zsh - Programmable Completion

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# Programmable Completion

`compctl [ -CDT ] options [ command ... ]`

`compctl [ -CDT ] options`
`[ -x pattern options - ... -- ] [ + options [ -x ... -- ] ... [+] ]`
`[ command ... ]`

`compctl -L [ -CDT ] [ command ... ]`

`compctl + command ...`

Control the editor's completion behaviour according to the supplied set of options. Various editing commands, notably `expand-or-complete-word`, usually bound to `TAB`, will attempt to complete a word typed by the user, while others, notably `delete-char-or-list`, usually bound to `^D` in emacs editing mode, list the possibilities; `compctl` controls what those possibilities are. They may for example be filenames (the most common case, and hence the default), shell variables, or words from a user-specified list.

## Command Flags

Completion of the arguments of a command may be different for each command or may use the default. The behaviour when completing the command word itself may also be separately specified. These correspond to the following flags and arguments, all of which (except for ``-L'`) may be combined with any combination of the options described subsequently in section Options Flags.

`command ...`
  controls completion for the named commands, which must be listed last on the command line. If completion is attempted for a command with a pathname containing slashes and no completion definition is found, the search is retried with the last pathname component. Note that aliases are expanded before the command name is determined unless the `COMPLETE_ALIASES` option is set. Commands should not be combined with the ``-D'`, ``-C'` or ``-T'` flags.
`-D`
  controls default completion behavior for the arguments of commands not assigned any special behavior. If no `compctl -D` command has been issued, filenames are completed.
`-C`
  controls completion when the command word itself is being completed. If no `compctl -C` command has been issued, the names of any executable command (whether in the path or specific to the shell, such as aliases or functions) are completed.
`-T`
  supplies completion flags to be used before any other processing is done, even those given to specific commands with other `compctl` definitions. This is only useful when combined with extended completion (the ``-x'` flag. See section Extended Completion). Using this flag you can define default behaviour which will apply to all commands without exception, or you can alter the standard behaviour for all commands. For example, if your access to the user database is too slow and/or it contains too many users (so that completion after `~` is too slow to be usable), you can use `compctl -Tx 'C[0,*/*]' -f - 's[~]' -k friends -S/` to complete the strings in the array friends after a `~`. The first argument is necessary so that this form of `~`-completion is not tried after the directory name is finished.
`-L`
  lists the existing completion behaviour in a manner suitable for putting into a start-up script; the existing behaviour is not changed. Any combination of the above forms may be specified, otherwise all defined completions are listed. Any other flags supplied are ignored.
`no argument`
  If no argument is given, `compctl` lists all defined completions in an abbreviated form; with a list of options, all completions with those flags set (not counting extended completion) are listed. If the `+` flag is alone and followed immediately by the command list, the completion behaviour for all the commands in the list is reset to the default. In other words, completion will subsequently use the options specified by the ``-D'` flag.

## Options Flags

`[ -fcFBdeaRGovNAIOPZEnbjrzu ]`
`[ -k array ] [ -g globstring ] [ -s subststring ]`
`[ -K function ] [ -H num pattern ]`
`[ -Q ] [ -P prefix ] [ -S suffix ]`
`[ -q ] [ -X explanation ]`
`[ -l cmd ] [ -U ]`

The remaining options specify the type of command arguments to look for during completion. Any combination of these flags may be specified; the result is a sorted list of all the possibilities. The options are described in the following sections.

### Simple Flags

These produce completion lists made up by the shell itself:

