditionally
inserted. Hardly a surprise, but it can be annoying if you really don't
want that choice. There is a style single-ignored
which you can set to
show
--- just show the single ignored match, don't insert it --- or to
menu
--- go to menu completion so that TAB cycles you between the
completion which _ignored
produced and what you originally typed. The
latter gives a very natural way of handling ignored files; it's sort of
saying `well, I found this but you might not like it, so hit tab again
if you want to go back to what you had before'.
I said this was like _prefix
, and indeed you can specify which
completers are called for the _ignored
completer in just the same way,
by giving the completer
style in the context
`:completion:*:ignored:*
'. That means my description has been a
little over-simplified: _ignored
doesn't really use the completions
which were ignored before; rather, when it's called it generates a list
of possibilities where the choices matched by ignore-patterns
--- or
internally using $fignore
--- are not ignored. So it should really be
called `_not_ignored
', but it isn't.
_match
This and the remaining completers are utilities, which affect the main completers given above when put into the completion list rather than doing completion themselves.
The _match
completer should appear after _complete
; it is a more
flexible form of the GLOB_COMPLETE
option. In other words, if
_complete
didn't succeed, it will try to match the word on the line as
a pattern, not just a fixed string, against the possible completions. To
make it work like normal completion, it usually acts as if a `*
' was
inserted at the cursor position, even if the word already contains
wildcards.
You can control the addition of `*
' with the `match-original
'
style; the normal behaviour occurs if this is unset. If it is set to
`only
', the `*
' is not inserted, and if it is `true
', or
actually any other string, it will try first without the `*
', then
with. For example, consider typing `setopt c*ect<TAB>
' with the
_match
completer in use. Normally this will produce two possibilities,
`correct
' and `correctall
'. After setting the style,
zstyle ':completion::match:*' original only
no `*
' would be inserted at the place where you hit `TAB
', so that
`correct
' is the only possible match.
The _match
completer uses the style insert-unambiguous
in just the
same way as does _approximate
.
_all_matches
This has a similar effect to performing expansion instead of completion:
all the possible completions are inserted onto the command line.
However, it uses the results of ordinary contextual completion to
achieve this. The normal way that the completion system achieves this is
by influencing the behaviour of any subsequent completers which are
called --- hence you will need to put _all_matches
in the list of
completers before any which you would like to have this behaviour.
You're unlikely to want to do this with every type of completion, so
there are two ways of limiting its effect. First, there is the
avoid-completer
style: you can set this to a list of completers which
should not insert all matches, and they will be handled normally.
Then there is the style old-matches
. This forces _all_matches
to use
an existing list of matches, if it exists, rather than what would be
generated this time round. You can set the style to only
instead of
true; in this case _all_matches
will never apply to the completions
which would be generated this time round, it will only use whatever list
of completions already exists.
This can be a nuisance if applied to normal completion generation ---
the usual list would never be generated, since _all_matches
would just
insert the non-existent list from last time --- so the manual recommends
two other ways of using the completer with this style. First, you can
add a condition to the use of the style:
zstyle -e ':completion:*' old-matches 'reply=(${NUMERIC:-false})'
This returns false unless there is a non-zero numeric argument; if you
type <ESC>1
in emacs mode, or just 1
in vi mode, before completion,
it will insert all the values generated by the immediately preceding
completion.
Otherwise, you can bind _all_matches
separately. This is probably the
more useful; copying the manual entry:
zle -C all-matches complete-word _generic
bindkey '^Xa' all-matches
zstyle ':completion:all-matches:*' completer _all_matches
zstyle ':completion:all-matches:*' old-matches only
Here we generate ourselves a new completion based on the complete-word
widget, called all-matches
--- this name is arbitrary but convenient.
We bind that to the keystroke ^Xa
, and give it two special styles
which normal completion won't see. For the completer
we set just
_all_matches
, and for old-matches
we set only
; the effect is that
^Xa
will only ever have the effect of inserting all the completions
which were generated by the last completion, whatever that was --- it
does not have to be an ordinary contextual completion, it may be the
result of any completion widget.
_list
If you have this in the list of completers (at the beginning is as good
as anything), then the first time you try completion, you only get a
list; nothing changes, not even a common prefix is inserted. The second
time, completion continues as normal. This is like typing ^D
, then
tab, but using just the one key. This differs from the usual AUTO_LIST
behaviour in that is entirely irrespective of whether the completion is
ambiguous; you always get the list the first time, and it always does
completion in the usual way the second time.
The _list
completer also uses the condition
style, which works a bit
like the styles for the _expand
completer: it must be set to one of
the values corresponding to `true' for the _list
delaying behaviour
to take effect. You can test for a particular value of $NUMERIC
or any
other condition by using the -e
option of zstyle
when defining the
style.
Finally, the boolean style word
is also relevant. If false or unset,
_list
examines the whole line when deciding if it has changed, and
hence completion should be delayed until the next keypress. If true, it
just examines the current word. Note that _list
has no knowledge of
what happens between those completion calls; looking at the command line
is its only resource.
_menu
This just implements menu completion in shell code; it should come
before the `real' completion generators in the completers
style. It
ignores the MENU_COMPLETION
option and other related options and the
normal menu-completion widgets don't work well with it. However, you can
copy it and write your own completers.
_oldlist
This completer is most useful when you are in the habit of using special completion functions, i.e. commands other than the standard completion system. It is able to hang onto an old completion list which would otherwise be replaced with a newly generated one. There are two aspects to this.
First, listing. Suppose you try to complete something from the shell
history, using the command bound to `ESC-/
'. For example, I typed
`echo ma<ESC-/>
' and got `max-errors
'. At this point you might
want to list the possible completions. Unfortunately, if you type ^D
,
it will simply list all the usual contextual completions --- for the
echo
command, which is not handled specially, these are simply files.
So it doesn't work. By putting the _oldlist
completer into the
completers
style before _complete
, it does work, because the old
list of matches is kept for ^D
to use.
In this case, you can force old-listing on or off by setting the
old-list
style to always
or never
; usually it shows the listing
for the current set of completions if that isn't already displayed, and
otherwise generates the standard listing. You can even set the value of
old-list
to a list of completers which will always have their list
kept in this way.
The other place where _oldlist
is useful is in menu completion, where
exactly the same problem occurs: if you generate a menu from a special
command, then try to cycle through by hitting tab, completion will look
for normal contextual matches instead. There's a way round this time ---
use the special command key repeatedly instead of tab. This is rather
tedious with multiple key sequences. Again, _oldlist
cures this, and
again you can control the behaviour with a style, old-menu
, which
takes a boolean value (it is on by default). As Orwell put it,
oldlisters unbellyfeel menucomp.
Ordering completers
I've given various suggestions about the order in which completers should come in, which might be confusing. Here, therefore, is a suggested order; just miss out any completers you don't want to use:
_all_matches _list _oldlist _menu _expand _complete _match
_ignored _correct _approximate _prefix
Other orders are certainly possible and maybe even useful: for example,
the _all_matches
completer applies to all the completers following not
listed in the avoid-completer
style, so you might have good reason to
shift it further down the list.
Here's my example of labels for completers, which I mentioned just above the list of different completers, whereby completers can be looked up under different names.
zstyle ':completion:*' completer _complete _approximate:-one \
_complete:-extended _approximate:-four
zstyle ':completion:*:approximate-one:*' max-errors 1
zstyle ':completion:*:complete-extended:*' \
matcher 'r:|[.,_-]=* r:|=*'
zstyle ':completion:*:approximate-four:*' max-errors 4
This tries the following in order.
- Ordinary, no-frills completion.
- Approximation with one error, as given by the second style.
- Ordinary completion with extended completion turned on, as given by
the third style. Sorry, this will be a black box until I talk about
the
matcher
style later on; for now, you'll just have to take my word for it that this style allows the characters in the square brackets to have a wildcard in front, so `a-b
' can complete to `able-baker
', and so on. - Approximation with up to four errors, as given by the final style.
Here's a rather bogus example. You have a directory containing:
foobar fortified-badger frightfully-barbaric
Actually, it's not bogus at all, since I just created one. First try
`echo foo<TAB>
'; no surprise, you get `foobar
'. Now try completing
with `fo-b<TAB>
' after the `echo
': basic completion fails, it gets
to `_approximate:-one' and finds that it's allowed one error, so
accepts the completion `foobar
' again. Now try `fort-ba<TAB>
'.
This time nothing kicks in until the third completion, which effectively
allows it to match `fort*-ba*<TAB>
', so you see `fortified-badger
'
(no, I've never seen one myself, but they're nocturnal, you know).
Finally, try `fortfully-ba<TAB>
'; the last entry, which allows up to
four errors, thoughtfully corrects `or
' to `righ
', and you get
`frightfully-barbaric
'. All right, the example is somewhat unhinged,
but I think you can see the features are useful. If it makes you feel
better, it took me four or five attempts to get the styles right for
this.
6.5.2: Changing the format of listings: groups etc.
format
You can use this style if you want to find out where the completions in
a completion listing come from. The most basic use is to set it for the
descriptions
tag in any completion context. It takes a string value in
which `%d
' should appear; this will be replaced by a description of
whatever is being completed. For example, I use:
zstyle ':completion:*:descriptions' format 'Completing %d'
and if I type cd^D
, I see a listing like this (until I define the
group-name
style, that is):
Completing external command
Completing builtin command
Completing shell function
cd cddbsubmit cdp cdrecord
cdctrl cdecl cdparanoia cdswap
cdda2wav cdmatch cdparanoia-yaf
cddaslave cdmatch.newer cdplay
cddbslave cdot cdplayer_applet
The descriptions at the top are related to the tag names --- usually
there's a unique correspondence --- but are in a more readable form; to
get the tag names, you need to use ^Xh
. You will no doubt see
something different, but the point is that the completions listed are a
mixture of external commands (e.g. cdplay
), builtin commands (cd
)
and shell functions (cdmatch
, which happens to be a leftover from
old-style completion, showing you how often I clean out my function
directory), and it's often quite handy to know what you have.
You can use some prompt escapes in the description, specifically those
that turn on or off standout mode (`%S
', `%s
'), bold text
(`%B
', `%b
'), and underlined text (`%U
', `%u
'), to make the
descriptions stand out from the completion lists.
You can set this for some other tag than descriptions
and the format
thus defined will be used only for completions of that tag.
group-name
, group-order
In the format
example just above, you may have wondered if it is
possible to make the different types of completion appear separately,
together with the description. You can do this using groups. They are
also related to tags, although as you can define group names via the
group-name
style it is possible to give different names for completion
in any context. However, to start off with it is easiest to give the
value of the style an empty string, which means that group names are
just the names of the tags. In other words,
zstyle ':completion:*' group-name ''
assigns a different group name for each tag. Later, you can fine-tune
this with more specific patterns, if you decide you want various tags to
have the same group name. If no group name is defined, the group used is
called `-default-
', so this is what was happening before you issued
the zstyle
command above; all matches were in that group.
The reason for groups is this: matches in the same group are shown
together, matches in different groups are shown separately. So the
completion list from the previous example, with both the format
and
group-name
styles set, becomes:
Completing external command
cdctrl cddbsubmit cdparanoia cdrecord
cdda2wav cdecl cdparanoia-yaf
cddaslave cdot cdplay
cddbslave cdp cdplayer_applet
Completing builtin command
cd
Completing shell function
cdmatch cdmatch.newer cdswap
which you may find more helpful, or you may find messier, depending on deep psychological factors outside my control.
If (and only if) you are using group-name
, you can also use
group-order
. As its name suggests, it determines the order in which
the different completion groups are displayed. It's a little like
tag-order
, which I described when tags were first introduced: the
value is just a set of names of groups, in the order you want to see
them. The example from the manual is relevant to the listing I just
showed:
zstyle ':completion:*:-command-' group-order \
builtins functions commands
--- remember that the `-command-
' context is used when the names of
commands, rather than their arguments, are being completed. Not
surprisingly, that listing now becomes:
Completing builtin command
cd
Completing shell function
cdmatch cdmatch.newer cdswap
Completing external command
cdctrl cddbsubmit cdparanoia cdrecord
cdda2wav cdecl cdparanoia-yaf
cddaslave cdot cdplay
cddbslave cdp cdplayer_applet
and if you investigate the tags available by using ^Xh
, you'll see
that there are others such as aliases whose order we haven't defined.
These appear after the ones for which you have defined the order and in
some order decided by the function which generated the matches.
tag-order
As I already said, I've already described this, but it's here again for completeness.
verbose
, auto-description
These are relatives of format
as they add helpful messages to the
listing. If verbose
is true, the function generating the matches may,
at its discretion, decide to show more information about them. The most
common case is when describing options; the standard function
_describe
that handles descriptions for a whole lot of options tests
the verbose
style and will print information about the options it is
completing.
You can also set the string style auto-description
; it too is useful
for options, in the case that they don't have a special description, but
they do have a single following argument, which completion already knows
about. Then the description of the argument for verbose printing will be
available as `%d
' in auto-describe
, so that something like the
manual recommendation `specify: %d
' will document the option itself.
So if a command takes `-o <output-file>
' and the argument has the
description `output file
', the `-o
', when it appears as a possible
completion, will have the description `specify: output file
' if it
does not have its own description. In fact, most options recognized by
the standard completion functions already have their own descriptions
supplied, and this is more subtlety than most people will probably need.
list-colors
This is used to display lists of matches for files in different colours
depending on the file type. It is based on the syntax of the
$LS_COLORS
environment variable, used by the GNU version of ls
. You
will need a terminal which is capable of displaying colour such as a
colour xterm, and should make sure the zsh/complist
library is loaded,
(it should be automatically if you are using menu selection set up with
the menu
style, or if you use this style). But you can make sure
explicitly:
zmodload -i zsh/complist
The -i
keeps it quiet if the module was already loaded. To install a
standard set of default colours, you can use:
zstyle ':completion:*' list-colors ''
--- note the use of the `default
' tag --- since a null string sets
the value to the default.
If that's not good enough for you, here are some more detailed
instructions. The parameter $ZLS_COLORS
is the lowest-level part of
the system used by zsh/complist
. There is a simple builtin default,
while having the style set to the empty string is equivalent to:
ZLS_COLORS="no=00:fi=00:di=01;34:ln=01;36:\
pi=40;33:so=01;35:bd=40;33;01:cd=40;33;01:\
ex=01;32:lc=\e[:rm=m:tc=00:sp=00:ma=07:hi=00:du=00
It has essentially the same format as $LS_COLORS
, and indeed you can
get a more useful set of values by using the dircolors
command which
comes with ls
:
ZLS_COLORS="no=00:fi=00:di=01;34:ln=01;36:\
pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:\
or=40;31;01:ex=01;32:*.tar=01;31:*.tgz=01;31:\
*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.zip=01;31:\
*.z=01;31:*.Z=01;31:*.gz=01;31:*.deb=01;31:\
*.jpg=01;35:*.gif=01;35:*.bmp=01;35:*.ppm=01;35:\
*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:\
*.mpg=01;37:*.avi=01;37:*.gl=01;37:*.dl=01;37:"
You should see the manual for the zsh/complist
module for details, but
note in particular the addition of the type `ma
', which specifies how
the current match in menu selection is displayed. The default for that
is to use standout mode --- the same effect as the sequence %S
in a
prompt, which you can display with `print -P %Sfoo
'.
However, you need to define the style directly, since the completion
always uses that to set $ZLS_COLORS
; otherwise it doesn't know whether
the value it has found has come from the user or is a previous value
taken from some style. That takes this format:
zstyle ':completion:*' list-colors "no=00" "fi=00" ...
You can use an already defined $LS_COLORS
:
zstyle ':completion:*' list-colors ${(s.:.)LS_COLORS}
(which splits the parameter to an array on colons) as $LS_COLORS
is
still useful for ls
, even though it's not worth setting $ZLS_COLORS
directly. This should mean GNU ls and zsh produce similar-looking lists.
There are some special effects allowed. You can use patterns to tell how
filenames are matched: that's part of the default behaviour, in fact,
for example '*.tar=01;31' forces tar files to be coloured red. In that
case, you are limited to `*
' followed by a string. However, there's a
way of specifying colouring for any match, not just files, and for any
pattern: use =<pat>=<col>
. Here are two ways of getting jobs coloured
red in process listings for the `kill
' command.
zstyle ':completion:*:*:kill:*' list-colors '=%*=01;31'
This uses the method just described; jobs begin with `%
'.
zstyle ':completion:*:*:kill:*:jobs' list-colors 'no=01;31'
This uses the tag, rather than the pattern, to match the jobs lines. It
has various advantages. Because you are using the tag, it's much easier
to alter this for all commands using jobs, not just kill --- just miss
out `kill
' from the string. That wasn't practical with the other
method because it would have matched too many other things you didn't
want. You're not dependent on using a particular pattern, either. And
finally, if you try it with a `format
' description you'll see that
that gets the colour, too, since it matched the correct tag. Note the
use of the `no
' to specify that this is to apply for a normal match;
the other two-letter codes for file types aren't useful here.
However, there is one even more special effect you can use with the
general pattern form. By turning on `backreferences' with `(#b)
'
inside the pattern, parentheses are active and the bits they match can
be coloured separately. You do this by extending the list of colours,
each code preceded by an `=
' sign, and the extra elements will be
used to colour what the parenthesis matched. Here's another example for
`kill
', which turns the process number red, but leaves the rest
alone.
zstyle ':completion:*:*:kill:*:processes' list-colors \
'=(#b) #([0-9]#)*=0=01;31'
The hieroglyphics are extended globbing patterns. You should note that
the EXTENDED_GLOB
option is always on inside styles --- it's required
for the `#b
' to take effect. In particular, `#
' means `zero or
more repetitions of the previous bit of the pattern' with extended glob
patterns; see the globbing manual page for full details.
ignored-patterns
Many shells, including zsh, have a parameter $fignore
, which gives a
list of suffixes; filenames ending in any of these are not to be used in
completion. A typical value is:
fignore=(.o \~ .dvi)
so that normal file completion will not produce object files, EMACS backup files, or TeX DVI files.
The ignored-patterns
style is an extension of this. It takes an array
value, like fignore
, but with various differences. Firstly, these
values are patterns which should match the whole value to be
completed, including prefixes (such as the directory part of a filename)
as well as suffixes. Secondly, they apply to all completions, not just
files, since you can use the style mechanism to tune it to apply
wherever you want, down to particular tags.
Hence you can replace the use of $fignore
above with the following:
zstyle ':completion:*:files' ignored-patterns '*?.o' '*?~' '*?.dvi'
for completion contexts where the tag `files
' is in use. The extra
`?
's are because $fignore
was careful only to apply to real
suffixes, i.e. strings which had something in front of them, and the
`?
