## With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

No credit card required

# 6.1. Integer Numbers

## Problem

You want to find various kinds of integer decimal numbers in a larger body of text, or check whether a string variable holds an integer decimal number.

## Solution

Find any positive integer decimal number in a larger body of text:

`\b[0-9]+\b`
 Regex options: None Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Check whether a text string holds just a positive integer decimal number:

`\A[0-9]+\Z`
 Regex options: None Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby
`^[0-9]+\$`
 Regex options: None Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python

Find any positive integer decimal number that stands alone in a larger body of text:

`(?<=^|\s)[0-9]+(?=\$|\s)`
 Regex options: None Regex flavors: .NET, Java, PCRE, Ruby 1.9

For Perl and Python, we have to tweak the preceding solution, because they do not support alternatives of different lengths inside lookbehind:

`(?:^|(?<=\s))[0-9]+(?=\$|\s)`
 Regex options: None Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby 1.9

Find any positive integer decimal number that stands alone in a larger body of text, allowing leading whitespace to be included in the regex match:

`(^|\s)([0-9]+)(?=\$|\s)`
 Regex options: None Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Find any integer decimal number with an optional leading plus or minus sign:

`[+-]?\b[0-9]+\b`
 Regex options: None Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Check whether a text string holds just an integer decimal number with optional sign:

`\A[+-]?[0-9]+\Z ...`

## With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

No credit card required