August 2012
Intermediate to advanced
609 pages
19h 16m
English
Content preview from Regular Expressions Cookbook, 2nd Edition
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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 ...
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