' forces there to be at least one character present.
Actually, this isn't quite the same as $fignore
, since there are other
file tags than files
; apart from those for directories, which you've
already met, there are globbed-files
and all-files
. The former is
for cases where a pattern is specified by the completion function, for
example `*.dvi
' for files following the command name dvips
. These
don't use this style, because the pattern was already sufficiently
specified. This follows the behaviour for $fignore
in the old
completion system. Another slight difference, as I said above when
discussing the _ignored
completer, is that you get to choose whether
you want to see those ignored files if the normal completions fail, by
having _ignored
in the completer list or not.
The other tag, all-files
, applies when a globbed-files
tag failed,
and says any old file is good enough in that case; you can arrange how
this happens with the tag-order
style. In this example,
zstyle ':completion:*:*:dvips:argument*' \
tag-order globbed-files all-files
is enough to say that you want to see all files if no files were
produced from the pattern, i.e. if there were no `*.dvi
' files in the
directory. Finally the point of this ramble: as the all-files
tag is
separate from the files
tag, in this case you really would see all
files (except for those beginning with a `.
', as usual). You might
find this useful, but you can easily make the all-files
tag behave the
same way as files
:
zstyle ':completion:*:(all-|)files' ignored-patterns ...
Here's the example of using tag labels I promised earlier; it's simply taken from the manual. To refresh your memory: tag labels are a way of saying that tags should be looked up under a different name. Here we'll do:
zstyle ':completion:*:*:-command-:*' tag-order 'functions:-non-comp'
This applies in command position, from the special `-command-
'
context, the place where functions occur most often, along with other
types of command which have their own tags. This says that when
functions are first looked up, they are to be looked up with the name
`functions-non-comp
' --- remember that with a hyphen as the first
character of the label part, the bit after the colon, the functions
tag name itself, the bit before the colon, is to be stuck in front to
give the full label name `functions-non-comp
'. We can use it as
follows:
zstyle ':completion:*:functions-non-comp' ignored-patterns '_*'
In the context of this tag label, we have told completion to ignore any
patterns --- i.e. any function names --- beginning with an underscore.
What happens is this: when we try completion in command position,
tag-order
is looked up and finds we want to try functions first, but
under the name functions-non-comp
; this completes functions apart from
ones beginning with an underscore (presumably completion functions you
don't want to run interactively). Since tag-order
normally tries all
the other tags, unless it was told not to, in this case all the normal
command completions will appear, including functions under their normal
tag name, so this just acts as a sort of filter for the first attempt at
completion. This is typically what tag labels are intended for ---
though maybe you can think up a lot of other uses, since the idea is
quite powerful, being backed up by the style mechanism.
You way wonder why you would want to ignore such functions at this
point. After all, you're only likely to be doing completion when you've
already typed the first character, which either is `_
' or it isn't.
It becomes useful with correction and approximation --- particularly
since many completion functions are similar to the names of the commands
for which they handle completion. You don't want to be offered
`_zmodload
' as a completion if you really want `zmodload
'. The
combination of labels and ignored patterns does this for you.
You can generalise this using another feature: tags can actually be patterns, which I mentioned but didn't demonstrate. Here's a more sophisticated version of the previous example, adapted from the manual:
zstyle ':completion:*:*:-command-:*' tag-order \
'functions:-non-comp:non-completion\ functions *' functions
It's enhanced so that completion tries all other possible tags at the
same time as the labelled functions
. However, it only ever tries a tag
once at each step, so the `*
' doesn't put back functions
as you
might expect --- that's still tried under the label
`functions-non-comp
', and the ignored-patterns
style we set will
still work. In the final word, we try all possible functions, so that
those beginning with an underscore will be restored.
Use of the `_ignored
' completer can allow you to play tricks without
having to label your tags:
zstyle ':completion:*' completer _complete _ignored
zstyle ':completion:*:functions' ignored-patterns '_*'
Now anywhere the functions
tag is valid, functions matching `_*
'
aren't shown until completion reaches the `_ignored
' in the completer
list. Of course, you should manipulate the completer list the way you
want; this just shows the bare bones.
prefix-hidden
, prefix-needed
You will know that when the shell lists matches for files, the directory
part is removed. The boolean style prefix-hidden
extends this idea to
various other types of matches. The prefixes referred to are not just
any old common prefix to matches, but only some places defined in the
completion system: the -
prefix to options, the `%
' prefix to jobs,
the -
or +
prefix to directory stack entries are the most commonly
used.
The prefix-needed
applies not to listings, but instead to what the
user types on the command line. It says that matches will only be
generated if the user has typed the prefix common to them. It applies on
broadly the same occasions as prefix-hidden
.
list-packed
, list-rows-first
, accept-exact
, last-prompt
,
menu
The first two of these have already been introduced, and correspond to
the LIST_PACKED
and LIST_ROWS_FIRST
options. The accept-exact
and
last-prompt
styles correspond essentially to the REC_EXACT
and
ALWAYS_LAST_PROMPT
options in the same way.
The style menu
roughly corresponds to the MENU_COMPLETE
option, but
there is also the business of deciding whether to use menu selection, as
described above. These two uses don't interfere with each other ---
except that, as I explained, menu completion must be started to use menu
selection --- so a value like `true select=6
' is valid; it turns on
menu completion for the context, and also activates menu selection if
there are at least 6 choices.
There are some other, slightly more obscure, choices for menu
:
yes=
num
turn on menu completion only if there are at least num matches;no=
num
turn off menu completion if there are as many as num matches;yes=long
turn on menu completion if the list does not fit on the screen, and completion was attempted;yes=long-list
the same, but do it even if listing, not completion, was attempted;select=long
likeyes=long
, but this time turn on menu selection, too;select=long-list
likeyes=long-list
, but turn on menu selection, too.
In case your eyes glazed over before the end, here's a full description
of the last one, select=long-list
, which is quite useful: if you are
attempting completion or even just listing completions, and the list of
matches would be too long to fit on the screen, then menu selection is
turned on, so that you can use the cursor keys (and other selection
keys) to move up and down the list. Generally, the above possibilities
can be combined, unless the combined effect wouldn't work.
As always, yes
and true
are equivalent, as are no
and false
. It
just hurts the eyes of programmers to read something which appears to
assign a value to true
.
hidden
This is a little obscure for most users. Its context should be
restricted to specific tags; any corresponding matches will not be shown
in completion listings, but will be available for inserting into the
command line. If its value is `true
', then the description for the
tag may still appear; if the value is `all
', even that is suppressed.
If you don't want the completions even to be available for insertion,
use the tag-order
style.
6.5.3: Styles affecting particular completions
The styles listed here are for use only with certain completions as noted. I have not included the styles used by particular completers, which are described with the completer in question in the subsection `Specifying completers and their options'. I have also not described styles used only in separate widgets that do completion; the relevant information is all together in the next section.
Filenames (1): patterns: file-patterns
It was explained above for the tag-order
style that when a function
uses pattern matching to generate file completions, such as all *.ps
files or all *.gz
files, the three tags globbed-files
, directories
and all-files
are tried, in that order.
The file-patterns
style allows you to specify a pattern to override
whatever would be completed, even in what would otherwise be a simple
file completion with no pattern. Since this can easily get out of hand,
the best way of using this style is to make sure that you specify it for
a narrowly enough defined context. In particular, you probably want to
restrict it to completions for a single command and for a particular one
of the tags usually applying to files. As always, you can use ^Xh
to
find out what the context is. It has a labelling mechanism --- you can
specify a tag with a pattern for use in looking up other styles. Hence
`*.o:object-files
' gives a pattern `*.o
' and a tag name
`object-files
' by which to refer to these.
The patterns you specify are tried in order; you don't need to use
tag-order
. In fact file-patterns
replicates its behaviour in that
you can put patterns in the same word to say they should be tried
together, before going on to the pattern(s) in the next word. Also, you
can give a description after a second colon in the same way. Indeed,
since file-patterns
gets its hands on the tags first, any ordering
defined there can't be overridden by tag-order
.
So, for example, after
zstyle ':completion:*:*:foo:*:*' file-patterns \
'*.yo:yodl-files:yodl\ files *(-/):directories'
the command named `foo
' will complete files ending in `.yo
', as
well as directories. For once, you don't have to change the completer to
alter what's completed: `foo
' isn't specially handled, so it causes
default completion, and that means completing files, so that
file-patterns
is active anyway.
Here's a slightly enhanced example; it shows how file-patterns
can be
used instead of tag-order
to offer the tags in the order you want.
zstyle ':completion:*:*:foo:*:*' file-patterns \
'*.yo:yodl-files:yodl\ files' '*(-/):directories:directories' \
'^*.yo(-^/):other-files:other\ files'
Completion will first try to show you only `.yo
' files, if there are
any; otherwise it will show you directories, if there are any; otherwise
it will show you any other files: `^*.yo(-^/)
' is an extended glob to
match any file which doesn't end in `.yo
' and which isn't a directory
and doesn't link to a directory. As always, you can cycle through the
sets of possibilities using the `_next_tag
' completion command.
Note that file-patterns
is an exception to the general rule that
styles don't determine which tags are called only where they're
called, or what their behaviour is: this time, you actually get to
specify the set of tags which will be used. This means it doesn't use
the the standard file tags (unless you use those names yourself, of
course), just `files
' if you don't specify one. Hence it's good style
to add the tags, following colons, although it'll work without.
Another thing to watch out for is that if there is already a completion
which handles a file type --- for example, if we had tried to alter the
effect of file completion for the `yodl
' command instead of the
fictitious `foo
' --- the results may well not be quite what you want.
Another feature is that `%p
' in the pattern inserts the pattern which
would usually be used. That means that the following is essentially the
same as what file completion normally does:
zstyle ':completion:*' file-patterns '%p:globbed-files' \
'*(-/):directories' '*:all-files'
You can turn completion for a command that usually doesn't use a pattern into one that does. Another example taken from the manual:
zstyle ':completion:*:*:rm:*:globbed-files' file-patterns \
'*.o:object-files' '%p:all-files'
So if there are any *.o
files around, completion for rm
will just
complete those, even if arguments to rm
are otherwise found by default
file completion (which they usually are). The %p
will use whatever
file completion normally would have; probably any file at all. You can
change this, if you like; there may be files you don't ever want
automatically completed after rm
.
Remember that using explicit patterns overrides the effect of
$fignore
; this is obviously useful with rm
, since the files you want
to delete are often those you usually don't want to complete.
Filenames (2): paths: ambiguous
, expand
, file-sort
,
special-dirs
, ignore-parents
, list-suffixes
, squeeze-slashes
Filename completion is powerful enough to complete all parts of a path
at once, for example `/h/p/z
' will complete to `/home/pws/zsh
'.
This can cause problems when the match is ambiguous; since several
components of the path may well be ambiguous, how much should the
completion system complete, and where should it leave the cursor? This
facility is associated with all these styles affecting filenames.
With ordinary completion, the usual answer is that the completion is
halted as soon as a path component matches more than one possibility,
and the cursor is moved to that point, with the remainder of the string
left unaltered. With menu completion, you can simply cycle through the
possibilities with the cursor moved to the end as usual. If you set the
style ambiguous
, then the system will leave the cursor at the point of
the first ambiguity even if menu completion is in use. Note that this is
always used with the `paths
' tag, i.e. the context ends in
`...:paths
'.
The style expand
is similar and is also applied with the `paths
'
tag. It can include either or both of the strings prefix
and suffix
.
Be careful when setting both --- they have to be separate words, for
example
zstyle ':completion:*' expand prefix suffix
Don't put quotes around `prefix suffix
' as it won't work.
With prefix
, expand
tells the completion system always to expand
unambiguous prefixes in a path (such as `/u/i
' to `/usr/in
', which
matches both /usr/include
and /usr/info
) --- even if the remainder
of the string on the command line doesn't match any file. So this
expansion will now happen even if you try this on
`/u/i/ALoadOfOldCodswallop
', which it otherwise wouldn't.
Including suffix
in the value of expand
extends path completion in
another way: it allows extra unambiguous parts to be added even after
the first ambiguous one. So if `/home/p/.pr
' would match
`/home/pws/.procmailrc
' or `/home/patricia/.procmailrc
', and
nothing else, the last word would be expanded. Set up like this, you
will always get the longest unambiguous match for all parts of the path.
In older versions of the completion system, suffix
wasn't used if you
had menu completion active by default, although it was if menu
completion was only started by the AUTO_MENU
option. However, in
recent versions, the setting is always respected. This means that
setting the expand
style to include the value suffix
allows menu
completion to cycle through all possible completions, as if there were a
`*
' after each part of the path, so `/u/i/k
' will offer all
matches for `/u*/i*/k*
'.
The file-sort
style allows files to be sorted in a way other than by
alphabetical order: sorting applies both to the list of files, and to
the order in which menu completion presents them. The value should
include one of the following: `size
', `links
', `modification
'
(same as `time
', `date
'), `access
', `inode
' (same as
`change
'). These pick the obvious properties for sorting: file size,
number of hard links, modification time, access time, inode change time.
You can also add the string `reverse
' to the value, which reverses
the order. In this case the tag is always `files
'.
The special-dirs
style controls completion of the special directories
`.
' and `..
'. Given that you usually need to type an initial dot
to complete anything at all beginning with one, the idea of
`completing' `.
' is a little odd; it simply means that the directory
is accepted when the completion is started on it. You can set the style
to true
to allow completion to both of the two, or to `..
' to
complete `..
' but not `.
'. Like ambiguous
, this is used with the
tag set to `paths
'.
The style ignore-parents
is used with the files
tag, since it
applies to paths, but not necessarily completion of multiple path names
at once; it can be used when completing just the last element. There are
two main uses, which can be combined. The first case is to include the
string `parent
' in the style. This means that when you complete after
(say) foo/../
, the string foo
won't appear as a choice, since it
already appeared in the string. Secondly, you can include `pwd
' in
the value; this means don't complete the current working directory after
`../
' --- you can see the sense in that: if you wanted to complete
there, you wouldn't have typed the `..
' to get out if it.
Actually, the function performs both those tests on the directories in
question even if the string `..
' itself hasn't been typed. That might
be more confusing, and you can make sure that the tests for parent
and
pwd
are only made when you typed the `..
' by including a `..
' in
the style's value. Finally, you can include the string `directory
' in
the values: that means the tests will only be performed when directories
are being completed, while if some other sort of file, or any file, can
be completed, the special behaviour doesn't occur. You may have to read
that through a couple of times before deciding if you need it or not.
Next, there is list-suffixes
. It applies when expanding out earlier
parts of the filename path, not just the last part. In this case, it is
possible that early parts of the path were ambiguous. Normally
completion stops at the point where it finds the ambiguity, and leaves
the rest of the path alone. When list-suffixes
is set, it will list
all the possible values of all ambiguous components from the point of
ambiguity onward.
Lastly, there is the style squeeze-slashes
. This is rather simpler.
You probably already know that in a UNIX filename multiple slashes are
treated just like a single slash (with a few minor exceptions on some
systems). However, path completion usually assumes that multiple slashes
mean multiple directories to be completed: `//termc
' completes to
`/etc/termcap
' because of this rule. If you want to stick with the
ordinary UNIX rule you can set squeeze-slashes
to true
. Then in this
example only files in the root directory will be completed.
Processes: command
, insert-ids
Some functions, such as kill
, take process IDs (i.e. numbers) as
arguments. These can be completed by using the ps
command to generate
the process numbers. The command
style allows you to specify which
arguments are to be passed to ps
to generate the numbers; it is simply
eval
'd to generate the command line. For example, if you are root and
want to have all processes as possible completions, you might use
`-e
', for many modern systems, or `ax
', for older BSD-like
systems. The completion system tries to find a column which is headed
`PID
' or `pid
' (or even `Pid
', in fact) to use for the process
IDs; if it doesn't find one, it just uses the first column.
The default is not to use any arguments; most variants of ps
will then
just show you interactive processes from your current session. To show
all your own processes on a modern system, you can probably use the
value `ps -u$USER
' for the style --- remembering to put this in
single quotes. Clearly, you need to make sure the context is narrow
enough to avoid unexpectedly calling odd commands.
You can make the value begin with a hyphen, then the usual command line
will put afterward and the hyphen removed. The suggested use for this is
adding `command
' or `builtin
' to make sure the right version of a
command is called.
The completion system allows you to type the name of a command, for
example `emacs
', which will be converted to a PID. Note that this is
different from a job name beginning with `%
'; in this case, any
command listed by ps
, given the setting of the command
style, can be
used. Obviously, command names can be ambiguous, unlike the process IDs
themselves, so the names are usually converted immediately to PIDs; if
the name could refer to more than one process, you get a menu of
possible PIDs.
The style insert-ids
allows the completion system to keep using the
names rather than the PIDs. If it is set to single
, the name will be
retained until you type enough to identify a particular process. If it
is set to true
(or anything else but menu
, actually), menu
completion is delayed until you have typed a string longer than the
common prefix of the PIDs. This is intended to be similar to
completion's usual logic --- don't do anything which gets rid of
information supplied by the user --- so is probably more useful in
practice than it sounds.
Job control: numbers
Builtin functions that take process IDs usually also take job
specifications, strings beginning with `%
' and followed either by a
small number or a string. The style numbers
determines how these are
completed. By default, the completion system will try to complete an
unambiguous string from the name of the job. If you set numbers
to
true, it will instead complete the job number --- though the listing
will still show the full information --- and if you set it to a number,
it will only use that many words of the job name, and switch to using
numbers if those are not unique. In other words, if you set it to `1
'
and you have two jobs `vi foo
' and `vi bar
', then they will
complete as `%1
' and `%2
' (or maybe other numbers) since the first
words are the same.
Note also that prefix-needed
applies here; if it is set, you need to
type the `%
' to complete jobs rather than processes.
System information: users, groups, hosts etc.
There are many occasions where you complete the names of users on the
system, groups on the system (not to be confused with completion
groups), names of other hosts you connect to via the network, and ports,
which are essentially the names of internet services available on
another host such as nntp
or smtp
.
By default, the completion system will query the usual system files to
find the names of users, groups, hosts and ports, though in the final
case it will only look in the file `/etc/hosts
', which often includes
only a very small number of not necessarily very useful hosts. It is
possible to tell the completion system always to use a specified set by
setting the appropriate style --- users
, groups
, hosts
, ports
--- to the set of possibilities you want. This is nearly always useful
with hosts
, and on some systems you may find it takes an inordinate
amount of time for the system to query the database for groups and
users, so you may want to specify a subset containing just those you use
most often.
There are also three sets of combinations: hosts-ports
,
hosts-ports-users
and users-hosts
. These are used for commands which
can take both or all three arguments. Currently, the command socket uses
hosts-ports
, telnet uses hosts-ports-users
, while the style
users-hosts
is used by remote login commands such as rsh
and ssh
,
and anywhere the form `user@host
' is valid.
