path: root/Doc/Zsh/compsys.yo

texinode(Completion System)(Zftp Function System)(Zsh Modules)(Top)
chapter(Completion System)
cindex(completion system)
cindex(completion, programmable)
cindex(completion, controlling)
sect(Description)

This describes the shell code for the new completion system.  It consists
of various shell functions; those beginning `tt(comp)' are to be called
directly by the user, while those beginning `tt(_)' are called by the
completion code.  The shell functions of the second set which implement
completion behaviour and which may be bound to keystrokes, are referred to
as `widgets'.

Note that with the function-based completions described here, it
is also possible to use the 
tt(compmatchers) special array to specify
global matching control, such as case-insensitivity (`tt(abc)' will complete
to a string beginning `tt(ABC)'), or wildcard behaviour on
certain anchors (`tt(a-d)' will complete to abc-def as if there were a
`tt(*)' after the `a').  See
ifzman(the section `Matching Control' in zmanref(zshcompwid))\
ifnzman(noderef(Matching Control))
for further details.

startmenu()
menu(Initialization)
menu(Completion System Configuration)
menu(Control Functions)
menu(Bindable Commands)
menu(Completion Functions)
menu(Completion Directories)
endmenu()

texinode(Initialization)(Completion System Configuration)()(Completion System)
sect(Initialization)
findex(compinstall)
cindex(completion system, installing)

The function tt(compinstall) can be run by a user to set up the completion
system for use, which also provides options for more advanced usage.
However, if the system was installed completely, it should be enough to
call the shell function tt(compinit) from your initialization file; see the
next section.

Usually, tt(compinstall) will insert code into tt(.zshrc), although if
that is not writable it will save it in another file and tell you that
file's location.  Note that it is up to you to make sure that the lines
added to tt(.zshrc) are actually run; you may, for example, need to move
them to an earlier place in the file if tt(.zshrc) usually returns early.
So long as you keep them all together (including the comment lines at the
start and finish), you can rerun tt(compinstall) and it will correctly
locate and modify these lines.  Note, however, that any code you add to
this section by hand is likely to be lost if you rerun tt(compinstall).
The new code will take effect next time you start the shell, or run
tt(.zshrc) by hand.

To run it, you will need to make sure it is in a directory mentioned in your
tt($fpath) parameter, and that it is autoloaded (`tt(autoload -U
compinstall)' is recommended).  It will ask you various questions about how
you would like completion set up.  It is in two parts; the basic part
locates the completion files and decides where to put your personal
dumpfile, used to speed up initialization after the first time.  After
that, you will be asked if you wish to go on to the advanced set-up; if you
answer tt(n), you can rerun tt(compinstall) later without having to
re-enter any of the basic settings.

You can abort the installation any time you are being prompted for
information, and your tt(.zshrc) will not be altered at all.

After initialization all the builtin completion widgets such as
tt(expand-or-complete) will be redefined to use the new completion system.
Should you need to, you can still bind keys to the old functions by putting
a `tt(.)' in front, e.g. `tt(.expand-or-complete)'.

subsect(Use of compinit)
findex(compinit)
cindex(completion system, initializing)

This section describes the use of tt(compinit) to initialize completion for
the current session when run directly by the user; if you have run
tt(compinstall) it will be called automatically from your tt(.zshrc).

To initialize the system, the function tt(compinit) should be in a
directory mentioned in the tt($fpath) variable, and should be autoloaded
(`tt(autoload -U compinit)' is recommended).  When run, it will define a
few utility functions, arrange for all the necessary shell functions to be
autoloaded, and will then re-bind all keys that do completion to use the
new system.

To speed up the running of tt(compinit), it can be made to produce a dumped
configuration which will be read in on future invocations; this is the
default, although it can be turned off by calling tt(compinit) with the
option tt(-D).  The dumped file is tt(.zcompdump) in the same
directory as the startup files (i.e. tt($ZDOTDIR) or tt($HOME));
alternatively, an explicit file name can be given by `tt(compinit -d)
var(dumpfile)'.  On the next call to tt(compinit), the dumped file will be
read instead of a full initialization.

If the number of completion files changes, tt(compinit) will recognise this
and produce a new dump file.  However, if the name of a function or the
arguments in the first line of a tt(#compdef) function (as described below)
change, it is easiest to delete the dump file by hand so that the next time
tt(compinit) will re-create it.

The dumping is actually done by another function, tt(compdump), but you
will only need to run this yourself if you change the configuration
(e.g. using tt(compdef)) and then want to dump the new one.  The name of
the old dumped file will be remembered for this purpose.

If the parameter tt(_compdir) is set, tt(compinit) uses it as a directory
where completion functions can be found; this is only necessary if they are
not already in the function search path.

subsect(Autoloaded files)
cindex(completion system, autoloaded functions)

The convention for autoloaded functions used in completion is that they
start with an underscore; as already mentioned, the tt(fpath/FPATH)
parameter must contain the directory in which they are stored.  If tt(zsh)
was properly installed on your system, then tt(fpath/FPATH) automatically
contains the required directories.

For incomplete installations, if tt(compinit) does not find enough files
beginning with an underscore (fewer than twenty) in the search path, it
will try to find more by adding the directory tt(_compdir) to the search
path; if you have run tt(compinstall), this will be set automatically.
Furthermore, if the directory in question ends in the path segment
tt(Core), or has a subdirectory named tt(Core), tt(compinit) will add all
subdirectories of the directory where tt(Core) is to the path: this allows
the functions to be in the same format as in the tt(zsh) source
distribution.

When tt(compinit) is run, it searches all such files accessible via
tt(fpath/FPATH) and reads the first line of each of them.  This line should
contain one of the tags described below. Files whose first line does not
start with one of these tags are not considered to be part of the
completion system and will not be treated specially.

The tags are:

startitem()
item(tt(#compdef) var(names...))(
The file will be made autoloadable and the function defined 
in it will be called when completing var(names), each of which is
either the name of a command whose arguments are to be completed or one of
a number of special contexts in the form tt(-)var(context)tt(-) described
below for the tt(_complete) function.
)
item(tt(#compdef -p) var(pattern))(
The file will be made autoloadable and the function defined in it will be
called when completing for a command whose name matches the given
var(pattern) (a standard globbing pattern).  Note that only one
var(pattern) may be given.
)
item(tt(#compdef -P) var(pattern))(
Like the previous one, but the function will be called only if no
completion function for the command on the line could be found.
)
item(tt(#compdef -k) var(style key-sequences...))(
This can be used to bind special completion functions to the
var(key-sequences).  It creates a widget behaving like the builtin widget
var(style), which must be one of those that perform completion, namely
tt(complete-word), tt(delete-char-or-list), tt(expand-or-complete),
tt(expand-or-complete-prefix), tt(list-choices), tt(menu-complete),
tt(menu-expand-or-complete), or tt(reverse-menu-complete). If the
tt(complist) module is loaded (see
ifzman(zmanref(zshmodules))\
ifnzman(noderef(The zsh/complist Module))\
), the tt(menu-select) widget can be used, too.  Note that the
bindings will not be used if the key is already bound (that
is, is bound to something other than tt(undefined-key)).

The widget is then bound to all the var(key-sequences) given, if any: when
one of the var(key-sequences) is typed, the function in the file will
be invoked to generate the matches. The widget created has the same
name as the file and can also be bound to other keys using tt(bindkey) 
as usual.
)
item(tt(#compdef -K) var(widget-name) var(style) var(key-sequences) ...)(
This is similar to tt(-k), with the same var(style) and var(key-sequences)
arguments arguments, preceeded by a string giving the name of a widget.
In this case only one var(key-sequences) argument may be given, but the
entire set of three arguments may be repeated with a different set of
arguments.  In particular, the var(widget-name) must be distinct in each
set.  It should begin with `tt(_)', else one will be added, and should not
clash with the name of any existing widget: names based on the name of the
function are most useful.  For example,

example(#compdef -K _foo_complete complete-word "^X^C" \ 
  _foo_list list-choices "^X^D")

(all on one line) defines a widget tt(_foo_complete) for completion, bound
to `tt(^X^C)', and a widget tt(_foo_list) for listing, bound to `tt(^X^D)'.
)
item(tt(#autoload))(
This is used for files defining utility function that are not to be
called directly as completion functions but should be loaded automatically
when invoked.  Typically they are to be called from within one of the
completion functions.
)
enditem()

Note that the tt(#) is part of the tag name and no white space is allowed
after it.  The tt(#compdef) tags use the tt(compdef) function described
below; the main difference is that the name of the function is supplied
implicitly.

subsect(Functions)

The tt(compinit) file defines the following functions, which may
also be called directly by the user.

findex(compdef)
cindex(completion system, adding definitions)
startitem()
xitem(tt(compdef) [ tt(-an) ] var(function names...))
xitem(tt(compdef -d) var(names...))
xitem(tt(compdef -p) [ tt(-a) ] var(function pattern))
xitem(tt(compdef -P) [ tt(-a) ] var(function pattern))
xitem(tt(compdef -k) [ tt(-an) ] var(function style key-sequences...))
item(tt(compdef -K) [ tt(-an) ] var(function name style key-sequences ...))(
The first form tells the completion system to call the given
var(function) when completing for the contexts or commands
whose var(names) are given:  this is like the tt(#compdef) tag.  If the
tt(-n) option is given, any existing completion behaviour for particular
contexts or commands will not be altered.  These definitions can be deleted
by giving the tt(-d) option as in the second form.

The form with tt(-p) is similar to the first, but var(function) will be
called for all commands whose name matches the var(pattern); this is like
the tt(#compdef -p) function tag.

The form with tt(-P) is like the third, but the var(function) will be
called only if no function for the command itself was found or if one
was found and it set the tt(_compskip) parameter to a value em(not)
containing the substring tt(patterns).

The form with tt(-k) defines a widget with the same name as the var(function)
which will be called for each of the var(key-sequences); this is like the
tt(#compdef -k) tag.  The function should generate the completions needed
and will otherwise behave like the builtin widget whose name is given as
the var(style) argument. The widgets usable for this are:
tt(complete-word), tt(delete-char-or-list), tt(expand-or-complete),
tt(expand-or-complete-prefix), tt(list-choices), tt(menu-complete),
tt(menu-expand-or-complete), and tt(reverse-menu-complete), as well as
tt(menu-select) if the tt(zsh/complist) module is loaded.  The option tt(-n)
prevents the key being bound if it is already to bound to something other
than tt(undefined-key).

The form with tt(-K) is similar and defines multiple widgets based on the
same var(function), each of which requires the set of three arguments
var(name), var(style) and var(key-sequences), where the latter two are as
for tt(-k) and the first must be a unique widget name beginning with an
underscore.

In each of the forms supporting it the tt(-a) option makes the
var(function) autoloadable (exactly equivalent to
tt(autoload -U )var(function)).
)
enditem()

texinode(Completion System Configuration)(Control Functions)(Initialization)(Completion System)
sect(Completion System Configuration)
cindex(completion system, configuration)

This section gives a short overview of how the completion system works,
and then more detail on how users can configure how and when matches are
generated.

subsect(Overview)

When completion is attempted somewhere on a command line the
completion system first tries to find out the context where completion 
was tried.  The context depends on such things as the name of the
command when completing an argument, and possibily also
the name of an option when completing an argument to that option.

