<GRegex>

<GRegex>

Description

The g_regex_*() functions implement regular expression pattern matching using syntax and semantics similar to Perl regular expression.

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.

When setting the G_REGEX_JAVASCRIPT_COMPAT flag, pattern syntax and pattern matching is changed to be compatible with the way that regular expressions work in JavaScript. More precisely, a lonely ']' character in the pattern is a syntax error; the '\x' escape only allows 0 to 2 hexadecimal digits, and you must use the '\u' escape sequence with 4 hex digits to specify a unicode codepoint instead of '\x' or 'x{....}'. If '\x' or '\u' are not followed by the specified number of hex digits, they match 'x' and 'u' literally; also '\U' always matches 'U' instead of being an error in the pattern. Finally, pattern matching is modified so that back references to an unset subpattern group produces a match with the empty string instead of an error. See pcreapi(3) for more information.

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](http://www.pcre.org/) library written by Philip Hazel.

Functions

get-capture-count

(define-values (%return) (regex:get-capture-count self))

Returns the number of capturing subpatterns in the pattern.

Parameters

regex

a GRegex

Passed as self

get-compile-flags

(define-values (%return) (regex:get-compile-flags self))

Returns the compile options that regex was created with.

Depending on the version of PCRE that is used, this may or may not include flags set by option expressions such as (?i) found at the top-level within the compiled pattern.

Parameters

regex

a GRegex

Passed as self

get-has-cr-or-lf?

(define-values (%return) (regex:get-has-cr-or-lf? self))

Checks whether the pattern contains explicit CR or LF references.

Parameters

regex

a GRegex structure

Passed as self

get-match-flags

(define-values (%return) (regex:get-match-flags self))

Returns the match options that regex was created with.

Parameters

regex

a GRegex

Passed as self

get-max-backref

(define-values (%return) (regex:get-max-backref self))

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

Parameters

regex

a GRegex

Passed as self

get-max-lookbehind

(define-values (%return) (regex:get-max-lookbehind self))

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.

Parameters

regex

a GRegex structure

Passed as self

get-pattern

(define-values (%return) (regex:get-pattern self))

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

Parameters

regex

a GRegex structure

Passed as self

get-string-number

(define-values (%return) (regex:get-string-number self name))

Retrieves the number of the subexpression named name.

Parameters

regex

GRegex structure

Passed as self

name

name of the subexpression

Passed as name

match

(define-values (%return match-info) (regex:match self string match-options))

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.

Unless G_REGEX_RAW is specified in the options, string must be valid UTF-8.

A GMatchInfo structure, used to get information on the match, is stored in match_info if not NULL. Note that if match_info is not NULL then it is created even if the function returns FALSE, i.e. you must free it regardless if regular expression actually matched.

To retrieve all the non-overlapping matches of the pattern in string you can use g_match_info_next().

static void
print_uppercase_words (const gchar *string)
{
  // Print all uppercase-only words.
  GRegex *regex;
  GMatchInfo *match_info;
 
  regex = g_regex_new ("[A-Z]+", 0, 0, NULL);
  g_regex_match (regex, string, 0, &match_info);
  while (g_match_info_matches (match_info))
    {
      gchar *word = g_match_info_fetch (match_info, 0);
      g_print ("Found: %s\n", word);
      g_free (word);
      g_match_info_next (match_info, NULL);
    }
  g_match_info_free (match_info);
  g_regex_unref (regex);
}

string is not copied and is used in GMatchInfo internally. If you use any GMatchInfo method (except g_match_info_free()) after freeing or modifying string then the behaviour is undefined.

Parameters

regex

a GRegex structure from g_regex_new()

Passed as self

string

the string to scan for matches

Passed as string

match_options

match options

Passed as match-options

match_info

pointer to location where to store the GMatchInfo, or NULL if you do not need it

Passed as match-info

match-all

(define-values
  (%return match-info)
  (regex:match-all self string match-options))

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().

A GMatchInfo structure, used to get information on the match, is stored in match_info if not NULL. Note that if match_info is not NULL then it is created even if the function returns FALSE, i.e. you must free it regardless if regular expression actually matched.

string is not copied and is used in GMatchInfo internally. If you use any GMatchInfo method (except g_match_info_free()) after freeing or modifying string then the behaviour is undefined.

Parameters

regex

a GRegex structure from g_regex_new()

Passed as self

string

the string to scan for matches

Passed as string

match_options

match options

Passed as match-options

match_info

pointer to location where to store the GMatchInfo, or NULL if you do not need it

Passed as match-info

match-all-full

(define-values
  (%return match-info)
  (regex:match-all-full self string start-position match-options))

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 "<a> <b> <c>" against the pattern "<.*>" you get "<a> <b> <c>".