The last is probably the most useful, so I'll illustrate that. By setting:
zstyle ':completion:*' users-hosts \
pws:foo.bar.uk peters@frond.grub.uk
you tell rsh
and friends the possible user/host combinations. Note
that for the separator you can use either `:
', as usual inside the
completion system, or `@
', which is more natural in this particular
case. If you type `rsh -l
', a username is expected and either
pws
or peters
will be completed. Suppose you picked pws
; then for
the next argument, which should be a host, the system now knows that it
must be foo.bar.uk
, since the username for the other host doesn't
match.
If you don't need that much control, completion for all these commands
will survive on just the basic `hosts
', `users
', etc. styles; it
simply won't be as clever in recognising particular combinations. In
fact, even if you set the combined styles, anything that doesn't match
will be looked up in the corresponding basic style, so you can't lose,
in principle.
The other combined styles work in exactly the same way; just set the
values separated by colons or `@
', it doesn't matter which.
URLs for web browsers
Completion for URLs is done by setting a parallel path somewhere on your
local machine. The urls
style specifies the top directory for this.
For example, to complete the URL http://zsh.org/
, you need to make a
set of subdirectories of the path
directory http/zsh.org/
. You can
extend this for however many levels of directory you need; as you would
expect, if the last object is a file rather than a directory you should
create it with `touch
' rather than `mkdir
'. The style will always
use the tag `urls
' for this purpose, i.e. the context always matches
`:completion:*:urls
'. This is a neat way of using the ordinary filing
system for doing the dirty work of turning URLs into components.
Arguably the system should be able to scan your browser's bookmarks
file, but currently it won't; there is, however, a tool provided with
the shell distribution in Misc/make-zsh-urls
which should be able to
help --- ask your system administrators about this if it isn't
installed, I'm sure they'll be delighted to help.
If you only have a few URLs you want to complete, you can use one of two
simpler forms for the urls
style. First, if the value of the style
contains more than one word, the values are used directly as the URLs to
be completed, e.g.:
zstyle ':completion:*:urls' urls \
http://www.foo.org/ ftp://ftp.bar.net
Alternatively, you can set the urls
style to the name of a normal
file, which contains the URLs to complete separated by white space or
newlines.
Note that many modern browsers allow you to miss out an initial
`http://
', and that lots of pseudo-URLs appear in newspapers and
advertisements without it. The completion system needs it, however.
There is a better way when the web pages actually happen to be hosted on
a system whose directories you can access directly. Set the local
style to an array of three strings: a hostname to be considered local
(you can only give one per context), the directory corresponding to the
root of the files, and the directory where a user places their own web
pages, relative to their home directory. For example, if your home page
is usually retrieved as http://www.footling.com/
, and that looks for
the index file (often called index.html
) in the directory
/usr/local/www/files
, and your own web pages live under `~/www
',
then you would set
zstyle ':completion:*:urls' local \
www.footling.com /usr/local/www/files www
and when you type `lynx http://www.footling.com/
', all the rest will
be completed automatically.
The X files
There is another use for the path
style with the tag `colors
': it
gives the path to a file which contains a list of colour names
understood by the X-windows system, usually in file named `rgb.txt
'.
This is used in such contexts as `xsetroot -solid
', which
completes the name of a colour to set your root window (wallpaper) to.
It may be that the default value works on your system without your
needing to set this.
6.6: Command widgets
6.6.1: _complete_help
You've already met this, usually bound to `^Xh
' unless you already
had that bound when completion started up (in which case you should pick
your own binding and use `bindkey
'), but don't forget it, since it's
by far the easiest way of finding out what context to use for setting
particular styles.
6.6.2: _correct_word
, _correct_filename
, _expand_word
The first and last of these have been mentioned in describing the
related completers: _correct_word
, usually bound to ^Xc
, calls the
_correct
completer directly to perform spelling correction on the
current word, and _expand_word
, usually bound to ^Xe
, does the same
with the _expand
completer. The contexts being
`:completion:complete-word
' and `:completion:expand-word
'
respectively, so that they can be distinguished in styles from the
ordinary use of the completer. If you want the same styles to be used in
both contexts, but not others, you should define them for patterns
beginning `:completion:complete(|-word)...
'.
The middle one simply corrects filenames, regardless of the completion
context. Unlike the others, it can also be called as an ordinary
function: pass it an argument, and it will print out the possible
corrections. It does this because it bypasses most of the usual
completion system. Probably you won't often need it, but it is usually
bound to `^XC
' (note the capital `C
').
6.6.3: _history_complete_word
This is usually bound to `<ESC-/>
' for completing back in the
history, and `<ESC-,>
' for completing forward --- this will
automatically turn on menu completion, temporarily if you don't normally
have that set, to cycle through the matches. It will complete words from
the history list, starting with the most recent. Hence
touch supercalifragilisticexpialidocious
cat sup<ESC-/>
will save you quite a bit of typing --- although in this particular
case, you can use `<ESC-.>
' to insert the last word of the previous
command.
Various styles are available. You can set the `stop
' style which
makes it stop once before cycling past the end (or beginning) of the
history list, telling you that the end was reached.
You can also set the `list
' style to force matches to be listed, the
`sort
' style to sort matches in alphabetical order instead of by
their age in the history list, and the `remove-all-dups
' style, which
ensures that each match only occurs once in the completion list ---
normally consecutive identical matches are removed, but the code does
not bother searching for identical matches elsewhere in the list of
possibilities. Finally, the range
style is supported via the
_history
completer, which does the work. This style restricts the
number of history words to be searched for matches and is most useful if
your history list is large. Setting it to a number n specifies that
only the last n history words should be searched for possible matches.
Alternatively, it can be a value of the form `max:
slice', in
which case it will search through the last slice history words for
matches, and only if it doesn't find any, the slice words before that;
max gives an overall limit on the maximum number of words to search
through.
6.6.4: _most_recent_file
This function is normally bound to `^Xm
'. It simply completes the
most recently modified file that matches what's on the line already. Any
pattern characters in the existing string are active, so this is a cross
between expansion and completion. You can also give it a numeric prefix
to show the N
th most recently modified file that matches the pattern.
By the way, you can actually do the same by setting appropriate styles,
without any new functions. The trick is to persuade the system to use
the normal _files
completer with the file-sort
style. By restricting
the use of the styles to the context of the widget --- which is simply
the _generic
completer described above:
zstyle ':completion:(match-word|most-recent-file):*' \
match-original both
zstyle ':completion:most-recent-file::::' completer \
_menu _files _match
zstyle ':completion:most-recent-file:*' file-sort modification
zstyle ':completion:most-recent-file:*' file-patterns \
'*(.):normal\ files'
zstyle ':completion:most-recent-file:*' hidden true
zstyle ':completion:most-recent-file:*:descriptions' format ''
bindkey '^Xm' most-recent-file
zle -C most-recent-file menu-complete _generic
It may not be obvious how this works, so here's a blow by blow account if you are interested. (It works even if you aren't interested, however.)
- The `
zle -C
' defines a widget which does menu completion, and behaves like ordinary completion (that's what_generic
is for) except that the context uses the name of the widget we define. - When we invoke the widget, the system uses the
completer
style to decide what completions to perform. This instructs it: use menu completion, complete files, use pattern matching if the completion so far didn't work. - First,
_menu
comes along; it actually does nothing more than tell the system to use menu completion. - Then
_files
generates a list of files. This uses thefile-sort
andfile-patterns
styles defined for themost-recent-file
context. They produce a set of files in modification time order, and include only regular files (so not directories, symlinks, device files and so on). - If that failed, the
_match
style allows the word on the command line to be treated as a pattern; for example,*.c
to complete the most recent C source file. This uses thematch-original
style; the setting tells it that it should try first without adding an extra `*
' for matching (this is what we want for the case where we already have a complete pattern like*.c
), and if that fails, add a*
at the end and try again. - The
hidden
style means that the matches aren't listed; all that happens is the first is inserted on the line. The setting for theformat
tag similarly simplifies the display in this case by removing verbose descriptions. - The net result is the first step of a menu completion: insert the
first matched file (the most recently modified) onto the line. This
is exactly what you want. Note, however, that as we are in menu
completion you can keep on hitting
^xm
and the shell will cycle through the matches, which here gives you files that are progressively less recently modified.
Omit the file-patterns
line if you don't want the match restricted to
regular files (I sometimes need the most recently modified directory,
but often it's irrelevant). The whole version using styles comes from
Oliver Kiddle, who recommends using _generic
in this way any time you
want to generate a widget from a specific completion such as _files
.
There is a brief section on _generic
below.
6.6.5: _next_tags
This is a very neat way of getting round the order of tags just with a
key sequence. An example is the best way of showing it; it's bound by
default to the key sequence `^Xn
'.
% tex ^D
Completing TeX or LaTeX file
bar.tex foo.tex guff.tex
Our file is not in that directory, but by default we don't get to see
the directory if there was a file that matched the pattern --- here
`*.tex
'. (This will actually change in 4.1, since most people don't
know about _next_tags
but do know about directories, but you can still
cycle through the different sets of tags.) You can set the tag-order
style to alter whether they appear at the same time, but _next_tags
lets you do this very simply. Just hit ^Xn
. You're now looking at
Completing TeX or LaTeX file
dir1/ dir2/ dir3/
and if you carry on hitting ^Xn
you will get to all files, and then
you will be taken back to the .tex
files again. (Where our file
actually is, is left as an exercise for the reader.)
Of course this works with any set of tags whatsover; it simply has the effect of cycling you around the tag order.
6.6.6: _bash_completions
This function provides compatibility with a set of completion bindings
in bash, in which escape followed by one of the following characters
causes a certain type of (non-contextual) completion: `!
', command
names; `$
', environment variables; `@
', host names; `/
',
filenames, and `~
' user names. `^X
' followed by the same
characters causes the possible completion to be listed. This function
decides by examining its own binding which of those it should be doing,
then calls the appropriate completion function. If you want to use it
for all those possible bindings, you need to issue the right statements
in your .zshrc
, since only the bindings with `~
' are set up by
default to avoid clashes. This will do it:
for key in '!' '$' '@' '/'; do
bindkey "\e$key" _bash_complete-word
bindkey "^X$key" _bash_list-choices
done
Unlike most widgets, which are tied to functions of the same name to
minimize confusion, the function _bash_completions
is actually called
under the names of the two different widgets shown in that code so as to
be able to implement both completion and listing behaviour.
6.6.7: _read_comp
This function, usually bound to `^X^R
', does on-the-fly completion.
When you call it, it prompts for you to enter a type of completion;
usually this will be the name of a completion function with the required
arguments. Thus it's not much use unless you already have some fairly
in-depth knowledge of how the system is set up. For example, try it,
then enter `_files -/
', which generates directories. There is a
rudimentary completion for the function names built into it.
The next time you start it up, it will produce the same type of completion. You need to give it a numeric prefix to tell it to prompt for a different sort.
6.6.8: _generic
Rather than being directly bound, like the others, this widget gives you a way of creating your own special completions. You define it as a widget and bind it as if it were any completion function:
zle -C foo complete-word _generic
bindkey '<keys>' foo
Now the keys bound will perform ordinary contextual completion, but any
styles will be looked up with the command context `foo
'. So you can
give it its own set of completers:
zstyle ':completion:foo:*' completer _expand
and, indeed, give it special values for any style you like. To put it another way, you've now got a complete, separate copy of the completion system where the only difference is the extra word in the context.
Good example of the use of this function were given above in the
descriptions of _all_matches
and _most_recent_file
.
6.6.9: predict-on
, incremental-complete-word
These are not really complete commands at all in the strict sense, they
are normal editing commands which happen to have the effect of
completion. This means that they are not part of the completion system,
and though they are installed with other shell functions they will not
automatically be loaded. You will therefore need an explicit `autoload -U predict-on
', etc. --- remember that the `-U
' prevents the
functions from expanding any of your own aliases when they are read in
--- as well as an explicit `bindkey
' command to bind each function,
and a `zle -N
' statement to tell the line editor that the function is
to be regarded as an editing widget. The predict-on
file, when loaded,
actually defines two functions, predict-on
and predict-off
, both of
which need to be defined and bound for them to work. So to use all of
these,
autoload -U incremental-complete-word predict-on
zle -N incremental-complete-word
zle -N predict-on
zle -N predict-off
bindkey '^Xi' incremental-complete-word
bindkey '^Xp' predict-on
bindkey '^X^P' predict-off
`Prediction' is a sort of dynamic history completion. With predict-on
in effect, the line editor will try to retrieve a line back in the
history which matches what you type. If it does, it will show the line,
extending past the current cursor position. You can then edit the line;
characters which do not insert anything mostly behave as normal. If you
continue to type, and what you type does not match the line which was
found, the line editor will look further back for another line; if no
line matches, editing is essentially as normal. Often this is flexible
enough that you can leave predict-on
in effect, but you can return to
basic editing with predict-off
.
Note that, with prediction turned on, deleting characters reverses the direction of the history search, so that you go back to previous lines, like an ordinary incremental search; unfortunately the previous line found could be one you've already half-edited, because they don't disappear from the list until you finally hit `return' on an edited line to accept it. There's another problem with moving around the line and inserting characters somewhere else: history searching will resume as soon as you try to insert the new characters, which means everything on the right of the cursor is liable to disappear again. So in that case you need to turn prediction off explicitly. A final problem: prediction is bad with multi-line buffers.
If prediction fails with predict-on
active, completion is
automatically tried. The context for this looks like
`:completion:predict::::
'. Various styles are useful at this point:
`list
' could be set to always
, which will show a possible
completion even if there is only one, for example. The style `cursor
'
may have the values `complete
' to move to the end of the word
completed, `key
' to move past the rightmost occurrence of the
character just typed, allowing you just to keep typing, or anything else
not to move the cursor which is the default behaviour.
The incremental-complete-word
function allows you to see a list of
possible completions as you type them character by character after the
first. The function is quite basic; it is really just an example of
using various line editor facilities, and needs some work to make a
useful system. It will understand DEL
to delete the previous
character, return to accept, ^G
to abort, TAB
to complete the word
as normal and ^D
to list possibilities; otherwise, keys which do not
insert are unlikely to have a useful effect. The completion is done
behind the scenes by the standard function complete-word
.
6.7: Matching control and controlling where things are inserted
The final matter before I delve into the system for writing new
completion functions is matching control; the name refers in this case
to how the matching between characters already typed on the command line
and characters in a trial completion is performed. This can be done in
two ways: by setting the matcher-list
style, which applies to all
completions, or by using an argument (-M
) to the low-level completion
functions. Mostly we will be concerned with the first. All this is best
illustrated by examples, which are taken from the section `Matching
Control' in the zshcompwid
manual page; in the printed manual and
the `info' pages this occurs within the section `Completion Widgets
'.
The matcher-list
style takes an array value. The values will be tried
in order from left to right. For example,
zstyle ':completion:*' matcher-list 'm:{a-z-}={A-Z_}' \
'r:|[-_./]=* r:|=*'
tries the first specification, which is for case-insensitive completion,
and if no matches are generated tries the second, which does partial
word completion; I'll explain both these specifications in detail as we
go along. You can make it do both forms the second time round simply by
combining the values with a space, i.e. the last word on the command
line becomes 'm:{a-z-}={A-Z_} r:|[-_./]=* r:|=*'
. It is also perfectly
valid to have a first matcher empty, i.e. '``'
; this means that
completion is tried with no matching rule the first time, and will only
go on to subsequent matchers in the list if that fails. This is quite a
good practice as it avoids surprises.
6.7.1: Case-insensitive matching
To perform case-insensitive matching for all completions, you can set:
zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}'
The `m:
' specifies standard matching, with the `{a-z}
' describing
what's on the command line, and the `{A-Z}
' what's in the trial
completion. The braces indicate `correspondence classes', which are not
lessons taken by email (that's a joke), but a relative of the more usual
character classes like `[a-z]
', which, as you no doubt know, would
match any of the letters between a
and z
. In this context, with the
braces, the letters are forced to match on the left and right hand side
of the `=
', so an `a
' on the command line must match an `A
' in
the trial completion, a `b
' must match a `B
', and so on. Since an
a
in the command line will always match an `a
' in the trial
completion, matcher or no matcher, this means that if you type an `a
'
it will match either `a
' or `A
' --- in other words,
case-insensitively. The same goes for any other lowercase letter you
type. The difference from `m:[a-z]=[A-Z]
' is that, because ordinary
character classes are unordered, any lowercase letter would have
matched any uppercase letter, which isn't what you want. The rest of
the shell doesn't know about correspondence classes at all.
Finally, the use of a lowercase `m
' at the start means that the
characters actually inserted onto the line are those from the trial
completion --- if you type `make<TAB>
', the completion process
generates file names, and matcher-list
allows what you type to match
the file `Makefile
', then you need the latter to be inserted on the
command line. Use of `M:
' at the start of the matcher would keep
whatever was on the line to begin with there.
If you want completely case-insensitive matching, so that typing
`MAKE<TAB>
' would also potentially complete to `Makefile
' or
`makefile
' (and so on), the extension is fairly obvious:
zstyle ':completion:*' matcher-list 'm:{a-zA-Z}={A-Za-z}'
because now as well as `a
' matching `A
', `A
' will match `a
'
--- and, of course, `a
' and `A
' each still match themselves.
More detail on the patterns: they do not, in fact, allow all the
possible patterns you can use elsewhere in the shell, since that would
be too complicated to implement with little extra use. Apart from
character classes and correspondence classes, you can use `?
' which
has its usual meaning of matching one character, or literal characters,
which match themselves; or the pattern for the trial completion only can
be a single `*
'. which matches anything. That's it, however; you
can't do other things with the `*
' since it's too difficult for the
system to guess what characters should be covered by it.
For the same reason, the `*
' must be in an anchored pattern, the
idea behind which is shown in the next example.
6.7.2: Matching option names
I explained back in chapter 1 that zsh didn't
care too much how you specified options: `noglob
' and `NOGLOB
' and
`No_Glob
' and `__NO_GLOB_
' are all treated the same way. Also,
this is the negation of the option `glob
'. Having learnt how to match
case-insensitively, we have two further challenges: how to ignore a
`_
' anywhere in the word, and how to ignore the NO
at the beginning
so that we can complete an unnegated option name after it.