The completion system represents contexts as hierarchical name s
with components separated by colons. For example, take the context
`tt(:completion:complete::dvips::-o-1)'.  The tt(:completion) at the
beginning just says that this context is used in the completion system 
and the tt(:complete) after it is the `completer', which is in overall
control of how completion is to be performed; `tt(complete)' is the
basic one for ordinary completion, but completers may perform various
related tasks such as correction, or modify the behaviour of a later
completer (see
ifzman(the section `Control Functions' below)\
ifnzman(noderef(Control Functions)) 
for more information).  Strictly, the completer is `tt(_complete)', but the
underscore is omitted from the context; this is also true of `tt(correct)',
`tt(approximate)', etc.  The tt(::dvips:) shows that we are
completing arguments for the tt(dvips) command.  The doubled colon
will appear only before and after the name of the command, but note
that the second colon after the command name is only added when 
there is at least one more component (otherwise the whole name ends in 
a colon, e.g. `tt(...dvips:)').  Finally, the string tt(-o-1) says that we
are completing the first argument of the option `tt(-o)' to the command.
Note that the existence of a context like this does not necessarily mean it
is handled specially by the completion system; this is determined by trying
to match the context as specifically as possible, as described below.

In many of the possible contexts the completion system can generate
matches, often multiple types of matches.  These types are represented as
simple names called `tags'.  The completion system will decide internally
what sort of tags are allowed; a list of the standard possibilities is given
below.  To determine in which order the tags are to be used by the
completion function, the `tt(tag-order)' style for the appropriate
context may be set, as described in the list of standard styles below.
Only those types of matches whose tags were selected by this style
will be produced, and in the order given.

The tt(_complete_help) bindable command described in 
ifzman(the section `Bindable Commands' below)\
ifnzman(noderef(Bindable Commands))
can be invoked to find out the context and tag names used at a particular
point in completion.  It shows a list of context names and the 
tag names used in those contexts if completion were tried at the
current cursor position.  Hence one can easily find out all the
information needed to change the behaviour of the tt(tag-order) style
for a particular context.

Completion behaviour can be modified by various other
`styles' defined with the tt(zstyle) builtin command
(see
ifzman(zmanref(zshmodules))\
ifnzman(noderef(The zsh/zutil Module))).
The full context used in looking up styles is the prefix `tt(:completion)'
followed by the context as described above, followed by another colon and
the name of the tag currently being tried for completion.

Styles determine such things as how the matches are generated; some of them
correspond to shell options (for example, the use of menu completion), but
styles provide more specific control.  They can have any number of strings as
their value.  Looking up the value of a style therefore consists of two
things:  the context, which may be matched as a pattern, and the name of
the style itself, which must be given exactly.

For example, many completion functions can generate matches in a
simple and a verbose form and use the tt(verbose) style to decide
which form should be used. To make all such functions always use the
verbose form one can simply call

example(zstyle ':completion:*' verbose yes)

in one of the startup files like tt(.zshrc). This definition simply
means that the tt(verbose) style has tt(yes) as its value in every
context inside the completion system.  If the pattern were `tt(*)', it
would mean that the verbose style had this value anywhere the style
mechanism is used.

As a more specific example, the completion function for the tt(kill)
builtin command uses the tt(verbose) style to decide if jobs and processes
are listed only as job numbers and process identifiers or if they are
listed with the full job texts and the command lines of the processes (the
latter is achieved by calling the tt(ps) command). To make this builtin
list the matches only as numbers one could call:

example(zstyle ':completion:*::kill:*' verbose no)

Furhtermore, if one wanted to see the command lines for processes but not the
job texts one could use the fact that the tag name is appended to the
context name when styles are looked up.  As the function for the tt(kill)
builtin command uses the tags tt(jobs) and tt(processes), we have:

example(zstyle ':completion:*::kill:*:jobs' verbose no)

Note that the order in which styles are em(defined) does not matter; the
style mechanism uses the most specific possible match for a particular
style to determine the set of values.  More precisely, strings are
preferred over patterns (for example, `tt(:completion:complete:foo)' is
more specific than `tt(:completion:complete:*')), and longer patterns are
preferred over shorter patterns.

As for tags, completion functions can use any number of styles, so
there can't be a complete list. However, the following two sections
list those tags and styles that are used in many places of the
completion system.

subsect(Standard Tags)
cindex(completion system, tags)

Here are the tags currently used by the completion system. Note that
some of these tags are not actually used while generating matches,
but are only used by some completion functions when looking up
styles.

startitem()
item(tt(accounts))(
used to look up the tt(users-hosts) style
)
item(tt(all-files))(
for the names of all files
)
item(tt(all-expansions))(
used by the tt(_expand) completer when adding the string containing
all expansions
)
item(tt(arguments))(
when an argument of a command may be completed
)
item(tt(arrays))(
for names of array parameters
)
item(tt(association-keys))(
for keys of associative arrays (e.g. when completing inside a
subscript of such a parameter)
)
item(tt(bookmarks))(
when completing bookmarks (e.g. for URLs and the tt(zftp) function suite)
)
item(tt(builtins))(
for names of builtin commands
)
item(tt(characters))(
used for commands like tt(stty) when completing characters; also used
when completing character classes after a opening bracket
)
item(tt(colors))(
for color names
)
item(tt(commands))(
for names of external commands and names of sub-commands (used by some 
commands like tt(cvs))
)
item(tt(corrections))(
used by the tt(_approximate) and tt(_correct) completers for the possible
corrections
)
item(tt(cursors))(
for cursor names used by X programs
)
item(tt(cvs))(
used only to look up the value of the tt(disable-stat) style
)
item(tt(default))(
used to look up default values for various styles that may also be set 
for tags that are used when generating matches
)
item(tt(descriptions))(
used when looking up the value of the tt(format) style for
descriptions
)
item(tt(devices))(
for names of device special files
)
item(tt(directories))(
for names of directories
)
item(tt(directory-stack))(
for entries in the directory stack
)
item(tt(displays))(
for X display names
)
item(tt(domains))(
for network domains
)
item(tt(expansions))(
used by the tt(_expand) completer for possible expansions
)
item(tt(extensions))(
for X server extensions
)
item(tt(files))(
used by completion functions that can complete some kind of filenames
and different types of matches
)
item(tt(fonts))(
used for X font names
)
item(tt(functions))(
names of functions (shell functions or other kinds of functions for
some commands)
)
item(tt(globbed-files))(
for names of files matching the glob pattern used by completion
functions that expect a certain type of file
)
item(tt(groups))(
used when completing names of user groups
)
item(tt(history-words))(
for words from the history
)
item(tt(hosts))(
for hostnames
)
item(tt(indexes))(
used for array indexes
)
item(tt(jobs))(
used for jobs
)
item(tt(keymaps))(
for names of zsh keymaps
)
item(tt(keysyms))(
for names of X keysyms
)
item(tt(local-directories))(
for names of directories in the current working directory when
completing for the tt(cd) builtin command
)
item(tt(libraries))(
for names of system libraries
)
item(tt(limits))(
for system limits
)
item(tt(manuals))(
for names of manual pages
)
item(tt(maps))(
for map names (e.g. YP maps)
)
item(tt(messages))(
used to look up the tt(format) style for messages
)
item(tt(modifiers))(
for names of X modifiers
)
item(tt(modules))(
for modules (e.g. tt(zsh) modules)
)
item(tt(my-accounts))(
used to look up the tt(users-hosts) style
)
item(tt(named-directories))(
for named directories (you wouldn't have guessed that, would you?)
)
item(tt(names))(
for all kinds of names
)
item(tt(nicknames))(
for nicknames of YP maps
)
item(tt(options))(
for command options
)
item(tt(original))(
used by the tt(_approximate), tt(_correct) and tt(_expand) completers when
adding the original string
)
item(tt(other-accounts))(
used to look up the tt(users-hosts) style
)
item(tt(packages))(
for packages (e.g. tt(rpm) packages)
)
item(tt(parameters))(
for names of parameters
)
item(tt(path-directories))(
for names of directories in directories from the tt(cdpath) array when
completing for the tt(cd) builtin command
)
item(tt(paths))(
used to look up the values of the tt(expand), tt(cursor) and
tt(special-dirs) styles
)
item(tt(pods))(
for perl pods
)
item(tt(ports))(
for communication ports
)
item(tt(prefixes))(
for prefixes (like those of an URL)
)
item(tt(printers))(
for printer names
)
item(tt(processes))(
for process identifiers
)
item(tt(ps))(
used to look up the tt(arguments) and tt(list-arguments) styles
)
item(tt(sequences))(
for sequences (e.g. tt(mh) sequences)
)
item(tt(sessions))(
for sessions in the tt(zftp) function suite
)
item(tt(signals))(
for signal names
)
item(tt(strings))(
for strings (e.g. the replacement strings for the tt(cd) builtin
command)
)
item(tt(tags))(
for tags (e.g. tt(rpm) tags)
)
item(tt(targets))(
for makefile targets
)
item(tt(types))(
for types of whatever (e.g. adress types for the tt(xhost) command)
)
item(tt(urls))(
used to look up the tt(path) and tt(local) styles when completing URLs
)
item(tt(users))(
for usernames
)
item(tt(values))(
when completing a value out of a set of values (or a list of such
values)
)
item(tt(warnings))(
used to look up the tt(format) style for warnings
)
item(tt(widgets))(
for zsh widget names
)
item(tt(windows))(
for IDs of X windows
)
item(tt(zsh-options))(
for shell options
)
enditem()

subsect(Standard Styles)
cindex(completion system, styles)

Here are the names of the styles used by the completion system. Note
that the values of several of these styles represent boolean
values. In all these cases any of the strings `tt(true)', `tt(on)',
`tt(yes)', and `tt(1)' can be used for the truth value `true' and
the strings `tt(false)', `tt(off)', `tt(no)', and `tt(0)' are
interpreted as `false'.  The behavior for any other value is undefined 
unless the description for the particular style mentions other
possible values.

startitem()
item(tt(accept-exact))(
This is tested for the default tag and the tags used when generating
matches. If it is set to `true' for at least one match which is the
same as the string on the line, this match will immediately be
accepted.
)
item(tt(arguments))(
The value of this style is given to the tt(ps) command by functions
that call it when generating process identifiers as matches.
)
item(tt(auto-description))(
If set, this style's value will be used as the description for options which
are not described by the completion functions, but that have exactly
one argument. The sequence `tt(%d)' in the value will be replaced by
the description for this argument. Depending on personal preferences,
it may be useful to set this style to something like `tt(specify: %d)'. 
Note that this may not work for some commands.
)
item(tt(completer))(
The strings given as the value of this style give the names of the
completer functions to use. The available completer functions are
described in
ifzman(the section `Control Functions' below)\
ifnzman(noderef(Control Functions))\
.

Note that the widget functions from the distribution that call the
completion code (namely, the tt(incremental-complete-word) and the
tt(predict-on) widgets) set up their top-level context name before
calling completion. This allows one to define different sets of
completer functions for normal completion and for these widgets. For
example, to use completion, approximation and correction for normal
completion, completion and correction for incremental completion and
only completion for prediction one could use:

example(zstyle ':completion:*' completer _complete _correct _approximate
zstyle ':completion:incremental' completer _complete _correct
zstyle ':completion:predict' completer _complete)
)
item(tt(completions))(
This style is used by the tt(_expand) completer function.

If this is set to an non-empty string it should be an expression
usable inside a `tt($((...)))' arithmetical expression. The completer
function evaluates this expression and if the result is `tt(1)', no
expansions will be generated, but instead the completions will be
generated as normal and all of them will be inserted into the command
line.
)
item(tt(condition))(
This style is used by the tt(_list) completer function.