`-f`
  Filenames and file-system paths.
`-c`
  Command names, including aliases, shell functions, builtins and reserved words.
`-F`
  Function names.
`-B`
  Names of builtin commands.
`-m`
  Names of external commands.
`-w`
  Reserved words.
`-a`
  Alias names.
`-R`
  Names of regular (non-global) aliases.
`-G`
  Names of global aliases.
`-d`
  This can be combined with ``-F'`, ``-B'`, ``-w'`, ``-a'`, ``-R'` and ``-G'` to get names of disabled functions, builtins, reserved words or aliases.
`-e`
  This option (to show enabled commands) is in effect by default, but may be combined with ``-d'`; ``-de'` in combination with ``-F'`, ``-B'`, ``-w'`, ``-a'`, ``-R'` and ``-G'` will complete names of functions, builtins, reserved words or aliases whether or not they are disabled.
`-o`
  Names of shell options. See section Options.
`-v`
  Names of any variable defined in the shell.
`-N`
  Names of scalar (non-array) parameters.
`-A`
  Array names.
`-I`
  Names of integer variables.
`-O`
  Names of read-only variables.
`-p`
  Names of parameters used by the shell (including special parameters).
`-Z`
  Names of shell special parameters.
`-E`
  Names of environment variables.
`-n`
  Named directories.
`-b`
  Key binding names.
`-j`
  Job names: the first word of the job leader's command line. This is useful with the kill builtin.
`-r`
  Names of running jobs.
`-z`
  Names of suspended jobs.
`-u`
  User names.

### Flags with arguments

These have user supplied arguments to determine how the list of completions is to be made up:

`-k array`
  Names taken from the elements of `$array` (note that the `$` does not appear on the command line). Alternatively, the argument `array` itself may be a set of space or comma separated values in parentheses, in which any delimiter may be escaped with a backslash; in this case the argument should be quoted. For example, ``compctl -k "(cputime filesize datasize stacksize coredumpsize resident descriptors)" limit'`.
`-g globstring`
  The globstring is expanded using filename globbing; it should be quoted to protect it from immediate expansion. The resulting filenames are taken as possible completions. Use `*(/)` instead of `*/` for directories. The `fignore` special parameter is not applied to the resulting files. More than one pattern may be given separated by blanks. (Note that brace expansion is not part of globbing. Use the syntax (`either|or`) to match alternatives.)
`-K function`
  Call the given function to get the completions. The function is passed two arguments: the prefix and the suffix of the word on which completion is to be attempted, in other words those characters before the cursor position, and those from the cursor position onwards. The function should set the variable `reply` to an array containing the completions (one completion per element); note that `reply` should not be made local to the function. From such a function the command line can be accessed with the ``-c'` and ``-l'` flags to the `read` builtin. For example, `function whoson { reply=(`users`); }`
  `compctl -K whoson talk` completes only logged-on users after ``talk'`. Note that `whoson` must return an array so that just `reply=`users`` is incorrect.
`-H num pattern`
  The possible completions are taken from the last num history lines. Only words matching pattern are taken. If num is zero or negative the whole history is searched and if pattern is the empty string all words are taken (as with `*`). A typical use is `compctl -D -f + -H 0 '' -X '(No file found; using history)'` which forces completion to look back in the history list for a word if no filename matches. The explanation string is useful as it tells the user that no file of that name exists, which is otherwise ambiguous. (See the next section for ``-X'`.)

### Control Flags

These do not directly specify types of name to be completed, but manipulate the options that do:

`-Q`
  This instructs the shell not to quote any metacharacters in the possible completions. Normally the results of a completion are inserted into the command line with any metacharacters quoted so that they are interpreted as normal characters. This is appropriate for filenames and ordinary strings. However, for special effects, such as inserting a backquoted expression from a completion array (``-k'`) so that the expression will not be evaluated until the complete line is executed, this option must be used.
`-P prefix`
  The prefix is inserted just before the completed string; any initial part already typed will be completed and the whole prefix ignored for completion purposes. For example, `compctl -j -P "%" kill` inserts a `%` after the `kill` command and then completes job names.
`-S suffix`
  When a completion is found the suffix is inserted after the completed string. In the case of menu completion the suffix is inserted immediately, but it is still possible to cycle through the list of completions by repeatedly hitting the same key.
`-q`
  If used with a suffix as specified by the previous option, this causes the suffix to be removed if the next character typed is a blank or does not insert anything (the same rule as used for the `AUTO_REMOVE_SLASH` option). The option is most useful for list separators (comma, colon, etc.).
`-l cmd`
  This option cannot be combined with any other option. It restricts the range of command line words that are considered to be arguments. If combined with one of the extended completion patterns ``p[...]'`, ``r[...]'`, or ``R[...]'` (See section Extended Completion.) the range is restricted to the arguments specified in the brackets. Completion is then performed as if these had been given as arguments to the cmd supplied with the option. If the cmd string is empty the first word in the range is instead taken as the command name, and command name completion performed on the first word in the range. For example, `compctl -x 'r[-exec,;]' -l '' -- find` completes arguments between `-exec` and the following `;` (or the end of the command line if there is no such string) as if they were a separate command line.
`-U`
  Use the whole list of possible completions, whether or not they actually match the word on the command line. The word typed so far will be deleted. This is most useful with a function (given by the ``-K'` option) which can examine the word components passed to it (or via the `read` builtin's ``-c'` and ``-l'` flags) and use its own criteria to decide what matches. If there is no completion, the original word is retained.
`-X explanation`
  Print explanation when trying completion on the current set of options. A `%n` in this string is replaced by the number of matches.

