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bash-completion

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Programmable completion functions for bash

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# bash-completion

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## Introduction

bash-completion is a collection of
[command-line completion](https://en.wikipedia.org/wiki/Command-line_completion)
recipes for a number of commands for the completion system of the
[Bash shell](https://www.gnu.org/software/bash/).
These recipes enhance Bash's typical plain completion of filenames to
provide better suggestions of options and arguments for many commands.
Also provided is a collection of helper functions to assist in creating new
recipes, and a set of facilities for loading recipes automatically on
demand, as well as installing them.

## Installation

The easiest way to install this software is to use a package; refer to
[Repology](https://repology.org/project/bash-completion) for a comprehensive
list of operating system distributions, package names, and available versions.

Depending on the package, you may still
need to source it from either `/etc/bashrc` or `~/.bashrc` (or any
other file sourcing those). If you have _only_ bash >= 4.2 installed, you can
do this by using:

```bash
# Use bash-completion, if available, and avoid double-sourcing
[[ $PS1 &&
  ! ${BASH_COMPLETION_VERSINFO:-} &&
  -f /usr/share/bash-completion/bash_completion ]] &&
    . /usr/share/bash-completion/bash_completion
```

If you have older bash versions in use, their loading of `bash_completion`
should be prevented. See further for more info.

If you don't have the package readily available for your distribution, or
you simply don't want to use one, you can install bash-completion using the
standard commands for GNU autotools packages:

```shell
autoreconf -i      # if not installing from prepared release tarball
./configure
make               # GNU make required
make check         # optional
make install       # as root
make installcheck  # optional, requires python3 with pytest >= 3.6, pexpect
```

These commands install the completions and helpers, as well as a
`profile.d` script that loads `bash_completion` where appropriate.

If your system does not use the `profile.d` directory (usually below
`/etc`) mechanism (i.e., does not automatically source shell scripts in
it), you can source the `$sysconfdir/profile.d/bash_completion.sh`
script in `/etc/bashrc` or `~/.bashrc`.

The `profile.d` script provides a configuration file hook that can be
used to prevent loading `bash_completion` on a per user basis when it's
installed system wide. To do this:

1. Turn off programmable completion with `shopt -u progcomp` in
   `$XDG_CONFIG_HOME/bash_completion` (or `~/.config/bash_completion`
   if `$XDG_CONFIG_HOME` is not set)
2. Turn it back on (for example in `~/.bashrc`) if you want to use
   programmable completion for other purposes.

### macOS (OS X)

If you're using macOS (formerly OS X), `/etc/bashrc` is apparently not sourced
at all, and `~/.bashrc` is not sourced from `~/.bash_profile` by default
(because `~/.bash_profile` is not created by default).  In this case, the
standard way is to configure `~/.bash_profile` to source `~/.bashrc` and write
interactive settings in `~/.bashrc`.  You can source `~/.bashrc` in
`~/.bash_profile` in the following way:

```bash
# ~/.bash_profile

if [[ -f ~/.bashrc ]]; then
  source ~/.bashrc
fi
```

Then, you can source `bash-completion` in your `~/.bashrc`.  It should be noted
that `bash-completion` should not be sourced in `~/.bash_profile` because
`~/.bash_profile` is only loaded in interactive _login_ shell sessions.  If you
start nested Bash sessions, the interactive settings in `~/.bash_profile` will
disappear.  It is strongly recommended to source `~/.bashrc` from
`~/.bash_profile` and write interactive settings in `~/.bashrc`.

For example, if you install `bash-completion` using Homebrew, it will install
the entry point of `bash-completion` to
`$HOMEBREW_PREFIX/etc/profile.d/bash_completion.sh`.  You can source it by
adding the following to your startup file `~/.bashrc`:

```bash
if [[ -s $HOMEBREW_PREFIX/etc/profile.d/bash_completion.sh ]]; then
  . "$HOMEBREW_PREFIX/etc/profile.d/bash_completion.sh"
fi
```

## Troubleshooting

If you find that a given function is producing errors or does not work
as it should under certain circumstances when you attempt completion,
try running `set -x` or `set -v` prior to attempting the completion
again. This will produce useful debugging output that will aid us in
fixing the problem if you are unable to do so yourself. Turn off the
trace output by running either `set +x` or `set +v`.

