bash url decode

url_decode.sh

#!/bin/bash

urldecode() {
  arg="$1"
  i="0"
  while [ "$i" -lt ${#arg} ]; do
    c0=${arg:$i:1}
    if [ "x$c0" = "x%" ]; then
     c1=${arg:$((i+1)):1}
     c2=${arg:$((i+2)):1}
     printf "\x$c1$c2"
     i=$((i+3))
    else
     echo -n "$c0"
     i=$((i+1))
   fi
  done
}

urldecode "a%27b%27c"