If it is not set or set to the empty string, the insertion of
matches will be delayed unconditionally. If it is set, the value
should be an expression usable inside a `tt($((...)))'
arithmetical expression. In this case, delaying will be done if the
expression evaluates to `tt(1)'. For example, with

example(zstyle ':completion:list' condition 'NUMERIC != 1')

delaying will be done only if given an explicit numeric argument
other than `tt(1)'.
)
item(tt(cursor))(
This is used together with the tt(paths) tag by the function
generating filenames as matches to find out if the cursor should be left
after the first ambiguous pathname component even when menucompletion
is used.
)
item(tt(disable-stat))(
This is used with the tt(cvs) tag by the function completing for the
tt(cvs) command to decide if the tt(zsh/stat) module should be used to
generate only names of modified files in the appropriate places.
)
item(tt(domains))(
If set, gives the names of network domains that should be
completed. If this is not set by the user domain names mentioned in
tt(/etc/resolv.conf) will be used.
)
item(tt(expand))(
Like tt(cursor), this style is used with the tt(paths) tag. If its
value contains the string tt(prefix), the partially typed path from
the line will be expanded as far as possible even if trailing pathname
components can not be completed. If it contains the string tt(suffix)
and normal (non-menu-) completion is used, matching names for
components after the first ambiguous one will be added, too. This
means that the resulting string is the longest unambiguous string
possible, but if menucompletion is started on the list of matches
generated this way (e.g. due to the option tt(AUTO_MENU) being set),
this will also cycle through the names of the files in pathname
components after the first ambiguous one.
)
item(tt(file-patterns))(
The completion system uses two functions to complete filenames,
tt(_files) and tt(_path_files), with one of them calling the other,
but this second one is sometimes also called directly. Depending on
how it is called, the first one uses the tags tt(globbed-files),
tt(directories) and tt(all-files). The second one, when called
directly, uses the tag tt(files).

Using this style one can specify which filenames should be completed
in certain contexts. It is tested by tt(_files) and, if called
directly, tt(_path_files) with the tags mentioned above. If it is set
for these tags, the value is taken as a list of glob-patterns that
should be used to select filenames when completing for the tag. Note
that with tt(_files), calling completion function may specify that
all files are to be completed. Normally this would make tt(_files) use 
only the tt(all-files) tag, but if this style is set for any of the
other two tags (tt(globbed-files) and tt(directories)), these tags
will be used, too, in the normal order given above (unless the user
specified another order to be used with the tt(tag-order) style).

For example, to make the completion system first try only filenames
matching the pattern tt(*.o) for the tt(rm) command, one would use:

example(zstyle ':completion:*::rm*:globbed-files' file-patterns '*.o')

With this, using only filenames ending in tt(.o) will be the first
choice and other filenames will only be used if what is on the line
matches none of the tt(.o) files (or if there are none).

Note also that during the execution of completion functions, the
tt(EXTENDED_GLOB) option is in effect, so the characters `tt(#)',
`tt(~)' and `tt(^)' have special meanings in the patterns.
)
item(tt(format))(
If this is set for the tt(descriptions) tag, its value is used as a
string to display above matches in completion lists. The sequence
`tt(%d)' in this string will be replaced with a short description of
what these matches are. This string may also contain the sequences to
specify output attributes, such as `tt(%b)' and `tt(%s)'.

For the same purpose, this style is also tested with the tags used
when matches are generated before it is tested for the
tt(descriptions) tag. This gives the possibility to define different
format strings for different types of matches.

Note also that some completer functions define additional
`tt(%)'-sequences. These are described for the completer function that 
make use of them.

For the tt(messages) tag, this defines a string used by some
completion functions to display messages. Here, the `tt(%d)' is
replaced with the message given by the completion function.

Finally, for the tt(warnings) tag, it is printed when no matches could 
be generated at all. In this case the `tt(%d)' is replaced with the
descriptions for the matches that were expected.

Here and in all other cases where the completion system uses `tt(%)'
sequences, the `tt(%)' may be followed by field with specifications as 
described for the tt(zformat) builtin command from the tt(zutil)
module, see
ifzman(zmanref(zshmodules))\
ifnzman(noderef(The zsh/zutil Module))\
.
)
item(tt(glob))(
Like tt(completions), this is used by the tt(_expand) completer.

The value is used like the one for tt(completions) and if it evaluates to 
`tt(1)', globbing will be attempted on the words resulting from
substitution (see the tt(substitute) style) or the original string
from the line.
)
item(tt(group-name))(
The completion system can put different types of matches in different
groups which are then displayed separately in the list of possible
completions. This style can be use to give the names for these groups
for particular tags. For example, in command position the completion
system generates names of builtin and external commands, names of
aliases and shell functions and reserved words as possible
completions. To have the external commands and shell functions listed
separately, one can set:

example(zstyle ':completion:*:-command-:commands' group-name commands
zstyle ':completion:*:-command-:functions' group-name functions)

This also means that if the same name is used for different types of
matches, then those matches will be displayed together in the same
group.

If the name given is the empty string, then the name of the tag for
the matches will be used as the name of the group. So, to have all
different types of matches displayed separately, one can just set:

example(zstyle ':completion:*' group-name '')

All matches for which no group name is defined will be put in a group
named tt(-default-).
)
item(tt(group-order))(
This style is to be used together with the tt(group-name) style. Once
different types of matches are put into different groups, this style
can be used to define in which order these groups should appear in the 
list. The strings in the value are taken as group names and the named
groups will be shown in the order in which their names appear in the
value. All groups whose names are not given in the value of this style 
will appear in the order defined by the function generating the
matches.

For example, to have names of builtin commands, shell functions and
external commands appear in this order when completing in command
position one would set:

example(zstyle ':completion:*:-command-' group-order builtins functions commands)
)
item(tt(groups))(
A style holding the names of the groups that should be completed. If
this is not set by the user, the group names from the YP database or
the file `tt(/etc/group)' will be used.
)
item(tt(hidden))(
If this is set to one of the `true' values, the matches for the tags
for which this is set will not appear in the list; only the
description for the matches as set with the tt(format) style will be
shown. If this is set to tt(all), not even the description will be
displayed.

Note that the matches will still be completed, they are just not shown 
in the list. To avoid having matches considered as possible
completions at all the tt(tag-order) style can be modified as described
below.
)
item(tt(hosts))(
A style holding the names of hosts that should be completed. If this
is not set by the user the hostnames in `tt(/etc/hosts)' will be used.
)
item(tt(hosts-ports))(
This style is used by commands that need or accept hostnames and
ports. The strings in the value should be of the form
`var(host)tt(:)var(port)'. These hostnames and ports are completed
depending on the information already on the line, so that if, for
example, the hostname is already typed, only those ports will be
completed for which pairs with the hostname from the line exist.
)
item(tt(hosts-ports-users))(
Like tt(hosts-ports) but used for commands like tt(telnet) and
containing strings of the form `var(host)tt(:)var(port)tt(:)var(user)'.
)
item(tt(ignore-parents))(
When completing files it is possible to make names of directories
already mentioned on the line or the current working directory be
ignored. The style is tested for the tt(files) tag and if its value
contains the string tt(parent), then the name of any directory whose
path is already contained in the word on the line is ignored. For
example, when completing after tt(foo/../), the directory tt(foo) will
not be considered a valid completion.

If the style contains the string tt(pwd), then the name of the current 
working directory will not be completed, so that, for example,
completion after tt(../) will not use the name of the current
directory.

If the style contains the string tt(..) both tests will only be
performed if the word on the line contains the substring tt(../) and
if the value contains the string tt(directory), then the tests will
only be performed if only names of directories are completed.

Note that names of directories ignored because of one of the tests
will be placed in the alternate set of completions so that they will
be completed if there are no other possible completions.
)
item(tt(ignored-patterns))(
This style is used with the tags used when adding matches and gives a
number of patterns. All matches that are matched by any of these
patterns will be ignored as long as there are other matches not
matched by any of the patterns.  It is a more configurable version
of the shell parameter tt($fignore).

Note that during the execution of completion functions, the
tt(EXTENDED_GLOB) option is in effect, so the characters `tt(#)',
`tt(~)' and `tt(^)' have special meanings in the patterns.
)
item(tt(insert-unambiguous))(
This is used by the tt(_match) and tt(_approximate) completer
functions. If it is set to `true', the completer will start menu
completion only if no unambiguous string could be generated that is at
least as long as the original string from the line.
)
item(tt(last-prompt))(
This is used to determine if the completion code should try to put the
cursor back onto the previous command line after showing a completion
listing (as for the tt(ALWAYS_LAST_PROMPT) option). Like several other 
styles it is tested for the tt(default) tag and all tags used when
generating matches. The cursor will be moved back to the previous line 
if this style is `true' for all types of matches added. Note also that 
this is independent of the numeric argument -- unlike the
tt(ALWAYS_LAST_PROMPT) option.
)
item(tt(list))(
This is used by the tt(_oldlist) completer (context
`tt(:completion:oldlist)'), the tt(_history_complete_word) bindable command
(context `tt(:completion:history-words)') and by the
tt(incremental-complete-word) widget (context `tt(:completion:incremental)).

For tt(_oldlist), if this is set to tt(always), then standard
widgets which perform listing will retain the current list of matches,
however they were generated.  If it is set to tt(never), this will not
be done (the behaviour without the tt(_oldlist) completer).  If it is
unset, or any other value, then the existing list of completions will
be displayed if it is not already; otherwise, the standard completion
list will be generated:  this is the default behaviour of
tt(_oldlist). However, if there is an old list and this style contains
the name of the completer function that generated the list, then the
old list will be used even if it was generated by a widget which does
not do listing.

For example, suppose you type tt(^Xc) to use the tt(_correct_word)
widget, which generates a list of corrections for the word under the
cursor.  Usually, typing tt(^D) would generate a standard list of
completions for the word on the command line, and show that.  With
tt(_oldlist), it will instead show the list of corrections already
generated.

As another example consider the tt(_match) completer: with the
tt(insert-unambiguous) style set to `true' it inserts only an
unambiguous prefix string if there is any. But since this may remove
parts of the original pattern, attempting completion again may result
in more matches than on the first attempt. But by using the
tt(_oldlist) completer and setting this style to tt(_match), the list of 
matches generated on the first attempt will be used again.

The tt(_history_complete_word) bindable command uses this style to
decide if the available matches should be shown.

When using the tt(incremental-complete-word) widget, this style says
if the matches should be listed on every key press (if they fit on the 
screen).
)
item(tt(list-arguments))(
Like the tt(arguments) style, but used when calling the tt(ps) command 
to generate the list to display.
)
item(tt(list-colors))(
If the tt(zsh/complist) module is used, this style can be used to set
color specifications as with the tt(ZLS_COLORS) and tt(ZLS_COLOURS)
parameters (see
ifzman(the section `The zsh/complist Module' in zmanref(zshmodules))\
ifnzman(noderef(The zsh/complist Module))\
).

If this style is set for the tt(default) tag, the strings in the value 
are taken as specifications that are to be used everywhere. If it is
set for other tags, the specifications are used only for matches of
the type described by the tag.

To be able to share the same specifications one has set up for the GNU
version of the tt(ls) command one can use:

example(zstyle ':completion:*:default' list-colors ${(s.:.)LS_COLORS})

And to get the default colors (which are the same as for the GNU
tt(ls) command) one should set the style to an empty value.
)
item(tt(list-packed))(
Like the tt(list-colors) style, this is tested with the tt(default)
tag and all tags used when generating matches. If it is set to `true'
for a tag, the matches added for it will be listed as if the
tt(LIST_PACKED) option were set for them. If it is set to `false',
they are listed normally.
)
item(tt(list-rows-first))(
This style is tested like the tt(list-packed) style and determines if
matches are to be listed in a rows-first fashion, as for the
tt(LIST_ROWS_FIRST) option.
)
item(tt(local))(
This style is used by completion functions which generate URLs as
possible matches to add suitable matches when a URL points to a
local web server. Its value should consist of three strings: a
hostname, the path to the default web pages for the server and the
directory name used by a user placing web pages within their home
area.
)
item(tt(matcher))(
This style is tested for tags used when generating matches. Its value
is used as an additional match specification to use when adding the
matches as described in
ifzman(the section `Matching Control' in zmanref(zshcompwid))\
ifnzman(noderef(Matching Control))\
.
)
item(tt(max-errors))(
This is used by the tt(_approximate) and tt(_correct) completer functions
to determine the maximum number of errors to accept. The completer will try
to generate completions by first allowing one error, then two errors, and
so on, until either a match was found or the maximum number of errors
given by this style has been reached.