Well, here's how. Since you don't want this for all completions, just
for option names, I shall show it as an argument for the `compadd
'
command, which gives the system the list of possible completions. The
option names should then appear as the remaining arguments to the
command, and the easiest way of doing that is to have the
zsh/parameter
module loaded, which it always is for new completion,
and use the keys of the special associative array $options
:
compadd -M 'B:|[nN][oO]= M:_= M:{A-Z}={a-z}' - ${(k)options}
Here, we're interested in the thing in quotes --- it means exactly the
same here as it would as an element of the matcher list, except that it
only applies to the trial completions given after the `-
'. It's in
three bits, separated by spaces; as they're in the same word, all are
applied one after the other regardless of any previous ones having
matched.
Starting from the right, you can see that the last part matches letters
case-insensitively; the capital `M
' means that, this time, the
letters on the command line, not those in the trial completion are kept;
this is safe because of the way options are parsed, and reduces
unexpected changes.
Moving left, you can now guess `M:_=
': it means that the `_
'
matches nothing at all in the trial completion --- in other words, it is
simply ignored. The rule for matching across the `=
' is that you move
from left to right, pairing off characters or elements of character
classes as I already described, and when you run out, you treat any
missing characters as, well, missing.
The first part has an `anchor', indicated by what lies between the
`:
' and the `|
'. The B
specifies that the case insensitive match
of `no
' must occur at the start of the word on the command line (with
`b
' it would be the word in the list of matches), but here it is lax
enough to allow this to happen after the `M:_=
' has stripped any
initial underscores away. Hence it matches no
, NO
, No
or nO
at
the start of the string, and, just like the `M:_=
' part, it ignores
it, since there's nothing on the right. Again, the capital `B
' at the
start means keep what's on the command line: that's important in this
case, since if you lost the `no
', the meaning would change
completely.
So consider the combined effect when trying to complete NO_GL
. The
first specification allows it to match against _GL
; the second allows
it to match against GL
; the third, against gl
; and finally the usual
effect of completion means that any option beginning gl
may be
completed. Try `setopt NO_GL^D
' and you should see something like:
NO_GLob NO_GLobassign NO_GLobdots
NO_GLobalrcs NO_GLobcomplete NO_GLobsubst
--- after the bit you've typed, the form of the words reverts to
whatever's in the trial completion, i.e. lowercase letters with no
`_
's.
6.7.3: Partial word completion
This example shows the other sort of anchoring, on the right, and also
how to use a `*
' in the right hand part of a pattern. Consider:
zstyle ':completion:*' matcher-list 'r:|.=* r:|=*'
The `r:
' specifies a right-anchored match, using the characters from
the trial completion rather than what's already on the command line. As
the anchor is on the right this time, the pattern (between `:
' and
`|
') is empty, and its anchor (between `|
' and `=
') is `.
'.
So this specifies that nothing --- a zero length string, or a gap
between characters if you want to think of it like that --- when
followed by a `.
', matches anything at all in the trial completion.
Consequently, the second part says that nothing anchored on the right by nothing --- in other words, the right hand end of the command line string --- matches anything. This is what completion normally does, add anything at all at the end of the string; we've added this part to the matcher in case the cursor is in the middle of the word. It means that the right hand end will always be completed, too.
Let's see that in action. Here are the actual contents of my actual
tmp
directory, never mind why:
regframe.rpm t.c testpage.dvi testpage.log testpage.ps
Now I set the matcher-list
style as above and type:
echo t.p<TAB>
and get
echo testpage.ps
So, apart from the normal completion at the end (p
to ps
), the empty
string followed by a .
was allowed to match anything, too, and I got
the effect of completing both bits of the word.
You might wonder what happens when there's a file testpage.old.ps
around, i.e. the anchor appears twice in that. With the matcher set as
given above, that won't be completed; the anchor needs to be matched
explicitly, not by a wildcard. If you don't like that, you can change
the `*
' after the `=
' in the specification to `**
'; this form
allows the anchor to occur in the string being matched. You can think of
`*
' and `**
' as taking the shortest and the longest possible
matches respectively. If you use a lot of `**
' specifications in your
matches, things can get very confusing, however.
Other shells have a facility for completing inside words like this,
where it goes by such names as `enhanced' completion, although it is
usually not so flexible. In the case of tcsh, not just `.
' but also
`-
' and `_
' have this effect. You can force this with
zstyle ':completion:*' matcher-list 'r:|[._-]=* r:|=*'
6.7.4: Substring completion
I've mentioned `r
' and `B
', but corresponding to `r
' there is
`l
', which anchors on the left instead of the right, and
corresponding to `B
' there is `E
' which matches at the end instead
of the beginning; and, of course, all exist in both upper- and lowercase
forms, meaning `keep what the user typed' and `keep what is in the
list of possible matches', respectively.
Here is an example of using `l:|=*
' to match anything at the start of
the word: this is the effect of having an empty anchor, as you saw with
`r
' above, but note with `l
', the anchor appears, logically
enough, on the left of the `|
', in the order they would appear on the
command line. By combining this with the `r
' form, you can make the
completion system work when what is on the command line matches only a
substring of a trial completion --- i.e., has anything else on the left
and on the right. Since this can potentially generate a lot of matches,
it might by an idea to try it after any other matcher specifications you
have. So the following tries case-insensitive completion, then
partial-word completion (case-sensitively), then substring completion:
zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}' \
'r:|[._-]=* r:|=*' 'l:|=* r:|=*'
6.7.5: Partial words with capitals
This section illustrates another feature: if you use `||
' when
specifying anchors for `L
' or `R
' or their lowercase variants, the
pattern part for what appears on the command line, which would usually
be translated into some other pattern, is treated instead as another
anchor on the other side of the pattern --- which isn't matched against
the pattern in the word, it just has to appear. In other words, this
part matches without being `swallowed up' in the process. An example
(again adapted from the manual) will make this clearer.
compadd -M 'r:[^A-Z0-9]||[A-Z0-9]=** r:|=*' \
LikeTHIS LooHoo foo123 bar234
The four possible completions are on the second line. The second of the
two matcher specifications just allows anything to match on the right,
so if we are inside the word, the remainder may be completed. The first
word is where the action is; it says `A part of the completion which
has on the left something other than an upper case letter or a digit,
and on the right an upper case letter or a digit, may match anything,
including the anchor'. So in particular, this would allow `LH
' to
complete to `LooHoo
' --- and only that, since `LikeTHIS
' has an
uppercase letter to the left of the `H
', which is not allowed. In
other words, the chunks of word beginning with uppercase letters and
digits act like the start of substrings. (If you like, remember that
last sentence and the specification, and forget the rest.)
6.7.6: Final notes
To put everything together, the possible specifications are
`m:...=...
', `l:...|...=...
', `r:...|...=...
',
`b:...|...=...
' and `e:...|...=...
', which cause the command line
to be altered to the match found, and their counterparts with an
uppercase letter, which cause what's already on the command line to be
left alone and the remaining characters to be inserted directly from the
completion found. The `...
' are patterns, which all use the same
format. They can include literal characters, a `?
', and character or
correspondence classes, while the rightmost pattern in each type may
also consist of a `*
' on its own. Characters are matched from left to
right; a missing character matches an empty string, `*
' matches any
number of characters. Specifications may be joined in a single string,
in which case all parts will be applied together.
When using the matcher-list
style, a list of different specifications
can be given; in this case, they will be tried in turn until one of them
generates matches, and the rest will not be used.
There's another style apart from matcher-list
, called matcher
. This
can be set for a particular context, possibly with specific tags, and
will add the given matcher specifications using exactly the same syntax
as matcher-list
for that context, except that here all specifications
are used at once, even if they are given as different elements of an
array. This is possibly useful because matcher-list
is only aware of
the completer, not of any more specific part of the context.
Although I won't talk about matching control after this section, there
may be cases where you want to include `compadd -M ...
' in a
completion function of your own to help the user. Many of the existing
completion functions provide partial word completion where it seems
useful; for example, completion of zle functions allows i-c-w
to be
completed to incremental-complete-word
in this way.
Actually, you can configure this to a considerable extent without altering a function, using styles and labelled tags. From the manual:
zstyle ':completion:*:*:foo:*' tag-order '*' '*:-case'
zstyle ':completion:*-case' matcher 'm:{a-z}={A-Z}'
In command foo
, whatever the tags are, they are to be tried normally
first (the `*
' argument to tag-order
), then under the same name
with `-case
' appended. The second style defines a matcher for any tag
ending in the suffix `-case
', which allows lowercase characters to
match uppercase ones. The upshot is that completion of anything at all
for the command foo
will be tried first case-sensitively, then
case-insensitively.
6.8: Tutorial
Before bamboozling you with everything there is to know about writing
your own completion function, I'll give you an example of something I
wrote myself recently. If you were doing this yourself, you would then
just stick this function somewhere in your function search path, and
next time you started the shell it would start doing its work. However,
the file already exists: it's called _perforce
and you should find it
in the function search for versions 4.1.1 and above of zsh. I apologize
if it's not the ideal function to start with, but it is fresh in my
mind, so what I'm saying has some chance of being correct.
This section is subtitled, `How I struggled to write a set of completions for Perforce'. Perforce is a commercial configuration management tool (as they now call revision control systems); consult http://www.perforce.com/ for details. It's concepts aren't a million miles from CVS, the archetypal system of this kind, but it was sufficiently different that the completion functions needed rewriting from the ground up. You won't need to know anything about CVS or Perforce, because at each stage I'll explain what I'm trying to complete and why. This should give you plenty of meat for writing completions of your own. After the tutorial, the chapter goes into the individual details, which will expand on some of the things that appeared briefly in the tutorial.
What I tend to find the most complicated part of this is making sure the completion system knows the correct types of completions and their tags to be completed at once. This probably won't be your first priority when trying to write completions of your own, but if you do it right, all the stuff about selecting types and arranging them in groups that I showed above will just work. In this tutorial we arrange to use enough of the higher level functions that it will work without too much (apparent) effort. Of course, working out from scratch which those functions are isn't always that easy; hence the tutorial.
Needless to say, I will simplify grossly at a lot of points. You can see the finished product in the zsh 4.1 distribution. It even has a few comments in.
Basic structure
Like the cvs
command and a few other of the more complicated commands
you might use, Perforce is run by a single command, p4
, followed by an
argument giving the particular Perforce command, followed by an options
and arguments to that command.
This dictates the basic tasks the completion functions must do:
- If we are in the first argument, complete the name of the subcommand.
- If we are in a subsequent argument, look up the name of the subcommand and call the function which handles its arguments.
This is more complicated than most commands you will write completions for. However, one useful feature of the completion system is you can do completions in a recursive fashion. So once you get to the point where you are handling arguments for a particular subcommand, you can completely forget about the first step --- as if the subcommand was the command on the line.
In addition to the subcommands, there are lots of other types of object Perforce knows about: files, obviously, plus revisions of files, set of changes (`changelists') applied at once, numbers of fixes applied to files (essentially a way of tying changlists to a particular change request for bugtracking purposes), types of file --- text, binary, etc., and several others. We will break down each of these completions into its own function. That means that any time we need to complete a particular type of object, wherever it appears (and many of these objects can appear in lots of different places), we just call the same function.
Hence there are a large number of different functions:
- The main dispatcher for the command, called
_perforce
for clarity --- the main command it handles is `p4
', but the name Perforce is more familiar. - One function for each subcommand.
- One function for each type of object Perforce knows about and we complete (we don't bother completing dates, for example).
- In some cases, in particular files, multiple functions since there are different types of file --- regular files and directories completed in the normal way, files completed by asking Perforce where it has stored them, files opened for some form of change to be made to them, and so on. Each of these is completed by a different function.
This makes it impractical to put all the functions in separate files
since editing them would be a nightmare. What's more, since we will
always go through the dispatcher _perforce
, we don't need to tell the
shell to autoload all the other functions; it can just hook them in from
the main file. The file _perforce
therefore has the structure:
#compdef p4
# Main dispatcher
_perforce() {
# ...
}
# Helper functions for the various types of object
_perforce_files() {
# ...
}
# ...
# Dispatchers for the individual subcommands.
_perforce_cmd_help() {
# ...
}
# Code to make sure _perforce is run when we load it
_perforce "$@"
That last line is probably the least obvious. It's because of the fact
that zsh (unlike other shells) usually treats the file of an autoloaded
function as being the body of the function. Since everything else here
just defines a function, without the last line nothing would happen the
first time it was run; it would define _perforce
and all the other
functions, but that was it. The last line makes sure _perforce
gets
run with all the arguments passed down. The shell is smart enough to
know that the _perforce
function we defined in the file is the one to
keep for future use, not the entire file, so from then on things are
easy; we just have a complete set of ready-defined files.
In fact the various helper functions didn't even need to use the `_
'
convention for completion functions, since the completion system didn't
see them directly. However, I've kept it for consistency.
There's one extra trick: apart from _perforce
itself, the function
definitions look like this:
(( $+functions[_perforce_cmd_diff] )) ||
_perforce_cmd_diff() {
# body of function
}
This is to allow the user to override each function separately. The test
uses the $functions
special associative array from the zsh/parameter
module, which the completion system loads. If the function is already
defined, because the corresponding element in the $functions
parameter
is set, then we skip the definition of the function here, because the
user has already defined it. So if you were to write your own
_perforce_cmd_diff
and put it into the function path, it would be
used, as you no doubt intended.
6.8.1: The dispatcher
This top level is only necessary for complex commands with multiple subcommands. There are interesting titbits here, but if you just want to know how to complete a command with ordinary UNIX-style argument parsing, skip to the next section.
The main _perforce
function has the two purposes described at the top
of the previous subsection. We need to decide whether we are in the
first word after the p4
command itself. A simple way of doing that is:
if (( CURRENT > 2 )); then
# Remember the subcommand name
local cmd=${words[2]}
# Set the context for the subcommand.
curcontext="${curcontext%:*:*}:p4-$cmd"
# Narrow the range of words we are looking at to exclude `p4'
(( CURRENT-- ))
shift words
# Run the completion for the subcommand
_perforce_cmd_$cmd
else
local hline
local -a cmdlist
_call_program help-commands p4 help commands | while read -A hline; do
(( ${#hline} < 2 )) && continue
[[ $hline[1] = (#i)perforce ]] && continue
cmdlist=($cmdlist "${hline[1]}:${hline[2,-1]}")
done
_describe -t p4-commands 'Perforce command' cmdlist
fi
This already looks a bit horrific, but it breaks down quite easily. We
test the $CURRENT
parameter, which is a special parameter in the
completion system giving the word on the command line we are on. This is
the syntactic word --- the completion system has already done the hard
job (and that's not an overstatement, I can tell you) of deciding what
makes up a word on the command line, taking into account quoting and
special characters. The array of words is stored, unsurprisingly, in the
array $words
. So word 1 will be `p4
' and word 2 the subcommand.
Hence if we are past word 2, we look at ${words[2]}
to get the
subcommand, and use that to decide what to do next. The change to
$curcontext
is a bit of cleverness to make it easy for the user to
defined styles for particular subcommands; refresh your mind by looking
at the discussion of styles and contexts above if you need to. For
example, if you are completing after `p4 diff
', the context will look
something like
`:completion::complete:p4-diff:argument-1:opened-files
' where the
remainder says you are on the first argument and are complete the tag
`opened-files
', We'll see down below how we tell the system to use
that tag; the `argument-1
' is handled by the _arguments
utility
function, which takes away a lot of the load of handling options and
arguments in a standard UNIX format.
Next, we pretend that the `p4
' at the start wasn't there by removing
the front of $words
and decrementing $CURRENT
so as to reflect its
new position in $words
. The reason for doing this is that we are going
to use _arguments
for handling the subcommand. As is only sensible,
this function looks at the first element of $words
to find the command
word, and treats the rest as options or arguments to the command.
We then dispatch the right function for the command simply by
constructing the name of the function on the fly. Of course it's a
little neater to check the function exists first;
$+functions[_perforce_cmd_$cmd]
would come to our aid again.
However, if we're still on the second (original) word, we have to
generate a list of functions to complete. We will do this by asking
Perforce's help system to list them, and store the results in the array
$cmdlist
. The loop has a couple of checks to remove blank lines and
the title line at the start. The remaining lines have a command and a
description. We take the command, but also tack the description on after
a colon --- we can then show the user the description, too, as a bit of
extra help.
Actually, the Perforce command that generates the list of subcommands is
simply `p4 help command
'. (That's really all you need to know; skip
the rest of the paragraph if you just want the basics.) The
`_call_program help-commands
' was stuck in front for the name of
configurability. Before executing the command, the system checks in the
current context with the given tag help-commands
for the style
command
. If it finds a value for that style, it will use that as the
command to execute in the place of the remaining arguments. If the style
it read began with -
, then the command it was going to execute ---
i.e. `p4 help commands
' is appended to the end of the command read
from the style, so that the user's command can process the original
command if it needs to. This is really extreme sophistication; you will
rarely actually need the command
style, but if you are writing a
completion for others to use it's polite to give them a chance to
intercept calls in this way.
The _describe
command then does the work for us. The `-t p4-commands
' gives the tag we are going to use; the convention is that
tag names are plural, though there's nothing to enforce this. Then we
give an overall description --- this is what appears after
`Completing
' in the examples of the format
style above; if you
don't have that set, you won't see it. Finally, we give the array name
--- note it is the name, not the substituted value. This is more
efficient because the shell doesn't need to extract the values until the
last minute; until then it can pass around just the single word. The
_description
function knows about the `completion:description
'
syntax; reread what I said about the verbose
style for what the system
does with the descriptions for the completion.
The _describe
function is one level above the completion system's
basic builtin command, compadd
; it just knows about a single tag, with
a little icing sugar to display verbose descriptions. Later, we'll see
ways of building up alternatives where different types of completion can
be completed at the same point. There are lots of ways of doing this;
some of the more complicated are relegated to the detailed descriptions
that follow the tutorial.
6.8.2: Subcommand completion: _arguments
Suppose we are now completing after `p4 diff
'. We have altered the
command line so that the function now sees the `diff
' as the first
word, as if this were the command. This makes the next step easier; the
_arguments
function won't see irrelevant words on the command line,
since it is designed to handle the arguments to a simple command in the
standard form `command [ options ] arguments ...
'. Here's the simple
version.
_perforce_cmd_diff() {
_arguments -s : \
'-f[diff every file]' \
'-t[include non-text files]' \
'(-sd -se -sr)-sa[opened files, different or missing]' \
'(-sa -se -sr)-sd[unopened files, missing]' \
'(-sa -sd -sr)-se[unopened files, different]' \
'(-sa -sd -se)-sr[opened files, same as depot]' \
'-d-[select diff option]:diff option:'\
'((b\:ignore\ blanks c\:context n\:RCS s\:summary'\
'u\:unified w\:ignore\ all\ whitespace))' \
"*::file:_perforce_files"
}
I've split the argument beginning -d
into three lines to fit, but it's
just a single argument. Also, for clarity I've missed out the line with
the `$+functions
' test to see if _perforce_cmd_diff
was already
defined; I'll forget about that for now.
