Regular Expressions
A Regular Expression is a compact way to express a text search or replacement.
- Regular expression calculator: Regular Expression Calculator
- Regular expression text calculator: Regular Expression Text Processor
- Regular expression information: Regular Expression Information
- Using Regular Expressions in PeopleSoft - PeopleSoft Regular Expressions
About Regular Expressions
A Regular Expression is a compact way of expressing patterns to search for and, optionally, a replace. It started life within Unix grep, but has now been implemented in many different technologies, for example:
Languages: AWK, Perl, Java, JavaScript
Text Editors: TextPad, UltraEdit
Over the years, there have been extensions to the Regular Expression syntax, but there is a core which all implementations accept.
Search String Rules
^ - matches start of line
$ - matches end of line
. - matches any single character
[abc] - matches single a or b or c
[^abc] - matches a character other than a or b or c
(ab|cd) - matches ab or cd
* - matches zero or any number of the previous character/expression
+ - matches one or more of the previous character/expression
? - matches zero or one of the previous character/expression
{3} - matches three of the previous character/expression
{3,} - matches at least three of the previous character/expression
{3,5} - matches between three and five of the previous character/expression
\n - matches New Line character
\t - matches Tab character
\f - matches Form Feed character
\r - matches Carriage Return character
\v - matches Vertical Tab character
\d - matches any digit
\D - matches a character other than a digit
\w - matches any letter, digit or underscore (_)
\W - matches a character other than a letter, digit or underscore (_)
\s - matches any white space
\S - matches a character other than a white space
\b - matches a word boundary
\B - matches a character other than a word boundary
\. - matches an actual dot (works for all meta characters - including \)
Other characters match with themselves
Replacement String Rules
& - replace with entire matched string
$1 ... $99 - replace with first ... ninety-ninth matched bracketed () expression (provided there are that many in the match expression)
Other Links
Using Regular Expressions for NI Number Validation
