Regular Expressions Cookbook, 2nd Edition

8.16. Matching IPv4 Addresses

Problem

You want to check whether a certain string represents a valid IPv4 address in 255.255.255.255 notation. Optionally, you want to convert this address into a 32-bit integer.

Solution

Regular expression

Simple regex to check for an IP address:

^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Accurate regex to check for an IP address, allowing leading zeros:

^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}↵
(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Accurate regex to check for an IP address, disallowing leading zeros:

^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}↵
(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])$

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Simple regex to extract IP addresses from longer text:

\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Accurate regex to extract IP addresses from longer text, allowing leading zeros:

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

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Accurate regex to extract IP addresses from longer text, dis25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9]allowing leading zeros:

\b(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}↵ (?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\b ...