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NAME

Complete::Bash - Completion routines for bash shell

VERSION

This document describes version 0.27 of Complete::Bash (from Perl distribution Complete-Bash), released on 2016-02-03.

DESCRIPTION

This module provides routines related to tab completion in bash shell.

About programmable completion in bash

Bash allows completion to come from various sources. The simplest is from a list of words (-W):

 % complete -W "one two three four" somecmd
 % somecmd t<Tab>
 two  three

Another source is from a bash function (-F). The function will receive input in two variables: COMP_WORDS (array, command-line chopped into words) and COMP_CWORD (integer, index to the array of words indicating the cursor position). It must set an array variable COMPREPLY that contains the list of possible completion:

 % _foo()
 {
   local cur
   COMPREPLY=()
   cur=${COMP_WORDS[COMP_CWORD]}
   COMPREPLY=($( compgen -W '--help --verbose --version' -- $cur ) )
 }
 % complete -F _foo foo
 % foo <Tab>
 --help  --verbose  --version

And yet another source is an external command (-C) including, from a Perl script. The command receives two environment variables: COMP_LINE (string, raw command-line) and COMP_POINT (integer, cursor location). Program must split COMP_LINE into words, find the word to be completed, complete that, and return the list of words one per-line to STDOUT. An example:

 % cat foo-complete
 #!/usr/bin/perl
 use Complete::Bash qw(parse_cmdline format_completion);
 use Complete::Util qw(complete_array_elem);
 my ($words, $cword) = @{ parse_cmdline() };
 my $res = complete_array_elem(array=>[qw/--help --verbose --version/], word=>$words->[$cword]);
 print format_completion($res);

 % complete -C foo-complete foo
 % foo --v<Tab>
 --verbose --version

About the routines in this module

First of all, parse_cmdline() is the function to parse raw command-line (such as what you get from bash in COMP_LINE environment variable) into words. This makes it easy for the other functions to generate completion answer. See the documentation for that function for more details.

format_completion is what you use to format completion answer structure for bash.

FUNCTIONS

format_completion($completion, $opts) -> str|array

Format completion for output (for shell).

Bash accepts completion reply in the form of one entry per line to STDOUT. Some characters will need to be escaped. This function helps you do the formatting, with some options.

This function accepts completion answer structure as described in the Complete POD. Aside from words, this function also recognizes these keys:

  • as (str): Either string (the default) or array (to return array of lines instead of the lines joined together). Returning array is useful if you are doing completion inside Term::ReadLine, for example, where the library expects an array.

  • esc_mode (str): Escaping mode for entries. Either default (most nonalphanumeric characters will be escaped), shellvar (like default, but dollar sign $ will not be escaped, convenient when completing environment variables for example), filename (currently equals to default), option (currently equals to default), or none (no escaping will be done).

  • path_sep (str): If set, will enable "path mode", useful for completing/drilling-down path. Below is the description of "path mode".

    In shell, when completing filename (e.g. foo) and there is only a single possible completion (e.g. foo or foo.txt), the shell will display the completion in the buffer and automatically add a space so the user can move to the next argument. This is also true when completing other values like variables or program names.

    However, when completing directory (e.g. /et or Downloads) and there is solely a single completion possible and it is a directory (e.g. /etc or Downloads), the shell automatically adds the path separator character instead (/etc/ or Downloads/). The user can press Tab again to complete for files/directories inside that directory, and so on. This is obviously more convenient compared to when shell adds a space instead.

    The path_sep option, when set, will employ a trick to mimic this behaviour. The trick is, if you have a completion array of ['foo/'], it will be changed to ['foo/', 'foo/ '] (the second element is the first element with added space at the end) to prevent bash from adding a space automatically.

    Path mode is not restricted to completing filesystem paths. Anything path-like can use it. For example when you are completing Java or Perl module name (e.g. com.company.product.whatever or File::Spec::Unix) you can use this mode (with path_sep appropriately set to, e.g. . or ::).

This function is not exported by default, but exportable.

Arguments ('*' denotes required arguments):

  • completion* => hash|array

    Completion answer structure.

    Either an array or hash. See function description for more details.

  • opts => hash

Return value: Formatted string (or array, if `as` is set to `array`) (str|array)

join_wordbreak_words() -> [status, msg, result, meta]

Post-process parse_cmdline() result by joining some words.

parse_cmdline(), like bash, splits some characters that are considered as word-breaking characters:

 "'@><=;|&(:

So if command-line is:

 command -MData::Dump bob@example.org

then they will be parsed as:

 ["command", "-MData", "::", "Dump", "bob", '@', "example.org"]

Normally in Perl applications, we want :, @ to be part of word. So this routine will convert the above into:

 ["command", "-MData::Dump", 'bob@example.org']

This function is not exported by default, but exportable.

No arguments.

Returns an enveloped result (an array).

First element (status) is an integer containing HTTP status code (200 means OK, 4xx caller error, 5xx function error). Second element (msg) is a string containing error message, or 'OK' if status is 200. Third element (result) is optional, the actual result. Fourth element (meta) is called result metadata and is optional, a hash that contains extra information.

