Regular expressions

See also

[]

Square brackets define a list or range of characters to search for:

[abc]

corresponds to a, b or c

[a-z]

corresponds to any lower case letter

[A-Za-z]

corresponds to each letter

[A-Za-z0-9]

corresponds to any letter or digit

Number

.

corresponds to a single character

*

corresponds to zero or more times the preceding element, for example colou*r matches color, colour, colouur etc.

?

corresponds to zero or once the preceding element. colou?r matches color and colour.

+

matches the previous element one or more times, for example .+ matches ., .., ... etc.

{N}

corresponds N times to the preceding element.

{N,}

matches the previous element N or more times.

{N,M}

corresponds at least N times to the preceding element, but not more than M times.

Position

^

puts the position at the beginning of the line.

$

puts the position at the end of the line.

Escape characters and literals

\

is used to search for a special character, for example to find .org you have to use the regular expression \.org because . is the special character that matches every character.

[\b]

Backspace character

\d

matches every single digit.

\D

matches any non-digit.

\w

matches any part of a word character and is equivalent to [A-Za-z0-9].

\W

matches any non-word character.

\s

matches any space, tab or newline.

\S

matches any non-whitespace character.

\A

Start of a string.

\Z

End of a string.

\b

matches a pattern on a word boundary.

\B

matches any non-word boundary.