How to ignore invalid arguments with getopts and continue parsing?

Question

I've the following simple code:

#!/usr/bin/env bash
while getopts :f arg; do
  case $arg in
    f) echo Option $arg specified. ;;
    *) echo Unknown option: $OPTARG. ;;
  esac
done

and it works in simple scenarios such as:

$ ./test.sh -f
Option f specified.
$ ./test.sh -a -f
Unknown option: a.
Option f specified.

However it doesn't work for the following:

$ ./test.sh foo -f

$ ./test.sh -a abc -f
Unknown option: a.

How do I fix above code example to support invalid arguments?

Answer 1

It seems getopts simply exits loop once some unknown non-option argument (abc) is found.

I've found the following workaround by wrapping getopts loop into another loop:

#!/usr/bin/env bash
while :; do
  while getopts :f arg; do
    case $arg in
      f)
        echo Option $arg specified.
        ;;
      *)
        echo Unknown option: $OPTARG.
        ;;
    esac
  done
  ((OPTIND++)) 
  [ $OPTIND -gt $# ] && break
done

Then skip the invalid arguments and break the loop when maximum arguments is reached.

Output:

$ ./test.sh abc -f
Option f specified.
$ ./test.sh -a abc -f
Unknown option: a.
Option f specified.