如何使用正则表达式匹配IP地址?

ailms

我也是和烈火兄的方法一样

ubuntun

下面这个表达式是正确的

1. 
   
2. egrep '^([1-9][0-9]?|1[0-9]{2}|2[0-2][0-9]|23[0-2])(\.(1?[0-9]{1,2}|2[0-4][0-9]|25[0-5])){3}$'  filename
   

复制代码

使用regex来控制数字的大小，感觉真是麻烦，呵呵

[ 本帖最后由 ubuntun 于 2008-1-6 19:50 编辑 ]

nianzong

都够长的啊呵呵

zhangzhu1984

Now that we have a subexpression to match a single number from 0 through 255, we can wrap it in parentheses and insert it in place of each \d{1,3} in the earlier regex. This gives us (broken across lines to fit the width of the page):

    ^([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.
        ([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])$



Quite a mouthful! Was it worth the trouble? You have to decide for yourself based upon your own needs. It matches only syntactically correct IP addresses, but it can still match semantically incorrect ones, such as 0.0.0.0 (invalid because all the digits are zero). With lookahead (☞133), you can disallow that specific case by putting (?!0+\.0+\.0+\.0+$) after ^, but at some point, you have to decide when being too specific causes the cost/benefit ratio to suffer from diminishing returns. Sometimes it's better to take some of the work out of the regex. For example, if you go back to ^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$ and wrap each component in parentheses to stuff the numbers into the program's version of $1, $2, $3, and $4, you can then validate them by other programming constructs.


参考：Mastering.Regular.Expressions.3rd.Edition.Aug.2006.chm 5.2节

wzx623

"([0-9]{1,3}\.){3}[0-9]{1,3}" 即可

hanye韩也

ifconfig  eth0 | sed -n '2p' | awk -F':' '{print $2}' | awk '{print $1}'
拿去