regexp.5 (2010 09)

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regexp(5) regexp(5)

NAME

regexp - regular expression and pattern matching notation deﬁnitions

DESCRIPTION

A Regular Expression is a mechanism supported by many utilities for locating and manipulating pat-

terns in text. Pattern Matching Notation is used by shells and other utilities for ﬁle name expansion.

This manual entry deﬁnes two forms of regular expressions: Basic Regular Expressions and

Extended Regular Expressions; and the one form of Pattern Matching Notation.

BASIC REGULAR EXPRESSIONS

Basic regular expression (RE) notation and construction rules apply to utilities deﬁned as using basic

REs. Any exceptions to the following rules are noted in the descriptions of the speciﬁc utilities that use

REs.

REs Matching a Single Character

The following REs match a single character or a single collating element:

Ordinary Characters

An ordinary character is an RE that matches itself. An ordinary character is any character in the sup-

ported character set except newline and the regular expression special characters listed in Special

Characters below. An ordinary character preceded by a backslash (

\) is treated as the ordinary charac-

ter itself, except when the character is (, ), {, or }, or the digits

1 through 9 (see REs Matching Mul-

tiple Characters). Matching is based on the bit pattern used for encoding the character; not on the

graphic representation of the character.

Special Characters

A regular expression special character preceded by a backslash is a regular expression that matches the

special character itself. When not preceded by a backslash, such characters have special meaning in the

speciﬁcation of REs. Regular expression special characters and the contexts in which they have special

meaning are:

.[\ The period, left square bracket, and backslash are special except when used in a

bracket expression (see RE Bracket Expression).

* The asterisk is special except when used in a bracket expression, as the ﬁrst charac-

ter of a regular expression, or as the ﬁrst character following the character pair \(

(see REs Matching Multiple Characters).

^ The circumﬂex is special when used as the ﬁrst character of an entire RE (see

Expression Anchoring) or as the ﬁrst character of a bracket expression.

$ The dollar sign is special when used as the last character of an entire RE (see

Expression Anchoring).

delimiter Any character used to bound (i.e., delimit) an entire RE is special for that RE.

Period

A period (.), when used outside of a bracket expression, is an RE that matches any printable or nonprint-

able character except newline.

RE Bracket Expression

A bracket expression enclosed in square brackets (

[]) is an RE that matches a single collating element

contained in the nonempty set of collating elements represented by the bracket expression.

The following rules apply to bracket expressions:

bracket expression

A bracket expression is either a matching list expression or a non-matching

list expression, and consists of one or more expressions in any order. Expressions

can be: collating elements, collating symbols, noncollating characters, equivalence

classes, range expressions, or character classes. The right bracket (

]) loses its spe-

cial meaning and represents itself in a bracket expression if it occurs ﬁrst in the list

(after an initial ˆ, if any). Otherwise, it terminates the bracket expression (unless

it is the ending right bracket for a valid collating symbol, equivalence class, or char-

acter class, or it is the collating element within a collating symbol or equivalence

class expression). The special characters

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (8 pages)

PAGE 1
regexp(5) regexp(5) NAME regexp - regular expression and pattern matching notation definitions DESCRIPTION A Regular Expression is a mechanism supported by many utilities for locating and manipulating patterns in text. Pattern Matching Notation is used by shells and other utilities for file name expansion. This manual entry defines two forms of regular expressions: Basic Regular Expressions and Extended Regular Expressions; and the one form of Pattern Matching Notation.
PAGE 2
regexp(5) regexp(5) . * [ \ (period, asterisk, left bracket, and backslash) lose their special meaning within a bracket expression. The character sequences: [. [= [: (left-bracket followed by a period, equal-sign or colon) are special inside a bracket expression and are used to delimit collating symbols, equivalence class expressions and character class expressions. These symbols must be followed by a valid expression and the matching terminating .], =], or :].
PAGE 3
regexp(5) regexp(5) For example, with the above collating order and assuming that E is a noncollating character, then both the expressions [[=A=]-E] and [d-a] are invalid. An ending range point can also be the starting range point in a subsequent range expression. Each such range expression is evaluated separately. For example, the bracket expression [a-m-o] is treated as [a-mm-o].
PAGE 4
regexp(5) regexp(5) $RE $ A subexpression can be defined within an RE by enclosing it between the character pairs $ and $. Such a subexpression matches whatever it would have matched without the $ and $. Subexpressions can be arbitrarily nested. An asterisk immediately following the $ loses its special meaning and is treated as itself. An asterisk immediately following the $ is treated as an invalid character.
PAGE 5
regexp(5) regexp(5) have their special meaning are: . [ \ ( ) * + ? $ | The period, left square bracket, backslash, left parenthesis, right parenthesis, asterisk, plus sign, question mark, dollar sign, and vertical bar are special except when used in a bracket expression (see ERE Bracket Expression). ^ The circumflex is special except when used in a bracket expression in a nonleading position. delimiter Any character used to bound (i.e., delimit) an entire ERE is special for that ERE.
PAGE 6
regexp(5) regexp(5) [ ] square brackets * + ? asterisk, plus sign, question mark ^ $ anchoring concatenation alternation | For example, the ERE abba|cde is interpreted as "match either abba or cde. It does not mean "match abb followed by a or c followed in turn by de (because concatenation has a higher order of precedence than alternation). Expression Anchoring An ERE can be limited to matching strings that begin or end a line (i.e.
PAGE 7
regexp(5) regexp(5) Patterns Matching Multiple Characters The following rules may be used to construct patterns matching multiple characters from patterns matching a single character: * The asterisk (*) is a pattern that matches any string, including the null string. RERE The concatenation of patterns matching a single character is a valid pattern that matches the concatenation of the single characters or collating elements matched by each of the concatenated patterns.
PAGE 8
regexp(5) regexp(5) Multiple alternative patterns in a single clause can be specified by separating individual patterns with the vertical bar character (|); strings matching any of the patterns separated this way will cause the corresponding command list to be selected. SEE ALSO ksh(1), sh(1), fnmatch(3C), glob(3C), regcomp(3C), setlocale(3C), environ(5). STANDARDS CONFORMANCE