检查IP有效性 [英] Check for IP validity

问题描述

如何检查Shell脚本中IP地址的有效性，该IP地址在0.0.0.0到255.255.255.255的范围内?

How do I check the validity of an IP address in a shell script, that is within the range 0.0.0.0 to 255.255.255.255?

推荐答案

如果您使用的是bash，则可以对模式进行简单的正则表达式匹配，而无需验证四边形:

If you're using bash, you can do a simple regex match for the pattern, without validating the quads:

#!/usr/bin/env bash

ip=1.2.3.4

if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
  echo "success"
else
  echo "fail"
fi

如果您坚持使用POSIX shell，则可以使用expr来做基本相同的事情，使用BRE而不是ERE:

If you're stuck with a POSIX shell, then you can use expr to do basically the same thing, using BRE instead of ERE:

#!/bin/sh

ip=1.2.3.4

if expr "$ip" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; then
  echo "success"
else
  echo "fail"
fi

请注意，expr假定您的正则表达式已锚定在字符串的左侧，因此不需要开头的^.

Note that expr assumes that your regex is anchored to the left-hand-side of the string, so the initial ^ is unnecessary.

如果重要的是验证每个四边形是否小于256，显然您将需要更多代码:

If it's important to verify that each quad is less than 256, you'll obviously require more code:

#!/bin/sh

ip=${1:-1.2.3.4}

if expr "$ip" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; then
  for i in 1 2 3 4; do
    if [ $(echo "$ip" | cut -d. -f$i) -gt 255 ]; then
      echo "fail ($ip)"
      exit 1
    fi
  done
  echo "success ($ip)"
  exit 0
else
  echo "fail ($ip)"
  exit 1
fi

或者甚至更少的管道:

#!/bin/sh

ip=${1:-1.2.3.4}

if expr "$ip" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; then
  IFS=.
  set $ip
  for quad in 1 2 3 4; do
    if eval [ \$$quad -gt 255 ]; then
      echo "fail ($ip)"
      exit 1
    fi
  done
  echo "success ($ip)"
  exit 0
else
  echo "fail ($ip)"
  exit 1
fi

或者再次，如果您的shell是bash，那么您可以在不喜欢算术的情况下使用繁琐的正则表达式进行四边形验证:

Or again, if your shell is bash, you could use a cumbersome regular expression for quad validation if you're not fond of arithmetic:

#!/usr/bin/env bash

ip=${1:-1.2.3.4}

re='^(0*(1?[0-9]{1,2}|2([0-4][0-9]|5[0-5]))\.){3}'
 re+='0*(1?[0-9]{1,2}|2([‌​0-4][0-9]|5[0-5]))$'

if [[ $ip =~ $re ]]; then
  echo "success"
else
  echo "fail"
fi

这也可以用BRE表示，但这比我的手指输入要多.

This could also be expressed in BRE, but that's more typing than I have in my fingers.

最后，如果您喜欢将此功能...放入功能中的想法:

And lastly, if you like the idea of putting this functionality ... in a function:

#!/usr/bin/env bash

ip=${1:-1.2.3.4}

ipvalid() {
  # Set up local variables
  local ip=${1:-1.2.3.4}
  local IFS=.; local -a a=($ip)
  # Start with a regex format test
  [[ $ip =~ ^[0-9]+(\.[0-9]+){3}$ ]] || return 1
  # Test values of quads
  local quad
  for quad in {0..3}; do
    [[ "${a[$quad]}" -gt 255 ]] && return 1
  done
  return 0
}

if ipvalid "$ip"; then
  echo "success ($ip)"
  exit 0
else
  echo "fail ($ip)"
  exit 1
fi

您可以通过多种方式执行此操作.我只给你看了几个.

There are many ways you could do this. I've shown you just a few.

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