您可以单独使用下列正则表达式，也可以将它们组合在一个联合或表达式中使用。

ValidIpAddressRegex = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$";

ValidHostnameRegex = "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$";

valididpaddressregex匹配有效的IP地址，ValidHostnameRegex匹配有效的主机名。根据您使用的语言，\可能必须用\进行转义。

ValidHostnameRegex根据RFC 1123有效。最初，RFC 952规定主机名段不能以数字开头。

http://en.wikipedia.org/wiki/Hostname

原规格 RFC中的主机名 952年, 规定标签不能开始 用数字或连字符，和 不能以连字符结尾。然而,一个 后续规范(RFC 1123) 允许启动主机名标签 与数字。

Valid952HostnameRegex = "^(([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z]|[A-Za-z][A-Za-z0-9\-]*[A-Za-z0-9])$";

"^((\\d{1,2}|1\\d{2}|2[0-4]\\d|25[0-5])\.){3}(\\d{1,2}|1\\d{2}|2[0-4]\\d|25[0-5])$"

Regarding IP addresses, it appears that there is some debate on whether to include leading zeros. It was once the common practice and is generally accepted, so I would argue that they should be flagged as valid regardless of the current preference. There is also some ambiguity over whether text before and after the string should be validated and, again, I think it should. 1.2.3.4 is a valid IP but 1.2.3.4.5 is not and neither the 1.2.3.4 portion nor the 2.3.4.5 portion should result in a match. Some of the concerns can be handled with this expression:

grep -E '(^|[^[:alnum:]+)(([0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])\.){3}([0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])([^[:alnum:]]|$)' 

The unfortunate part here is the fact that the regex portion that validates an octet is repeated as is true in many offered solutions. Although this is better than for instances of the pattern, the repetition can be eliminated entirely if subroutines are supported in the regex being used. The next example enables those functions with the -P switch of grep and also takes advantage of lookahead and lookbehind functionality. (The function name I selected is 'o' for octet. I could have used 'octet' as the name but wanted to be terse.)

grep -P '(?<![\d\w\.])(?<o>([0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5]))(\.\g<o>){3}(?![\d\w\.])'

如果IP地址在一个包含句子形式文本的文件中，那么点号的处理实际上可能会产生错误的否定，因为句号可以跟在后面，而不是点号符号的一部分。上面的一个变体可以修复这个问题:

grep -P '(?<![\d\w\.])(?<x>([0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5]))(\.\g<x>){3}(?!([\d\w]|\.\d))'

在php: filter_var(gethostbyname($dns)， FILTER_VALIDATE_IP) == true ?'ip': '非ip'

试试这个:

((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)

这对我来说是有效的。

/^(?:[a-zA-Z0-9]+|[a-zA-Z0-9][-a-zA-Z0-9]+[a-zA-Z0-9])(?:\.[a-zA-Z0-9]+|[a-zA-Z0-9][-a-zA-Z0-9]+[a-zA-Z0-9])?$/