Regular Expressions Cookbook, 2nd Edition

6.9. Integer Numbers with Separators

Problem

You want to find various kinds of integer numbers in a larger body of text, or check whether a string variable holds an integer number. Underscores are allowed as separators between groups of numbers, to make the integers easier to read. Numbers may not begin or end with an underscore. You want to allow decimal, octal, hexadecimal, and binary numbers. Hexadecimal and binary numbers must be prefixed with 0x and 0b.

0b0111_1111_1111_1111_1111_1111_1111_1111, 0177_7777_7777, 2_147_483_647, and 0x7fff_ffff are examples of valid numbers.

Solution

Find any decimal or octal integer with optional underscores in a larger body of text:

\b[0-9]+(_+[0-9]+)*\b

Regex options: None

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

Find any hexadecimal integer with optional underscores in a larger body of text:

\b0x[0-9A-F]+(_+[0-9A-F]+)*\b

Regex options: Case insensitive

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

Find any binary integer with optional underscores in a larger body of text:

\b0b[01]+(_+[01]+)*\b

Regex options: Case insensitive

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

Find any decimal, octal, hexadecimal, or binary integer with optional underscores in a larger body of text:

\b([0-9]+(_+[0-9]+)*|0x[0-9A-F]+(_+[0-9A-F]+)*|0b[01]+(_+[01]+)*)\b

Regex options: Case insensitive

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

Check whether a text string holds just a decimal, octal, hexadecimal, ...