Reset the groups for all users matching "user.name" to be primary group "developers", supplementary group "user.name"

usrgrp-reset.sh

#!/bin/bash
function usage() {
    echo -e "Usage: " 1>&2;
    echo -e "\t${0} [-h|-f|-i]" 1>&2;
    echo -e "Description: " 1>&2;
    echo -e "\tReset all users to have \`developer' as their primary group" 1>&2;
}

while getopts ":hfi" FLAG; do
    case "${FLAG}" in
        f)
            ACTION=1
            ;;
        h)
            usage
            exit 0
            ;;
        i)
            ACTION=0
            ;;
        *)
            echo "Invalid option: ${FLAG}"
            usage
            exit 1
            ;;
    esac
done
shift $((OPTIND-1))

if [ -z "${ACTION}" ]; then
    gawk 'BEGIN { FS = ":" } /^\w+\.\w+/ { print "usermod -g developer -G " $1 " " $1 }' /etc/passwd
    echo
    echo "Use \`-f' to force reset of groups "
elif [ $ACTION -eq 0 ]; then
    gawk 'BEGIN { FS = ":" } /^\w+\.\w+/ { system("groups " $1) }' /etc/passwd
    echo
    echo "Use \`-f' to force reset of groups "
elif [ $ACTION -eq 1 ]; then
    gawk 'BEGIN { FS = ":" } /^\w+\.\w+/ { system("usermod -g developer -G " $1 " " $1) }' /etc/passwd
fi

exit 0