Character lists [a-z] and classes \s

A character list matches one character in the specified range:

[a-z]	Any English letter (from a to z)
[aeiouy]	Any English vowel
[^aeiouy ]	Not vowel and not space
[0-9a-f]	A hexadecimal digit (from 0 to 9, or from A to F)

A character class matches one character of the specified type (letter, digit, etc.):

\d	A digit
\s	Space, tab or line separator
\w	A letter

Dot (.) matches any character.

Repetitions * + ?

The star * matches the previous element zero or more time, the plus + matches it one or more times, and ? matches it zero or one times. Use *? and +? for non-greedy matching.

0*	None or several zeros
\w+	A word (one or more letters)
(http://)?	Optional http:// string
<b>(.*?)</b>	<b> tag

Anchors ^ and $

Caret ^ matches at the beginning of the line, dollar sign $ matches at the end of the line:

^[0-9]	Digit at the beginning of a line
\\$	Backslash at the end of a line

Alternative |

(http|ftp|https)://

Any of the these protocols: http:// or ftp:// or https://

Backreferences \1

Parentheses mark subexpressions, which are numbered from left to right. You can refer to previously defined subexpressions with \1, \2, etc. syntax:

(\d+) \1

Find two equal numbers with space between them (e.g., 123 123)

Text and metacharacters

If you want to search for a word or a number, you could enter them as is. For example, to search for cocoa, just type this word.

The metacharacters are:

[ ] * + ? { } . ( ) ^ $ | \

If you want to find one of metacharacters, type \ before it. For example, to find the text $100, use \$100. If you want to find the backslash itself, repeat it: \\.