# Poco

# class RegularExpression

Library: Foundation
Package: RegExp
Header: Poco/RegularExpression.h

## Description

A class for working with regular expressions. Implemented using PCRE2, the Perl Compatible Regular Expressions library by Philip Hazel (see http://www.pcre.org).

## Member Summary

Member Functions: compileOptions, extract, match, matchOptions, operator !=, operator ==, split, subst, substOne

## Nested Classes

### struct Match

## Types Aliases

### GroupMap

using GroupMap = std::map < int, std::string >;

### MatchVec

using MatchVec = std::vector < Match >;

## Enumerations

### Options

Some of the following options can only be passed to the constructor; some can be passed only to matching functions, and some can be used everywhere.

- Options marked [ctor] can be passed to the constructor.
- Options marked [match] can be passed to match, extract, split and subst.
- Options marked [subst] can be passed to subst.

See the PCRE documentation for more information.

RE_CASELESS = 0x00000001

case insensitive matching (/i) [ctor]

RE_MULTILINE = 0x00000002

enable multi-line mode; affects ^ and $ (/m) [ctor]

RE_DOTALL = 0x00000004

dot matches all characters, including newline (/s) [ctor]

RE_EXTENDED = 0x00000008

totally ignore whitespace (/x) [ctor]

RE_ANCHORED = 0x00000010

treat pattern as if it starts with a ^ [ctor, match]

RE_DOLLAR_ENDONLY = 0x00000020

dollar matches end-of-string only, not last newline in string [ctor]

RE_EXTRA = 0x00000040

enable optional PCRE functionality [ctor]

RE_NOTBOL = 0x00000080

circumflex does not match beginning of string [match]

RE_NOTEOL = 0x00000100

$ does not match end of string [match]

RE_UNGREEDY = 0x00000200

make quantifiers ungreedy [ctor]

RE_NOTEMPTY = 0x00000400

empty string never matches [match]

RE_UTF8 = 0x00000800

assume pattern and subject is UTF-8 encoded [ctor]

RE_NO_AUTO_CAPTURE = 0x00001000

disable numbered capturing parentheses [ctor, match]

RE_NO_UTF8_CHECK = 0x00002000

do not check validity of UTF-8 code sequences [match]

RE_FIRSTLINE = 0x00040000

an unanchored pattern is required to match before or at the first newline in the subject string, though the matched text may continue over the newline [ctor]

RE_DUPNAMES = 0x00080000

names used to identify capturing subpatterns need not be unique [ctor]

RE_NEWLINE_CR = 0x00100000

assume newline is CR ('\r'), the default [ctor]

RE_NEWLINE_LF = 0x00200000

assume newline is LF ('\n') [ctor]

RE_NEWLINE_CRLF = 0x00300000

assume newline is CRLF ("\r\n") [ctor]

RE_NEWLINE_ANY = 0x00400000

assume newline is any valid Unicode newline character [ctor]

RE_NEWLINE_ANYCRLF = 0x00500000

assume newline is any of CR, LF, CRLF [ctor]

RE_GLOBAL = 0x10000000

replace all occurences (/g) [subst]

RE_NO_VARS = 0x20000000

treat dollar in replacement string as ordinary character [subst]

## Constructors

### RegularExpression

RegularExpression(
const std::string & pattern,
int options = 0,
bool study = true
);

Creates a regular expression and parses the given pattern. Note: the study argument is only provided for backwards compatibility and is ignored since POCO release 1.12, which uses PCRE2. For a description of the options, please see the PCRE documentation. Throws a RegularExpressionException if the patter cannot be compiled.

## Destructor

### ~RegularExpression

~RegularExpression();

Destroys the regular expression.

