bash-completion: the greatest things since bash completion

March 1st, 2009 edited by Tincho

Article submitted by Andre Masella. Guess what? We still need you to submit good articles about software you like!

Pressing the tab key in bash to auto-complete a file name is one of the most time saving tricks especially when dealing with very long file names. Unfortunately, file name completion is not always the right behavior. Take Subversion for example. The first argument to svn is the sub-command to use. The file name is also restricted: svn add only takes files not under revision control and svn rm only takes files that are under revision control.

This is where the bash-completion package steps in. After installing it with a quick apt-get install bash-completion, a few lines need to be uncommented in sudo vim /etc/bash.bashrc and the shell restarted. After that, try this:

$ svn <TAB><TAB>
add         cl          diff        list        move        propdel     rename      unlock
annotate    cleanup     export      lock        mv          propedit    resolve     update
blame       co          -h          log         pdel        propget     resolved    --version
cat         commit      help        ls          pedit       proplist    revert
changelist  copy        --help      merge       pget        propset     rm
checkout    cp          import      mergeinfo   plist       pset        status
ci          delete      info        mkdir       praise      remove      switch

Ta-da! Smarter completion for subversion.

bash-completion will alter the behavior of most commands to limit the display to relevant files. For example, mpg321 will only display MP3 files in the list. Programs like rmmod, iwconfig, ifup, and lvm will display relevant choices that are not files at all. Even bash’s fg and bg will now tab-complete with job identifiers.Completion for man is useful as it will auto-complete only man pages that exist and allows you to incrementally narrow your search by providing the beginning of the man page name, just like with regular files.

Occasionally, it doesn’t behave as expected. Particularly, sometimes a file with the wrong extension will be filtered out by bash-completion. For example, if you save an image for certain Internet forums, the file will sometime lack an extension. bash-completion will then filter out that file because it does not have the right extension. This can also happen if the capitalization is unusual. For example, bash-completion will suggest files that end in .mp3 or .MP3 for mpg321, but not .Mp3. In that case, either rename the file or insert # at the beginning of the line. The # makes bash think this line is a comment and bash-completion returns to regular file name completion. Once finished, remove the # and run the command.

bash-completion is available in Debian and Ubuntu. If it isn’t available, it is very easy to install from source.

Posted in Debian, Ubuntu |

18 Responses

  1. Samat Says:

    Hrm, I’ve had the bash-completion package installed for a long while. I noticed after reading this article that it _isn’t_ enabled till you edit /etc/bash.bashrc.

  2. IceBrain Says:

    I didn’t know this, that is one of the reasons I installed Zsh. On the other hand, it’s not the only reason :P

  3. Sebastian Says:

    It also reads SSH configuration (~/.ssh/config) and parses the hosts defined there (even host aliases defined like “Host example”, a feature which is undocumented in ssh_config man page, to my knowledge)

    Also useful: when using cdargs bookmarks utility, you can not only jump to your bookmarks via “cv” alias, but you can also descend into the directories behind them via bash tab-completion.


  4. annoyed by bash Says:

    yes ist is better than nothing but for me as regular shell-user its too often annoying… why not show all files if tab is pressed once more? nothing.. the tip with the # is not cool!

    i switched to zsh two days ago. this is also very annoying, but its getting better, since everything is configurable (see compinstall). maybe i’ll stay with zsh.

    but for bash this is a must-have compared to the buit-in completion

  5. Erik Says:

    Instead of the # trick, I use alt-/. That will always do normal completion instead of the programmable completion.

  6. John Carter Says:

    I wish there was a key combo, say shift-tab that reverted to ye olde dumb, but sometimes more useful,current working directory files filename completion.

    eg. When I’m using cvs, most cvs modules that I wish to refer to are already in my cwd, and I explicitly _don’t_ wish to refer to any other.

    Alas, smart completion goes off and checks out CVSROOT/modules and presents a LARGE list I really don’t want.

  7. John Carter Says:

    Ok, so I didn’t read all 5 comments. I should have. Thanks Erik for preanswering my question. At least you now have the surety that your comment is appreciated!

  8. Marius Gedminas Says:

    One thing to note, though, is that enabling bash-completion slows down the startup time of bash. If you’re like me and open new terminals willy-nilly (Ctrl+Alt+T is reason enough to madly love GNOME Terminal: instant new shell in the right $PWD) this becomes very noticeable. I once took the time to extract the completions I liked most (like remote filename completion in scp command lines, awesome if you use ssh-agent) into a cut-down version sourced from my .bashrc.

    Nice tricks with the #, and Alt-/

  9. Martin Rakhmanov Says:

    typo: mpg321
    also bash-completion will show directories as well for mpg123.

  10. James Says:

    Are there docs somewhere on how to make your own program supply auto-complete information to bash? I’m just wondering how it figures out “available” items.

  11. Vicho Says:

    You can learn more about how bash-completion works in a very nice Debian Administration article: part 1 and part 2. If you want more detail, you can always check the bash manpage.

  12. Neko Says:

    Hot damn, thanks for that Alt-/ tip! Bash completion is nice, but I know it has infuriated me in the past when the filename extension filter got too zealous.

  13. Kevin Mitchell Says:

    The following ~/.inputrc tweaks are indispensable (though I’m not sure why their equivalents don’t seem to work in ~/.bashrc):

    # tired of having to mash tab twice?
    set show-all-if-ambiguous on

    # no “are you sure you want to see this many completions?” prompt
    set completion-query-items 10000

    # more is the most annoying program on the planet
    set page-completions off

  14. bitty Says:

    You may also want to turn on inline mode for tab completion:

    “\t”: menu-complete

  15. z Says:

    When will linux distros get rid of the obsolete bash to replace it with the all-mighty zsh ?

  16. lefty.crupps Says:

    > a few lines need to be uncommented in sudo vim /etc/bash.bashrc

    Aaah, which lines would those be? My bash.bashrc doesn’t have any lines there that mention this package/functionality.

  17. Linulin Says:

    $ grep -C1 completion .bashrc

    # enable programmable completion features (you don’t need to enable
    # this, if it’s already enabled in /etc/bash.bashrc and /etc/profile
    # sources /etc/bash.bashrc).
    if [ -f /etc/bash_completion ]; then
    . /etc/bash_completion

  18. Linulin Says:

    $ grep -C1 completion /etc/bash.bashrc

    # enable bash completion in interactive shells
    #if [ -f /etc/bash_completion ]; then
    # . /etc/bash_completion