If the value for this style contains the string tt(numeric), the 
completer function will take any numeric argument as the
maximum number of errors allowed. For example, with

example(zstyle ':completion:approximate' accept 2 numeric)

two errors will be allowed if no numeric argument is given. However,
with a numeric argument of six (as in `tt(ESC-6 TAB)'), up to six
errors are accepted.  Hence with a value of `tt(0 numeric)', no correcting
completion will be attempted unless a numeric argument is given.

If the value contains the string tt(not-numeric), the completer
will em(not) try to generate corrected
completions when given a numeric argument, so in this case the number given
should be greater than zero.  For example, `tt(2 not-numeric)' specifies that
correcting completion with two errors will usually be performed, but if a
numeric argument is given, correcting completion will not be performed.
)
item(tt(menu))(
This style is tested for the tt(default) tag and the tags used when
adding matches. The value should be one of the `true' values (tt(yes), 
tt(true), tt(1), or tt(on)) if menu completion should be started when
matches for the given tag (or always in case of the tt(default) tag)
are generated. If none of these values is defined for any of the tags
used, but for at least one of these tags the value is the string
tt(auto), this says that the same behavior as for the tt(AUTO_MENU)
option should be used. Finally, if menucompletion is started by some 
other means (e.g. by setting the tt(MENU_COMPLETE) option) and the
value for one of the tags used is `false' (i.e. tt(no), tt(false),
tt(0), or tt(off)), then menucompletion will em(not) be started for
this completions. Note that the values defined for normal tags
override the value set for the tt(default) tag.

Either instead of or in addition to one of the values above, the value
for this style may also contain the string tt(select), optionally
followed by an equal sign and a number. In this case menuselection
(as defined by the tt(zsh/computil) module) will be started. Without the
optional number, it will be started unconditionally and with a number
it will be started only if at least that many matches are generated
(if the values for more than one tag defines such a number, the
smallest one is taken). Starting menuselection can explicitly be
turned off by defining a value containing the string
tt(no-select). Note that all this only works if the tt(complist)
module is explicitly loaded by the user, though.

This is also used by the tt(_oldlist) completer. Here it controls how menu
completion behaves when a completion has already been inserted and the
user types a standard completion key type such as tt(TAB). The default
behaviour of tt(_oldlist) is that menu completion always continues
with the existing list of completions.  If this style is set to
`false', however, a new completion is started if the old list was
generated by a different completion command (the behaviour without the 
tt(_oldlist) completer).

For example, suppose you type tt(^Xc) to generate a list of corrections,
and menu completion is started in one of the usual ways.  Usually, typing
tt(TAB) at this point would start trying to complete the line as it now
appears.  With tt(_oldlist), it will instead continue to cycle through the
list of completions.
)
item(tt(numbers))(
This is used with the tt(jobs) tag. If it is `true', the completions
will use the job numbers instead of the shortest unambiguous strings
of the jobs' command lines. If the value is a number, job numbers will 
only be used if for at least one of the jobs that many (or more) words 
from the command line string have to be used to make the strings
unambiguous. E.g. if it is set to `tt(1)', strings will only be used
if all jobs differ in the first word on their command lines.
)
item(tt(original))(
This is used by the tt(_approximate), tt(_correct) and tt(_match)
completers. The first two use it to decide if the original string should
be added as one possible completion. Normally, this is done only if there
at least  two possible corrections, but if this style is set to `true', it
will always be added.

For the tt(_match) completer, if this style is set to
tt(only), it will try to generate matches without inserting a
`tt(*)' at the cursor position. If set to any other non-empty value,
it will first try to generate matches without inserting the `tt(*)'
and if that yields no matches, it will try again with the `tt(*)'
inserted.
)
item(tt(path))(
This is used together with the the tt(urls) tag by completion
functions that generate URLs as possible matches. It should be set to
the path of a directory containing sub-directories named like
`tt(http)', `tt(ftp)', `tt(bookmark)', and so on. These
sub-directories should contain files and other sub-directories whose
pathnames are possible completions after the initial `tt(http://)',
`tt(ftp://)', etc. See the description in the file tt(_urls) in the
tt(User) sub-directory of the completion system for more information.

Also, the function that completes color names uses this style with the 
tt(colors) tag. Here, the value should be the pathname of a file
containing color names in the format of an X11 tt(rgb.txt) file. That
file (if it can be found) will be used as the default if the style is
not set.
)
item(tt(ports))(
A style holding the service names of ports to complete. If this is
not set by the user, the service names from `tt(/etc/services)' will
be used.
)
item(tt(prefix-hidden))(
This is used when matches with a common prefix are added (e.g. option
names). If it is `true', this prefix will not be shown in the list of
matches.
)
item(tt(prefix-needed))(
This, too, is used for matches with a common prefix. If it is set to
`true' this common prefix has to be typed by the user to generate the
matches. E.g. for options this means that the `tt(-)', `tt(+)', or
`tt(-)tt(-)' has to be on the line to make option names be completed at
all.
)
item(tt(prompt))(
The tt(incremental-complete-word) widget shows the value of this
style in the status line during incremental completion. The sequence
`tt(%u)' is replaced by the unambiguous part of all matches if there
is any and it is different from the word on the line. A `tt(%s)' is
replaced with `tt(-no match-)', `tt(-no prefix-)', or an empty string
if there is no completion matching the word on the line, if the
matches have no common prefix different from the word on the line or
if there is such a common prefix, respectively. The sequence `tt(%c)'
is replaced by the name of the completer function that generated the
matches (without the leading underscore). Finally, `tt(%n)' is
replaced by the number of matches generated, `tt(%a)' is replaced by
an empty string if the matches are in the normal set (i.e. the one
without file names with one of the suffixes from the
tt(ignored-suffixes) style) and with `tt( -alt-)' if the matches are
in the alternate set, and if the tt(list) style is set, `tt(%l)' is
replaced by `tt(...)' if the list of matches is too long to fit on the
screen and with an empty string otherwise. If the tt(list) style is
`false', `tt(%l)' will always be removed.
)
item(tt(remove-all-dups))(
The tt(_history_complete_word) bindable command uses this to decide if 
all duplicate matches should be removed, rather than just consecutive
duplicates.
)
item(tt(sort))(
If set to `true', completion functions that generate words from the
history as possible matches sort these words alphabetically instead of
keeping them in the order in which they appear in the history (from
youngest to oldest).

The completion function that generates filenames as possible matches
uses this style with the tt(files) tag to determine in which order the 
names should be listed and completed when using menucompletion. The
value may be one of tt(size) to sort them by the size of the file,
tt(links) to sort them by the number of links to the file,
tt(modification) (or tt(time) or tt(date)) to sort them by the last
modification time, tt(access) to sort them by the last access time, or 
tt(inode) (or tt(change)) to sort them by the last inode change
time. Any other value (or not setting this style at all) makes them be 
sorted alphabetically by name. If the value contains the string
tt(reverse), sorting is done in decreasing order.

This is also used by the tt(_expand) completer. Here, if it is set to
`true', the expansions generated will always be sorted. If it is set
to tt(menu), then the expansions are only sorted when they are offered 
as single strings (not in the string containing all possible
expansions).
)
item(tt(special-dirs))(
Normally, the completion code will not produce the directory names
tt(.) and tt(..) as possible completions. If this style is set to
`true', it will add both `tt(.)' and `tt(..)' as possible completions,
if it is set to tt(..), only `tt(..)' will be added.
)
item(tt(squeeze-slashes))(
If set to `true', sequences of slashes (like in `tt(foo//bar)') will be
treated as if they were only one slash when completing pathnames.
)
item(tt(stop))(
If set to `true', the tt(_history_complete_word) bindable
command will always insert matches as if menucompletion were started
and it will stop when the last match is inserted. If this style is set
to tt(verbose) a message will be displayed when the last match is reached.
)
item(tt(substitute))(
If this is unset or set to the empty string, the tt(_expand) completer
will first try to expand all substitutions in the string (such as
`tt($LPAR()...RPAR())' and `tt(${...})'). If this is set to an
non-empty string it should be an expression usable inside a `tt($((...)))'
arithmetical expression. In this case, expansion of substitutions will
be done if the expression evaluates to `tt(1)'. For example, with

example(zstyle ':completion:expand' substitute '${NUMERIC:-1} != 1')

substitution will be performed only if given an explicit numeric
argument other than `tt(1)', as by typing `tt(ESC 2 TAB)'.
)
item(tt(tag-order))(
This provides a mechanism for sorting how the tags available in a
particular context will be used.

The values for the style are sets of space-separated lists of tags.
The tags in each value will be tried at the same time; if no match is
found, the next value is used.

For example,

example(
  zstyle :completion:complete::gunzip: tag-order \ 
    'globbed-files directories' all-files
)

specifies that, when completing arguments of the command tt(gunzip),
files generated by patterns (in this case, those ending in tt(.gz)) and
any directories will be presented first, and if that fails, any other files
will be tried.  A string starting with an exclamation mark (`tt(!)')
specifies names of tags that are not to be used -- the effect will be
the same as if all other possible tags for the context had been
listed.  If any string in the value consists of only a hyphen
(`tt(-)'), then only the tags selected by the other strings will be
generated.  Normally all tags not explicitly selected will be tried at
the end if the selected tags did not generate any matches.  This means 
that a value of only one hyphen turns off completion in a particular
context.

Strings in the value may also be of the form `var(func)tt(())'. In
this case the function var(func) will be called which can then define
in which order tags are to be used based on additional context
information. See the tt(_sort_tags) function below for a description
of how such functions can be implemented.

If no style has been defined for a context, all tags will be used.
)
item(tt(users))(
This may be set to a list of names that should be completed whenever 
a username is needed. If it is not set or the string on the line
doesn't match any of the strings in this list, all usernames will be
completed.
)
item(tt(users-hosts))(
The values of this style should be of the form
`var(user)tt(:)var(host)'. It is used for commands that need pairs of
user- and hostnames. For such commands, only the pairs from this style 
are used and if, for example, the username is already typed, then only 
the hostnames for which there is a pair with that username is defined.

If set for the tt(my-accounts) tag, this is used for commands such as
tt(rlogin) and tt(ssh). I.e. the style should contain the names of the 
user's own accounts. With the tt(other-accounts) this is used for
commands such as tt(talk) and tt(finger) and should contain other
people's accounts. Finally, this may also used by some commands with
the tt(accounts) tag.
)
item(tt(verbose))(
This is used in several contexts to decide if only a simple or a
verbose list of matches should be generated. For example some commands 
show descriptions for option names if this style is true.
)
item(tt(word))(
To find out if listing should be performed on its own, the tt(_list)
completer normally compares the contents of the line with the contents
the line had at the time of the last invocation. If this style is set to
`true', comparison is done using only the current word. In this case,
attempting completion on a word equal to the one when completion was called
the last time will not delay the generation of matches.
)
enditem()

texinode(Control Functions)(Bindable Commands)(Completion System Configuration)(Completion System)
sect(Control Functions)
cindex(completion system, choosing completers)

The initialization script tt(compinit) redefines all the widgets
which perform completion to call the supplied widget function
tt(_main_complete). This function acts as a wrapper calling the
so-called `completer' functions that generate matches. If
tt(_main_complete) is called with arguments, these are taken as the
names of completer functions to be called in the order given.  If no
arguments are given, the set of functions to try is taken from the
tt(completer) style. For example, to use normal completion and
correction if that doesn't generate any matches:

example(zstyle ':completion:*' completer _complete _correct)

after calling tt(compinit). The default value for this style set up
in tt(compinit) is `tt(_complete)', i.e. normally only ordinary
completion is tried. The tt(_main_complete) function uses the return
value of the completer functions to decide if other completers should be
called. If the return value is zero, no other completers are tried and the
tt(_main_complete) function returns.

Immediately before returning the tt(_main_complete) function calls all
functions whose names are given in the tt(comppostfuncs) array and
then resets it to an empty array. This can be used by completion
functions or by other ZLE widgets calling completion to register code
that is to be executed after all matches have been added.