The function _arguments
has been described as having `the syntax from
hell', but with the arguments already laid out in front of you it
doesn't look so bad. The are three types of argument: options to
_arguments
itself, arguments saying how to handle options to the
command (i.e. `p4 diff
'), and arguments saying how to handle normal
arguments to the command.
The first two are for _arguments
itself; `-s
' tells it that
single-letter options are allowed, i.e. they can be combined as in
`-ft
'. Luckily for our purposes, that doesn't stop us having multiple
word options, too. The colon on its own then says everything else is an
argument relating to the command line being handled.
We then start off with some simple options; as you can probably guess
straight away, the first two say that `p4 diff -f
' passes a flag to
say any file can be diff'ed (not just ones open for editing), and that
`p4 diff -t
' passes a flag to say that binary files can be diff'ed
(not just text files). Note the use of square brackets for giving a
description; this is handled by the verbose
style as I mentioned for
_describe
. In fact, the list of possible options and arguments,
suitably rearranged, will end up passing through _describe
. The
descriptions in square brackets are optional, as the use of square
brackets might suggest; you could just have `-f
' and `-t
' (making
it fairly obvious why the `:
' to separate off _arguments's own
options is a good idea).
The next step in complexity is that set of functions with the list in
parentheses in front. These give mutually exclusive options. In other
words, if there's already a -sa
on the command line, don't complete
any of -sd
, -se
or -sr
, and so on. (Remember that by default you
need to type the first `-
' of an option, or the system will go
straight to normal arguments, which we'll come to in a moment.)
Next comes the specification for the option -d
. All those colons
indicate that this option has an argument, and the -
following
straight after the -d
indicates that it has to be in the same word,
i.e. follow the -d
without a space. After the first colon comes a
description for the argument. This is what you see when you try to
complete the after -d
; compare this with the expression in square
brackets before, which is what you see when you try to complete the -d
itself. Then after the second colon is an expression saying how to
complete that argument.
This final part of the specification for an option with an argument can
take various forms. The simplest is just a single space; this means
there's nothing to complete, but the system is aware the user needs to
type something for that word and can prompt with the description. The
next simplest is a set of words in parentheses: here, we could have had
`(b c n s u w)
'. Instead, we've had a variant on that which gives yet
another set of descriptions, namely those for the individual completions
that appear after -d
. Note various things: the parentheses are doubled
and the colons and spaces within the completion options are backslashed.
All of these are simply there to make it easy for _arguments
to parse
the string. The upshot of this is that in the following context:
p4 diff -d
a verbose completion using the format
style as described above looks
like:
Completing diff option
b # ignore blanks
c # context
n # RCS
s # summary
u # unified
w # ignore all whitespace
or similar --- I have the list-separator
style set to `#
', because
it looks like a comment normal shell syntax, but in your case you may
get `-``-
' as the separator.
(In case you were wondering why the colons needed to be quoted when it
seemed you'd already got to the last argument: it's possible for options
to have multiple arguments, and you can continue having sets of
:
description:
action pairs. This means the system needs some way
of distinguishing these colons from ones inside arguments. While I'm
digressing, you may also have noticed that I could have written the
-s
X as an option with arguments, in which case you can have a bonus
point.)
The final argument starts with a `*
', which means it applies to all
remaining arguments to `p4 diff
' after the options have been
processed. Most of the rest is similar to the form for options, except
for the doubled colon, which indicates that $CURRENT
and $words
should be altered to reflect only the arguments being handled by this
argument specifier --- exactly what we did before calling
_perforce_cmd_diff
in the first place, in fact. As we mentioned
before, this makes the next step of processing easier if happens to call
_arguments
again. (Actually it doesn't in this case.) The `file
'
then describes the arguments and the final part, _perforce_files
,
tells the system to call that function to complete a file name.
There are numerous (it sometimes seems, endless) subtleties to
_arguments
. I won't try to go into them in the tutorial; see the
description of _arguments
below for something more detailed to refer
to, and if you are feeling really brave look at the description in the
zshcompsys
manual page. Even better, dig into one of the existing
completion functions --- something handling completion for a UNIX
command is probably good, since these make heavy use of _arguments
---
and see how those work. Despite the complexities, I would definitely
suggest using _arguments
wherever possible to take away any need on
your part to do processing of command line arguments.
6.8.3: Completing particular argument types
Now we'll look inside the _perforce_files
function as an example of
the nitty gritty of completing one particular type of argument, which
might have some quite complicated internal structure. This is true in
Perforce as the filename can have extra information tacked on the end:
`file#
revision' indicates the revision of a file,
`file@
change' indicates a change status, and in some cases you can
get `file@
change1,
change2' to indicate a range of changes
(likewise revisions). Furthermore, file
can be specified in different
ways, and the file to be completed may be limited by some kind of
context information. We'll start from simple filenames and gradually add
these possibilities in.
Different types of file, part 1
There are so many possibilities for files that I'm going to split up
_perforce_files
into individual functions handling different aspects.
For example, even if we are just handling ordinary files in the way the
completion system normally does, Perforce commands understand a special
file name `...
' which means `every subdirectory to any depth'.
(Interestingly, zsh used to have this to mean the same thing, instead of
`**
'; it was changed in zsh because as the `.
's are regular
characters there's no easy way of quoting them. You didn't need to know
this.)
I'm going to say we can complete both like this:
_alternative \
"files:file:_path_files" \
"subdirs:subdirectory search:_perforce_subdir_search"
The function _alternative
is a little bit like _arguments
, but
thankfully much simpler. It's name gives away its purpose; every
argument specifies one of a set of possible alternatives, all of which
are valid at that point --- so the user is offered anything which
matches out of the choices, unlike _arguments
, which has to decide
between the various possibilities. It's a sort of glorified loop around
`_describe
', with _arguments
's conventions on the action for
generating completions (up to a point --- _alternative
doesn't have
all the whackier ones, though it does have the ones I've been talking
about so far).
Each set of possibilities consists of the name of a tag, a description,
and an argument. The tag isn't present in _arguments
. If you use ^xh
to tell you about valid tags, you'll see _arguments
has its own
generic tag, argument-rest
; this isn't usually all that useful, so we
are going to supply more specific ones.
In the first possibility, it's the standard one for files, `files
.
The function is the basic low-level one for completing files, too; it's
described below, but you already know a lot about the effect since it's
the completion system's workhorse which you use it all the time without
realising. Actually, it will supply its own tags, but that doesn't
matter since they will silently override what we say.
The second possibility is the new one we're adding. I've therefore
invented a suitable tag `subdirs
', a description, `subdirectory search
', and the name of the function I'm going to supply to do the
completion. This is quite simple:
_perforce_subdir_search() {
compset -P '*/'
compadd "$@" '...'
}
The first line tells the completion system to ignore anything up to the
last `/
'. That's so we can append a `...
' to any directory which
already exists on the command line. The builtin compset
does various
low-level transformations of this time. Note that the -P
is `greedy'
--- it looks for the longest possible pattern match, which is the usual
default in zsh and other UNIX pattern matchers.
The second line actually adds the `...
' as a completion; compadd
is
the key builtin for the whole completion system. I've actually passed
some on the arguments which we got to `_perforce_subdir_search
' via
`"$@"
'. In fact, looking back it seems as if there weren't any!
However, _alternative
actually passed some behind my back --- and it's
a good thing, too, since it's exactly those arguments that give the tag
`subdirs
' and the description `subdirectory search
'. So that extra
`"$@"
' is actually quite important. The buck stops here; there's
nothing below compadd
. A function of this simplest only works well
when the handling of tags and contexts has already been done; but we
just saw that _alternative
did that, so as long as we always call
_perforce_subdir_search
suitably, we're in the clear.
Different types of file, part 2
Furthermore, a Perforce file specification can look like a normal UNIX file path, or it can look like:
//depot/dirs/moredirs/file
(don't get confused with paths to network resources, which also use the
doubled slash or backslash on some systems, notably Cygwin). We could
use _alternative
to handle this, too, and if I was writing _perforce
again I probably would for simplicity. However, I decided to do it just
by testing for the `//
' in _perforce_files
. This means that the
structure of p4_files
so far looks like:
if [[ $PREFIX = //* ]]; then
# ask Perforce for files that match
local -a altfiles
altfiles=(
'depot-files:file in depot:_perforce_depot_files'
depot-dirs:directory in depot:_perforce_depot_dirs'
)
# add other alternatives, such as the `...' thing
altfiles=($altfiles
"subdirs:subdirectory search:_perforce_subdir_search"
)
_alternative $altfiles
else
_alternative \
"files:file:_path_files" \
"subdirs:subdirectory search:_perforce_subdir_search"
fi
where we are still to write the functions for the first two alternatives
in the first branch; the `...
' is still valid for that branch, so
I've added that as the third alternative. I've used the array
$altfiles
because, actually, the structure is more complicated than
I've shown; doing it this way makes it easier to add different sets of
alternatives.
The choice of which branch is made by examining the $PREFIX
special
variable, which contains everything (well, everything interesting) that
comes before the cursor position in the word being completed. There is a
counterpart $SUFFIX
which we will see in a moment. The `almost
everything' comes because sometimes we definitely don't want to see the
whole $PREFIX
. Completing the three dots was such as case --- we
didn't want to see anything up to the last /
. What that `compset -P '*/'
' actually did was move the matched pattern from the front of
$PREFIX
to the end of $IPREFIX
, another special parameter which
contains parts of the completion we aren't currently interested in, but
which are still there. This allows us to concentrate on a particular
part of the completion. However you do that --- whether by compset
or
directly manipulating $PREFIX
and friends --- the completion system
usually restores the parameters when you exit the function where you
altered them. This fits in nicely with what we're doing here with
_alternative
--- if we handle adding `...
' by ignoring everything
up to the last slash, for example, we don't want the next completion we
try to continue to ignore that; other file completions will want to look
at the directory path.
`Depot' is Perforce's name for what CVS calls a repository --- the
central location where all versions of all files are stored, and from
where they are retrieved when you ask to look at one. I've separated out
`depot-dirs
' and `depot-files
' for various reasons. First, the
commands to examine files and directories are different, so the
completion function is different. Second, we can offer different tags
for files and directories --- this is what _path_files
does for normal
UNIX files. Third, it will later allow us more control --- some commands
only operate on directories. Here's _perforce_depot_files
;
_perforce_depot_dirs
is extremely similar:
_perforce_depot_files() {
# Normal completion of files in depots
local pfx=${(Q)PREFIX} expl
local -a files
compset -P '*/'
files=(${${${(f)"$(\
_call_program files p4 files \
\"\$pfx\*\$\{\(Q\)SUFFIX\}\" 2>/dev/null)"}%\#*}##*/})
[[ $#files -eq 1 && $files[1] = '' ]] && files=()
compadd "$@" -a files
}
A little messy (and still not quite the full horror). I've split the key
line in the middle which fetches the list from Perforce to make it fit.
If you ploughed through chapter 5, you'll recognised what's going on
here --- we're reading a list of files, one per line, from the command
`p4 files
', and we're stripping off the directory at the front, and
everything from a `#
' on at the end. The latter is a revision number;
we're not handling those at this point, though we will later.
Notice the way I remembered $PREFIX
before I told the system to ignore
it for the word we're now completing. I remembered it as
`${(Q)PREFIX}
' in order to remove any quotes from the name. For
example, if the name on the line so far had a space, $PREFIX
(which
comes from what is on the command line without any quotes being
stripped) would have the space quoted somehow, e.g. `name\ with\ space
'. We arrange for $pfx
to contain `name with space
', which is
how Perforce knows the file, using the (Q)
parameter flag. We then
pass the argument "$pfx*${(Q)SUFFIX}"
to `p4 files
'; this generates
matching files internally. The extra layer of backslash-quoting is for
the benefit of _call_program
, which re-evaluates its arguments; this
ensures the argument is expanded at the point it gets passed to p4 files
. All this goes to show just how difficult getting the quoting
right can be.
Once we've got the list of bare filenames, we check to see if the list
is just one element with no length. That's an artefact of the the
"$(cmd)"
syntax; if the output is empty, because its quoted you still
get one zero-length string output, which we don't want.
Finally, we pass the result to compadd
as before. Again, tags and the
description have already been handled and we just need to make sure the
appropriate options get passed in with "$@"
. This time we use the
`-a
' option which tells compadd
that any arguments are array name,
not a list of completions. This is more efficient; compadd only needs to
expand the array internally instead of the shell passing a potentially
huge list to the builtin.
Handling extra bits on a completion
`Extra bits' on a completion could be anything; common examples include
an extra value for a comma-separated list (the _values
functions is
for this), or some kind of modifier applied to the completion you have
already. We've already seen an example, in fact, since the principle of
handling the directory and basename parts of a file is very similar. The
phrase `extra bits' may already alert you to the fact that we are
heading towards the deeper recesses of completion.
Anyway, here's how we tack a revision or change number onto the end of a file.
I'll stick with revisions: `filename#
revision', where revision
is a number. For the full sophistication, there are three steps to this.
First, make it easy for the user to add `#
' to an existing filename;
second, recognise that a `#
' is already there so that revisions need
to be completed; third, find out the actual revisions which can be
completed. As a revision is just a number, you might think completing it
was a bit pointless. However, given the sophistication of zsh's
completion system there's actually one very good reason --- we can
supply a description with the revisions, so that the user is given
information about the revisions and can pick the right one without
running some external command to find out. There was the same sort of
rationale behind the `-d
' option to p4 diff
; there was just one
letter to type, but zsh was able to generate extra information to
describe the possibilities, so it wasn't just laziness.
First part: make it easy for the user to add the `#
'. This actually
depends on a new feature in version 4.1 of zsh; in 4.0 you couldn't play
the trick we need or grabbing the keyboard input after a completion was
finished unless you specified a particular suffix to add to the
completion (such as the `/
' after a directory --- this is
historically where this feature came from).
The method is to add an extra argument everywhere we complete a file
name. For example, change the compadd
in _perforce_depot_files
to:
compadd "$@" -R _perforce_file_suffix -a files
where the option argument specifies a function:
_perforce_file_suffix() {
[[ $1 = 1 ]] || return
if [[ $LBUFFER[-1] = ' ' ]]; then
if [[ $KEYS = '#' ]]; then
# Suffix removal with an added backslash
LBUFFER="$LBUFFER[1,-2]\\"
elif [[ $KEYS = (*[^[:print:]]*|[[:blank:]\;\&\|@]) ]]; then
# Normal suffix removal
LBUFFER="$LBUFFER[1,-2]"
fi
fi
}
This has been simplified, too; I've ignored revision ranges in the form
file#
rev1,
rev2. However, I've handled changes (`@
'
following a filename) as well as revisions. You'll see this function
looks much more like a zle widget rather than a completion widget ---
which is exactly what it is; it's not called as part of the completion
system at all. After the specified completion, zle reads in the next
keystroke, which is stored in $KEYS
, and calls this function as a zle
widget. This means it can manipulate the line buffer; we only need to
look at what is at the left of the cursor, stored in $LBUFFER
.
The function is called with the length of the suffix added to the function. In this case, it's just a space --- we've finished a normal completion, so the system has automatically added a space to what's on the command line. We therefore check we've just got one single character in the suffix, to avoid getting confused.
Next, we look at what's immediately left of the cursor, which is the
last character in $LBUFFER
, i.e. $LBUFFER[-1]
, to make sure this is
a space.
If everything looks OK, we consider the keys typed and decide whether to
modify the line. You may already have noticed that in some cases zsh
automatically removes that space by itself; for example, if you hit
return --- or any other non-printing character --- or if it's a
character that terminates a command such as `&
' or `;
'. We emulate
that behaviour --- most of the second test is simply to do that. The
only differences from normal are if the key typed was `@
' or `#
'.
The `@
' is simple --- we just remove the last character, the same as
we do for the other characters. For `#
', however, we also add a
backslash to the command line before the `#
'. That's because `#
'
is a special character with extended globbing, and the completion system
generally runs with extended globbing switched on. Adding the backslash
means the user doesn't have to; it's never harmful.
To show the next effect, suppose we complete a file name:
p4 diff fil<TAB>
to get:
p4 diff filename _
where `_
' shows the cursor position, and then typed `#
'; we would
get:
p4 diff filename\#
with the cursor right at the end.
So far so good. For the second step, we need to modify _perforce_files
to spot that there is a `#
' on the line before the cursor, and to
call the revision code. To do this we add an extra branch at the start
of the `if
' in _perforce_files
--- at the start, because any `#
'
before the cursor forces us to look at revisions, so this takes
precedence over the other choices. When this is added, the code will
look like:
if [[ -prefix *\# ]]; then
_perforce_revisions
elif [[ $PREFIX = //* ]]; then
# as before.
In fact, that -prefix
test is just a fancy way of saying the same
thing as the `[[ $PREFIX = *\# ]]
' and if I wasn't so hopelessly
inconsistent I would have written both tests the same.
So now the third step: write _perforce_revisions
to complete revisions
numbers with the all-important descriptions.
_perforce_revisions() {
local rline match mbegin mend pfx
local -a rl
pfx=${${(Q)PREFIX}%%\#*}
compset -P '*\#'
# Numerical revision numbers, possibly with text.
if [[ -z $PREFIX || $PREFIX = <-> ]]; then
# always allowed (same as none)
rl=($rl 0)
_call_program filelog p4 filelog \$pfx 2>/dev/null |
while read rline; do
if [[ $rline = (#b)'... #'(<->)*\'(*)\' ]]; then
rl=($l "${match[1]}:${match[2]}")
fi
done
fi
# Non-numerical (special) revision names.
if [[ -z $PREFIX || $PREFIX != <-> ]]; then
rl=($rl 'head:head revision' 'none:empty revision'
'have:current synced revision')
fi
_describe -t revisions 'revision' rl
}
Thankfully, a lot of the structure of this is already familiar. We
extract the existing prefix before the `#
', being careful about
quoting --- this is the filename for which we want a list of revisions.
We ignore everything in the command argument before the `#
'. After
generating the completions, we use the _describe
function to add them
with the tag `revisions
' and the description `revision
'.
The main new part is the loop over output from `p4 filelog
', which is
the Perforce command that tells us about the revisions of a file. We
extract the revision number and the comment from the line using
backreferences (see previous chapter) and weld them together with a
colon so that _describe
will be able to separate the completion from
its description. Then we add a few special non-numerical revisions which
Perforce allows, and pass this list down to _describe
. The extra
if
's are a very minor optimization to check if we are completing a
numerical or non-numerical revision.
