Customize tab completion in shell

Question

This may be have a better name than "custom tab completion", but here's the scenario:

Typically when I'm at the command line and I enter a command, followed with {TAB} twice, I get a list of all files and subdirectories in the current directory. For example:

[user@host tmp]$ cat <TAB><TAB>
chromatron2.exe                  Fedora-16-i686-Live-Desktop.iso  isolate.py
favicon.ico                      foo.exe                          James_Gosling_Interview.mp3

However, I noticed at least one program somehow filters this list: wine. Consider:

[user@host tmp]$ wine <TAB><TAB>
chromatron2.exe  foo.exe

It effectively filters the results to *.exe.

Thinking it might be some sort of wrapper script responsible for the filtering, a did a which and file an it turns out wine is not a script but an executable.

Now, I don't know whether this "filter" is somehow encoded in the program itself, or otherwise specified during the default wine install, so I'm not sure whether this question is more appropriate for stackoverflow or superuser, so I'm crossing my fingers and throwing it here. I apologize if I guessed wrong. (Also, I checked a few similar questions, but most were irrelevant or involved editing the shell configuration.)

So my question is, how is this "filtering" accomplished? Thanks in advance.

Answer 1

You will likely find a file on your system called /etc/bash_completion which is full of functions and complete commands that set up this behavior. The file will be sourced by one of your shell startup files such as ~/.bashrc.

There may also be a directory called /etc/bash_completion.d which contains individual files with more completion functions. These files are sourced by /etc/bash_completion.

This is what the wine completion command looks like from the /etc/bash_completion on my system:

complete -f -X '!*.@(exe|EXE|com|COM|scr|SCR|exe.so)' wine

This set of files is in large part maintained by the Bash Completion Project.