Question

I am trying to write a wrapper shell script that caches information every time a command is called. It only needs to store the first non-option argument. For example, in

$ mycommand -o option1 -f another --spec more arg1 arg2

I want to retrieve “arg1.”

How can this be done in bash?

Answer 1

Using getopt is probably the way to go.

If you wanted to see argument scanning code in bash, the non-getopt way is:

realargs="$@"
while [ $# -gt 0 ]; do
    case "$1" in
      -x | -y | -z)
        echo recognized one argument option $1 with arg $2
        shift
        ;;
      -a | -b | -c)
        echo recognized zero argument option $1, no extra shift
        ;;
      *)
        saveme=$1
        break 2
        ;;
    esac
    shift
done
set -- $realargs
echo saved word: $saveme
echo run real command: "$@"