Returns the number of capturing subpatterns in the pattern.
the number of capturing subpatterns
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.
flags from GLib.RegexCompileFlags
Checks whether the pattern contains explicit CR or LF references.
true if the pattern contains explicit CR or LF references
Returns the match options that regex was created with.
flags from GLib.RegexMatchFlags
Returns the number of the highest back reference in the pattern, or 0 if the pattern does not contain back references.
the number of the highest back reference
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.
the number of characters in the longest lookbehind assertion.
Gets the pattern string associated with regex, i.e. a copy of
the string passed to g_regex_new().
the pattern of regex
Retrieves the number of the subexpression named name.
name of the subexpression
The number of the subexpression or -1 if name does not exists
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 GLib.Regex structures.
Unless GLib.RegexCompileFlags.RAW is specified in the options, string must be valid UTF-8.
A GLib.MatchInfo 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]+", G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, 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 GLib.MatchInfo internally. If
you use any GLib.MatchInfo method (except g_match_info_free()) after
freeing or modifying string then the behaviour is undefined.
the string to scan for matches
match options
true is the string matched, false otherwise
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 GLib.MatchInfo 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 GLib.MatchInfo internally. If
you use any GLib.MatchInfo method (except g_match_info_free()) after
freeing or modifying string then the behaviour is undefined.
the string to scan for matches
match options
true is the string matched, false otherwise
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 GLib.RegexMatchFlags.NOTBOL in the case of a pattern
that begins with any kind of lookbehind assertion, such as "\b".
Unless GLib.RegexCompileFlags.RAW is specified in the options, string must be valid UTF-8.
A GLib.MatchInfo 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 GLib.MatchInfo internally. If
you use any GLib.MatchInfo method (except g_match_info_free()) after
freeing or modifying string then the behaviour is undefined.
the string to scan for matches
starting index of the string to match, in bytes
match options
true is the string matched, false otherwise
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 GLib.Regex structures.
Setting start_position differs from just passing over a shortened
string and setting GLib.RegexMatchFlags.NOTBOL in the case of a pattern
that begins with any kind of lookbehind assertion, such as "\b".
Unless GLib.RegexCompileFlags.RAW is specified in the options, string must be valid UTF-8.
A GLib.MatchInfo 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 GLib.MatchInfo internally. If
you use any GLib.MatchInfo 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]+", G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, 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);
}
}
the string to scan for matches
starting index of the string to match, in bytes
match options
true is the string matched, false otherwise
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:
If you do not need to use backreferences use g_regex_replace_literal().
The replacement string must be UTF-8 encoded even if GLib.RegexCompileFlags.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 GLib.RegexMatchFlags.NOTBOL in the case of a pattern that
begins with any kind of lookbehind assertion, such as "\b".
the string to perform matches against
starting index of the string to match, in bytes
text to replace each match with
options for the match
a newly allocated string containing the replacements
Replaces occurrences of the pattern in regex with the output of
eval for that occurrence.
Setting start_position differs from just passing over a shortened
string and setting GLib.RegexMatchFlags.NOTBOL in the case of a pattern
that begins with any kind of lookbehind assertion, such as "\b".
The following example uses g_regex_replace_eval() to replace multiple
strings at once:
static gboolean
eval_cb (const GMatchInfo *info,
GString *res,
gpointer data)
{
gchar *match;
gchar *r;
match = g_match_info_fetch (info, 0);
r = g_hash_table_lookup ((GHashTable *)data, match);
g_string_append (res, r);
g_free (match);
return FALSE;
}
...
GRegex *reg;
GHashTable *h;
gchar *res;
h = g_hash_table_new (g_str_hash, g_str_equal);
g_hash_table_insert (h, "1", "ONE");
g_hash_table_insert (h, "2", "TWO");
g_hash_table_insert (h, "3", "THREE");
g_hash_table_insert (h, "4", "FOUR");
reg = g_regex_new ("1|2|3|4", G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, NULL);
res = g_regex_replace_eval (reg, text, -1, 0, 0, eval_cb, h, NULL);
g_hash_table_destroy (h);
...
string to perform matches against
starting index of the string to match, in bytes
options for the match
a function to call for each match
a newly allocated string containing the replacements
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 GLib.RegexMatchFlags.NOTBOL in the
case of a pattern that begins with any kind of lookbehind
assertion, such as "\b".