## Member Functions

### extract

int extract(
const std::string & subject,
std::string & str,
int options = 0
) const;

Matches the given subject string against the pattern. Returns the captured string. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### extract

int extract(
const std::string & subject,
std::string::size_type offset,
std::string & str,
int options = 0
) const;

Matches the given subject string, starting at offset, against the pattern. Returns the captured string. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### match

int match(
const std::string & subject,
Match & mtch,
int options = 0
) const;

Matches the given subject string against the pattern. Returns the position of the first captured substring in mtch. If no part of the subject matches the pattern, mtch.offset is std::string::npos and mtch.length is 0. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### match

int match(
const std::string & subject,
std::string::size_type offset,
Match & mtch,
int options = 0
) const;

Matches the given subject string, starting at offset, against the pattern. Returns the position of the captured substring in mtch. If no part of the subject matches the pattern, mtch.offset is std::string::npos and mtch.length is 0. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### match

int match(
const std::string & subject,
std::string::size_type offset,
MatchVec & matches,
int options = 0
) const;

Matches the given subject string against the pattern. The first entry in matches contains the position of the captured substring. The following entries identify matching subpatterns. See the PCRE documentation for a more detailed explanation. If no part of the subject matches the pattern, matches is empty. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### match

bool match(
const std::string & subject,
std::string::size_type offset = 0
) const;

Returns true if and only if the subject matches the regular expression.

Internally, this method sets the RE_ANCHORED and RE_NOTEMPTY options for matching, which means that the empty string will never match and the pattern is treated as if it starts with a ^.

### match

bool match(
const std::string & subject,
std::string::size_type offset,
int options
) const;

Returns true if and only if the subject matches the regular expression.

### match

static bool match(
const std::string & subject,
const std::string & pattern,
int options = 0
);

Matches the given subject string against the regular expression given in pattern, using the given options.

### operator !=

bool operator != (
const std::string & subject
) const;

Returns true if and only if the subject does not match the regular expression.

Internally, this method sets the RE_ANCHORED and RE_NOTEMPTY options for matching, which means that the empty string will never match and the pattern is treated as if it starts with a ^.

### operator ==

bool operator == (
const std::string & subject
) const;

Returns true if and only if the subject matches the regular expression.

Internally, this method sets the RE_ANCHORED and RE_NOTEMPTY options for matching, which means that the empty string will never match and the pattern is treated as if it starts with a ^.

### split

int split(
const std::string & subject,
std::vector < std::string > & strings,
int options = 0
) const;

Matches the given subject string against the pattern. The first entry in captured is the captured substring. The following entries contain substrings matching subpatterns. See the PCRE documentation for a more detailed explanation. If no part of the subject matches the pattern, captured is empty. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### split

int split(
const std::string & subject,
std::string::size_type offset,
std::vector < std::string > & strings,
int options = 0
) const;

Matches the given subject string against the pattern. The first entry in captured is the captured substring. The following entries contain substrings matching subpatterns. See the PCRE documentation for a more detailed explanation. If no part of the subject matches the pattern, captured is empty. Throws a RegularExpressionException in case of an error. Returns the number of matches.

### subst

int subst(
std::string & subject,
const std::string & replacement,
int options = 0
) const;

Substitute in subject all matches of the pattern with replacement. If RE_GLOBAL is specified as option, all matches are replaced. Otherwise, only the first match is replaced. Occurrences of $<n> (for example, $1, $2, ...) in replacement are replaced with the corresponding captured string. $0 is the original subject string. Returns the number of replaced occurrences.

### subst

int subst(
std::string & subject,
std::string::size_type offset,
const std::string & replacement,
int options = 0
) const;

Substitute in subject all matches of the pattern with replacement, starting at offset. If RE_GLOBAL is specified as option, all matches are replaced. Otherwise, only the first match is replaced. Unless RE_NO_VARS is specified, occurrences of $<n> (for example, $0, $1, $2, ... $9) in replacement are replaced with the corresponding captured string. $0 is the captured substring. $1 ... $n are the substrings matching the subpatterns. Returns the number of replaced occurrences.

### compileOptions

static int compileOptions(
int options
);

### matchOptions

static int matchOptions(
int options
);

### substOne

std::string::size_type substOne(
std::string & subject,
std::string::size_type offset,
const std::string & replacement,
int options
) const;