Regular Expressions Getting started with Regular Expressions Character Guide
Example
Note that some syntax elements have different behavior depending on the expression.
| Syntax | Description |
|---|---|
? | Match the preceding character or subexpression 0 or 1 times. Also used for non-capturing groups, and named capturing groups. |
* | Match the preceding character or subexpression 0 or more times. |
+ | Match the preceding character or subexpression 1 or more times. |
{n} | Match the preceding character or subexpression exactly n times. |
{min,} | Match the preceding character or subexpression min or more times. |
{,max} | Match the preceding character or subexpression max or fewer times. |
{min,max} | Match the preceding character or subexpression at least min times but no more than max times. |
- | When included between square brackets indicates to; e.g. [3-6] matches characters 3, 4, 5, or 6. |
^ | Start of string (or start of line if the multiline /m option is specified), or negates a list of options (i.e. if within square brackets []) |
$ | End of string (or end of a line if the multiline /m option is specified). |
(...) | Groups subexpressions, captures matching content in special variables (\1, \2, etc.) that can be used later within the same regex, for example (\w+)\s\1\s matches word repetition |
(?<name>...) | Groups subexpressions, and captures them in a named group |
(?:...) | Groups subexpressions without capturing |
. | Matches any character except line breaks (\n, and usually \r). |
[...] | Any character between these brackets should be matched once. NB: ^ following the open bracket negates this effect. - occurring inside the brackets allows a range of values to be specified (unless it's the first or last character, in which case it just represents a regular dash). |
\ | Escapes the following character. Also used in meta sequences - regex tokens with special meaning. |
\$ | dollar (i.e. an escaped special character) |
\( | open parenthesis (i.e. an escaped special character) |
\) | close parenthesis (i.e. an escaped special character) |
\* | asterisk (i.e. an escaped special character) |
\. | dot (i.e. an escaped special character) |
\? | question mark (i.e. an escaped special character) |
\[ | left (open) square bracket (i.e. an escaped special character) |
\\ | backslash (i.e. an escaped special character) |
\] | right (close) square bracket (i.e. an escaped special character) |
\^ | caret (i.e. an escaped special character) |
\{ | left (open) curly bracket / brace (i.e. an escaped special character) |
\| | pipe (i.e. an escaped special character) |
\} | right (close) curly bracket / brace (i.e. an escaped special character) |
\+ | plus (i.e. an escaped special character) |
\A | start of a string |
\Z | end of a string |
\z | absolute of a string |
\b | word (alphanumeric sequence) boundary |
\1,\2, etc. | back-references to previously matched subexpressions, grouped by (), \1 means the first match, \2 means second match etc. |
[\b] | backspace - when \b is inside a character class ( [] )matches backspace |
\B | negated \b - matches at any position between two-word characters as well as at any position between two non-word characters |
\D | non-digit |
\d | digit |
\e | escape |
\f | form feed |
\n | line feed |
\r | carriage return |
\S | non-white-space |
\s | white-space |
\t | tab |
\v | vertical tab |
\W | non-word |
\w | word (i.e. alphanumeric character) |
{...} | named character set |
| | or; i.e. delineates the prior and preceding options. |