Return value: (any)

parse_cmdline($cmdline, $point, $opts) -> array

Parse shell command-line for processing by completion routines.

This function basically converts COMP_LINE (str) and COMP_POINT (int) into something like (but not exactly the same as) COMP_WORDS (array) and COMP_CWORD (int) that bash supplies to shell functions.

The differences with bash are (these differences are mostly for parsing convenience for programs that use this routine; this comparison is made against bash versions 4.2-4.3):

1) quotes and backslashes are stripped (bash's COMP_WORDS contains all the quotes and backslashes);

2) quoted phrase that contain spaces, or phrase that contains escaped spaces is parsed as a single word. For example:

 command "First argument" Second\ argument

   bash would split it as (represented as Perl):

 ["command", "\"First", "argument\"", "Second\\", "argument"]

   which is not very convenient. We parse it into:

 ["command", "First argument", "Second argument"]

3) variables are substituted with their values from environment variables except for the current word (COMP_WORDS[COMP_CWORD]) (bash does not perform variable substitution for COMP_WORDS). However, note that special shell variables that are not environment variables like $0, $_, $IFS will not be replaced correctly because bash does not export those variables for us.

4) tildes (~) are expanded with user's home directory except for the current word (bash does not perform tilde expansion for COMP_WORDS);

Caveats:

  • Like bash, we group non-whitespace word-breaking characters into its own word. By default COMP_WORDBREAKS is:

    "'@><=;|&(:

    So if raw command-line is:

    command --foo=bar http://example.com:80 mail@example.org Foo::Bar

    then the parse result will be:

    ["command", "--foo", "=", "bar", "http", ":", "//example.com", ":", "80", "Foo", "::", "Bar"]

    which is annoying sometimes. But we follow bash here so we can more easily accept input from a joined COMP_WORDS if we write completion bash functions, e.g. (in the example, foo is a Perl script):

    foo () { local words=(${COMPCWORDS[@]}) # add things to words, etc local point=... # calculate the new point COMPREPLY=( COMP_LINE="foo ${words[@]}" COMP_POINT=$point foo ) }

    To avoid these word-breaking characters to be split/grouped, we can escape them with backslash or quote them, e.g.:

    command "http://example.com:80" Foo\:\:Bar

    which bash will parse as:

    ["command", "\"http://example.com:80\"", "Foo\:\:Bar"]

    and we parse as:

    ["command", "http://example.com:80", "Foo::Bar"]

  • Due to the way bash parses the command line (see above), the two below are equivalent:

    % cmd --foo=bar % cmd --foo = bar

Because they both expand to ['--foo', '=', 'bar']. But obviously Getopt::Long does not regard the two as equivalent.

This function is not exported by default, but exportable.

Arguments ('*' denotes required arguments):

  • cmdline => str

    Command-line, defaults to COMP_LINE environment.

  • opts => hash

    Options.

    Optional. Known options:

    • truncate_current_word (bool). If set to 1, will truncate current word to the position of cursor, for example (^ marks the position of cursor): --vers^oo to --vers instead of --versoo. This is more convenient when doing tab completion.

  • point => int

    Point/position to complete in command-line, defaults to COMP_POINT.

Return value: (array)

Return a 2-element array: [$words, $cword]. $words is array of str, equivalent to COMP_WORDS provided by bash to shell functions. $cword is an integer, roughly equivalent to COMP_CWORD provided by bash to shell functions. The word to be completed is at $words->[$cword].

Note that COMP_LINE includes the command name. If you want the command-line arguments only (like in @ARGV), you need to strip the first element from $words and reduce $cword by 1.

point($cmdline, $marker) -> any

Return line with point marked by a marker.

This is a utility function useful for testing/debugging. parse_cmdline() expects a command-line and a cursor position ($line, $point). This routine expects $line with a marker character (by default it's the caret, ^) and return ($line, $point) to feed to parse_cmdline().

Example:

 point("^foo") # => ("foo", 0)
 point("fo^o") # => ("foo", 2)

This function is not exported by default, but exportable.

Arguments ('*' denotes required arguments):

  • cmdline => str

    Command-line which contains a marker character.

  • marker => str (default: "^")

    Marker character.

Return value: (any)

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Complete-Bash.

SOURCE

Source repository is at https://github.com/perlancar/perl-Complete-Bash.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Complete-Bash

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

SEE ALSO

Complete, the convention that this module uses.

Some higher-level modules that use this module (so you don't have to use this module directly): Getopt::Long::Complete (via Complete::Getopt::Long), Getopt::Long::Subcommand, Perinci::CmdLine (via Perinci::Sub::Complete).

Other modules related to bash shell tab completion: Bash::Completion, Getopt::Complete, Term::Bash::Completion::Generator.

Programmable Completion section in Bash manual: https://www.gnu.org/software/bash/manual/html_node/Programmable-Completion.html

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2016 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.