shell中怎么判断用户输入，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
#!/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。
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