How can I parse long-form arguments in shell?

Question

Everything I see uses getopt or the slightly-fancier getopts which only supports one-character options (e.g., -h but not --help). I want to do fancy long options.

Answer 1

I've done something like this:

_setArgs(){
  while [ "${1:-}" != "" ]; do
    case "$1" in
      "-c" | "--configFile")
        shift
        configFile=$1
        ;;
      "-f" | "--forceUpdate")
        forceUpdate=true
        ;;
      "-r" | "--forceRetry")
        forceRetry=true
        ;;
    esac
    shift
  done
}

As you can see, this supports both the single-character and the longer options nicely. It allows for values to be associated with each argument, as in the case of --configFile. It's also quite extensible, with no artificial limitations as to what options can be configured, etc.

As included above, the "${1:-}" prevents an "unbound variable" error when running in bash "strict" mode (set -euo pipefail).

Answer 2

Assuming that you "want to do fancy long options" regardless of the tool, just go with getopt (getopts seems to be mainly used when portability is crucial). Here's an example of about the maximum complexity that you'll get:

params="$(getopt -o e:hv -l exclude:,help,verbose --name "$(basename "$0")" -- "$@")"

if [ $? -ne 0 ]
then
    usage
fi

eval set -- "$params"
unset params

while true
do
    case $1 in
        -e|--exclude)
            excludes+=("$2")
            shift 2
            ;;
        -h|--help)
            usage
            ;;
        -v|--verbose)
            verbose='--verbose'
            shift
            ;;
        --)
            shift
            break
            ;;
        *)
            usage
            ;;
    esac
done

With this code, you can specify -e/--exclude more than once, and ${excludes[@]} will contain all of the given excludes. After processing (-- is always present) anything remaining is stored in $@.