### Struct

# GLib Regex

since: 2.14

#### Description

    struct GRegex {
      /* No available fields */
    }

A `GRegex` is the “compiled” form of a regular expression pattern.

`GRegex` implements regular expression pattern matching using syntax and semantics similar to Perl regular expression. See the PCRE documentation for the syntax definition.

Some functions accept a `start_position` argument, setting it differs from just passing over a shortened string and setting `G_REGEX_MATCH_NOTBOL` in the case of a pattern that begins with any kind of lookbehind assertion. For example, consider the pattern “\Biss\B” which finds occurrences of “iss” in the middle of words. (“\B” matches only if the current position in the subject is not a word boundary.) When applied to the string “Mississipi” from the fourth byte, namely “issipi”, it does not match, because “\B” is always false at the start of the subject, which is deemed to be a word boundary. However, if the entire string is passed , but with `start_position` set to 4, it finds the second occurrence of “iss” because it is able to look behind the starting point to discover that it is preceded by a letter.

Note that, unless you set the `G_REGEX_RAW` flag, all the strings passed to these functions must be encoded in UTF-8. The lengths and the positions inside the strings are in bytes and not in characters, so, for instance, “\xc3\xa0” (i.e. “à”) is two bytes long but it is treated as a single character. If you set `G_REGEX_RAW` the strings can be non-valid UTF-8 strings and a byte is treated as a character, so “\xc3\xa0” is two bytes and two characters long.

When matching a pattern, “\n” matches only against a “\n” character in the string, and “\r” matches only a “\r” character. To match any newline sequence use “\R”. This particular group matches either the two-character sequence CR + LF (“\r\n”), or one of the single characters LF (linefeed, U+000A, “\n”), VT vertical tab, U+000B, “\v”), FF (formfeed, U+000C, “\f”), CR (carriage return, U+000D, “\r”), NEL (next line, U+0085), LS (line separator, U+2028), or PS (paragraph separator, U+2029).

The behaviour of the dot, circumflex, and dollar metacharacters are affected by newline characters, the default is to recognize any newline character (the same characters recognized by “\R”). This can be changed with `G_REGEX_NEWLINE_CR`, `G_REGEX_NEWLINE_LF` and `G_REGEX_NEWLINE_CRLF` compile options, and with `G_REGEX_MATCH_NEWLINE_ANY`, `G_REGEX_MATCH_NEWLINE_CR`, `G_REGEX_MATCH_NEWLINE_LF` and `G_REGEX_MATCH_NEWLINE_CRLF` match options. These settings are also relevant when compiling a pattern if `G_REGEX_EXTENDED` is set, and an unescaped “#” outside a character class is encountered. This indicates a comment that lasts until after the next newline.

Creating and manipulating the same `GRegex` structure from different threads is not a problem as `GRegex` does not modify its internal state between creation and destruction, on the other hand `GMatchInfo` is not threadsafe.

The regular expressions low-level functionalities are obtained through the excellent PCRE library written by Philip Hazel.

Available since: 2.14

#### Constructors

###### g_regex_new

Compiles the regular expression to an internal form, and does the initial setup of the `GRegex` structure.

since: 2.14

#### Functions

###### g_regex_check_replacement

Checks whether `replacement` is a valid replacement string (see g_regex_replace()), i.e. that all escape sequences in it are valid.

since: 2.14

###### g_regex_error_quark

No description available.

since: 2.0

###### g_regex_escape_nul

Escapes the nul characters in `string` to “\x00”. It can be used to compile a regex with embedded nul characters.

since: 2.30

###### g_regex_escape_string

Escapes the special characters used for regular expressions in `string`, for instance “a.b*c” becomes “a.b*c”. This function is useful to dynamically generate regular expressions.

since: 2.14

###### g_regex_match_simple

Scans for a match in `string` for `pattern`.

since: 2.14

###### g_regex_split_simple

Breaks the string on the pattern, and returns an array of the tokens. If the pattern contains capturing parentheses, then the text for each of the substrings will also be returned. If the pattern does not match anywhere in the string, then the whole string is returned as the first token.

since: 2.14

#### Instance methods

###### g_regex_get_capture_count

Returns the number of capturing subpatterns in the pattern.

since: 2.14

###### g_regex_get_compile_flags

Returns the compile options that `regex` was created with.

since: 2.26

###### g_regex_get_has_cr_or_lf

Checks whether the pattern contains explicit CR or LF references.

since: 2.34

###### g_regex_get_match_flags

Returns the match options that `regex` was created with.

since: 2.26

###### g_regex_get_max_backref

Returns the number of the highest back reference in the pattern, or 0 if the pattern does not contain back references.

since: 2.14

###### g_regex_get_max_lookbehind

Gets the number of characters in the longest lookbehind assertion in the pattern. This information is useful when doing multi-segment matching using the partial matching facilities.

since: 2.38

###### g_regex_get_pattern

Gets the pattern string associated with `regex`, i.e. a copy of the string passed to g_regex_new().

since: 2.14

###### g_regex_get_string_number

Retrieves the number of the subexpression named `name`.

since: 2.14

###### g_regex_match

Scans for a match in `string` for the pattern in `regex`. The `match_options` are combined with the match options specified when the `regex` structure was created, letting you have more flexibility in reusing `GRegex` structures.

since: 2.14

###### g_regex_match_all

Using the standard algorithm for regular expression matching only the longest match in the string is retrieved. This function uses a different algorithm so it can retrieve all the possible matches. For more documentation see g_regex_match_all_full().

since: 2.14

###### g_regex_match_all_full

Using the standard algorithm for regular expression matching only the longest match in the `string` is retrieved, it is not possible to obtain all the available matches. For instance matching “ ” against the pattern “<.*>” you get “ “.

since: 2.14

###### g_regex_match_full

Scans for a match in `string` for the pattern in `regex`. The `match_options` are combined with the match options specified when the `regex` structure was created, letting you have more flexibility in reusing `GRegex` structures.

since: 2.14

###### g_regex_ref

Increases reference count of `regex` by 1.

since: 2.14

###### g_regex_replace

Replaces all occurrences of the pattern in `regex` with the replacement text. Backreferences of the form ‘\number’ or ‘\g‘ in the replacement text are interpolated by the number-th captured subexpression of the match, ‘\g‘ refers to the captured subexpression with the given name. ‘\0’ refers to the complete match, but ‘\0’ followed by a number is the octal representation of a character. To include a literal ‘' in the replacement, write ‘\’.

since: 2.14

###### g_regex_replace_eval

Replaces occurrences of the pattern in regex with the output of `eval` for that occurrence.

since: 2.14

###### g_regex_replace_literal

Replaces all occurrences of the pattern in `regex` with the replacement text. `replacement` is replaced literally, to include backreferences use g_regex_replace().

since: 2.14

###### g_regex_split

Breaks the string on the pattern, and returns an array of the tokens. If the pattern contains capturing parentheses, then the text for each of the substrings will also be returned. If the pattern does not match anywhere in the string, then the whole string is returned as the first token.

since: 2.14

###### g_regex_split_full

Breaks the string on the pattern, and returns an array of the tokens. If the pattern contains capturing parentheses, then the text for each of the substrings will also be returned. If the pattern does not match anywhere in the string, then the whole string is returned as the first token.

since: 2.14

###### g_regex_unref

Decreases reference count of `regex` by 1. When reference count drops to zero, it frees all the memory associated with the regex structure.

since: 2.14