var="12345" copy=${var} len=${#copy} for((i=$len-1;i>=0;i--)); do rev="$rev${copy:$i:1}"; done echo "var: $var, rev: $rev"
1. Create a temporary byte[] of length equal to the length of the input string. 2. Store the bytes (which we get by using getBytes() method) in reverse order into the temporary byte[] . 3. Create a new String abject using byte[] to store result.