If you are filing an issue, please attach the generated debugging output
in `set -x` mode copy-pasted to a separate, attached file in the report.
Before doing so, be sure to review the output for anything you may not want
to share in public, and redact as appropriate.

To debug dynamic loading of a completion, tracing needs to be turned
on before the debugged completion is attempted the first time. The
easiest way to do this is to start a new shell session, and to turn
tracing on in it before doing anything else there.

## Known problems

1. Many of the completion functions assume GNU versions of the various
   text utilities that they call (e.g. `grep`, `sed`, and `awk`). Your
   mileage may vary.

## FAQ

**Q1. The bash-completion code inhibits some commands from completing on
   files with extensions that are legitimate in my environment. Do I
   have to disable completion for that command in order to complete on
   the files that I need to?**

A. No. If needed just once in a while,
   use `M-/` to (in the words of the bash man page) attempt file
   name completion on the text to the left of the cursor. This will
   circumvent any file type restrictions put in place by the bash
   completion code. If needed more regularly, see the next question:

**Q2. How can I override a completion shipped by bash-completion or install a
   new completion for a user account?**

A. To override a completion for a specific command, you can install your own
   completion file for the command into an appropriate place.  It will take
   precedence over the one shipped by us or the one installed systemwide.  To
   install a completion on per user basis, put the completion file at
   `<userdir>/completions/<cmd>.bash`, where `<cmd>` is the command name and
   `<userdir>` is one of the user directories.  The user directories are
   specified by the colon-separated `$BASH_COMPLETION_USER_DIR` (defaults to
   `$XDG_DATA_HOME/bash-completion`, or `~/.local/share/bash-completion` if
   `$XDG_DATA_HOME` is not set).  They will be loaded automatically on demand
   when the respective command is being completed.

> [!NOTE]
   > See also the answer to Q4 for considerations for those files' names, they
   > apply here as well.

Completion settings that should be loaded on initialization of
   bash-completion should be defined in a startup completion file.  A startup
   completion file can be added in the directory `<userdir>/startup` (see the
   previous paragraph for `<userdir>`).  A prefix of the form
   `[0-9][0-9][0-9]_` may be prepended to the filename of the startup files to
   control the loading order.  To override a existing startup file installed
   systemwide or shipped by us, you can put your own version with the same
   filename in `<userdir>/startup`.  In identifying the overridden startup
   file, the prefixes `[0-9][0-9][0-9]_` are ignored.  If you want to disable a
   startup completion file, you can use an empty file.

You can also define eagerly loaded settings in the user file
   (`${BASH_COMPLETION_USER_FILE:-$HOME/.bash_completion}`).  Instead of
   preparing separate files for specific commands, you may write completion
   settings for specific commands directly in the user file.  When you want to
   modify the default completion setting set by `complete -D` (which is
   available in Bash >= 4.1), you can override it in the user file or in a user
   startup file.  If you want to use bash's default completion instead of one
   of ours, in the user file or in a user startup script, you can define
   something like this:

```bash
   complete -o default -o bashdefault $cmd
   ```

where `$cmd` is the command to override completion for.

**Q3. How can I override a completion shipped by bash-completion systemwide?**

A. Install a local completion appropriately for the desired command, and it
   will take precedence over the one shipped by us.

A completion file for a specific command `<cmd>` can be placed at
   `<localdir>/completions/<cmd>.bash`, where `<localdir>` is
   `/usr/local/share/bash-completion` if `XDG_DATA_DIRS` is not defined, or
   `<datadir>/bash-completion` where `<datadir>` is one of the directories
   listed in `XDG_DATA_DIRS`.

> [!NOTE]
   > See also the answer to Q4 for considerations for those files' names, they
   > apply here as well.

Similarly, systemwide startup files can be placed in the directory
   `<localdir>/startup`.

**Q4. I author/maintain a distribution package and would like to maintain my
   own completion code for this package. Where should I put it to be sure that
   interactive bash shells will find it and source it?**

> [!NOTE]
   > Here, how to make the completion code visible to bash-completion is
   > explained.  We do not require always making the completion code visible to
   > bash-completion.  In what condition the completion code is installed
   > should be determined at the author/maintainers' own discretion.