The following completer functions are contained in the distribution (users
may write their own):

cindex(completion system, completers)
startitem()
findex(_complete)
item(tt(_complete))(
This completer generates all possible completions in a context-sensitive
manner, i.e. using the settings defined with the tt(compdef) function
explained above and the current settings of all special parameters.

To complete arguments of commands, tt(_complete) uses the utility function
tt(_normal), which is in turn responsible for finding the particular
function; it is described below.  Various contexts of the form
tt(-)var(context)tt(-), as mentioned above for the tt(#compdef) tag, are
handled specially.  These are:

startitem()
item(tt(-equal-))(
for completion after an equal sign, other than one occurring in a
shell-variable assignment.
)
item(tt(-tilde-))(
for completion after a tilde (`tt(~)') character, but before a slash.
)
item(tt(-redirect-))(
for completion after a redirection operator.
)
item(tt(-math-))(
for completion inside mathematical contexts, such as
`tt(LPAR()LPAR())...tt(RPAR()RPAR())'.
)
item(tt(-subscript-))(
for completion inside subscripts.
)
item(tt(-value-))(
for completion on the right hand side of an assignment.
)
item(tt(-array-value-))(
for completion on the right hand side of an array-assignment
(`tt(foo=LPAR()...RPAR())').
)
item(tt(-condition-))(
for completion inside conditions (`tt([[...]])').
)
item(tt(-parameter-))(
for completing the name of a parameter expansion (`tt($...)').
)
item(tt(-brace-parameter-))(
for completing the name of a parameter expansion within braces
(`tt(${...})').
)
item(tt(-first-))(
for adding completions before any other completion functions are
tried; if this
function sets the tt(_compskip) parameter to tt(all), no other
completion functions will be called, if it is set to a string
containing the string tt(patterns), no pattern completion functions
will be called, and if it is set to a string containing tt(default)
the function for the `tt(-default-)' context will not be called, but
functions defined for commands will.
)
item(tt(-default-))(
for generating completions when no special completion function is used.
)
item(tt(-command-))(
for completing in a command position.
)
enditem()

Default implementations are supplied for each of these
contexts, in most cases named after the context itself
(e.g. completion for the `tt(-tilde-)' context is done by the function 
named `tt(_tilde)').

Before trying to find a function for a specific context, tt(_complete) 
checks if the parameter `tt(compcontext)' is set to a non-empty
value. If it is, the value is taken as the name of the context to use
and the function defined for that context will be called.
)
findex(_approximate)
item(tt(_approximate))(
This completer function uses the tt(_complete) completer to generate
a list of strings for the context the cursor is currently in, allowing 
you to specify a maximum number of errors:  see the description of
approximate matching in
ifzman(\
zmanref(zshexpn)
)\
ifnzman(\
noderef(Filename Generation)
)\
for how errors are
counted. The resulting list of corrected and completed strings is then
presented to the user. The intended use of this completer function is to
try after the normal tt(_complete) completer by setting:

example(zstyle ':completion:*' completer _complete _approximate)

This will give correcting completion if and only if
normal completion doesn't yield any possible completions. When
corrected completions are found, the completer will normally start
menucompletion allowing you to cycle through these strings.

This completer uses the tags tt(corrections) and tt(original) when
generating the possible coprrections and the original string. The
tt(format) style for the former may contain the additional sequences
`tt(%e)' and `tt(%o)' which will be replaced by the number of errors
accepted to generate the corrections and the original string,
respectively.

Like all completers tt(_approximate) uses its name without the
undersccore as the top-level context name. Once it has started trying
to generate matches, it will add another context name component
containing the number of errors accepted in this attempt. So on the
first try the context name starts with `tt(:approximate:1)', on the
second try with `tt(:approximate:2)', and so on.
)
findex(_correct)
item(tt(_correct))(
Generate corrections (but not completions) for the current word; this is
similar to spell-checking.  This calls tt(_approximate) but uses a
different top-level context name.

For example, with:

example(zstyle ':completion:*' completer _complete _correct _approximate
zstyle ':completion:correct' accept 2 not-numeric
zstyle ':completion:approximate' accept 3 numeric)

correction will accept up to two errors. If a numeric argument is
given, correction will not be performed, but correcting completion
will be, and will accept as many errors as given by the numeric
argument. Without a numeric argument, first correction and then
correcting completion will be tried, with the first one accepting two
errors  and the second one accepting three errors.

This completer function is intended to be used without the
tt(_approximate) completer or, as in the example, just before
it. Using it after the tt(_approximate) completer is useless since
tt(_approximate) will at least generate the corrected strings
generated by the tt(_correct) completer -- and probably more.
)
findex(_match)
item(tt(_match))(
This completer is intended to be used after the tt(_complete)
completer. It allows one to give patterns on the command line and
to complete all strings matching these patterns from the set of
possible completions for the context the cursor is in, without having
to set the tt(GLOB_COMPLETE) option.

Normally this will be done by taking the pattern from the line,
inserting a `tt(*)' at the cursor position and comparing the resulting
pattern with the possible completions generated. However, if the
tt(original) style has a value of tt(only), no `tt(*)' will be
inserted. If tt(original) has any other non-empty string as its
value, this completer will first try to generate matches without, then
with a `tt(*)' inserted at the cursor position.

The generated matches will be offered in a menucompletion unless the
tt(insert-unambiguous) style is set to `true'. In
this case menucompletion will only be started if no unambiguous string
could be generated that is at least as long as the original string.

Note that the matcher specifications defined globally or used by the
completion functions will not be used.
)
findex(_expand)
item(tt(_expand))(
This completer function does not really do completion, but instead
checks if the word on the command line is eligible for expansion and,
if it is, gives detailed control over how this expansion is done. When 
using this, one should not use the tt(expand-or-complete) widget, but
instead use tt(complete-word), as otherwise tt(expand-or-complete)
will expand the string on the line before the completion widget is
called. Also, this completer should be called before the tt(_complete) 
completer function.

The tags used when generating expansions are tt(all-expansions) for
the string containing all possible expansions, tt(expansions) when
adding the possible expansions as single matches and tt(original) when 
adding the original string from the line. In which order these strings 
are generated and which of these strings are generated at all can be
controlled by using the tt(group-order) style and by modifying the
tt(tag-order) style, as usual.

The format string for tt(all-expansions) and for tt(expansions) may
contain the sequence `tt(%o)' which will be replaced by the original
string from the line.

In a different mode selected by the tt(completions) style, all
em(completions) generated for the string on the line are inserted.
)
findex(_list)
item(tt(_list))(
This completer allows one to delay the insertion of matches until
completion is attempted a second time without the word on the line
being changed. On the first attempt, only the list of matches will be
shown. Styles used are tt(condition) and tt(word), see
ifzman(the section `Completion System Configuration' above)\
ifnzman(noderef(Completion System Configuration)).
)
findex(_menu)
item(tt(_menu))(
This completer is a simple example function implemented to show how
menucompletion can be done in shell code. It should be used as the
first completer and has the effect of making the code perform
menucompletion. Note that this is independent of the setting of the
tt(MENU_COMPLETE) option and does not work with the other
menucompletion widgets such as tt(reverse-menu-complete), or
tt(accept-and-menu-complete).
)
findex(_oldlist)
item(tt(_oldlist))(
This completer controls how the standard completion widgets behave
when there is an existing list of completions which may have been
generated by a special completion (i.e. a separately-bound completion
command).  It should appear in the list of completers before any of
the widgets which generate matches.  It uses two styles: tt(list) and
tt(menu), see
ifzman(the section `Completion System Configuration' above)\
ifnzman(noderef(Completion System Configuration)).
)
enditem()

texinode(Bindable Commands)(Completion Functions)(Control Functions)(Completion System)
sect(Bindable Commands)
cindex(completion system, bindable commands)

In addition to the context-dependent completions provided, which are
expected to work in an intuitively obvious way, there are a few widgets
implementing special behaviour which can be bound separately to keys.  The
following is a list of these and their default bindings.

startitem()
findex(_bash_completions)
item(tt(_bash_completions))(
This function is used by two widgets, tt(_bash_complete-word) and
tt(_bash_list-choices).  It exists to provide compatibility with
completion bindings in bash.  The last character of the binding determines
what is completed: `tt(!)', command names; `tt($)', environment variables;
`tt(@)', host names; `tt(/)', file names; `tt(~)' user names.  In bash, the
binding preceeded by `tt(\e)' gives completion, and preceeded by `tt(^X)'
lists options.  As some of these bindings clash with standard zsh
bindings, only `tt(\e~)' and `tt(^X~)' are bound by default.  To add the
rest, the following should be added to tt(.zshrc) after tt(compinit) has
been run:

example(for key in '!' '$' '@' '/' '~'; do
  bindkey "\e$key" _bash_complete-word
  bindkey "^X$key" _bash_list-choices
done)

This includes the bindings for `tt(~)' in case they were already bound to
something else; the completion code does not override user bindings.
)
findex(_correct_filename (^XC))
item(tt(_correct_filename (^XC)))(
Correct the filename path at the cursor position.  Allows up to six errors
in the name.  Can also be called with an argument to correct
a filename path, independently of zle; the correction is printed on
standard output.
)
findex(_correct_word) (^Xc)
item(tt(_correct_word) (^Xc))(
Performs correction of the current argument using the usual contextual
completions as possible choices. This uses the top-level context name
`tt(:correct-word)' and then calls the tt(_correct) completer.
)
findex(_expand_word (^Xe))
item(tt(_expand_word (^Xe)))(
Performs expansion on the current word:  equivalent to the standard
tt(expand-word) command, but using the tt(_expand) completer. Before
calling it, the top-level context name is set to `tt(:expand-word)'.
)
findex(_history_complete_word) (\e/)
item(tt(_history_complete_word) (\e/))(
Complete words from the shell's command history. This uses the
tt(list), tt(remove-all-dups), tt(sort), and tt(stop) styles.
)
findex(_most_recent_file (^Xm))
item(tt(_most_recent_file (^Xm)))(
Complete the name of the most recently modified file matching the pattern
on the command line (which may be blank).  If given a numeric argument
var(N), complete the var(N)th most recently modified file.  Note the
completion, if any, is always unique.
)
findex(_read_comp (^X^R))
item(tt(_read_comp (^X^R)))(
Prompt the user for a string, and use that to perform completion on the
current word.  There are two possibilities for the string.  First, it can
be a set of words beginning `tt(_)', for example `tt(_files -/)', in which
case the function with any arguments will be called to generate the
completions.  Unambiguous parts of the function name will be completed
automatically (normal completion is not available at this point) until a
space is typed.

Any other string will be passed as a set of arguments to
tt(compadd) and should hence be an expression specifying what should
be completed.

A very restricted set of editing commands is available when reading the
string:  `tt(DEL)' and `tt(^H)' delete the last character; `tt(^U)' deletes
the line, and `tt(^C)' and `tt(^G)' abort the function, while `tt(RET)'
accepts the completion.  Note the string is used verbatim as a command
line, so arguments must be quoted in accordance with standard shell rules.

