Saving tab completion possibilities to a file

Question

Instead of displaying all possibilities on terminal screen, as in:

$ ls /etc/<TAB>
Display all 230 possibilities? (y or n)

I want to save all possibilities to a file.

ls /etc/ > file.txt will not always work. apt-get is an example:

$ apt-get <TAB>
autoclean        check            install          update
autoremove       clean            purge            upgrade
build-dep        dist-upgrade     remove           
changelog        dselect-upgrade  source

I'm looking for a command like tabcompletions 'ls /etc/' which outputs all possibilities, so that I can run a command like the one below, which compares the tab completion possibilities for two commands:

diff <(tabcompletions 'ls ') <(tabcompletions 'cd ')

Is that possible?

Also see http://unix.stackexchange.com/questions/23900/how-to-pipe-the-list-of-commands-displayed-by-of-tab-complete — cwd, Dec 31 '12 at 02:50

score 5 · Answer 1 · answered Sep 27 '11 at 14:23

5

In your ~/.bashrc you probably have something like this:

if [ -f /etc/bash_completion ] && ! shopt -oq posix
then
    source /etc/bash_completion
fi

Now, that's where to continue looking, and the header of _quote_readline_by_ref contains the necessary hint:

compgen -f /etc/

Tracing this back, it turns out that (via type compgen) compgen is a "shell builtin", which means it should appear in man bash:

compgen [option] [word]
       Generate possible completion matches for word according to the options ...

answered Sep 27 '11 at 14:23

l0b0

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An example using a completion function, as `_apt_get` would be interesting. – enzotib Sep 27 '11 at 15:59
@enzotib `compgen -F _apt_get`, except that it's not so simple: you would need to set a bunch of variables to emulate the real completion system. Zsh is even worse, the completion primitives (`compadd`, `compset`) only work if called from a completion widget, which in turns only works from the line editor, not from a script or even from a command line. – Gilles 'SO- stop being evil' Sep 27 '11 at 22:23

score 4 · Answer 2 · answered Sep 27 '11 at 21:31

4

Although, a crude method, you could use the command script

$ script -a lsdiff
Script started, file is lsdiff
$ ls <TAB>
a b c ...
$ <Ctrl-D>
Script done, file is lsdiff

Repeat the above for cd and compare the difference.

answered Sep 27 '11 at 21:31

Sudipta Chatterjee

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Gabriel Staples · Answer 3 · 2022-08-30T06:06:45.547

For the ls /etc/<TAB> auto-completion case, do this:

# print to screen
compgen -f /etc/ | sort
# store to file
compgen -f /etc/ | sort > output.txt
# print to screen *and* store to file
compgen -f /etc/ | sort | tee output.txt

See help compgen for more info. compgen apparently stands for "completion generator".

See also man bash and search for compgen, since it is a built-in executable built in to bash. man bash has a lot more info about the compgen command.

Ex: compgen -A command <cmd> is the same as compgen -c <cmd>, and compgen -A file is the same as compgen -f. Search man bash for -A action.

Saving tab completion possibilities to a file

3 Answers3

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