the string to perform matches against
starting index of the string to match, in bytes
text to replace each match with
options for the match
a newly allocated string containing the replacements
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".
the string to split with the pattern
match time option flags
a null-terminated gchar ** array. Free it using g_strfreev()
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 GLib.RegexMatchFlags.NOTBOL in the case of a pattern
that begins with any kind of lookbehind assertion, such as "\b".
the string to split with the pattern
starting index of the string to match, in bytes
match time option flags
the maximum number of tokens to split string into. If this is less than 1, the string is split completely
a null-terminated gchar ** array. Free it using g_strfreev()
Decreases reference count of regex by 1. When reference count drops
to zero, it frees all the memory associated with the regex structure.
Staticcheck_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 GLib.MatchInfo object.
the replacement string
Staticerror_Staticescape_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.
the string to escape
the length of string
Staticescape_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.
the string to escape
the length of string, in bytes, or -1 if string is nul-terminated
Staticmatch_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().
the regular expression
the string to scan for matches
compile options for the regular expression, or 0
match options, or 0
StaticnewStaticsplit_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".
the regular expression
the string to scan for matches
compile options for the regular expression, or 0
match options, or 0
A GLib.Regex is a compiled form of a regular expression.
After instantiating a GLib.Regex, you can use its methods to find matches in a string, replace matches within a string, or split the string at matches.
GLib.Regex implements regular expression pattern matching using syntax and semantics (such as character classes, quantifiers, and capture groups) similar to Perl regular expression. See the PCRE documentation for details.
A typical scenario for regex pattern matching is to check if a string matches a pattern. The following statements implement this scenario.
The constructor for GLib.Regex includes two sets of bitmapped flags:
Some regex patterns include backslash assertions, such as
\d(digit) or\D(non-digit). The regex pattern must escape those backslashes. For example, the pattern"\\d\\D"matches a digit followed by a non-digit.GLib’s implementation of pattern matching includes a
start_positionargument for some of the match, replace, and split methods. Specifying a start position provides flexibility when you want to ignore the first n characters of a string, but want to incorporate backslash assertions at character n - 1. For example, a database field contains inconsistent spelling for a job title:healthcare providerandhealth-care provider. The database manager wants to make the spelling consistent by adding a hyphen when it is missing. The following regex pattern tests for the stringcarepreceded by a non-word boundary character (instead of a hyphen) and followed by a space.An efficient way to match with this pattern is to start examining at
start_position6 in the stringhealthcareorhealth-care.The method GLib.Regex.match_full (and other methods implementing
start_pos) allow for lookback before the start position to determine if the previous character satisfies an assertion.Unless you set the GLib.RegexCompileFlags.RAW as one of the GLib.RegexCompileFlags, all the strings passed to GLib.Regex methods 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 setG_REGEX_RAW, the strings can be non-valid UTF-8 strings and a byte is treated as a character, so\xc3\xa0is two bytes and two characters long.Regarding line endings,
\nmatches a\ncharacter, and\rmatches a\rcharacter. More generally,\Rmatches all typical line endings: CR + LF (\r\n), 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), and PS (paragraph separator, U+2029).The behaviour of the dot, circumflex, and dollar metacharacters are affected by newline characters. By default, GLib.Regex matches any newline character matched by
\R. You can limit the matched newline characters by specifying the GLib.RegexMatchFlags.NEWLINE_CR, GLib.RegexMatchFlags.NEWLINE_LF, and GLib.RegexMatchFlags.NEWLINE_CRLF compile options, and with GLib.RegexMatchFlags.NEWLINE_ANY, GLib.RegexMatchFlags.NEWLINE_CR, GLib.RegexMatchFlags.NEWLINE_LF and GLib.RegexMatchFlags.NEWLINE_CRLF match options. These settings are also relevant when compiling a pattern if GLib.RegexCompileFlags.EXTENDED is set and an unescaped#outside a character class is encountered. This indicates a comment that lasts until after the next newline.Because GLib.Regex does not modify its internal state between creation and destruction, you can create and modify the same GLib.Regex instance from different threads. In contrast, GLib.MatchInfo is not thread safe.
The regular expression low-level functionalities are obtained through the excellent PCRE library written by Philip Hazel.
Since
2.14