Once a string has been read, the next call to tt(_read_comp) will use the
existing string instead of reading a new one.  To force a new string to be
read, call tt(_read_comp) with a numeric argument.
)
findex(_complete_help (^Xh))
item(tt(_complete_help (^Xh)))(
This widget displays information about the context names and tags used 
when completing at the current cursor position.
)
enditem()

texinode(Completion Functions)(Completion Directories)(Bindable Commands)(Completion System)
sect(Utility Functions)
cindex(completion system, utility functions)

Descriptions follow for utility functions that may be
useful when writing completion functions.  Most of these reside in the
tt(Core) subdirectory except where noted. Like the example 
functions for commands in the distribution, the utility functions
generating matches all follow the convention of returning zero if they
generated completions and non-zero if no matching completions could be 
added.

startitem()
findex(_funcall)
item(tt(_funcall) var(return) var(name) [ var(args) ... ])(
If a function var(name) exists, it is called with the arguments
var(args). Unless it is the empty string or a single hyphen,
var(return) is taken as the name of a parameter and the return status
from the called function is stored in it.
The return value of tt(_funcall) itself is zero if the function
var(name) exists and was called and non-zero otherwise.
)
findex(_compalso)
item(tt(_compalso) var(names) ...)(
This function looks up the definitions for the context and command
names given as arguments and calls the handler functions for them if
there is a definition (given with the tt(compdef) function). For
example, the function completing inside subscripts might use
`tt(_compalso -math-)' to include the completions generated for
mathematical environments.
)
findex(_normal)
item(tt(_normal))(
This function is used for normal command completion.  If
completion is attempted on the first word, command names are
completed. Otherwise, the arguments are completed by calling the
functions defined for this command, including those functions defined
for patterns matching the command name. This function can also be
called by other completion functions if they have to complete a range
of words as a separate command. For example, the function to complete after
the pre-command specifiers such as tt(nohup) removes the first word from
the tt(words) array, decrements the tt(CURRENT) parameter, then calls this
function.

When calling a function defined for a pattern, this function also
checks if the parameter tt(_compskip) is set and uses the value in the 
same way it is used after calling the completion function for the
tt(-first-) context. With this 
one can write a pattern completion function that keeps other functions 
from being tried simply by setting this parameter to any value.
)
findex(_description)
item(tt(_description) [ tt(-12VJ) ] var(tag) var(name) var(descr) [ var(specs) ... ])(
This function tests some styles for the var(tag) and and stores
options usable for tt(compadd) in the array with the given var(name)
which guarantee that the matches are generated as requested by the
user. The styles tested are: tt(format) (which is first tested for the
given tag and then for the tt(descriptions) tag if that isn't
defined), tt(hidden) and tt(group-name) (the last two are tested only
for the tag given as the first argument). This function also calls the
tt(_setup) function which tests some more styles.

The format string from the style (if any) will be modified so that the 
sequence `tt(%d)' is replaced by the var(descr) given as the third
argument. If tt(_description) is called with more than three
arguments, these var(specs) should be of the form
`var(char)tt(:)var(str)' and every appearance of `tt(%)var(char)' in
the format string will be replaced by var(string).

The options placed in the array will also make sure that the matches
are placed in a separate group, depending on the value of the
tt(group-name) style. Normally a sorted group will be used for this
(with the `tt(-J)' option), but if a option starting with `tt(-V)',
`tt(-J)', `tt(-1)', or `tt(-2)' is given, that option will be included
in the array, so that it is possible to make the group unsorted by
giving the option `tt(-V)', `tt(-1V)', or `tt(-2V)'. 

In most cases, this function will be used like this:

example(local expl
_description expl files file
compadd "$expl[@]" - "$files[@]")
)
findex(_message)
item(tt(_message) var(descr))(
The var(descr) is used like the third
argument to the tt(_description) function. However, the resulting
string will always be shown whether or not matches were
generated. This is useful to display help texts in places where no
completions can be generated automatically.

This function also uses the tt(format) style for the tt(messages) tag in
preference to the tt(format) style for the tt(descriptions) tag. The
latter is used only if the former is unset.
)
findex(_setup)
item(tt(_setup) var(tag))(
This function expects a tag as its argument and sets up the special
parameters used by the completion system appropriately for the tag,
using styles such as tt(list-colors) and tt(last-prompt).

Note that this function is called automatically from tt(_description)
so that one normally doesn't have to call it explicitly.
)
findex(_tags)
item(tt(_tags) [ tt(-C) var(name) [ var(tags) ... ] ])(
If called with arguments, these are taken as the names of the tags for 
the types of matches the calling completion function can generate in
the current context. These tags are stored internally and sorted by
using the tt(tag-order) style. Following calls to this function
without arguments from the same function will then select the first,
second, etc. set of tags requested by the user. To test if a certain
tag should be tried, the tt(_requested) function has to be called (see 
below).

The return value is zero if at least one of the tags is requested and
non-zero otherwise. 

This function also accepts the tt(-C) option followed by a
var(name). This name is temporarily (i.e. not visible outside
tt(_tags)) appended (with a colon before it) to the contents of the
tt(curcontext) parameter. This allows to make tt(_tags) use a more
specific context name without having to change and reset the
tt(curcontext) parameter (which would otherwise have the same effect).
)
findex(_requested)
item(tt(_requested) [ tt(-12VJ) ] var(tag) var(name) var(descr) [ var(specs) ... ])(
A function that uses tt(_tags) to register tags and then calls it to
loop over the requested sets of tags should call this function to
check if a certain tag is currently requested. This normally has to be 
done in a loop such as:

example(_tags foo bar baz
while _tags; do
  if _requested foo; then
    ...
  fi
  ... # test other tags
  ... # exit loop if matches were generated
done)

So, the first argument for tt(_requested) is used as the name of a tag 
and if that tag is currently requested, the return value is zero (and
non-zero otherwise).

If more than one argument is given, tt(_requested) calls the
tt(_description) function with all arguments, including the options.
This is often useful to do both the testing of the tag and
getting the description for the matches one is about to add at
once. E.g.:

example(local expl ret=1
_tags foo bar baz
while _tags; do
  _requested foo expl 'description' &&
      compadd "$expl[@]" foobar foobaz && ret=0
  ...
  (( ret )) || break
done)
)
findex(_wanted)
item(tt(_wanted) [ tt(-12VJ) ] var(tag) var(name) var(descr) [ var(specs) ... ])(
In many contexts only one type of matches can be generated but even
then it should be tested if the tag representing those matches is
requested by the user. This function makes that easier.

Like tt(_requested) it gets arguments as for tt(_description).
With the var(tag) it calls tt(_tags) and if that returns zero 
(i.e. the var(tag) is requested by the user) it calls tt(_description). So, 
if you want to offer only one tag and immediatly want to use the
description built, you can just do:

example(_wanted tag expl 'description' &&
    compadd "$expl[@]" matches...)

Note that you only need to use this function if you need a
description. If, for example, you use one of the utility functions
that adds a description itself, you only need to call tt(_tags) as in:

example(_tags tag && _helper)
)
findex(_alternative)
item(tt(_alternative) [ tt(-C) var(name) ] var(specs) ...)(
This function is useful if you offer multiple tags and building the
matches for them is easy enough. It basically implements a loop like
the one described above.

The tags to use and what to do if the tags are requested are described 
using the var(specs) which are of the form:
`var(tag)tt(:)var(descr)tt(:)var(action)'. The var(tag)s are offered
using tt(_tags) and if the tag is requested, the var(action) is
executed with the given var(descr) (description). The var(action)s
supported are those used by the tt(_arguments) function (described
below), without the `tt(->)var(state)' form.

For example, the var(action) may be a simple function call. With that
one could do:

example(_alternative \
    'users:user:_users' \
    'hosts:host:_hosts')

to offer usernames and hostnames as possible matches (which are
generated by the tt(_users) and tt(_hosts) functions respectively).

Like tt(_tags) this function supports the tt(-C) option to give an
additional context name component.
)
findex(_describe)
item(tt(_describe) var(descr) var(name1) [ var(name2) ] var(opts) ... tt(-)tt(-) ...)(
This function can be used to add options or values with descriptions
as matches. The var(descr) is taken as a string to display above
the matches if the tt(format) style for the tt(descriptions) tag is set.

After this one or two names of arrays followed by options to give
to tt(compadd) must be given. The first array contains the possible
completions with their descriptions (with the description separated
by a colon from the completion string). If the second array is given,
it should have the same number of elements as the first one and these
elements are added as possible completions instead of the strings from 
the first array. In any case, however, the completion list will show
the strings from the first array.

Any number of array/option sequences may be given separated by
`tt(-)tt(-)'. This allows one to display matches together that need
to be added with different options for tt(compadd).

Before the first argument, the option `tt(-o)' may be given. It says
that the matches added are option names. This will make tt(_describe)
use the tt(prefix-hidden), tt(prefix-needed) and tt(verbose) styles
to find out if the strings should be added at all and if the
descriptions should be shown. Without the `tt(-o)' option, only the
tt(verbose) style is used.
)
findex(_multi_parts)
item(tt(_multi_parts) var(sep) var(array))(
This function gets two arguments: a separator character and an
array.  As usual, the var(array) may be either the
name of an array parameter or a literal array in the form
`tt(LPAR()foo bar)tt(RPAR())' (i.e. a list of words separated by white 
space in parentheses). With these arguments, this function will
complete to strings from the array where the parts separated by the
separator character are completed independently. For example, the
tt(_tar) function from the distribution caches the pathnames from the
tar file in an array and then calls this function to complete these
names in the way normal filenames are completed by the
tt(_path_files) function.

Like other utility functions, this function accepts the `tt(-V)',
`tt(-J)', `tt(-1)', `tt(-2)', `tt(-n)', `tt(-X)', `tt(-M)', `tt(-P)',
`tt(-S)', `tt(-r)', `tt(-R)', and `tt(-q)' options and passes them to
the tt(compadd) builtin.
)
findex(_sep_parts)
item(tt(_sep_parts))(
This function gets as arguments alternating arrays and separators.
The arrays specify completions for parts of strings to be separated by the
separators. The arrays may be the names of array parameters or
a quoted list of words in parentheses. For example, with the array
`tt(hosts=(ftp news))' the call `tt(_sep_parts '(foo bar)' @ hosts)' will
complete the string  `tt(f)' to `tt(foo)' and the string `tt(b@n)' to
`tt(bar@news)'.

This function passes the `tt(-V)', `tt(-J)', `tt(-1)', `tt(-2)',
`tt(-n)', `tt(-X)', `tt(-M)', `tt(-P)', `tt(-S)', `tt(-r)', `tt(-R)',
and `tt(-q)' options and their arguments to the tt(compadd) builtin
used to add the matches.
)
findex(_path_files)
findex(_files)
item(tt(_path_files) and tt(_files))(
The function tt(_path_files) is used throughout the shell code
to complete filenames. It allows completion of partial paths. For
example, the string `tt(/u/i/s/sig)' may be completed to
`tt(/usr/include/sys/signal.h)'.  The option `tt(-/)' specifies that
only directories should be completed. The option `tt(-g) var(pattern)' 
says that only files matching the var(pattern) should be completed,
and the `tt(-f)' option, which is the default, completes all
filenames. The option `tt(-W) var(paths)' may be used to specify path
prefixes that are to be prepended to the string from the line to
generate the filenames but that should not be inserted in the line or
shown in a completion listing. The var(paths) may be the name of an
array parameter, a literal list of paths enclosed in parentheses or
an absolute pathname.
Additionally, the `tt(-F)'
option from the tt(compadd) builtin is supported, giving direct control
over which filenames should be ignored. If no such option is given,
the tt(ignored-suffixes) style is used.

The function tt(_files) calls tt(_path_files) with all the arguments
it was passed and, if that generated no matches, calls tt(_path_files) again
without any tt(-g) or tt(-/) option, thus generating all filenames.

These functions also accept the `tt(-J)', `tt(-V)', `tt(-1)',
`tt(-2)', `tt(-n)', `tt(-X)', `tt(-M)', `tt(-P)', `tt(-S)', `tt(-q)',
`tt(-r)', and `tt(-R)' options from the tt(compadd) builtin.

Finally, the tt(_path_files) function  uses the styles tt(expand),
tt(cursor) and tt(special-dirs) with the tt(paths) tag.
)
findex(_parameters)
item(tt(_parameters))(
This should be used to complete parameter names. All arguments are
passed unchanged to the tt(compadd) builtin.
)
findex(_options)
item(tt(_options))(
This can be used to complete option names. It uses a matching
specification that ignores a leading `tt(no)', ignores underscores and 
allows the user to type upper-case letters, making them match their
lower-case counterparts. All arguments passed to this function are
propagated unchanged to the tt(compadd) builtin.
)
findex(_set_options)
findex(_unset_options)
item(tt(_set_options) and tt(_unset_options))(
These functions complete only set or unset options, with the same
matching specification used in the tt(_options) function.