6.8.4: The rest
It's obvious that this tutorial could expand in any number of directions, but as it's really just to point out some possibilities and directions, that would would miss the point. So the rest of this chapter takes the completion system apart and looks at the individual components. It should at least now be a bit more obvious where each component fits.
6.9: Writing new completion functions and widgets
Now down to the nitty gritty. When I first talked about new completion,
I explained that the functions beginning `_
' were the core of the
system. For the remainder of the chapter, I'll explain what goes in them
in more detail than I did in the tutorial. However, I'll try to do it in
such a way that you don't need to know every single detail. The trade
off is that if you just use the simplest way of writing functions, many
of the mechanisms I told you about above, particularly those involving
styles and tags, won't work. For example, much of the code that helps
with smart formatting of completion listings is buried in the function
`_description
'; if you don't know how to call that --- which is often
done indirectly --- then your own completions won't appear in the same
format as the pre-defined ones.
The easiest way of getting round that is to take a dual approach: read
the following as far as you need, but also try to find the existing
completion that comes nearest to meeting your needs, then copy that and
change it. For example, here's a function that completes files ending in
.gz
(the supplied function which does this has now changed), which are
files compressed by the gzip
program, for use by the corresponding
program that does decompression, gunzip
--- hence the file and
function are called _gunzip
:
#compdef gunzip zcat
local expl
_description files expl 'compressed file'
_files "$expl[@]" -g '*.[gG][zZ]'
You can probably see straight away that if you want to design your own
completion function for a command which takes, say, files ending in
.exe
, you need to change three things: the line at the top, which
gives the names of programmes whose arguments are to be completed here,
the description `compressed file
' to some appropriate string, and the
argument following the -g
to something like '*.exe'
--- any globbing
pattern should work, just remember to quote it, since it shouldn't be
expanded until the inside of the function _files
. Once you've
installed that somewhere in your $fpath
and restarted the shell,
everything should work, probably following a longer pause than usual as
the completion system has to rescan every completion function when it
finds there is a new one.
What you might miss is that the first argument to _description
,
`files
', is the all-important mystical tag for the type of
completion. In this case, you would probably want to keep it. Indeed,
the _files
function is used for all file completions of any type, and
knows all about the other tags --- globbed-files
, directories
,
all-files
--- so virtually all your work's done for you here.
If you're adding your own functions, you will need your own functions
directory. This was described earlier in this guide, but just to remind
you: all you need to do is create a directory and add it to $fpath
in
either .zshenv
(which a lot of people use) or .zshrc
(which some
sticklers insist on, since it doesn't affect non-interactive shells):
fpath=(~/funcs $fpath)
It's best to put it before the standard completion directories, since then you can override a standard completion function simply by copying it into your own directory; that copy will then be found first and used. This is a perfectly reasonable thing to do with any completion function --- although if you find you need to tweak one of the larger standard functions, that's probably better done with styles, and you should suggest this to us.
6.9.1: Loading completion functions: compdef
The first thing to understand is that top line of _gunzip
. The
`#compdef
' tag is what tells the system when it checks through all
files beginning with `_
' that this is a function implementing a
completion. Files which don't directly implement completions, but are
needed by the system, instead have the single word `#autoload
' at
that point. All files are only loaded when needed, using the usual
autoloading system, to keep memory usage down.
You can supply various options to the `#compdef
' tag; these are
listed in the `Initialization
' section of the zshcompsys(1)
manual
page or `Completion System' info node. The most useful are -k
and
-K
, which allow you to define a completion command and binding rather
than a function used in a particular context. There are also -p
and
-P
which tell the system that what follows is a pattern rather than a
literal command name; any command matching the pattern will use that
completion function, unless you used -P
and a normal (non-pattern)
completion function for the name was found first.
For normal #compdef
entries, however, what comes next is a list of
command names --- or rather a list of contexts, since the form
`-context-
' can be used here. For example, the function _default
has the line `#compdef -default-
'. You can give as many words as you
like and that completion will be used for each. Note that contexts in
the colon-separated form can't appear here, just command names or the
special contexts named with hyphens.
The system does its work by using a function compdef
; it gets as
arguments more or less what you see, except that the function name is
passed as the first argument. Thus the _gunzip
completion is loaded by
`compdef _gunzip gunzip zcat
', _default
by `compdef _default -default-
', and so on. This simply records the name of the function
handling the context in the $_comps
associative array which you've
already met. You can make extra commands/contexts be handled by an
existing completion function in this way, too; this is generally more
convenient than copying and modifying the function. Just add `compdef <_function> <command-to-handle>
' to .zshrc
after the call to
compinit
.
It's also high time I mentioned an easy way of using the completion
already defined for an existing function: `compdef newcmd=oldcmd
'
tells the completion system that the completion arguments for
`newcmd
' are to be the same as the ones already defined for
`oldcmd
'; it will complain if nothing is known about completing for
oldcmd
. This works recursively; you can now define completions in
terms of that for newcmd
. If you happen to know the name of the
completion function called, you can use that; the following three lines
are broadly equivalent:
compdef $_comps[typeset] foo
compdef _vars_eq foo
compdef foo=typeset
since the completion for typeset
is stored in $_comps
along with all
the others, and this happens to resolve to _vars_eq
; but the last
example is easier and safer and the intention more obvious. The manual
refers to typeset
here as a `service' for foo
(guess what the shell
stores in the associative array element $_services[foo]
).
There's actually more to services: when a function is called, the
parameter $service
is set. Usually this will just be the name of the
command being completed for, or one of the special contexts like
`-math-
'. However, in a case like the last compdef
in the list
above, the service will be typeset
even though the command name may be
`foo
'.
This is also used in `#compdef
' lines. The top of `_gzip
'
contains:
#compdef gzip gunzip gzcat=gunzip
which says that the file provides two services, for gzip
and gunzip
,
and also handles completion for gzcat
, but with the service name
gunzip
. Only a few of the completion functions actually care what
service they provide (you can check, obviously, by looking to see if
they refer to $service
); but you may have uses for this. Note that if
you define services with a compdef
command, all the arguments must
be in the foo=
bar form; the mixed form is only useful after a
#compdef
inside completion functions.
6.9.2: Adding a set of completions: compadd
Once you know how to make a new completion function, there is only one
other basic command you need to know before you can create your own
completions yourself. This is the builtin compadd
. It is at the heart
of the completions system; all its arguments, after the options, are
taken as possible completions. This is the list from which the system
selects the possibilities that match what you have already typed. Here's
a very basic example which you can type or paste at the command line:
_foo() { compadd Yan Tan Tethera; }
compdef _foo foo
Now type `foo
' and experiment with completions after it. If only
it were all that simple.
There are a whole list of options to compadd
, and you will have to
look in the zshcompwid(1)
manual page or the `Completion Widgets'
info node for all of them. I've already mentioned -M
and (long ago)
-f
. Here are other interesting ones. -X <description>
provides a
description --- this is used by the format
style to pass descriptions,
and if you use the normal tags system you shouldn't pass it directly;
I'll explain this later.
-P <prefix>
and -S <suffix>
allow you to specify bits which are not
treated as part of the completion, but appear on the line none the less.
In fact, they do two different things: if the prefix or suffix is
already there, it is ignored, and if it isn't, it is inserted. There are
also corresponding hidden and ignored prefixes, necessary for the full
power of the completion system, but you will need to read the manual for
the full story. The -q
option is useful with -S
; it enables
auto-remove behaviour for the suffix you gave, just like /
with the
AUTO_REMOVE_SLASH
option when completing filenames.
-J <group>
is the way group names are specified, used by the
group-name
tag; there is also -V <group>
, but the group here is not
sorted (and is distinct from any group of the same name passed to -J
).
-Q
tells the completion code not to quote the words --- this is useful
where you need to have unquoted metacharacters in the final completion.
It is also useful when you are completion something where the result
isn't going to be expanded by the shell.
-U
tells compadd
to use the list of completions even if they don't
match what's on the command line; you will need this if your completion
function modifies the prefix or suffix so that they no longer fit what's
already there. If you use this, you might consider turning on menu
completion (using compstate[insert]=menu
), since it might otherwise be
difficult to select the appropriate completion.
Finally, note the -F
and -W
options which I describe below for
_files
actually are options to compadd
too.
6.9.3: Functions for generating filenames, etc.
However, for most types of completion the possibilities will not be a
simple list of things you already know, so that you need to have some
way of generating the required values. In this section, I will describe
some of the existing functions you can call to do the hard work. In the
next section I will show how to retrieve information from some special
parameters made available by the zsh/parameter
module.
Files etc.: the function _files
You have already seen _files
in action. Calling this with no arguments
simply adds all possible files as completions, taking account of the
word on the command line to establish directories and so on.
For more specific use, you can give it various options: `-/
' means
complete directories, and, as you saw, `-g "<pattern>"
' gives a
filename generation pattern to produce matching files.
A couple of other options, which can be combined with the ones above,
are worthy of mention. If you use `-W <dir>
', then completion takes
place under directory <dir
> rather than in the current directory ---
it has no effect if you are using an absolute path. Here, `<dir>
' can
also be a set of directories separated by spaces or, most usefully since
it avoids any problems with quoting, the name of an array variable which
contains the list of possible directories. This is essentially how
completion for cd
with the $cdpath
array works. So if you have a
program that looks for files with the suffix `.mph
', first in the
current directory, then in a standard directory, say,
/usr/local/oomph
', you can do this:
local oomph_dirs
oomph_dirs=(. /usr/local/oomph)
_files -W oomph_dirs -g '*.mph'
--- note there is no `$
' before the variable $oomph_dirs
here,
since it should only be expanded deep inside _files
.
The system that implements $fignore
and the ignored-patterns
style
can be intercepted, if you need to, with the option `-F "<pat>"
';
`<pat>
' is an array of patterns to ignore, in the usual completion
format, in other words the name of a real shell array, or a list of
values inside parentheses. If you make sure all the tags stuff is
handled properly, ignored-patterns
will work automatically, however,
and in addition extended globbing allows you to specify patterns with
exclusion directly, so you probably won't use this feature directly
unless you're in one of your superhero moods.
In addition, _files
also takes many of the standard completion options
which apply to compadd
, for convenience.
Actually, the function _path_files
is the real engine room of the
system. The advantage of using _files
is that it prepares all the tags
for you, deciding whether you want directories to be completed as well
as the globbed files, and so on. If you have particularly specific needs
you can use _path_files
directly, but you won't get the automatic
fallback one directories
and all-files
. Because it doesn't handle
the tags, _path_files
is too lowly to do the usual tricks with label
loops, i.e. pretending `dog:-setter
' is a tag `dog-setter
' with
the usual completions for `dog
'; likewise, it doesn't implement the
file-patterns
style. So you need to know what you're doing when you
use it directly.
Parameters and options
These can be completed by calls to the _parameters
and _options
functions, respectively. Both set up their own tags, and _options
uses
the matching control mechanism described above to allow options to be
given in all the available forms. As with _files
, they will also pass
standard compadd
options down to that function. Furthermore, they are
all at a high enough level to handle tags with labels: to translate that
into English, you can use them directly without any of the preprocessing
described later on which are necessary to make sure the styles dealing
with tags are respected.
For more detailed control with options, the functions _set_options
and
_unset_options
behave like _options
, but the possible completions
are limited to options which are set or unset, respectively. However,
it's not that simple: the completion system itself alters the options,
and you need to enable some code near the top of _main_complete
(it's
clearly marked) to remember the options which were set or unset when
completion started. A straw poll based on a sample of two zsh developers
revealed that in any case many people don't like the completion system
to second guess the options they want to set or unset in this way, so
it's probably better just to stick to _options
.
Miscellaneous
There are also many other completion functions adding matches of a
certain type. These can be used in the same way as _parameters
and
_options
; in other words they do all the work needed for tags
themselves and can be given options for compadd
as arguments.
Normally, these functions are named directly after the type of matches
they generate, like _users
, _groups
, _hosts
, _pids
, _jobs
,
etc.
6.9.4: The zsh/parameter
module
The new completion system automatically makes the zsh/parameter
module
available for use. This provides an easy way of generating arguments for
compadd
. To get the maximum use out of this, you should be familiar
with zsh's rather self-willed syntax for extracting bits out of
associative arrays. Note in particular ${(k)assoc}
, which expands to a
list of the keys of the associative array $assoc
, ${(v)assoc}
, which
expands to just its values (actually, so does $assoc
on its own), and
${(kv)assoc}
which produces key/value pairs. For all intents and
purposes, the keys and values, or the pairs of them, are in a random
order, but as the completion system does it's own sorting that shouldn't
be a problem. Mostly, the important parts for completion are in the
keys, i.e. to add all aliases as possible completions, you need
`compadd ${(k)aliases}
'.
Here's a list of associative and ordinary arrays provided; for more
information on the values of the associative arrays, which could be
useful in some cases, consult the section The zsh/parameter Module
in the zshmodules(1)
manual page or the corresponding info node.
First, the associative arrays.
$aliases
,$dis_aliases
,$galiases
The keys of these arrays give ordinary aliases, disabled ordinary aliases for those where you have donedisable -a <alias>
to turn them off temporarily, and global aliases as defined withalias -g
.$builtins
,$dis_builtins
The keys give active and disabled shell builtin commands.$commands
The keys are all external commands stored in the shells internal tables; it does this both for the purposes of fast completion, and to avoid having to search each time a command is executed. It's possible that a command is missing or incorrectly stored if the contents of your$path
directories has changed since the shell last updated its tables; therehash
command fixes it.$functions
,$dis_functions
The keys are active and disabled shell functions.$history
Here, the values are complete lines stored in the internal history. The keys are the numbers of the history line; it's an associative, rather than an ordinary, array because they don't necessarily start at line 1. However, see thehistorywords
ordinary array below.$jobtexts
,$jobdirs
,$jobstates
These give you information about jobs; the keys are the job numbers, as presented by thejobs
command, and the values give you the other information from jobs:$jobtexts
tells you what the job is executing,$jobdirs
its working directory, and$jobstates
its state, where the bit before the colon is the most useful as it refers to the whole job. The remainder describes the state of individual processes in the job.$modules
The keys give the names of modules which are currently available to the shell, i.e. loaded or to be autoloaded, essentially the same principle as with functions.$nameddirs
If you have named directories, either explicitly (e.g. assigning `foo=/mydir
' and using `~foo
') or via theAUTO_NAME_DIRS
option, the keys of this associative array give the names and the values the expanded directories.$options
,$parameters
The keys give shell options and parameters, and are used by the functions_options
and_parameters
for completion, so you will mostly not need to refer to them directly.$userdirs
The keys give all the users on the system. The values give the corresponding home directory, so `${userdirs[juser]}
' is equivalent to having~juser
expanded and is thus not all that interesting, except that by doing it this way you can test whether the expansion exists without causing an error.
Now here are the ordinary arrays, which you would therefore refer to
simply as ${reswords}
etc.
$dirstack
This contains your directory stack, what you see with `dirs -v
'. Note, however that the current directory, which appears as number 0 with that command, doesn't appear indirstack
. Of course it's easy to add it to a completion if you want.$funcstack
This is the call stack of functions, i.e. all the functions which are active at the time the array was referenced.^Xh
uses this to display which functions have been called for completion.$historywords
Unlike$history
, this contains just the individual words of the shell's command line history, and is therefore likely to be more useful for completion purposes.$reswords
,$dis_reswords
The active and disabled reserved words (effectively syntactically special commands) understood by the shell.
Other ways of getting at information
Since the arguments to compadd
undergo all the usual shell expansions,
it's easy to get words from other sources for completion, and you can
look in the existing completion functions for many examples. A good
understanding of zsh's parameter and command expansion mechanisms and a
strong stomach will be useful here.
For example, here is the expansion used by the _limits
function to
retrieve the names of resource limits from the limit
command itself:
print ${${(f)"$(limit)"}%% *}
which you can test does the right thing. Here's a translation:
"$(limit)"
calls the command in a quoted context, which means you get
the output as if it were a single file (just type `limit
' to see what
that is). ${(f)...}
splits this into an array (it is now outside
quotes, so splitting will generate an array) with one element per line.
Finally, ${...%% *}
removes the trailing end of each array element
from the first piece of whitespace on, so that `cputime unlimited
' is
reduced to `cputime
', and so on. Type `limit ^D
', and you will see
the practical upshot of this.
That's by no means the most complicated example. The nested expansion facility is used throughout the completion functions, which adds to brevity but subtracts considerably from readability. It will repay further study, however.
6.9.5: Special completion parameters and compset
Up to now, I've assumed that at the start of your completion function
you already know what to complete. In more complicated cases that won't
be the case: different things may need completing in different arguments
of a command, or even some part of a word may need to be handled
differently from another part, or you need to look for a word following
a particular option. I will first describe some of the lower level
facilities which allow you to manipulate this; see the manual page
zshcompwid(1)
or the info node Completion Widgets for the details
of these. Later, I will show how you can actually skip a lot of this for
ordinary commands with options and arguments by using such functions as
_arguments
, where you simply specify what arguments and options the
function takes and what sort of completion they need.
The heart of this is the special parameters made available in completion for testing what has already been typed. It doesn't matter if there are parameters of that name outside the completion system; they will be safely hidden, the special values used, and the original values restored when completion is over.
$words
is an array corresponding to the words on the command line ---
where by a `word' I mean as always a single argument to the command,
which may include quoted whitespace. $CURRENT
is the index into that
array of the current word. Note that to avoid confusion the ksh-like
array behaviour is explicitly turned off in _main_complete
, so the
command itself is $words[1]
, and so on.
The word being completed is treated specially. The reason is that you
may only want to complete some of it. An obvious example is a file with
a path: if you are completing at `foo/bar
', you don't want to have to
check the entire file system; you want the directory foo
to be fixed,
and completion just for files in that. There are actually two parts to
this. First, when completion is entered, $PREFIX
and $SUFFIX
give
you the part of the current word before the cursor, and the remainder,
respectively. It's done like this to make it possible to write functions
for completing inside a word, not just at the end. The simplest possible
way of completing a file is then to find everything that matches
$PREFIX*$SUFFIX
.
But there's more to it than that: you need to separate off the
directory, hence the second part. The parameters $IPREFIX
and
$ISUFFIX
contain a part of the string which will be ignored for
completion. It's up to you to decide what that is, then to move the bit
you want to be ignored from $PREFIX
to $IPREFIX
(that's the usual
case) or from $SUFFIX
to $ISUFFIX
, making sure that the word so far
typed is still given by $IPREFIX$PREFIX$SUFFIX$ISUFFIX
. Thus in
completing foo/bar
, you would strip foo/
from the start of $PREFIX
and tack it onto the end of $IPREFIX
--- after recording the fact that
you need to move to directory foo
, of course. Then you generate files
in foo
, and the completion system will happily accept barrack
or
barbarous
as completions because it doesn't care about the foo
any
more.
