Bash script to take a screenshot

screenshot.sh

#! /bin/bash
set -eu

usage() { echo "Usage: $0 [-w WAIT] [PNGFILE]" 1>&2; }

while getopts "w:h" o; do
  case "${o}" in
    w) wait=$((OPTARG));;
    h) usage; exit 0;;
    *) exit 1;;
  esac
done
shift $((OPTIND-1))

if (( ${wait:-0} > 0)); then
  sleep $wait
fi

if (( $# > 0 )); then
  exec > "$1"
fi

xwd | convert xwd:- png:-