A. Install it in one of the directories pointed to by bash-completion's
   `pkgconfig` file variables.

- The recommended directory for the completions of specific commands is
     `<completionsdir>`, which you can get with
     `pkg-config --variable=completionsdir bash-completion`.  From this
     directory, completions are automatically loaded on demand based on invoked
     commands' names, so be sure to name your completion file accordingly, and
     to include (for example) symbolic links in case the file provides
     completions for more than one command. The completion filename for command
     `foo` in this directory should be `foo.bash` to avoid conflicts with
     completions possibly shipped for the same command by the installed < 2.18
     version of bash-completion (which did not use the `.bash` suffix for any
     of its completion files), and because the `.bash` suffixed version has
     higher load order precedence. Unsuffixed `foo` also works,
     but is deprecated in >= 2.18 for these reasons.
   - Helper scripts used by completions may be placed in the directory
     `<helpersdir>`, which can be retrieved with `pkg-config
     --variable=helpersdir bash-completion`.  The completion files in
     `<completionsdir>` can reference the helper script `<helpersdir>/<helper>`
     as `${BASH_SOURCE[0]%/*}/../helpers/<helper>`.
   - The directory for startup files is `<startupdir>`, whose value in the
     current system can be retrieved by
     `pkg-config bash-completion --variable=startupdir`.  A typical value is
     `/usr/share/bash-completion/startup`.  Typically, the startup file can be
     used to override the `complete -D` settings set by bash-completion.
   - The other directory, which is only present for backwards compatibility and
     is not recommended to use, is `<compatdir>` (get it with
     `pkg-config --variable=compatdir bash-completion`).  From this
     directory, files are loaded eagerly when `bash_completion` is loaded.

For packages using GNU autotools the installation can be handled
   for example like this in `configure.ac`:

```m4
   PKG_CHECK_VAR(bashcompdir, [bash-completion], [completionsdir], ,
     bashcompdir="${datadir}/bash-completion/completions")
   AC_SUBST(bashcompdir)
   ```

...accompanied by this in `Makefile.am`:

```makefile
   bashcompdir = @bashcompdir@
   dist_bashcomp_DATA = your-completion-file.bash # completion files go here
   ```

For cmake we ship the `bash-completion-config.cmake` and
   `bash-completion-config-version.cmake` files. Example usage:

```cmake
   include(GNUInstallDirs)
   find_package(bash-completion)
   if(BASH_COMPLETION_FOUND)
     message(STATUS
       "Using bash completion dir ${BASH_COMPLETION_COMPLETIONSDIR}")
   else()
     set (BASH_COMPLETION_COMPLETIONSDIR "${CMAKE_INSTALL_DATADIR}/bash-completion/completions")
     message (STATUS
       "Using fallback bash completion dir ${BASH_COMPLETION_COMPLETIONSDIR}")
   endif()

install(FILES your-completion-file.bash DESTINATION
     ${BASH_COMPLETION_COMPLETIONSDIR})
   ```

In bash-completion >= 2.12, we search the data directory of
   `bash-completion` under the installation prefix where the target command is
   installed.  When one can assume that the version of the target
   bash-completion is 2.12 or higher, the completion script can actually be
   installed to `$PREFIX/share/bash-completion/completions/` under the same
   installation prefix as the target program installed under `$PREFIX/bin/` or
   `$PREFIX/sbin/`.  For the detailed search order, see also Q10 below.

Example for `Makefile.am`:

```makefile
   bashcompdir = $(datarootdir)/bash-completion/completions
   dist_bashcomp_DATA = your-completion-file.bash
   ```

Example for `CMakeLists.txt`:

```cmake
   install(FILES your-completion-file.bash DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/bash-completion/completions")
   ```

**Q5. When completing on a symlink to a directory, bash does not append
   the trailing `/` and I have to hit <kbd>&lt;Tab></kbd> again.
   I don't like this.**

A. This has nothing to do with `bash_completion`. It's the default for
   completing symlinks to directories since bash 2.05a, and was added
   because sometimes you want to operate on the symlink itself, rather
   than what it points to.

You can get the pre-2.05a behaviour back by putting `set
   mark-symlinked-directories on` in your `/etc/inputrc` or
   `~/.inputrc` file.

**Q6. Completion goes awry when I try to complete on something that contains
   a colon.**

A. This is actually a 'feature' of bash. bash recognises a colon as
   starting a new completion token, which is often what you want when
   completing something like a `PATH` variable:

```shell
   export PATH=/bin:/sbin:/usr<Tab>
   ```

Without the special treatment of the colon, the above wouldn't work
   without programmable completion, so it has long been a feature of
   the shell.

