Autodetect possible arguments in shell script for completion

Question

Here's a shell script that does some stuff according to with what parameter it was called:

if [ $1 = "-add" ] 
then
    ...
elif [ $1 = "-remove" ]
    ...
else
    ...
fi

A script is an executable one (a link to it was created in the /usr/bin directory). So, I can call it from shell by specifying the link name added in /usr/bin.

What I want, is auto-detecting the possible arguments of script (in my case they are -add, -remove) during it calling. It means that when I'll type a command, related to script calling, then type -re and press a tab button it will suggest that it's -remove and autofill it for me.

How the arguments need to be defined to reach that?

Tried to create aliases in shell config file or few links in /usr/bin directory for all possible inputs and it was working fine, but I don't think it's a best solution for that.

Answer 1

While it does require some configuration outside of your script, adding autocomplete options is fairly easy.

Here's a simple example of a ~/.bash_completion file that adds auto completion of --add and --remove to command yourscript. In a real world case you'd probably want to generate the options by querying the script directly; they're hard coded here for simplicity.

_yourscript_complete()
{
    # list of options for your script
    local options="--add --remove"

    # current word being completed (provided by stock bash completion)
    local current_word="${COMP_WORDS[COMP_CWORD]}"

    # create list of possible matches and store to ${COMREPLY[@}}
    COMPREPLY=($(compgen -W "${options}" -- "$current_word"))
}
complete -F _yourscript_complete yourscript

Note that the ~/.bash_completion is only sourced during login, so you'll need to spawn another login shell to see your changes in action. You may need to enable sourcing of user bash_completion files on your system, too.

The result:

$ yourscript --<tab><tab>
--add     --remove