This function uses a different algorithm (called DFA, i.e. deterministic finite automaton), so it can retrieve all the possible matches, all starting at the same point in the string. For instance matching "<a> <b> <c>" against the pattern "<.*>;" you would obtain three matches: "<a> <b> <c>", "<a> <b>" and "<a>".

The number of matched strings is retrieved using g_match_info_get_match_count(). To obtain the matched strings and their position you can use, respectively, g_match_info_fetch() and g_match_info_fetch_pos(). Note that the strings are returned in reverse order of length; that is, the longest matching string is given first.

Note that the DFA algorithm is slower than the standard one and it is not able to capture substrings, so backreferences do not work.

Setting start_position 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, such as "\b".

Unless G_REGEX_RAW is specified in the options, string must be valid UTF-8.

A GMatchInfo structure, used to get information on the match, is stored in match_info if not NULL. Note that if match_info is not NULL then it is created even if the function returns FALSE, i.e. you must free it regardless if regular expression actually matched.

string is not copied and is used in GMatchInfo internally. If you use any GMatchInfo method (except g_match_info_free()) after freeing or modifying string then the behaviour is undefined.

Parameters

regex

a GRegex structure from g_regex_new()

Passed as self

string

the string to scan for matches

Passed as string

string_len

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

start_position

starting index of the string to match, in bytes

Passed as start-position

match_options

match options

Passed as match-options

match_info

pointer to location where to store the GMatchInfo, or NULL if you do not need it

Passed as match-info

match-full

(define-values
  (%return match-info)
  (regex:match-full self string start-position match-options))

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.

Setting start_position 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, such as "\b".

Unless G_REGEX_RAW is specified in the options, string must be valid UTF-8.

A GMatchInfo structure, used to get information on the match, is stored in match_info if not NULL. Note that if match_info is not NULL then it is created even if the function returns FALSE, i.e. you must free it regardless if regular expression actually matched.

string is not copied and is used in GMatchInfo internally. If you use any GMatchInfo method (except g_match_info_free()) after freeing or modifying string then the behaviour is undefined.

To retrieve all the non-overlapping matches of the pattern in string you can use g_match_info_next().

static void
print_uppercase_words (const gchar *string)
{
  // Print all uppercase-only words.
  GRegex *regex;
  GMatchInfo *match_info;
  GError *error = NULL;
  
  regex = g_regex_new ("[A-Z]+", 0, 0, NULL);
  g_regex_match_full (regex, string, -1, 0, 0, &match_info, &error);
  while (g_match_info_matches (match_info))
    {
      gchar *word = g_match_info_fetch (match_info, 0);
      g_print ("Found: %s\n", word);
      g_free (word);
      g_match_info_next (match_info, &error);
    }
  g_match_info_free (match_info);
  g_regex_unref (regex);
  if (error != NULL)
    {
      g_printerr ("Error while matching: %s\n", error->message);
      g_error_free (error);
    }
}

Parameters

regex

a GRegex structure from g_regex_new()

Passed as self

string

the string to scan for matches

Passed as string

string_len

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

start_position

starting index of the string to match, in bytes

Passed as start-position

match_options

match options

Passed as match-options

match_info

pointer to location where to store the GMatchInfo, or NULL if you do not need it

Passed as match-info

ref

(define-values (%return) (regex:ref self))

Increases reference count of regex by 1.

Parameters

regex

a GRegex

Passed as self

replace

(define-values
  (%return)
  (regex:replace self string start-position replacement match-options))

Replaces all occurrences of the pattern in regex with the replacement text. Backreferences of the form '\number' or '\g<number>' in the replacement text are interpolated by the number-th captured subexpression of the match, '\g<name>' 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 '\\\\'.

There are also escapes that changes the case of the following text:

- \l: Convert to lower case the next character - \u: Convert to upper case the next character - \L: Convert to lower case till \E - \U: Convert to upper case till \E - \E: End case modification

If you do not need to use backreferences use g_regex_replace_literal().

The replacement string must be UTF-8 encoded even if G_REGEX_RAW was passed to g_regex_new(). If you want to use not UTF-8 encoded strings you can use g_regex_replace_literal().

Setting start_position 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, such as "\b".

Parameters

regex

a GRegex structure

Passed as self

string

the string to perform matches against

Passed as string

string_len

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

start_position

starting index of the string to match, in bytes

Passed as start-position

replacement

text to replace each match with

Passed as replacement

match_options

options for the match

Passed as match-options

replace-literal

(define-values
  (%return)
  (regex:replace-literal self string start-position replacement match-options))

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

Setting start_position 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, such as "\b".

