今天的案例是将 对用户输入的判断的

#!/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

解析脚本：
1） number="$1"; min="$2"; max="$3" 指用户的3个输入；
2）nodigits="$(echo $testvalue | sed 's/[[:digit:]]//g')" 为后面测试用户输入的是否全为数字做准备
3）if validint "$1" "$2" "$3" ; then 注意 "$1" "$2" "$3"要加引号。
4）testvalue变量是为了过滤负数后测试输入是否全为数字的。
5）感觉想得挺周全的。