FIT SKJ getperm

#!/bin/bash

[ $# -eq 0 ] || exit 2

r=0
w=0
x=0

while read -r -n 1 char
do
    char=$(echo -n $char | tr '[:upper:]' '[:lower:]' | tr -d '[:space:]')
    [ -z $char ] && continue
    [[ $char =~ ^[rwxst]$ ]] || exit 1
    [ $char = r ] && r=1
    [ $char = w ] && w=1
    [ $char = x -o $char = s -o $char = t ] && x=1
done

[ $r -eq 0 ] && printf 'r' || printf '-'
[ $w -eq 0 ] && printf 'w' || printf '-'
[ $x -eq 0 ] && printf 'x' || printf '-'
printf '\n'
exit 0