Appendix: Regular Expressions

\

Backslash

escape metacharacters

non-printable characters

character types

[ ]

Square Brackets

character class definition

( )

Parenthesis

sub-pattern, to use metacharacters on the enclosed string

{min[,max]}

Curly Brackets

min/max quantifier

{n} - exactly n occurrences

{n,m} - from n to m occurrences

{n,} - at least n occurrences

.

Dot

match any character

?

Question Mark

zero or one occurrences (equals {0,1})

*

Asterisk

zero or more occurrences of preceding character

+

Plus Sign

one or more occurrences (equals {1,})

|

Vertical Bar

alternative

^

Circumflex

anchor pattern to beginning of buffer (usually a word)

$

Dollar

anchor pattern to end of buffer (usually a word)

-

hyphen

range in character class

\a

alarm; the BEL character (hex code 07)

\cX

"control-X", where X is any character

\e

escape (hex code 1B)

\f

formfeed (hex code 0C)

\n

newline (hex code 0A)

\r

carriage return (hex code 0D)

\t

tab (hex code 09)

\ddd

character with octal code ddd

\xhh

character with hex code hh

\d

any decimal digit [0-9]

\D

any character that is not a decimal digit

\s

any whitespace character

\S

any character that is not whitespace

\w

any word character (underscore or alphanumeric character)

\W

any non-word character (not underscore or alphanumeric)