?

zero or one of previous, {0,1}

be?t

*

zero or more of previous, maximal, {0,}

b.*t

*?

zero or more of previous, minimal, {0,}?

b.*?t

+

one or more of previous, maximal, {1,}

b.+t

+?

one or more of previous, minimal, {1,}?

b.+?t

{n}

n times of previous

be{n}t

{n,}

n or more times of previous, maximal

b.{n,}t

{n,}?

n or more times of previous, minimal

b.{n,}?t

{n,m}

n to m times of previous

be{1,2}t

.

any character

b.t

[]

any one character in a class

[a-m]

[^]

any one not in a character class

[^a-m]

[\b]

one backspace character

my[\b]word

\d

any one digit, [0-9]

file\d

\D

any one not digit, [^0-9]

file\D

\s

any one white space character, [ \t\n\r\f\v]

my\sword

\S

any one not white space character, [^ \t\n\r\f\v]

my \sord

\w

any one word character, [a-zA-Z0-9_]

my big\w

\W

any one not word character, [^a-zA-Z0-9_]

my\Wbig

^

anchor to start of string

^string

$

anchor to end of string

string$

\b

anchor to word boundary

\bbig

\B

anchor to not word boundary

\Bbig

|

or

(bat)|(bet)

\n

group n

(bat)a\1

()

group

my(.?)fil

(?:)

group without capture

my(?:.?)fil

(?=)

group without capture with positive look ahead

my(?=.?)fil

(?!)

group without capture with negative look ahead

my(?!.?)fil

\f

form feed character

string\f

\n

newline

string\n

\r

carriage return character

string\r

\t

horizontal tab character

one\tfour

\v

vertical tab character

one\vtwo

\/

/ character

\/fil

\\

\ character

\\fil

\.

. character

fil\.bak

\*

* character

one\*two

\+

+ character

\+fil

\?

? character

when\?

\|

| character

one\|two

\(

( character

\(fil\)

\)

) character

\(fil\)

\[

[ character

\[fil\]

\]

] character

\[fil\]

\{

{ character

\{fil\}

\}

} character

\{fil\}

\C

a character itself. Seldom used.

b\at

\cC

a control character

one\cIfour

\x##

character by hexadecimal code

\x41

\###

character by octal code

\101

$n

group n in search pattern, $1, $2, . . . $9

big$1

$+

last group in search pattern

big$+

$`

text before matched pattern

big$`

$'

text after matched pattern

big$'

$&

text of matched pattern

big$&

\$

$ character

big\$