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这个shell是来判断输入的数字是否为合理的浮点数
实现代码如下：
#!/bin/sh
# validfloat -- Tests whether a number is a valid floating-point value.
# Note that this script cannot accept scientific (1.304e5) notation.
# To test whether an entered value is a valid floating-point number, we
# need to split the value at the decimal point. We then test the first part
# to see if it's a valid integer, then test the second part to see if it's a
# valid >=0 integer, so -30.5 is valid, but -30.-8 isn't.
. validint # Bourne shell notation to source the validint function
validfloat()
{
fvalue="$1"
if [ ! -z $(echo $fvalue | sed 's/[^.]//g') ] ; then
decimalPart="$(echo $fvalue | cut -d. -f1)"
fractionalPart="$(echo $fvalue | cut -d. -f2)"
if [ ! -z $decimalPart ] ; then
if ! validint "$decimalPart" "" "" ; then
return 1
fi
fi
if [ "${fractionalPart%${fractionalPart#?}}" = "-" ] ; then
echo "Invalid floating-point number: '-' not allowed \
after decimal point" >&2
return 1
fi
if [ "$fractionalPart" != "" ] ; then
if ! validint "$fractionalPart" "0" "" ; then
return 1
fi
fi
if [ "$decimalPart" = "-" -o -z "$decimalPart" ] ; then
if [ -z $fractionalPart ] ; then
echo "Invalid floating-point format." >&2 ; return 1
fi
fi
else
if [ "$fvalue" = "-" ] ; then
echo "Invalid floating-point format." >&2 ; return 1
fi
if ! validint "$fvalue" "" "" ; then
return 1
fi
fi
return 0
}
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notice：
1）： if [ ! -z $(echo $fvalue | sed 's/[^.]//g') ] 将输入，以.分成整数和小数部分。
2）：if [ "${fractionalPart%${fractionalPart#?}}" = "-" ] 判断小数点后面如果接‘-'号，这输出字符不合法
3）接着的一些if语句就是判断小数及整数部分合不合法
4）由于 valiint函数没给出，脚本不能完全执行，valiint函数是判断字符串是否全为数字.