Regular expression to match DNS hostname or IP Address?

Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?

It's easy to write one that works 95% of the time, but I'm hoping to get something that's well tested to exactly match the latest RFC specs for DNS hostnames.

---

You can use the following regular expressions separately or by combining them in a joint OR expression.

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])$";

ValidIpAddressRegex matches valid IP addresses and ValidHostnameRegex valid host names. Depending on the language you use could have to be escaped with .

---

ValidHostnameRegex is valid as per RFC 1123. Originally, RFC 952 specified that hostname segments could not start with a digit.

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

The original specification of hostnames in RFC 952, mandated that labels could not start with a digit or with a hyphen, and must not end with a hyphen. However, a subsequent specification (RFC 1123) permitted hostname labels to start with digits.

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])$";

---

The hostname regex of smink does not observe the limitation on the length of individual labels within a hostname. Each label within a valid hostname may be no more than 63 octets long.

ValidHostnameRegex="^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])
(.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]))*$"

Note that the backslash at the end of the first line (above) is Unix shell syntax for splitting the long line. It's not a part of the regular expression itself.

Here's just the regular expression alone on a single line:

^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])(.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]))*$

You should also check separately that the total length of the hostname must not exceed 255 characters . For more information, please consult RFC-952 and RFC-1123.

---

To match a valid IP address use the following regex:

(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}

instead of:

([01]?[0-9][0-9]?|2[0-4][0-9]|25[0-5])(.([01]?[0-9][0-9]?|2[0-4][0-9]|25[0-5])){3}

Explanation

Many regex engine match the first possibility in the OR sequence. For instance, try the following regex:

10.48.0.200

Test

Test the difference between good vs bad

链接地址: http://www.djcxy.com/p/92742.html

上一篇: 正则表达式匹配完全限定的类名

下一篇: 正则表达式匹配DNS主机名或IP地址？