#!/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 functionvalidfloat(){  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}

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.

      本文转自hb_fukua  51CTO博客，原文链接：http://blog.51cto.com/2804976/591504，如需转载请自行联系原作者