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<GRegex>
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.
(define-values (%return) (regex:get-capture-count self))
Returns the number of capturing subpatterns in the pattern.
(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.
(define-values (%return) (regex:get-has-cr-or-lf? self))
Checks whether the pattern contains explicit CR or LF references.
(define-values (%return) (regex:get-match-flags self))
Returns the match options that regex
was created with.
(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.
(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.
(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()
.
(define-values (%return) (regex:get-string-number self name))
Retrieves the number of the subexpression named name
.
(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.
(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.
(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.
regex |
a GRegex structure from Passed as |
string |
the string to scan for matches Passed as |
string_len |
the length of Inferred from |
start_position |
starting index of the string to match, in bytes Passed as |
match_options |
match options Passed as |
match_info |
pointer to location where to store
the GMatchInfo, or Passed as |
(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); } }
regex |
a GRegex structure from Passed as |
string |
the string to scan for matches Passed as |
string_len |
the length of Inferred from |
start_position |
starting index of the string to match, in bytes Passed as |
match_options |
match options Passed as |
match_info |
pointer to location where to store
the GMatchInfo, or Passed as |
(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".
regex |
a GRegex structure Passed as |
string |
the string to perform matches against Passed as |
string_len |
the length of Inferred from |
start_position |
starting index of the string to match, in bytes Passed as |
replacement |
text to replace each match with Passed as |
match_options |
options for the match Passed as |
(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".
regex |
a GRegex structure Passed as |
string |
the string to perform matches against Passed as |
string_len |
the length of Inferred from |
start_position |
starting index of the string to match, in bytes Passed as |
replacement |
text to replace each match with Passed as |
match_options |
options for the match Passed as |
(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".
(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".
regex |
a GRegex structure Passed as |
string |
the string to split with the pattern Passed as |
string_len |
the length of Inferred from |
start_position |
starting index of the string to match, in bytes Passed as |
match_options |
match time option flags Passed as |
max_tokens |
the maximum number of tokens to split Passed as |
(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.
(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.
(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
.
(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
.
(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()
.
(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".