## Alternative Completion

`compctl [ -CDT ] options + options [ + ... ] [ + ] command ...`

The form with `+` specifies alternative options. Completion is tried with the options before the first `+`. If this produces no matches completion is tried with the flags after the `+` and so on. If there are no flags after the last `+` and a match has not been found up to that point, default completion is tried.

## Extended Completion

`compctl [ -CDT ] options -x pattern options - ... -- [ command ... ]`

`compctl [ -CDT ] options [ -x pattern options - ... -- ]`
`[ + options [ -x ... -- ] ... [+] ] [ command ... ]`

The form with ``-x'` specifies extended completion for the commands given; as shown, it may be combined with alternative completion using `+`. Each pattern is examined in turn; when a match is found, the corresponding options, as described in section Options Flags, are used to generate possible completions. If no pattern matches, the options given before the ``-x'` are used.

Note that each pattern should be supplied as a single argument and should be quoted to prevent expansion of meta-characters by the shell.

A pattern is built of sub-patterns separated by commas; it matches if at least one of these sub-patterns matches (they are `or`'ed). These sub-patterns are in turn composed of other sub-patterns separated by white spaces which match if all of the sub-patterns match (they are `and`'ed). An element of the sub-patterns is of the form `c[...][...]`, where the pairs of brackets may be repeated as often as necessary, and matches if any of the sets of brackets match (an `or`). The example below makes this clearer.

The elements may be any of the following:

`s[string] ...`
  Matches if the current word on the command line starts with one of the strings given in brackets. The string is not removed and is not part of the completion.
`S[string] ...`
  Like s[string] except that the string is part of the completion.
`p[from,to] ...`
  Matches if the number of the current word is between one of the from and to pairs inclusive. The comma and to are optional; to defaults to the same value as from. The numbers may be negative: ``-n'` refers to the `n`'th last word on the line.
`c[offset,string] ...`
  Matches if the string matches the word offset by offset from the current word position. Usually offset will be negative.
`C[offset,pattern] ...`
  Like c but using pattern matching instead.
`w[index,string] ...`
  Matches if the word in position index is equal to the corresponding string. Note that the word count is made after any alias expansion.
`W[index,pattern] ...`
  Like w but using pattern matching instead.
`n[index,string] ...`
  Matches if the current word contains string. Anything up to and including the index'th occurrence of this string will not be considered part of the completion, but the rest will. index may be negative to count from the end: in most cases, index will be 1 or -1.
`N[index,string] ...`
  Like n[index,string] except that the string will be taken as a character class. Anything up to and including the index'th occurrence of any of the characters in string will not be considered part of the completion.
`m[min,max] ...`
  Matches if the total number of words lies between min and max inclusive.
`r[str1,str2] ...`
  Matches if the cursor is after a word with prefix str1. If there is also a word with prefix str2 on the command line it matches only if the cursor is before this word.
`R[str1,str2] ...`
  Like r but using pattern matching instead.

## Example

`compctl -u -x 's[+] c[-1,-f],s[-f+]' -g '~/Mail/*(:t)' - 's[-f],c[-1,-f]' -f -- mail`

This is to be interpreted as follows:

If the current command is `mail`, then

if ((the current word begins with `+` and the previous word is `-f`) or (the current word begins with `-f+`)), then complete the non-directory part (the `:t` glob modifier) of files in the directory ``~/Mail'`; else

if the current word begins with ``-f'` or the previous word was ``-f'`, then complete any file; else

complete user names.

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