I have adapted some code I had to handle just a single possible option. Either run the function or use the help option to give a brief description.

activate-jet ()
 local  iarg=0  narg="$#"
 while (( narg > 0 )); do
   opt="$1" ; iarg=$(( iarg + 1 ))
   case $opt in
     ("-h"|"--help")  echo "TODO" ; return ;;
     (*)  break ;;

I would like to simplify it more if I can, without introducing any strange behaviour by the user when called.

1 Answer 1


This is a possibility, since you state that you only need one argument, therefore there's no need for looping or "casing":

$ activate_jet() { 
    [[ "$#" -gt 1 ]] && echo "Invalid number of arguments" && return
    if [[ ! -z "$1" ]]; then 
      if [[ "$1" = "-h" || "$1" = "--help" ]]; then
        echo "TODO" && return
        echo "Bad argument" && return
    echo "jet activated"
$ activate_jet foo bar
Invalid number of arguments
$ activate_jet foo
Bad argument
$ activate_jet -h
$ activate_jet --help
$ activate_jet
jet activated

Now note that I changed the name of the function replacing the hyphen for an underscore: activate_jet instead of activate-jet, because the hyphen may not be compatible with some shells:


  • Hyphens are non-standard. Stay away from them if you want cross-shell compatibility.
  • Use underscores instead of hyphens: underscores are accepted everywhere.

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