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Tab Completion for Bash Script Sub-Commands

Taking advantage of the Programmable Tab Completion in Bash, Bash scripts that have subcommands can provide TAB completion in order to discover these subcommands in the following manner:

1. Gather a list of subcommands dynamically, say in a list COMMANDS

2. Use the following code to give completion output

     if [[ -n $COMP_LINE  ]]; then
       line=${COMP_LINE#* }
       for c in "${COMMANDS[@]}"; do
         [[ ${c:0:${#line}} == "${line,,}" ]] && echo "$c"
       done
       exit
     fi
   

   Explaination:

   • Check to see if we are in Tab completion mode. Presence of COMP_LINE is an indication or this.
   • Get the current word we are typing.
   • Match the incomplete work with names of commands in COMMANDS
   • echo any sub-commands that match

3. Add complete -C prog prog to ~/.bashrc, where prog is the program that the above completion code would be a part of.

Related:

• 20220113084600 Programmable Tab Completion in Bash
• 20220114044631 Bash Construct List of Sub-Commands

Reference:

• man bash
• @rwxrob’s Bash Command Template: https://github.com/rwxrob/template-bash-command

Tags:

#literature-note #scripting #tips

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