#!/bin/sh# validint -- Validates integer input, allowing negative ints too.function validint{ # Validate first field. Then test against min value $2 and/or # max value $3 if they are supplied. If they are not supplied, skip these tests. number="$1";   min="$2";   max="$3" if [ -z $number ] ; then  echo "You didn't enter anything. Unacceptable." >&2 ; return 1 fi if [ "${number%${number#?}}" = "-" ] ; then # is first char a '-' sign?testvalue="${number#?}"   # all but first character else  testvalue="$number" fi nodigits="$(echo $testvalue | sed 's/[[:digit:]]//g')" if [ ! -z $nodigits ] ; then  echo "Invalid number format! Only digits, no commas, spaces, etc." >&2  return 1 fi if [ ! -z $min ] ; then  if [ "$number" -lt "$min" ] ; then    echo "Your value is too small: smallest acceptable value is $min" >&2    return 1  fi fi if [ ! -z $max ] ; then   if [ "$number" -gt "$max" ] ; then    echo "Your value is too big: largest acceptable value is $max" >&2    return 1   fi fi return 0}if validint "$1" "$2" "$3" ; then echo "That input is a valid integer value within your constraints"fi