Regular expression quick start guide

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<tr><td>^</td><td>Matches beginning of a line</td></tr>
 
<tr><td>^</td><td>Matches beginning of a line</td></tr>
 
<tr><td>$</td><td>Matches the end of a line</td></tr>
 
<tr><td>$</td><td>Matches the end of a line</td></tr>
 +
<tr><td>\d</td><td>Matches a digit</td></tr>
 
<tr><td>[characters]</td><td>Matches any single character between the brackets</td></tr>
 
<tr><td>[characters]</td><td>Matches any single character between the brackets</td></tr>
 
<tr><td>re1|re2</td><td>Match either re1 or re2</td></tr>
 
<tr><td>re1|re2</td><td>Match either re1 or re2</td></tr>

Revision as of 01:30, 15 September 2009

Regular Expression PatternExplanations
^Matches beginning of a line
$Matches the end of a line
\dMatches a digit
[characters]Matches any single character between the brackets
re1|re2Match either re1 or re2
re*Matches zero or more occurrences of re
re+Matches one or more occurrences of re
re?Matches zero or one occurrences of re
Re{m,n}Matches at least “m” and at most “n” occurrences of re
(...)Parentheses are used to group regular expressions
\0, \1, \2, ...Substitute the value matched by the nth grouped sub-expression, used in remapped fields.

Here are some examples:

Add 2720 prefix:

/(\d+)/2720\1/

or

/([0-9]*)/2720\1/

Strip first 4 digits:

/([0-9]{4})([0-9]*)/\2/
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