Actually, this is already done by the the _files
and _path_files
functions for filename completion. Also, you can get some help using the
compset
builtin command. In this case, the incantation is
if compset -P "*/"; then
# do whatever you need to with the leading
# string up to / stripped off
else
# no prefix stripped, do whatever's necessary in this case
fi
In other words, any initial match of the pattern `*/
' in $PREFIX
is
removed and transferred to the end of $IPREFIX
; the command status
tells you whether this was done. Note that it is the longest possible
such match, so if there were multiple slashes, all will be moved into
$IPREFIX
. You can control this by putting a number <N>
between the
-P
and the pattern, which says to move only up to the <N>
th such
match; here, that would be a pattern with exactly <N>
slashes. Note
that -P
stands for prefix, not pattern; there is a corresponding -S
option for the suffix. See the manual for other uses of compset
; these
are probably the most frequent.
If you want to make the test made by compset
, but without the side
effect of changing the prefixes and suffixes, there are tests like this:
if [[ -prefix */ ]]; then
# same as with `compset -P "*/"', except prefixes were left alone.
fi
These have the advantage of looking like all the standard tests understood by the shell.
There are three other parameters special to completion. The $QIPREFIX
and $QISUFFIX
are a special prefix and suffix used when you are
dividing up a quoted word --- for example, in `zsh -c "echo hi"
', the
word "echo hi"
is going to be used as a command line in its own right,
so if you want to do completion there, you need to have it split up. You
can use `compset -q
' to split a word in this fashion.
There is also an associative array $compstate
, which allows you to
inspect and change the state of many internal aspects of completion,
such as use of menus, context, number of matches, and so on. Again,
consult the manual for more detail. Many of the standard styles work by
altering elements of $compstate
.
Finally, in addition to the parameters special to completion, you can
examine (but not alter) any of the parameters which appear in all
editing widgets: $BUFFER
, the contents of the current editing line;
$LBUFFER
, the part of that before the cursor; $RBUFFER
, the rest;
$CURSOR
, the index of the cursor into $BUFFER
(with the first
character at zero, in this case --- or you can think of the zero as
being the point before the first character, which is where insertion
would take place with the cursor on the first character); $WIDGET
and
$LASTWIDGET
, the names of the current and last editing or completion
widget; $KEYS
, the keys typed to invoke the current widget;
$NUMERIC
, any numeric prefix given, unset if there is none, and a few
other probably less useful values. These are described in the
zshzle(1)
manual page and the Zsh Line Editor info node. In
particular, I already mentioned $NUMERIC
as of possible use in various
styles, and it is used by the completers which understand a `numeric
'
value in their relevant styles; the $WIDGET
and $KEYS
parameters are
useful for deciding between different behaviours based on what the
widget is called (as in _history_complete_word
), or which keys are
used to invoke it (as in _bash_completions
).
Here are a few examples of using special parameters and compset
.
One of the shortest standard completions is this, _precommand
:
#compdef - nohup nice eval time rusage noglob nocorrect exec
shift words
(( CURRENT-- ))
_normal
It applies for all the standard commands which do nothing but evaluate
their remaining arguments as a command, with some change of state, e.g.
ignoring a certain signal (nohup
) or altering the priority (nice
).
All the completion system does here is shift the first word off the end
of the $words
array, decrement the index of the current word into
$words
, and call _normal
. This is the function called when
completion occurs not in one of the special -context-
s, in other words
when an argument to an ordinary command is being completed. It will look
at the new command word $words[1]
, which was previously the first
argument to nohup
or whatever, and start completion again based on
that, or even complete that word itself as a command if necessary. The
net effect is that the first word is ignored completely, as required.
Here's just an edited chunk of the file _user_at_host
; as its name
suggests, it completes words of the form <user>@<host>
, and it's used
anywhere the user-hosts
style, described above, is appropriate:
if [[ -prefix 1 *@ ]]; then
local user=${PREFIX%%@*}
compset -P 1 '*@'
# complete the host for which we want the user
else
# no @, so complete the user
fi
We test to see if there is already a `<user>@
' part. If there is, we
extract the user with an ordinary parameter substitution (so ordinary
even other shells could do it). Then we strip off that from the bit to
be completed with compset
; we already know it matches the prefix, so
we don't need to test the return value. Then we just do normal hostname
completion on what remains --- except that the user-hosts
style might
be able to give us a clue as to which hosts have such a user. If the
original test failed, then we simply complete what's there as a user.
Finally, here is essentially what the function _most_recent_file
uses
to extract the $NUMERIC
th (default first) most recently modified file.
local file
file=($~PREFIX*$~SUFFIX(om[${NUMERIC:-1}]N))
(( $#file )) && compadd -U -i "$IPREFIX" -I "$ISUFFIX" -f -Q - $file
Instead of doing it with mirrors, this uses globbing qualifiers to
extract the required file; om
specifies ordering by modification time,
and the expression in square brackets selects the single match we're
after. The N
turns on NULL_GLOB
, so $file
is empty if there are no
matches, and the parameter expansions with `$~
' force patterns in
$PREFIX
and $SUFFIX
to be available for expansion (a little extra
feature I use, although ordinary completion would work without).
Most of the compadd
command is bookkeeping to make sure the parts of
the prefix and suffix we've already removed, if there are any, get
passed on, but the reason for that deserves a mention, since normally
this is handled automatically. The difference here is that -U
usually
replaces absolutely everything that was in the word before, so if you
need to keep it you have to pass it back to compadd
. For example,
suppose you were in a context where you were completing after
`file=...
and you had told the completion system that everything up
to `file=
' was not to count and not to be shown as part of the
completion. You would want to keep that when the word was put back on
the command line. However, `-U
' would delete that too. Hence the
`-i "$IPREFIX"
' to make sure it's retained. The same argument goes
for the ignored suffix. However, there's currently no way of getting
_most_recent_file
to work on only a part of a string, so this
explanation really only applies when you call it from another completion
function, not directly from the command line.
6.9.6: Fancier completion: using the tags and styles mechanism
At this point, you should be in a position to construct, although maybe
not in the best possible way, pretty much any completion list you want.
Now I need to explain how you make sure it all fits in with the usual
tags and styles system. You will need to pick appropriate tags for your
completions. Although there is no real restriction, it's probably best
to pick one of the standard tags, some of which are suitably general to
cover just about anything: files
, options
, values
, etc. There is a
list in the completion system manual entry. Remember that the main use
for tags is to choose what happens when more than one tag can be
completed in the same place. Finding such things that can't be separated
using the standard tag names is a good reason for inventing some new
ones; you don't have to do anything special if the tag names are new,
just make sure they're documented for anyone using the completion
function.
How to call functions so that `It Just Works'
The simplest way of making your own completion function recognize tags
is to use the _description
function, which is usually called with
three arguments: the name of the tag you're completing for, the name of
a variable which will become an array containing arguments to pass to
compadd
, and the full description. Then you have to make sure that
array gets passed down to compadd
, or to any of the higher-level
completion functions which will pass the arguments on to compadd
. For
example,
local expl
_description files expl 'my special files'
_files "$expl[@]"
This sets the files tag; _description
sets $expl
to pass on the
description, and maybe other things such as a group name for the tag, in
the appropriate format; we pass this down to _files
which will use it
for calling compadd
. Generally, you will call _description
for each
time you call compadd
or something that in turn calls compadd
.
The _description
function calls another function _setup
to do much
of the setting up of styles for the particular tag. Mostly, _setup
is
buried deeply enough that you don't need to worry about it yourself.
Sometimes you can't do completion, and just want to print a message
unconditionally to say so, irrespective of tags etc.; the function
_message
does this, taking the message as its sole argument.
There are two levels above that; these implement the tags mechanism in
full. In _description
, all that happens is that the user is informed
what tag is coming up; there's no check what preferences the user has
for tags (the first level), nor whether he wants tags to be split up
using the labelling mechanism, e.g. picking out certain sorts of files
using the labelled tag `file:-myfiles
' to get the final tag
`file-myfiles
' (the second level).
To get this for simple cases you use the function _wanted
. Unlike
_description
, it's an interface to the function that generates
completion as well as a handler for tags --- that's so it can loop over
the generated tags, checking the labels. The call above would now look
like this:
_wanted files expl 'my special files' _files
Note that you now don't pass the "$expl[@]"
, which hasn't even been
set yet; _wanted
will generate the string using the parameter name you
say (here `expl
', as usual), and assume that the function generating
the completions can use the result passed down to it. This is true of
pretty much anything you are likely to want to use.
Note also the fact you need to pass `_files
', i.e. the function
generating the completion. You can put pretty much any command line
which generates completions here, down to a simple `compadd
'
expression. The reason it has to be here is the tag labelling business:
_wanted
could check whether the tag you specify, `files
', is wanted
by the user and then return control to you, but it wouldn't be able to
split up and loop over labelled tags set in this case for the
file-patterns
style and in other case by the tag-order
style.
Unless you're really going into the bowels, _wanted
is probably the
lowest level you will want to use. I'd suggest you remember that one,
and only go back and look at the other stuff if you need to do something
more complicated.
If your function handles multiple tags, you need to loop over the
different tags to find out which sort the tag order wants next. For
this, you first need to tell the system which tags are coming up, using
the _tags
function with a list. Then you need to to test whether each
tag in turn actually needs to be completed, and go on doing this until
you run out of tags which need completions performing; the _tags
function without arguments does this. Finally, you need to use
_requested
, which works a bit like _wanted
but is made to fit inside
the loop we are using. The end result looks like this:
local expl ret=1
_tags foo bar rod
while _tags; do
_requested foo expl "This is the description for tag foo" \
compadd all foos completions && ret=0
_requested bar expl "This is the description for tag bar" \
compadd all bars completions && ret=0
_requested rod expl "This is the description for tag rod" \
compadd all rods completions && ret=0
(( ret )) || return 0 # leave if matches were generated
done
If you do include the completion function line as arguments, the loop
over labels for the tag you specify is automatically handled as with
_wanted
. It may be a little confusing that both _requested
and
_wanted
exist: the specific difference is that with _requested
you
call the _tags
function yourself, whereas _wanted
assumes the only
valid tag is its argument and acts accordingly, and can be used only for
simple, `one-shot' completions.
With _requested
, unlike _wanted
, you can separate out the arguments
to the completion generator itself --- here compadd
--- into a
different statement, remembering the "$expl[@]"
argument in that case.
You can miss out the second and third arguments for _requested
in this
way. This time the loop which generates labels for tags is not
performed, and you have to arrange it yourself, with the usual trade off
of greater complexity for greater flexibility. To do this, there are two
other functions: _all_labels
and _next_label
. The simpler case is
with _all_labels
, which just implements the loop over the labels using
the same arguments as _wanted
:
_requested values &&
_all_labels values expl 'values for my special things' \
compadd alpha bravo charlie delta echo foxtrot.
In case you haven't understood (and it's quite complicated, I'm afraid):
the _requested
looks at whether the tag you use has been asked for by
the user. Having found out that it is, the _all_labels
function calls
the command compadd
which actually adds the completions, but it does
it in such a way as to take account of labelled tags --- you might have
both a plain `values
' tag and `values:-special
' labelled tag, and
_all_labels
is needed to decide which is being used here. This last
example is actually exactly what _requested
does when given the
compadd
as argument, so it's only really useful when there is some
code between the _requested
and the _all_labels
, for example to
compute the strings to complete.
The most complicated case you are likely to come across is when inside
the part of the tags loop which handles a particular tag (i.e. the
_requested
lines in the example above), you actually want to add more
than one possible sort of completion. Then _all_labels
is no longer
enough, because completion needs to sort out the different things which
are being added. This can also happen when there is only one valid tag,
but that has multiple completions so that _wanted
isn't any use. In
this case you need to use _next_label
inside a loop, which, as its
names suggests, fixes up labels for the current tag and stops when it's
found the right one. Here's a stripped down example which handles
completion of messages from the MH
mail handling system; you'll find
it complete inside the function _mh
.
_tags sequences
while _tags; do
while _next_label sequences expl sequence; do
compadd "$expl[@]" $(mark $foldnam 2>/dev/null |
awk -F: '{ print $1 }') && ret=0
compadd "$expl[@]" reply next cur prev \
first last all unseen && ret=0
_files "$expl[@]" -W folddir -g '<->' && ret=0
done
(( ret )) || return 0
done
Here's what's going on. The _tags
call works just as it did in the
first example I showed for that, deciding whether the tag in question,
sequences
, has been asked for; the tag name comes because MH allows
you to define sets of messages called exactly `sequences'. The first
`while
' selects all values from tag-order
where the `sequences
'
tag appears, with or without a label. The second `while
' loop then
sorts out any occurrences of labelled sequences to be presented to the
user at the same time, i.e. given in the same element of the tag-order
value array. The first compadd
extracts from the folder (MH's name for
a directory) identified by the function the names of any sequences you
have defined; the second adds a lot of standard sequences --- although
strictly speaking unseen
isn't a standard sequence since you can name
it yourself in ~/.mh_profile
. Finally, the third adds files in the
folder itself whose names are just digits, which is how MH stores
messages. The handling of return
makes sure it stops as soon as you
have matches for one particular element of tag-order
; if you put it in
the inner loop, you would just have the first of those sets that
happened to be generated, while here, if you specify that all types of
sequence should appear in the same completion list, they are all
correctly collected.
Why, in that last example, is there no call to _requested
, now I've
gone to the trouble of explaining what that does? The answer is that
there is only one tag; _tags
can decide if we want it at all, and
after that the tag is known, so we don't need _requested
to find that
information out for us. It's only needed if there is more than one type
of match --- indeed, that's why we introduced it, so this is not
actually a new complication, although you can be forgiven for thinking
otherwise.
Here's an example of using that code for sequences. You might decide that you only want to see named sequences unless there aren't any, otherwise ordinary messages. You could do this by setting your styles as follows:
zstyle ':completion:*' tag-order sequences:-name sequences:-num
zstyle ':completion:*:sequences-name' ignored-patterns '(|,)<->'
zstyle ':completion:*:sequences-num' ignored-patterns '^<->'
which tries sequences
under the labels sequences-name
and
sequences-num
; which ignore completions which are all digits, and
those which are not all digits, respectively. The slight twiddle in the
pattern for sequences-name
ignores messages marked for deletion as
well, which have a comma stuck in front of the number (this is
configurable, so your version of MH may be different).
All of _description
, _wanted
, _requested
, _all_labels
and
_next_label
take the options -J
and -V
to specify sorted or
unsorted listings and menus, and the options -1
and -2
for removing
consecutive duplicates or all duplicates. These are also options to
compadd
; the reason for handling them here is that they can be
different for each tag, and the function called will set expl
appropriately.
If your requirements are simple enough, you can replace that _tags
loop above with a single function, _alternative
. This takes a series
of arguments each in the form `<tag>:<description>:<action>',
with the first two in the form you now know, and the third an action.
These are essentially the same as actions for the _arguments
function,
described below, except that the form `->state
', which says that the
calling function will handle the action itself by using the value of the
parameter $state
, is not available. The most common forms of action
here will be a call to another completion function, maybe with arguments
(e.g. `_files -/
'), or a simple list in parentheses (e.g. `(see saw margery daw)
'). Here, for example, is how the _cd
function handles
the two cases of local directories (under the current directory) and
directories reached via the $cdpath
parameter:
local tmpcdpath
tmpcdpath=(${(@)cdpath:#.})
_alternative \
'local-directories:local directories:_path_files -/' \
'path-directories:directories in cdpath:
_path_files -W tmpcdpath -/'
The only tricky bit is that $tmpcdpath
: it removes the `.
' from
$cdpath
, if it's present, so that the current directory is always
searched for with the tag `local-directories
', never with
`path-directories
'. Actually, you could argue that it should be
treated as being in `path-directories
' when it's present; but that
confuses the issue over what `local-directories
' really means, and it
is useful to have the distinction.
It's now an easy exercise to replace the example function I gave for
_requested
by a call to _alternative
with the arguments to compadd
turned into a list in parentheses as the <action>
part of the
arguments to _alternative
.
How to look up styles
If your completion function gets really sophisticated, you may want it
to look up styles to decide what its behaviour should be. The same
advice goes as for tags: only invent a new style if the old ones don't
seem to cover the use you want to make, since by using contexts you can
always restrict the scope of the style. However, by the same token don't
try to squeeze too much meaning into one style, which will force the
user to narrow the context --- it's always much easier to set a style
for the general context `:completion:*
' than to have to worry about
all the circumstances where you need a particular value.
Retrieving values of styles is no harder than defining them, but you
will need to know about the parameter $curcontext
, which is what
stores the middle part of the context, sans `:completion:
' and sans
tag. When you need to look something up, you pass this context to
zstyle
with `:completion:
' stuck in front:
zstyle -b ":completion:${curcontext}:tag" style-name parameter
If the tag is irrelevant, you can leave it empty, but you still need the
final colon since there should always be six in total. In some cases
where multiple tags apply it's useful to have a :default
tag context
as a fall back if none of the actual tags yield styles for that context;
hence you should test the style first for the specific tag, then with
the default
.
Style lookups all have the form just shown; the result for looking up
style-name
in the given context will be saved in the parameter
(which you should make local, obviously). In addition, zstyle
returns
a zero status if the lookup succeeded and non-zero if it failed. The
-t
lookup is different from the rest as it only returns a status for a
boolean, i.e. returns status 0 if the value is true
, yes
, 1
or
on
, and doesn't require a parameter name. There is also a -T
, which
is identical except that it returns status 0 if the style doesn't exist,
i.e. the style is taken to default to true.
The other lookup options return the style as a particular type in the
parameter with exit status zero if the lookup succeeded, i.e. a value
was found, and non-zero otherwise; -b
, -s
, and -a
specify boolean
(parameter
is either yes
or no
), scalar (parameter
is a scalar),
and array (parameter
is an array, which may still be a single word, of
course), You can retrieve an associative array with -a
as long as the
parameter has already been declared as one.
There's also a convenience option for matching, -m
; instead of a
parameter
this takes a pattern
as the final argument, and returns
status zero if and only if the pattern
matches one of the values
stored in the style for the given context.
Typical usages are thus:
if zstyle -t ":completion:${curcontext}:" foo; then
# do things in a fooish way
else
# do things in an unfooish way
fi
or to use the value:
local val
if zstyle -s ":completion:${curcontext}:" foo val; then
# use $val to establish how fooish to be
else
# be defaultly fooish
fi
6.9.7: Getting the work done for you: handling arguments etc.
