linux shell实现判断输入的数字是否为合理的浮点数

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
}

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.