#!/bin/sh

[ -z "$(echo $@ | grep "\-l")" ] && str="a-z A-Z" || [ -z "$(echo $@ | grep "\-u")" ] && str="A-Z a-z" || (echo "cs: missing operand" && exit)
[ -z "$(echo $@ | sed 's/\-l//g;s/\-u//g')" ] && words=$(< /dev/stdin) || words="$(echo $@ | sed 's/\-l//g;s/\-u//g')"

echo $words | tr $str