Unfortunately, you don't want the colon to be treated as a special
   case when doing something like:

```shell
   man File::B<Tab>
   ```

Here, the colons make bash think that it's completing a new token
   that begins with 'B'.

Unfortunately, there's no way to turn this off. The only thing you
   can do is escape the colons with a backslash.

**Q7. Why is `rpm` completion so slow with `-q`?**

A. Probably because the database is being queried every time and this uses a
   lot of memory.

You can make this faster by pregenerating the list of installed
   packages on the system. Make sure you have a readable file called
   `/var/log/rpmpkgs`. It's generated by `/etc/cron.daily/rpm` on
   some Red Hat and Mandrake and derivative Linux systems.

If you don't have such a cron job, make one:

```shell
   #!/bin/sh

rpm -qa --qf '%{name}-%{version}-%{release}.%{arch}.rpm\n' 2>&1 \
           | sort >/var/log/rpmpkgs
   ```

rpm completion will use this flat text file instead of the RPM database,
   unless it detects that the database has changed since the file was created,
   in which case it will still use the database to ensure accuracy.

**Q8. bash-completion interferes with my `command_not_found_handle` function
   (or the other way around)!**

A. If your `command_not_found_handle` function is not intended to address
   (possibly missing) commands invoked during bash programmable completion
   functions, you can account for this in the function by, for example, testing
   if the `$COMP_POINT` variable is set and taking appropriate action,
   typically returning early and silently with success.  For keybindings with
   `bind -x`, you may additionally want to check if the variable
   `$READLINE_POINT` is set to skip the action.

> [!Note]
   > We recommended checking whether `COMP_LINE` is _set_, which still works if
   > properly done with e.g. `[[ ${COMP_LINE+set} ]]`.  However, if you have
   > been checking if `COMP_LINE` is _non-empty_ with `[[ ${COMP_LINE:-} ]]`,
   > it may fail to detect programmable completion with the setting
   > `complete -E` (in Bash >= 4.1) because `COMP_LINE` can be empty in this
   > context. It is safer to test `COMP_POINT` as one does not need to care
   > about the differences between the set and non-empty states of variables.

**Q9. Can tab completion be made even easier?**

A. The `readline(3)` library offers a few settings that can make tab
   completion easier (or at least different) to use.

For example, try putting the following in either `/etc/inputrc` or
   `~/.inputrc`:

```inputrc
   set show-all-if-ambiguous on
   ```

This will allow single tab completion as opposed to requiring a
   double tab. This makes things much more pleasant, in our opinion.

```inputrc
   set visible-stats on
   ```

This will suffix each returned file completion with a character
   denoting its type, in a similar way to `ls(1)` with `-F` or `--classify`.

```inputrc
   set page-completions off
   ```

This turns off the use of the internal pager when returning long
   completion lists.

**Q10. What is the search order for the completion file of each target
   command?**

A. The completion files of commands are looked up by the shell function
  `_comp_load`.  Here, the search order in bash-completion >= 2.18 is
  explained.  We first list up the bash-completion directories:

1. `BASH_COMPLETION_USER_DIR`.  Each path in `BASH_COMPLETION_USER_DIR`
     separated by colons is considered for a completion directory.
  2. The location of the main `bash_completion` file. The directory
     containing `bash_completion` is considered.
  3. The location of the target command.  When the real location of the command
     is in the directory `<prefix>/bin` or `<prefix>/sbin`, the directory
     `<prefix>/share/bash-completion` is considered.
  4. `XDG_DATA_DIRS` (or the system directories `/usr/local/share:/usr/share`
     if empty).  The subdirectory `bash-completion` of each path
     in `XDG_DATA_DIRS` separated by colons is considered.

The completion files of the name `<cmd>.bash` or `<cmd>`, where `<cmd>` is
  the name of the target command, are searched in the subdirectory
  `completions` in the above bash-completion directories in order.  The file
  that is found first is used.  If no completion file has been found in any
  `completions` directories, the completion files in the subdirectory
  `completions-core` and `completions-fallback` at the location of the main
  `bash_completion` file are searched in order.

bash-completion

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