Parameters

regex

a GRegex structure

Passed as self

string

the string to perform matches against

Passed as string

string_len

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

start_position

starting index of the string to match, in bytes

Passed as start-position

replacement

text to replace each match with

Passed as replacement

match_options

options for the match

Passed as match-options

split

(define-values (%return) (regex:split self string match-options))

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.

As a special case, the result of splitting the empty string "" is an empty vector, not a vector containing a single string. The reason for this special case is that being able to represent an empty vector is typically more useful than consistent handling of empty elements. If you do need to represent empty elements, you'll need to check for the empty string before calling this function.

A pattern that can match empty strings splits string into separate characters wherever it matches the empty string between characters. For example splitting "ab c" using as a separator "\s*", you will get "a", "b" and "c".

Parameters

regex

a GRegex structure

Passed as self

string

the string to split with the pattern

Passed as string

match_options

match time option flags

Passed as match-options

split-full

(define-values
  (%return)
  (regex:split-full self string start-position match-options max-tokens))

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.

As a special case, the result of splitting the empty string "" is an empty vector, not a vector containing a single string. The reason for this special case is that being able to represent an empty vector is typically more useful than consistent handling of empty elements. If you do need to represent empty elements, you'll need to check for the empty string before calling this function.

A pattern that can match empty strings splits string into separate characters wherever it matches the empty string between characters. For example splitting "ab c" using as a separator "\s*", you will get "a", "b" and "c".

Setting start_position 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, such as "\b".

Parameters

regex

a GRegex structure

Passed as self

string

the string to split with the pattern

Passed as string

string_len

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

start_position

starting index of the string to match, in bytes

Passed as start-position

match_options

match time option flags

Passed as match-options

max_tokens

the maximum number of tokens to split string into. If this is less than 1, the string is split completely

Passed as max-tokens

unref

(define-values () (regex:unref self))

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

Parameters

regex

a GRegex

Passed as self

regex:new

(define-values (%return) (regex:new pattern compile-options match-options))

Undocumented

Parameters

pattern

Passed as pattern

compile_options

Passed as compile-options

match_options

Passed as match-options

regex:check-replacement

(define-values (%return has-references) (regex:check-replacement replacement))

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

If has_references is not NULL then replacement is checked for pattern references. For instance, replacement text 'foo\n' does not contain references and may be evaluated without information about actual match, but '\0\1' (whole match followed by first subpattern) requires valid GMatchInfo object.

Parameters

replacement

the replacement string

Passed as replacement

has_references

location to store information about references in replacement or NULL

Passed as has-references

regex:error-quark

(define-values (%return) (regex:error-quark))

Undocumented

regex:escape-nul

(define-values (%return) (regex:escape-nul string length))

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

For completeness, length can be -1 for a nul-terminated string. In this case the output string will be of course equal to string.

Parameters

string

the string to escape

Passed as string

length

the length of string

Passed as length

regex:escape-string

(define-values (%return) (regex:escape-string 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.

string can contain nul characters that are replaced with "\0", in this case remember to specify the correct length of string in length.

Parameters

string

the string to escape

Passed as string

length

the length of string, in bytes, or -1 if string is nul-terminated

Inferred from string

regex:match-simple?

(define-values
  (%return)
  (regex:match-simple? pattern string compile-options match-options))

Scans for a match in string for pattern.

This function is equivalent to g_regex_match() but it does not require to compile the pattern with g_regex_new(), avoiding some lines of code when you need just to do a match without extracting substrings, capture counts, and so on.

If this function is to be called on the same pattern more than once, it's more efficient to compile the pattern once with g_regex_new() and then use g_regex_match().

Parameters

pattern

the regular expression

Passed as pattern

string

the string to scan for matches

Passed as string

compile_options

compile options for the regular expression, or 0

Passed as compile-options

match_options

match options, or 0

Passed as match-options

regex:split-simple

(define-values
  (%return)
  (regex:split-simple pattern string compile-options match-options))

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.

This function is equivalent to g_regex_split() but it does not require to compile the pattern with g_regex_new(), avoiding some lines of code when you need just to do a split without extracting substrings, capture counts, and so on.

If this function is to be called on the same pattern more than once, it's more efficient to compile the pattern once with g_regex_new() and then use g_regex_split().

As a special case, the result of splitting the empty string "" is an empty vector, not a vector containing a single string. The reason for this special case is that being able to represent an empty vector is typically more useful than consistent handling of empty elements. If you do need to represent empty elements, you'll need to check for the empty string before calling this function.

A pattern that can match empty strings splits string into separate characters wherever it matches the empty string between characters. For example splitting "ab c" using as a separator "\s*", you will get "a", "b" and "c".

Parameters

pattern

the regular expression

Passed as pattern

string

the string to scan for matches

Passed as string

compile_options

compile options for the regular expression, or 0

Passed as compile-options

match_options

match options, or 0

Passed as match-options