Note that you need to uncomment a few lines in the tt(_main_complete)
function for these functions to work properly. The lines in question
are used to store the option settings in effect before the completion
widget locally sets the options it needs.
)
findex(_arguments)
item(tt(_arguments) var(specs) ...)(
This function resides in the tt(Base) subdirectory of the example
completion system because it is not used by the core system.

This function can be used to complete words on the line by simply
describing the arguments the command on the line gets. The description 
is given as arguments to this function, with each var(spec) describing
one option or normal argument of the command. The descriptions
understood are:

startitem()
item(var(n)tt(:)var(message)tt(:)var(action))(
This describes the var(n)'th normal argument. The var(message) will be 
printed above the matches generated and the var(action) says what can
be completed in this position (see below). If there are two colons
before the var(message), this describes an optional argument.
)
item(tt(:)var(message)tt(:)var(action))(
Like the previous one, but describing the em(next) argument. I.e. if
you want to describe all arguments a command can get, you can leave
out the numbers in the description and just use this form to describe
them one after another in the order they have to appear on the line.
)
item(tt(*:)var(message)tt(:)var(action))(
This describes how arguments are to be completed for which no
description with one of the first two forms was given. This also means 
that any number of arguments can be completed.

If there are two colons before the var(message) (as in
`tt(*::)var(message)tt(:)var(action)') the tt(words) special array and 
the tt(CURRENT) special parameter will be restricted to only the
normal arguments when the var(action) is executed or evaluated. With
three colons before the var(message) they will be restricted to only
the normal arguments covered by this description.
)
item(var(opt-spec)[var(description) ...])(
This describes an option and (if at least one var(description) is
given) the arguments that have to come after the option. If no
var(description) is given, this will only be used to offer the option
name as a possible completion in the right places. Each
var(description) has to be of the form
`tt(:)var(message)tt(:)var(action)' or
`tt(::)var(message)tt(:)var(action)', where the second form describes
an optional argument and the first one describes a mandatory argument.
The last description may also be of the form
`tt(:*:)var(message)tt(:)var(action)' or
`tt(:*)var(pattern)tt(:)var(message)tt(:)var(action)'. These describe
multiple arguments. In the first form all following words on the line
are to be completed as described by the var(action), in the second
form all words up to a word matching the given var(pattern) are to be
completed using the var(action). The `tt(*)' or the var(pattern) may
also be separated from the var(message) by two or three colons. With
two colons the tt(words) special array and the tt(CURRENT) special
parameter are modified to refer only to the words after the option
(with two colons) or to the words covered by this description (with
three colons) during the execution or evaluation of the
var(action). Note that only one such `tt(:*)'-specification is useful
and no other argument specification may be given after it.

In the simplest form the var(opt-spec) is just the option name
beginning with a minus or a plus sign, such as `tt(-foo)'. In this
case, the first argument for the option (if any) has to come as a
separate word directly after the option and the option may appear only 
once on the line (and if it is already on the line, the option name
will not be offered as a possible completion again). If the first
argument for the option has to come directly after the option name
em(in the same word), a minus sign should be added to the end of the
var(opt-spec), as in `tt(-foo-)'. If the first argument may be given
in one string with the option name, but may also be given as a
separate argument after the option, a plus sign should be used
instead. If the argument may be given as the next string or in same
string as the option name but separated from it by an equal sign, a
`tt(=)' should be used instead of the minus or plus sign.

If the option may be given more than once, a star
(`tt(*)') has to be added in front of the var(opt-spec).

An var(opt-spec) may also contain a list of other option names with
which the option described is mutually exclusive. Such a list is given 
in parentheses at the beginning, as in `tt((-two -three)-one:...)'. In 
this example, the options `tt(-two)' and `tt(-three)' will not be
offered as possible completions if the option `tt(-one)' is on the
line. Also, the list may contain a single colon as one of its elements 
to specify that the descriptions for normal (non-option-) arguments
should not be used if the option described is on the line.

Finally, the var(opt-spec) may contain a explanation string. This is
given in brackets at the end, as in `tt(-q[query operation])'. The
tt(verbose) style is used to decide if these
explanation strings should be printed when options are listed. If no
explanation string is given but the tt(auto-describe) style is
set and only one argument is described for this var(opt-spec), the
option will be described by the value of the style with any appearance
of the sequence `tt(%d)' in it replaced by the description for the
first argument.
)
enditem()

In each of the cases above, the var(action) says how the possible
completions should be generated. In cases where only one of a fixed
set of strings can be completed, these strings can directly be given as 
a list in parentheses, as in `tt(:foo:(foo bar baz))'. Such a list in
doubled parentheses, as in `tt(:foo:((a\:bar b\:baz)))' should contain 
strings consisting of the string to complete followed by a colon
(which needs to be preceded by a backslash) and a description. The
matches will be listed together with their descriptions if the
tt(description) style for the tt(values) tag is set.

An var(action) of the form `tt(->)var(string)' is used by functions
that implement a state machine. In this case, the `var(string)' (with
all leading and trailing spaces and tabs removed) will be stored in
the global parameter tt(state) and the function returns with a return
value of 300 (to make it distinguishable from other return values)
after setting the global `tt(context)', `tt(line)' and `tt(opt_args)'
parameters as described below and without resetting any changes made
to the special parameters such as tt(PREFIX) and tt(words). Note that
this means that a function calling tt(_arguments) with at least one
action containing such a `tt(->)var(string)' has to declare
appropriate local parameters as in:

example(local context state line
typeset -A opt_args)

This will ensure that tt(_arguments) does not create unused global
parameters.

A string in
braces will be evaluated to generate the matches and if the
var(action) does not begin with an opening parentheses or brace, it
will be split into separate words and executed. If the var(action)
starts with a space, this list of words will be invoked unchanged,
otherwise it will be invoked with some extra strings placed after the
first word which can be given as arguments to the tt(compadd) builtin
command and which make sure that the var(message) given
in the description will be shown above the matches. These arguments
are taken from the array parameter tt(expl) which will be set up
before executing the var(action) and hence may be used in it (normally 
in an expansion like `tt($expl[@])').

In places where no sensible matches can be generated, the action
should consist of only a space. This will make the var(message) be
displayed but no possible completions listed. Note that even in this
case the colon at the end of the var(message) is needed. The only case 
where it can be left is when neither a var(message), nor a var(action) 
is given.

To include a colon in the option name, the var(message) or the
var(action), it has to be preceded by a backslash.

During the evaluation or execution of the action the array `tt(line)'
will be set to the command name and normal arguments from the command
line, i.e. to the words from the command line excluding all options
and their arguments. These are stored in the associative array
`tt(opt_args)', using the option names as keys and their arguments as
the values. For options that have more than one argument these are
given as one string, separated by colons. All colons in the original
arguments are preceded with backslashes. The parameter `tt(context)'
will be set to the automatically created context name. This is either
a string of the form `var(-opt)tt(-)var(n)' for the var(n)'th argument 
of the option var(-opt), or a string of the form `tt(argument-)var(n)' 
for the var(n)'th argument (for rest arguments the var(n) is the
string `tt(rest)'). For example, when completing the argument of the tt(-o)
option, the name is `tt(-o-1)' and for the second normal (non-option-)
argument it is `tt(argument-2)'.

Also, during the evaluation of the var(action), the context name in
the tt(curcontext) parameter will be changed by appending the same
string that is stored in the tt(context) parameter.

Normally the option names are taken as multi-character names and a
word from the line is considered to contain only one option (or
none). By giving the tt(-s) option to this function (before the first
description), options are considered to be one-character options and the
strings from the line may contain more than one such option
letter. However, strings beginning with two hyphens (like
`tt(-)tt(-prefix)') are still considered to contain only one option
name. This allows the use of the `tt(-s)' option to describe
single-letter options together with such long option names.

Another option supported is `tt(-O) var(name)'. The var(name) will be
taken as the name of an array and its elements will be given to
functions called to generate matches when executing the
var(actions). For example, this allows one to give options for the
tt(compadd) builtin that should be used for all var(action)s.

Also, the tt(-M) option followed by a string may be given before the
first description. The string will be used as the match specification
when completing option names and values instead of the default
`tt(r:|[_-]=* r:|=*)'. 

Finally, the option tt(-C) can be given to make tt(_arguments) modify
the tt(curcontext) parameter when a action of the form
`tt(->)var(state)' is used. This parameter is used to keep track of
the current context and in this case it (and not the parameter
tt(context) as explained above) has to be made local to make sure that 
calling functions don't use the modified value. Also, the local
version of tt(curcontext) has to be initialised with the old value as
in:

example(local curcontext="$curcontext")

The function can also be made to automatically complete long options
for commands that support the `tt(-)tt(-help)' option as, for example,
most of the GNU commands do. For this, the string `tt(-)tt(-)' must be
given as one argument and if it is, the command from the line is
invoked with the `tt(-)tt(-help)' option and its output is parsed to find
possible option names. Note that this means that you should be careful
to make sure that this feature is not used for a command that does not
support this option.

For such automatically found options that get an argument after a
`tt(=)', the function also tries
to automatically find out what should be completed as the argument.
The possible completions for option-arguments can be described with
the arguments after the `tt(-)tt(-)' (which are not used as described
above). Each argument contains one description of the form
`var(pattern)tt(:)var(message)tt(:)var(action)'. The var(message) and
the var(action) have the same format as for the normal option
descriptions described above. The var(action) will be executed to
complete arguments of options whose description in the output of the
command from the line with the `tt(-)tt(-help)' option matches the
var(pattern). For example:

example(_arguments -- '*\*:toggle:(yes no)' \ 
              '*=FILE*:file:_files' \ 
              '*=DIR*:directory:_files -/')

Here, `tt(yes)' and `tt(no)' will be completed as the argument of
options whose description ends in a star, file names for options that
contain the substring `tt(=FILE)' in the description, and paths for
options whose description contains `tt(=DIR)'. In fact, the last two
patterns are not needed since this function always completes files
for option descriptions containing `tt(=FILE)' and paths for option
descriptions that contain `tt(=DIR)' or `tt(=PATH)'. These builtin
patterns can be overridden by patterns given as arguments, however.

Note also that tt(_arguments) tries to find out automatically if the
argument for an option is optional. If it fails to automatically
detect this, the colon before the var(message) can be doubled to tell
it about this as described for the normal option descriptions above.

The option `tt(-i) var(patterns)' (which must be given after the
`tt(-)tt(-)') can be used to give patterns for options which should not be
completed. The patterns can be given as the name of an array parameter
or as a literal list in parentheses. E.g. `tt(-i
"LPAR()-)tt(-(en|dis)able-FEATURE*RPAR()")' will make the options
`tt(-)tt(-enable-FEATURE)' and `tt(-)tt(-disable-FEATURE)' be ignored. The
option `tt(-s) var(pairs)' (again, after the `tt(-)tt(-)') can be used to
describe option aliases. Each var(pair) consists of a pattern and a
replacement. E.g. some tt(configure)-scripts describe options only as
`tt(-)tt(-enable-foo)', but also accept `tt(-)tt(-disable-foo)'. To allow
completion of the second form, one would use `tt(-s "LPAR()#-)tt(-enable-
-)tt(-disable-RPAR()")'.

