Regular Expression Supportedit

Topbeat supports a subset of the regular expression syntax accepted by RE2. Because we use the POSIX implementation, some patterns are currently not supported.

Note

We recommend that you wrap regular expressions in single quotation marks to work around YAML’s string escaping rules. For example, '^\[?[0-9][0-9]:?[0-9][0-9]|^[[:graph:]]+'.

For more examples of supported regexp patterns, see Managing Multiline Messages. Although the examples pertain to Filebeat, the regexp patterns are applicable to other use cases.

Supported Patternsedit

The following patterns are supported:

Pattern Description

Single Characters

x

single character

.

any character

[xyz]

character class

[^xyz]

negated character class

[[:alpha:]]

ASCII character class

[[:^alpha:]]

negated ASCII character class

Composites

xy

x followed by y

x|y

x or y (prefer x)

Repetitions

x*

zero or more x

x+

one or more x

x?

zero or one x

x{n,m}

n or n+1 or … or m x, prefer more

x{n,}

n or more x, prefer more

x{n}

exactly n x

x*?

zero or more x, prefer fewer

x+?

one or more x, prefer fewer

x??

zero or one x, prefer zero

x{n,m}?

n or n+1 or … or m x, prefer fewer

x{n,}?

n or more x, prefer fewer

x{n}?

exactly n x

Grouping

(re)

numbered capturing group (submatch)

Empty Strings

^

at beginning of text or line (m=true)

$

at end of text (like \z not \Z) or line (m=true)

Escape Sequences

\a

bell (same as \007)

\f

form feed (same as \014)

\t

horizontal tab (same as \011)

\n

newline (same as \012)

\r

carriage return (same as \015)

\v

vertical tab character (same as \013)

\*

literal *, for any punctuation character *

\123

octal character code (up to three digits)

\x7F

two-digit hex character code

\x{10FFFF}

hex character code

ASCII Character Classes

[[:alnum:]]

alphanumeric (same as [0-9A-Za-z])

[[:alpha:]]

alphabetic (same as [A-Za-z])

[[:ascii:]]

ASCII (same as \x00-\x7F])

[[:blank:]]

blank (same as [\t ])

[[:cntrl:]]

control (same as [\x00-\x1F\x7F])

[[:digit:]]

digits (same as [0-9])

[[:graph:]]

graphical (same as [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_` {|}~])

[[:lower:]]

lower case (same as [a-z])

[[:print:]]

printable (same as [ -~] == [ [:graph:]])

[[:punct:]]

punctuation (same as [!-/:-@[-`{-~])

[[:space:]]

whitespace (same as [\t\n\v\f\r ])

[[:upper:]]

upper case (same as [A-Z])

[[:word:]]

word characters (same as [0-9A-Za-z_])

[[:xdigit:]]

hex digit (same as [0-9A-Fa-f])

Unsupported Patternsedit

The following patterns are not supported.

Pattern Description

Unsupported Single Characters

\d

Perl character class

\D

negated Perl character class

\pN

Unicode character class (one-letter name)

\p{Greek}

Unicode character class

\PN

negated Unicode character class (one-letter name)

\P{Greek}

negated Unicode character class

Unsupported Grouping

(?P<name>re)

named & numbered capturing group (submatch)

(?:re)

non-capturing group

(?i)abc

set flags within current group, non-capturing

(?i:re)

set flags during re, non-capturing

(?i)PaTTeRN

case-insensitive (default false)

(?m)multiline

multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)

(?s)pattern.

let . match \n (default false)

(?U)x*abc

ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false)

Unsupported Empty Strings

\A

at beginning of text

\b

at ASCII word boundary (\w on one side and \W, \A, or \z on the other)

\B

not at ASCII word boundary

\z

at end of text

Unsupported Escape Sequences

\C

match a single byte even in UTF-8 mode

\Q...\E

literal text ... even if ... has punctuation

Unsupported Perl Character Classes

\d

digits (same as [0-9])

\D

not digits (same as [^0-9])

\s

whitespace (same as [\t\n\f\r ])

\S

not whitespace (same as [^\t\n\f\r ])

\w

word characters (same as [0-9A-Za-z_])

\W

not word characters (same as [^0-9A-Za-z_])