我要评论今天的案例是将 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。
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