Enable autocomplete for parsed arguments in getopts

Question

I have a bash script that uses getopts to parse command line arguments. One of the arguments, -l <name> is directed to an if statement that determines certain settings. Is it possible to have autocomplete work in the command line for entering the <name> parameter?

Here is the command line parsing part (getopts) of my script:

while getopts 'l:r:m:?h' c
do
  case $c in
    l) 
        library=$OPTARG 
        ;;
    r)  
        rename_config=$OPTARG 
        ;;
    m)  
        align_mm=$OPTARG
        ;;  
    h|?) usage 
        ;;
  esac
done

The library option (-l) refers to this part of the script:

if [ $library = "bassik" ];
    then
        read_mod="clip"
        clip_seq="GTTTAAGAGCTAAGCTGGAAACAGCATAGCAA"
        echo "Bassik library selected"
elif [ $library = "moffat_tko1" ];
    then
        read_mod="trim"
        sg_length=20    
        echo "Moffat TKO1 library selected"
elif [ $library = "sabatini" ];
    then
        read_mod="trim"
        sg_length=20    
        echo "Sabatini library selected"
fi

The part where the auto-completion should work are for "bassik", "moffat_tko1", and "sabatini" parameters. So far, I have tried just hitting <TAB> right after ./script.sh -l, but that does not work. I have googled it, but could not find anything that fits my situation (not sure also how to call this, new to bash).

Yes, it is possible. That's basically what an autocomplete script does. — KamilCuk, Jan 15 '21 at 15:10
It is possible, but you have to give a few more specifics – what do you call your script like, what are the autocompletion options (is it a list of words, or somehow dynamically generated?) Have you tried something that didn't work? — Benjamin W., Jan 15 '21 at 15:12
Thank you for your comments. I have edited my question to make it clearer — justinian482, Jan 15 '21 at 15:20

Rachid K. · Accepted Answer · 2021-01-16T07:32:00.260

First I copied your script snippet in a file called auto.sh and set the execution permission on it:

#!/bin/bash

while getopts 'l:r:m:?h' c
do
  case $c in
    l) 
        library=$OPTARG 
        ;;
    r)  
        rename_config=$OPTARG 
        ;;
    m)  
        align_mm=$OPTARG
        ;;  
    h|?) usage 
        ;;
  esac
done


if [ $library = "bassik" ];
    then
        read_mod="clip"
        clip_seq="GTTTAAGAGCTAAGCTGGAAACAGCATAGCAA"
        echo "Bassik library selected"
elif [ $library = "moffat_tko1" ];
    then
        read_mod="trim"
        sg_length=20    
        echo "Moffat TKO1 library selected"
elif [ $library = "sabatini" ];
    then
        read_mod="trim"
        sg_length=20    
        echo "Sabatini library selected"
fi

Then, to set up an auto-completion for the -l option, you can begin with those basics steps (this can be future enhanced):

1. Create a completion script (e.g. ./auto-complete.sh) which contains the libs function to be called upon completion request (-F parameter of complete command). The function triggers the display of the library names (content of COMPREPLY array variable) if -l option is the word preceding the completion place ($3 argument):

function libs()
{
  # $1 is the name of the command 
  # $2 is the word being completed
  # $3 is the word preceding the word being completed

  case $3 in
    -l) COMPREPLY+=("bassi")
        COMPREPLY+=("moffat_tko1")
        COMPREPLY+=("sabatini");;
  esac
}

complete -F libs auto.sh

2. Source the script in your local shell:

$ source ./auto-complete.sh

3. Launch the shell script and type TAB key twice after a space behind the -l option:

$ ./auto.sh -l <tab><tab>
bassik       moffat_tko1  sabatini
$ ./auto.sh  -l bassik
Bassik library selected

4. The preceding systematically lists all the choices when you type TAB key. To have a more accurate completion when typing the first letters, the completion script can be enhanced to use compgen command:

function libs()
{
  # $1 is the name of the command 
  # $2 is the word being completed
  # $3 is the word preceding the word being completed

  case $3 in
    -l) COMPREPLY=($(compgen -W "bassik moffat_tko1 sabatini" "${COMP_WORDS[$COMP_CWORD]}"));;
  esac
}

complete -F libs auto.sh

Brilliant, it worked! Thank you for you for putting so much effort in your answer. — justinian482, Jan 16 '21 at 21:02

Enable autocomplete for parsed arguments in getopts

1 Answers1