Regular expressions

.

Matches any character

^regex

Finds regex that must match at the beginning of the line.

regex$

Finds regex that must match at the end of the line.

[abc]

Set definition, can match the letter a or b or c.

[abc][vz]

Set definition, can match a or b or c followed by either v or z.

[^abc]

When a caret appears as the first character inside square brackets, it negates the pattern. This pattern matches any character except a or b or c.

[a-d1-7]

Ranges: matches a letter between a and d and figures from 1 to 7, but not d1.

X|Z

Finds X or Z.

XZ

Finds X directly followed by Z.

$

Checks if a line end follows.

\d

Any digit, short for [0-9]

\D

A non-digit, short for [^0-9]

\s

A whitespace character, short for [ \t\n\x0b\r\f]

\S

A non-whitespace character, short for

\w

A word character, short for [a-zA-Z_0-9]

\W

A non-word character [^\w]

\S+

Several non-whitespace characters

\b

Matches a word boundary where a word character is [a-zA-Z0-9_]

*

Occurs zero or more times, is short for {0,}

X* finds no or several letter X, <sbr /> .* finds any character sequence

+

Occurs one or more times, is short for {1,}

X+- Finds one or several letter X

?

Occurs no or one times, ? is short for {0,1}.

X? finds no or exactly one letter X

{X}

Occurs X number of times, {}describes the order of the preceding liberal

\d{3} searches for three digits, .{10} for any character sequence of length 10.

{X,Y}

Occurs between X and Y times,

\d{1,4} means \d must occur at least once and at a maximum of four.

*?

? after a quantifier makes it a reluctant quantifier. It tries to find the smallest match. This makes the regular expression stop at the first match.