The last piece of unfinished completion business is to explain the
higher level functions which can save you time writing completions for
commands which behave in a standard way, with arguments and options. The
good news is that all the higher functions here handle tags and labels
internally, so you don't need to worry about _tags
, _wanted
,
_requested
, etc. There's one exception: the `state' mechanism to be
described, where a function signals you that you're in a given state
using the parameter $state
, expects you to handle tag labels yourself
--- pretty reasonable, as you have requested that the function return
control to you to generate the completions. I've mentioned that here so
that I don't have to gum up the description of the functions in this
section by mentioning it again.
Handling ordinary arguments
The most useful function is _arguments
. There are many examples of
this in the completion functions for external commands, since so many
external commands take the standard format of a command with options,
some taking their own arguments, plus command arguments.
The basic usage is to call it with a series of arguments (which I'll call `specifications') like:
<where I am>:<description>:<what action to take>
although there are a whole series of more complicated possibilities.
The initial `<where I am>
' part tells the function whether the
specification applies to an argument in a particular position, or to an
option and possibly any arguments for that option. Let's start with
ordinary arguments, since these are simpler. In this case `<where I am>
' will be either a number, giving the number of the argument, or a
`*
', saying that this applies to all remaining arguments (or all
arguments, if you haven't used any of the other form). You can simplify
the first form, by just missing out the number; then the function will
assume it applies to the first argument not yet specified. Hence the
standard way of handling arguments is with a series of specifications
just beginning `:
' for arguments that need to be handled their own
way, if any, then one beginning `*:
for all remaining arguments, if
any.
The message that follows is a description to be passed on down to
_description
. You don't specify the tags at this point; that comes
with the action.
The action can have various forms, chosen to be easily distinguishable from one another.
-
A list of strings in parentheses, such as `
(red blue green)
'. These are the possible completions, passed straight down tocompadd
. -
The same, but with double parentheses; the list in this case consists of the completion, a backslashed colon, and a description. So an extended version of the previous action is `
((red\:The\ colour\ red blue:The\ colour\ blue))
' and so on. You can escape other colons inside the specifications in this way, too. -
A completion function to call, with any arguments, such as `
_files -/
' to complete directories. Usually this does the business with$expl
which should be familiar from the section on basic tag handling, however you can put an extra space in front of the action to have it called exactly as is, after word splitting. -
A word preceded by `
->
' for example `->state
'. This specifies that_arguments
should return and allow the calling function to process the argument. To signal back to the calling function, the parameter$state
will be set to what follows the `->
'. It's up to the calling function to make$state
a local parameter ---_arguments
can't do that, since then it couldn't return a value.You should also make the parameters
$context
and$line
local; the former is set to the new part to be added to$curcontext
, which, as you can find out from^Xh
, isoption-<option>-<arg>
, for exampleoption-file-1
for the first argument of theoption-file
option, orargument-N
, for exampleargument-2
for the second argument of the command.In simple cases, you will just test the parameter
$state
after_arguments
has returned to see what to do: the return value is 300 to distinguish it from other returns where_arguments
itself performed the completion. -
A chunk of code to evaluate, given in braces, which removes the need for a special function or processing states. Obviously this is best used for the simplest cases.
These are the main possibilities, but I have not described every variation. As always, you should see the manual for all the detail.
Here's a concocted example for that `->state
' action specifier, in
case it's confusing you. It's for a command that takes arguments
`alpha
', `beta
' and `gamma
', and takes a single option
`-type
' which takes one argument, either `normal
' or `unusual
'.
local context state line
typeset -A opt_args
_arguments '-type[specify type]:type:->type' \
'*:greek letter:->gklet' && return 0
case $state in
(type) compadd normal unusual && return 0
;;
(gklet) compadd alpha beta gamma && return 0
;;
esac
return 1
In fact the possibilities here are so simple that you don't need to use
$state
; you can just use the form with the values in parentheses as
the action passed to `_arguments
'. Anyway, if you put this into a
function `_foo
', type `compdef _foo foo
', and attempt completion
for the fictitious command `foo
', you will see _arguments
in
action.
I haven't shown the gory tag handling; as it's written, you'll see that
no tag is ever defined for the compadd
arguments shown. In this case
you could just use _wanted
. What you get for free with arguments,
however, is the context: in the first case, you would have
`:option-type-1
' in the argument field (the second last, just before
the tag), and in the second case `:argument-rest:
'. Go back to where
I originally described contexts if you've forgotten about these; I
didn't tell you at the time, but it's the _argument
function that is
responsible for them. (However, you can supply a `-C
' argument to
_wanted
to tell that a context.)
A note about the form: that `&& return 0
' makes the completion
function return if _arguments
was satisfied that it found a completion
on its own. It's useful in more complex cases. Remember that most
completion functions return status zero if and only if matches were
added; this function is written to follow that convention. I already
showed this in the section on tags, but you might have skipped that.
Note all the things you had to make local: $context
, $state
, $line
and the associative array $opt_args
. The last named allows you to
retrieve the values for a particular option; for example
`$opt_args[-o]
' contains any value already on the command line for
the option -o
. For options that take multiple arguments, these appear
separated by colons, so if the line contains `-P prefix 3
',
$opt_args[-P]
will contain `prefix:3
'.
Handling options
Option handling is broadly similar, with the `<where I am>
' part just
giving the option name --- I already showed one example with `-type
'
above. In this case, the option will just be completed to itself, the
first part of the specification, and the rest says how to complete its
arguments. Since options can take any number of arguments, including
zero, the :description:action
pair can be repeated, or omitted
entirely. Otherwise, it behaves similarly to the way described for
ordinary command arguments, with all the same possible actions. So a
simple option specification could be
_arguments '-turnmeon'
for an option with no arguments,
_arguments '-file:input file:_files'
for an option with one argument, or
_arguments '-iofiles:input file:_files:output file:_files'
for an option with two arguments, both files but with different descriptions.
The first part of the specification for an option can be more complicated, to reflect the fact that options can be used in all sorts of different ways. You can specify a description for the option itself --- as I tried to explain, the descriptions in the rest of the specification are instead for the arguments to the option. To specify an option description, just put that after the option, before any colons, in square brackets:
_arguments '-on[turn me on, why not]'
Next, some options to a command are mutually exclusive. As _arguments
has to read its way along the command line to parse it, it can record
what options have already appeared, and can ensure that an option
incompatible with one there already will not be completed. To do this,
you need to include the excluded option in parentheses before the option
itself:
_arguments '(-off)-on[turn me on, why not]' \
'(-on)-off[turn me off, please]'
This completes either of the options `-on
' or `-off
', but if
you've already given one, it won't complete the other on the same
command line. If you need to give multiple excluded options, just list
them separated by spaces, like `(-off -noton)
'.
Some options can themselves be repeated; _arguments
usually won't do
that (in a sense, they are mutually exclusive with themselves), but you
can allow it to happen by putting a `*
' in front of the option
specification:
_arguments '*-o[specify extra options]:option string:->option'
allows you to complete any number of `-o <option>
' sets using the
$state
mechanism. The *
appears after any list of excluded options.
There are also ways of allowing different methods of option handling. If
the option is followed by -
, that means the value must be in the same
word as the option, instead of in the next word; if that is allowed, but
the argument could be in the next word instead, the option should be
followed by a `+
'. The latter behaviour is very common for commands
which take single letter options. Some commands, particularly many
recent GNU commands, allow you to have the argument in the next word or
in the current word after an `=
' sign; you get this by putting an
`=
' after the option name. For example,
_arguments '-file=:input file:_files'
allows you to complete `-file
<filename>' or
`-file=
<filename>'. With
_arguments '-file=-:input file:_files'
only the second is possible, i.e. the argument must be after the `=
',
not in its own word.
You can handle optional and repeated arguments to options, too. This illustrates some possibilities:
_arguments '-option:first arg:->first::optional arg:->second'
The doubled colon indicates that the second argument is optional. In
other words, at that point on the command line _arguments
will either
try to complete via the state second
, or will try to start another
specification entirely.
_arguments '-option:first arg:->first:*:other args:->other'
Here, all arguments after the first --- everything else on the command
line --- is taken as an argument to the option, to be completed using
the state other
.
_arguments '-option:first arg:->first:*-:other args till -:->other'
This is similar, but less drastic: there is a pattern after the `*
',
here a `-
', and when that is encountered, processing of arguments to
`-option
' stops. A command using this might be called as follows:
cmdname -option <first> <other1> <other2> .... - <remainder>
where of course completion for <remainder>
might be handled by other
specifications.
There are yet more possible ways of handling options. I've assumed that
option names can have multiple letters and hence must occur in separate
words. You can specify single-letter options as well, of course, but
many commands allow you to combine these into one word. To tell
_arguments
that's OK you should give it the option -s
; it needs to
come before any specifications, to avoid getting mixed up with them.
After you specify this, a command argument beginning with a single
`-
' will be treated by _arguments
as a list of single options, so
`-lt
' is treated the same as `-l -t
'. However, options beginning
with `-``-
' are still treated as single options, so a `-``-prefix
'
on the command line is still handled as a single long option by
_arguments
.
One nice feature which can save a lot of trouble when using certain
commands, notably those written by the GNU project and hence installed
on most Linux-based systems, which take an option `-``-help
' that
prints out a list of all options. This is in a human-readable form, but
_arguments
is usually able to extract a list of available options
which use the `-``-...
' form, and even in many cases whether they
take an argument, and if so what type that is. It knows because
`<command> -``-help
' often prints out a message like
`-``-file=FILE
' which would tell _arguments
(1) that `-``-file
'
is a possible option (2) that it takes an argument because of the `=
'
(3) that that argument should be a file because of the message `FILE
'
at the end.
You specify that the command in question works in this way by using the
(fairly memorable) option `-``-
' to `_arguments
'. You can then
help it out with completion of option arguments by including a pattern
to be matched in the help test after the `-``-
'; the format is
otherwise similar to a normal specification. For example
`*=FILE*:file:_files
' says that any option with `=FILE
' in it has
the description `file
' and uses the standard _files
function for
completion, while `*=DIR*:directory:_files -/
' does the same for
directories. These two examples are so common that they are assumed by
`_arguments -``-
'.
So for example, here is the completion for gdb
, the GNU debugger,
which not surprisingly understands the GNU option format:
_arguments -- '*=(CORE|SYM)FILE:core file:_files' \
'*=EXECFILE:executable:_files -g \*\(\*\)' \
'*=TTY:terminal device:compadd /dev/tty\*' && return 0
If you run `gdb --help
', you'll see where these come from:
`--core=COREFILE
', `--exec=EXECFILE
' and `--tty=TTY
' are all
listed as possible option/argument pairs. Doing it this way neatly
allows the argument completions to work whatever the names of the
options --- though of course it's possible for the rest of the pattern
to change, too, and the commands, being written by lots of different
people, are not necessarily completely consistent in the way their help
text is presented.
6.9.8: More completion utility functions
This is now just a ragbag of other functions which might prove useful in
your own completion functions, and which haven't been mentioned before,
with some examples; once again, consult the manual for more detail. Note
that many of these functions can take the most useful arguments to
compadd
and pass them on, even where I haven't explicitly said so.
_call_function
This is a simple front end to calling a function which may not be defined and hanging onto the return status of the function. One good use for this is to call a possibly non-existent function which might have been defined by the user, before doing some default stuff the user might want to skip. That would look like this:
local ret # returned status from called function, if it was called
_call_function ret _hook_function arg1 arg2 && return ret
# if we get here, _hook_function wasn't called,
# so do the default stuff.
As you can work out, _call_function
itself returns status zero if the
function in the second argument got called, and in that case the first
argument is the name of a parameter with the return status from the
function itself. The whole point is that this is safe if
_hook_function
doesn't exist.
This function is too low level to know about the tags mechanism; use
_wanted
or similar to handle tags properly.
_contexts
This is another shorthand: the arguments it takes are a set of short
contexts, in other words either names of commands or special contexts
like `-math-
'. The completion for each of these contexts is tried in
turn; _contexts
simply handles all the boring looking up of functions
and testing the return values. The definition, if you want to look, is
reassuringly simple. It only has one use at the moment: _subscript
,
which handles the -subscript-
context we met early in the chapter,
calls `_contexts -math-
' to try mathematical completion, since
ordinary array subscripts can contain mathematical expressions.
This is also too low level to handle tags. In zsh 4.1, it is made obsolete by a cleverer mechanism for handling different contexts which can be used, for example, for handling of arguments to redirections for particular commands, or keys in a particular associative array. I expect I'll describe that when 4.1 is finally released.
_describe
Don't confuse this with _description
which was explained above and is
the basic function for adding a description to a set of completions of a
certain type. I mentioned in the description of the verbose
style that
this function was responsible for showing, or not showing, the
descriptions for a whole lot of options at once. It allows you to do
that with several different sets of completions that may require
different options to compadd
. The general form looks something like
this:
_describe "description of set 1" descs1 compls1 \
<compadd-opts-1> -- \
"description of set 2" ...
where you can have any number of sets separated by the `-``-
'. The
descs1
and compls1
are arrays of the same length, giving a list of
descriptions and a list of completions, respectively. Alternatively, you
need only give one array name and each element of that will contain a
completion and a description separated by the now-traditional colon. The
`<compadd-opts-1>
' are a set of any old options recognised by
compadd
, such as -q
, or -S=/
, or what have you. I won't give an
example for this, since to find something requiring it would almost need
me to rewrite the completion system from scratch.
_combination
This is the function at the heart of the completions such as
users-hosts
described above, where combinations of elements need to be
completed at the same time. It's easiest to describe with an example;
let's pick the users-hosts
example, and I'll assume you remember how
that works from the user's point of view, including the format of the
users-hosts
style itself. The completion for the username part is
performed as:
_combination my-accounts users-hosts users
where my-accounts
is the tag to be used for the completion, then comes
the style, and then the part of the style to be extracted.
Now suppose we come back into the completion function again to complete
the host later on the command line, so that the username is already
there. We can find that by searching the command line; suppose we store
what we find in $userarg
. Then we can complete the hostname as
follows:
_combination my-accounts users-hosts users=$userarg hosts
and the magic part, the fact that we can limit the hostnames to be
completed to only those with a user $userarg
, is handled by
_combination
. This extends to hosts-ports-users
and any larger
combined set in the obvious way: the first field not to contain an
`=
' is the one being completed. You don't need to supply other fields
if they are not known; in other words, the field to be completed doesn't
need to be the first one in sequence not known, it can be any, just as
long as it matches part of the style given in the second argument, so
you could have omitted the `users=$userarg
' in the last example if
you couldn't extract the right username.
There are various bells and whistles: after the field to be completed
you can add any options to be passed down to compadd
; you can give
_combination
itself the option `-s <sep>
' to specify a character
other than colon to separate the parts of the style values; if the style
lookup fails, but there is a corresponding function, which would be
called `_users
' or `_hosts
' in this example, it is called to
generate the matches, and gets the options at the end which are
otherwise destined for compadd
.
As you can see, this function is at a high enough level to handle the tags mechanism itself.
_multi_parts
This takes two arguments, a separator and a list of matches. The list of
matches is normal, except that each element is likely to contain the
separator. In the most obvious usage, the separator is `/
' and the
list of matches is a lot of files with path components. Here's another
reasonable usage:
local groups expl
groups=($(awk -F: '{ print $1 }' ~/.newsrc))
_wanted groups expl 'newsgroup' _multi_parts "$expl[@]" . groups
The generated array contains names of Usenet newsgroups, i.e. names with
components separated by a `.
', and _multi_parts
allows you to
complete these piece by piece instead of in one go. This is a good deal
better for use with menu completion, and the list which appears is
smaller too. The _wanted
part handles the tags mechanism, which
_multi_parts
doesn't.
_sep_parts
This also completes a word piece by piece, but unlike _multi_parts
the
trial completions are also only supplied for each piece. The arguments
are alternating arrays and separators; arrays are in the usual form, in
other words either the name of an array parameter, or a literal array in
parentheses, quoted to protect it from immediate shell expansion. The
separators are simply strings. For example
local expl
array1=(apple banana cucumber)
_wanted breakfast expl 'breakfast' \
_sep_parts array1 + '(bread toast croissant)' @ '(bowl plate saucer)';
completes strings like `apple+toast@plate
', piece by piece. This is
currently not used by the distributed completion code.
_values
This works a little like _arguments
, but is designed for completing
the values of a single argument in a form like
`key=val,flag,key=other
', in which you can specify the list
separator, here `,
' by using the option -s
, e.g. `-s ,
'. The
first argument to _values
is the overall description of the set of
arguments. The other arguments are very much like those to _arguments
except that, as you would expect from the form given, no pluses or minus
signs are involved and each value can only have one argument, which must
follow an `=
'. Virtually everything else is identical, with the
exception that the associative array where the arguments are stored for
each value is called $val_args
.
I won't bother giving the instructions for _arguments
again; instead,
here is an example based on the values used by the -o
option to the
mount
command:
local context state line
typeset -A val_args
_values -s , 'file system options' \
'(rw)ro[mount file system read-only]' \
'(ro)rw[mount file system read-write]' \
'uid[set owner of root]:user ID:' \
'gid[set group of root]:group ID:' \
'bs[specify block size]:block size:(512 1024 2048 4192)'
I've just picked out a few of the umpteen possibilities for
illustration; see the function _mount
if you want more. Remember that
the `(rw)
' before the `ro
' means that the options are mutually
exclusive, and the one in parentheses won't be offered if the other
appears on the command line; the strings in square brackets are
descriptions of the particular options; and if there is a colon after
the name of the value, the value takes an argument whose own description
comes next. The second colon is followed by possible completions for
that argument, using the usual convention for actions in _arguments
;
as you'll see from the local
statement, the $state
mechanism can be
used here. Only the `bs
' argument here is given possible completions;
for uid
and gid
you'll have to type in the number without
completion; ro
and rw
don't take arguments.
Hence a typical(?) list to be completed by this would be
`rw,uid=123,bs=2048
'.
Remember also that you can use a `*
' before the option name to say
that it can appear more than once in the value list. The _values
function handles the context and tags in a similar way to _arguments
.
_regex_arguments
This function is for use when the behaviour of a set of command
arguments is so complicated that even _arguments
can't help. It allows
you to describe the arguments as a regular expression (i.e. a pattern).
I won't explain it because I haven't yet figured out how it works. If
you think you need to use it, look at the manual entry and then at the
_apt
function which is currently its main application.
6.10: Finally
Completion is big and complex: this means that there are probably lots
of bugs around, and things that I haven't described simply enough or
which may be implemented in too complicated a way. Please send the
zsh-workers
mailing list any reports or constructive criticism on the
subject.
Last of all, remember that the new completion system is ideally just supposed to work without you needing to worry exactly how. That's a bold hope, but at least much of the time you should be able to get away with using just the tab key and ordinary characters.