Custom Bash tab completion for my program

I love Bash tab completion, and I want it for the command I am writing, so it can automatically complete parts of the command line when I run my program.

Bash

Code

Here is the script (install-bash-completion) I wrote to set it up (no need to be root - it installs in ~/.local):

#!/bin/bash

set -u
set -e

DIR=${BASH_COMPLETION_USER_DIR:-${XDG_DATA_HOME:-$HOME/.local/share}/bash-completion}/completions

mkdir -p ${DIR}

cp _myprogram ${DIR}

The actual completion script (_myprogram) it installs looks like this:

_myprogram_commands()
{
   local cur prev opts
   COMPREPLY=()
   cur="${COMP_WORDS[COMP_CWORD]}"
   prev="${COMP_WORDS[COMP_CWORD-1]}"
   opts=$(bash -c "./myprogram --commands")

   COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
   return 0
}
complete -F _myprogram_commands ./myprogram

Installing

To install it, run:

./install-bash-completion

Then log out and log in again.

Now when you type./myprogram and press TAB a couple of times, you should see the possible completions listed.

Notes

The completion script must be named to match the program name, with a leading underscore.

If I wanted it to work when it was installed in my PATH, I would need to change./myprogram to just myprogram in 2 places.

Notice the line opts=$(bash -c "./myprogram --commands") - it actually runs my program to get the list of completions. This means my program needs to accept a --commands option which prints the valid commands. Alternatively, I could have hard-coded it by replacing that line with just:

opts="cmd1 cmd2 --help --etc"

More info:

Creating a bash completion script by Lazarus Lazaridis

An introduction to bash completion from Debian Administration

Creating a bash completion script

An introduction to bash completion

Originally posted at 2020-03-11 17:35:15+00:00. Automatically generated from the original post : apologies for the errors introduced.

original post

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