Example:

example(_arguments '-l+:left border:' \ 
           '-format:paper size:(letter A4)' \ 
           '*-copy:output file:_files::resolution:(300 600)' \ 
           ':postscript file:_files -g *.(ps|eps)' \ 
           '*:page number:')

This describes three options: `tt(-l)', `tt(-format)', and
`tt(-copy)'. The first one gets one argument described as `var(left
border)' for which no completion will be offered because of the empty
action. The argument may come directly after the `tt(-l)' or it may be 
given as the next word on the line. The `tt(-format)' option gets one
argument (in the next word) described as `var(paper size)' for which
only the strings `tt(letter)' and `tt(A4)' will be completed. The
`tt(-copy)' option differs from the first two in that it may appear
more than once on the command line and in that it accepts two
arguments. The first one is mandatory and will be completed as a
filename. The second one is optional (because of the second colon
before the description `var(resolution)') and will be completed from
the strings `tt(300)' and `tt(600)'.

The last two descriptions say what should be completed as
arguments. The first one describes the first argument as a
`var(postscript file)' and makes files ending in `tt(ps)' or `tt(eps)' 
be completed. The last description says that all other arguments are
`var(page numbers)' but does not give possible completions.
)
findex(_values)
item(tt(_values) var(specs) ...)(
This is used to complete values (strings) and their arguments or
lists of such values.

If the first argument is the option `tt(-O) var(name)', this will be
used in the same way as by the tt(_arguments) function. I.e. the
elements of the var(name) array will be given to calls to tt(compadd)
and when executing an action.

Otherwise, if the first argument (or the first argument after the
`tt(-O) var(name)' option if that is used) is the option `tt(-s)', the
next argument is used as the character that separates multiple values.

The first argument (after the options and separator character if they
are given) is used as a string to print as a description before
listing the values.

All other arguments describe the possible values and their
arguments in the same format used for the description of options by
the tt(_arguments) function (see above). The only difference is that
there is no required minus or plus sign at the beginning and that
values can have only one argument.

Example:

example(_values -s , 'description' \ 
        '*foo[bar]' \
        '(two)*one[number]:first count:' \ 
        'two[another number]::second count:(1 2 3)')

This describes three possible values: `tt(foo)', `tt(one)', and
`tt(two)'. The first one is described as `tt(bar)', gets no argument 
and may appear more than once. The second one is described as
`tt(number)', may appear more than once, and gets one mandatory
argument described as `tt(first count)' for which no action is
specified so that it will not be completed automatically. The
`tt((two))' at the beginning says that if the value `tt(one)' is on
the line, the value `tt(two)' will not be  considered to be a possible
completion anymore. Finally, the last value (`tt(two)') is described
as `tt(another number)' and gets an optional argument decribed as
`tt(second count)' which will be completed from the strings `tt(1)',
`tt(2)', and `tt(3)'. The tt(_values) function will complete lists of
these values separated by commas.

Like tt(_arguments) this function temporarily adds another context
name component to the current context name while executing the
var(action). Here this name is just the name of the value for which
the argument is completed.

To decide if the descriptions for the values (not those for the
arguments) should be printed, the tt(verbose) is used.

One last difference to tt(_arguments) is that this function uses the
associative array
tt(val_args) to report values and their arguments (but otherwise this
is the same as the tt(opt_args) association used by
tt(_arguments)). This also means that the function calling tt(_values) 
should declare the tt(state), tt(line), tt(context) and tt(val_args)
parameters as in:

example(local context state line
typeset -A val_args)

when using an action of the form `tt(->)var(string)'. With this
function the tt(context) parameter will be set to the name of the
value whose argument is to be completed.

Like tt(_arguments), tt(_values) also supports the tt(-C) option in
which case you have to make the parameter tt(curcontext) local instead 
of tt(context) (as described above).
)
findex(_regex_arguments)
item(tt(_regex_arguments) var(name) var(specs) ...)(
This function is a compiler to generate a completion function.  The
first argument specifies the name of a generated function while the
remaining arguments specify a completion as a set of regular
expressions with actions.  The generated function has the structure of a
finite-state machine whose state corresponds to the state (i.e. the
context) of the completion. This state machine uses a command line,
which comes from concatentating the tt(words) array up to the current
cursor position using null characters as a separator with no extra
quotation.  This is analysed and at the end the appropriate action is
executed.

Specification arguments take one of following forms, in which
metacharacters such as `tt(LPAR())', `tt(RPAR())', `tt(#)' and `tt(|)'
should be quoted.

startitem()
item(tt(/)var(pattern)tt(/) [tt(%)var(lookahead)tt(%)] [tt(-)var(guard)] [tt(:)var(action)])(
This is a primitive element, corresponding to one
state of the compiled state machine.  The state is entered if the pattern
`tt((#b)LPAR()(#B))var(pattern)tt(RPAR()(#B))var(lookahead)tt(*)' matches
the command line string.  If it is matched, `var(guard)' is evaluated and
its return status is examined; if this is successful, the state is entered,
else the test fails and other candidates are tried.  The var(pattern)
string `tt([])' is guaranteed never to match.

If the test succeeds and the state is entered, the left part of the
command line string matched as `var(pattern)' is removed and the 
next state is tried, proceeding from inside to outside and from left to
right.

If no test succeeds and the remaining command line string contains no null
character, the completion target is restricted to the remainder of the
command line string and `var(action)'s for the target are evaluated.
In this case, nothing is actually removed from the command line string
so that any previous or neighbouring state may also have `var(actions)'s.
)
item(tt(/)var(pattern)tt(/+) [tt(%)var(lookahead)tt(%)] [tt(-)var(guard)] [tt(:)var(action)])(
This is similar to `tt(/)var(pattern)tt(/) ...' but the left part of
command line string is also considered as part of the completion target.
)
item(tt(/)var(pattern)tt(/-) [tt(%)var(lookahead)tt(%)] [tt(-)var(guard)] [tt(:)var(action)])(
This is similar to `tt(/)var(pattern)tt(/) ...' but `var(action)'s of the
current and previous states are ignored even if the following state's
`var(pattern)' matches the empty string.
)
item(tt(LPAR()) var(spec) tt(RPAR()))(
This groups `var(spec)'.
)
item(var(spec) tt(#))(
This allows any number of repetitions of `var(spec)'.
)
item(var(spec) var(spec))(
This represents the concatenation of two `var(spec)'s.
)
item(var(spec) tt(|) var(spec))(
Either of two `var(spec)'s can be matched.
)
enditem()
)
findex(_combination)
item(tt(_combination) [ tt(-s) var(spec) ] var(tag) var(style) var(specs) ... var(field) var(opts) ...)(
This function is used to complete combinations of values such as pairs 
of hostnames and usernames. The possible values will be taken from the 
var(style) whose name is given as the second argument. The first argument
is the var(tag) to use to do the lookup.

The style name should consist of multiple parts separated by
hyphens which are then used as fieldnames. Known values for such
fields can be given after the second argument in arguments of the form 
`var(field)tt(=)var(pattern)'. The first argument without a equal sign 
is taken as the name of the field for which completions should be
generated.

The matches generated will be taken from the value of the style. These 
values should contain the possible values for the combinations where
the values for the different fields are separated by colons or the
character given after the tt(-s) option to tt(_combination).

Only the values for the requested fields for which the patterns given
in the `var(field)tt(=)var(pattern)' match the respective fields in
the strings from the style value are generated as possible matches.

If no style with the given name is defined for the given tag but a
function named with the name of the requested field preceded by an
underscore is defined, that function will be called to generate the
matches. This is also done if none of the strings in the value of the
style match all the patterns given as arguments.

If the same name is used for more than one field, in both the
`var(field)tt(=)var(pattern)' and the argument that gives the field
name to complete for, the number of the field (starting with one) may
be given after the fieldname, separated from it by a colon.

All arguments after the requested fieldname are given to the
tt(compadd) used (when generating matches from the style value) and to 
the functions for the fields if they are called.
)
findex(_sort_tags)
item(tt(_sort_tags) var(tag) ...)(
As described above for the tt(tag-order) style, this is only provided
to show how functions that sort tags can be implemented.

Inside such functions the name of the current context can
be accessed using the tt(curcontext) parameter. For example, the
function generating file names (called tt(_files)) in the completion
system is often called to generate only filenames matching a given
glob pattern, in which case it uses the tags tt(globbed-files),
tt(directories), and tt(all-files).  This means that the function
offers to generate filenames matching the pattern, names of
directories or all filenames as possible matches. Example:

example(_sort_tags() {
  case $curcontext in
  (*::dvips:*)
    comptry globbed-files directories
    comptry all-files
    ;;
  (*)
    comptry globbed-files
    comptry directories
    comptry all-files
    ;;
  esac
})

Every call to the tt(comptry) function (actually a builtin
command defined by the tt(zsh/computil) module) gives a
set of tags to use; as soon as tt(comptry) produces some matches,
subsequent calls have no effect.  Hence in the example
this means that for the tt(dvips) command on the first attempt the
names of DVI files and directories will be generated (first call to
tt(comptry)). If none of those names match the string from the command
line the completion function will generate all filenames as
possible matches (second call to tt(comptry)).

For all other context names the second case-pattern matches, so that
normally the completion functions will only try the filenames matching 
the glob pattern (if any glob pattern is used). If that doesn't yield
any matches, names of directories are generated, and if that doesn't
yield any matching names either, all filenames will be generated.

In every context the function may call tt(comptry) as
often as it wants. Also, every string may be given as argument, even
if no tag with such a name was offered by the completion
function. This allows one to give a preferred ordering for some common 
tag sets without having to worry about sensible patterns for context
names. For example, many completion functions can generate both
arguments and option names for commands. These functions normally use
the tags tt(arguments) and tt(options). Depending on your preference
you may write in your sorting function:

example(_sort_tags() {
  comptry arguments options
  case $curcontext in
  ...
  esac
})

or

example(_sort_tags() {
  comptry arguments
  comptry options
  case $curcontext in
  ...
  esac
})

The former always adds both the matches for the argument and the
option names as possible matches. The latter forces matches for the
arguments to be preferred. In this case option names are only generated
as matches if the string on the line matches no possible completion
for the argument, which normally means that you have to type the
hyphen the option names start with yourself to see the list of option
names that can be completed.

Since the completion functions are free to choose the tag names they
use, there can't be a complete list. So to make sure that all types of 
matches are eventually tried as completions, one should  use a call to 
tt(comptry) with all arguments at the end of the sorting function. For
those contexts where one really wants to make sure that certain tags are
never used one can then use a call to tt(return) to circumvent that
last tt(comptry). For example:

example(_sort_tags() {
  ...
  case $curcontext in
  (*::kill:*)
    comptry processes
    return
    ;;
  esac
  comptry "$@"
})

The completion function for the tt(kill) builtin command offers the
tags tt(jobs) and tt(processes) which represent job references
(e.g. `tt(%1)') and process identifiers respectively. The function
above makes sure that for this builtin command only process
identifiers are generated as possible matches by using only the
tt(processes) tag in a call to tt(comptry). The immediate call to
tt(return) then makes sure that the default tt(comptry) at the end is
not executed.
)

enditem()

texinode(Completion Directories)()(Completion Functions)(Completion System)
sect(Completion Directories)
cindex(completion system, directory structure)

In the source distribution, the files are contained in various
subdirectories of the tt(Completion) directory.  They may have been
installed in the same structure, or into one single function directory.
The following is a description of the files found in the original directory
structure.  If you wish to alter an installed file, you will need to copy
it to some directory which appears earlier in your tt(fpath) than the
standard directory where it appears.

startitem()
item(tt(Core))(
The core scripts and functions.  You will certainly need these, though will
probably not need to alter them.  Many of these are documented above.
)
item(tt(Base))(
Other functions you will almost certainly want if you are going to use
any of the standard completion functions.  You may want to edit some of
these files.
)
item(tt(Builtins))(
Functions for completing arguments of shell builtin commands and
utility functions for this (which are also used by functions from the
tt(User) directory).
)
item(tt(User))(
Functions for completing arguments of external commands and suites of
commands.  They may need modifying for your system.
)
item(tt(Commands))(
Functions which implement special types of completion to be bound to
keystrokes rather than called by context.
)
enditem()