#!/bin/bash
usage() {
    echo "usage: $0 string"
    echo "shows all permutations of a string"
}

# If we don't have any arguments, then show how to use this script
if [ "$1" = "" ]; then
    echo "not enough arguments"
    usage
    exit 1
fi

perm() {
  items="$1"
  out="$2"
  [[ "$items" == "" ]] && echo "$out" && return
  for (( i=0; i<${#items}; i++ )) ; do
    ( perm "${items:0:i}${items:i+1}" "$out${items:i:1}" )
  done
}

perm "$1"