GI.GLib.Structs.Regex

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

Some functions accept a startPosition 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 startPosition 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 RegexCompileFlagsJavascriptCompat 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 Regex structure from different threads is not a problem as Regex does not modify its internal state between creation and destruction, on the other hand MatchInfo is not threadsafe.

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

Since: 2.14

Exported types

newtype Regex

Memory-managed wrapper type.

Constructors

Regex (ManagedPtr Regex)

Instances

BoxedObject Regex

Methods

boxedType :: Regex -> IO GType

noRegex :: Maybe Regex

A convenience alias for Nothing :: Maybe Regex.

Methods

checkReplacement

regexCheckReplacement

Arguments

:: (HasCallStack, MonadIO m)

=> Text

replacement: the replacement string

-> m Bool

(Can throw GError)

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

If hasReferences is not Nothing 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 MatchInfo object.

Since: 2.14

errorQuark

regexErrorQuark :: (HasCallStack, MonadIO m) => m Word32

No description available in the introspection data.

escapeNul

regexEscapeNul

Arguments

:: (HasCallStack, MonadIO m)

=> Text

string: the string to escape

-> Int32

length: the length of string

-> m Text

Returns: a newly-allocated escaped string

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.

Since: 2.30

escapeString

regexEscapeString

Arguments

:: (HasCallStack, MonadIO m)

=> [Text]

string: the string to escape

-> m Text

Returns: a newly-allocated escaped 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.

Since: 2.14

getCaptureCount

regexGetCaptureCount

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m Int32

Returns: the number of capturing subpatterns

Returns the number of capturing subpatterns in the pattern.

Since: 2.14

getCompileFlags

regexGetCompileFlags

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m [RegexCompileFlags]

Returns: flags from RegexCompileFlags

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.

Since: 2.26

getHasCrOrLf

regexGetHasCrOrLf

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> m Bool

Returns: True if the pattern contains explicit CR or LF references

Checks whether the pattern contains explicit CR or LF references.

Since: 2.34

getMatchFlags

regexGetMatchFlags

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m [RegexMatchFlags]

Returns: flags from RegexMatchFlags

Returns the match options that regex was created with.

Since: 2.26

getMaxBackref

regexGetMaxBackref

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m Int32

Returns: the number of the highest back reference

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

Since: 2.14

getMaxLookbehind

regexGetMaxLookbehind

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> m Int32

Returns: the number of characters in the longest lookbehind assertion.

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

getPattern

regexGetPattern

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> m Text

Returns: the pattern of regex

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

Since: 2.14

getStringNumber

regexGetStringNumber

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: Regex structure

-> Text

name: name of the subexpression

-> m Int32

Returns: The number of the subexpression or -1 if name does not exists

Retrieves the number of the subexpression named name.

Since: 2.14

match

regexMatch

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure from regexNew

-> Text

string: the string to scan for matches

-> [RegexMatchFlags]

matchOptions: match options

-> m (Bool, MatchInfo)

Returns: True is the string matched, False otherwise

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

A MatchInfo structure, used to get information on the match, is stored in matchInfo if not Nothing. Note that if matchInfo is not Nothing 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 matchInfoNext.

C code

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 MatchInfo internally. If you use any MatchInfo method (except matchInfoFree) after freeing or modifying string then the behaviour is undefined.

Since: 2.14

matchAll

regexMatchAll

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure from regexNew

-> Text

string: the string to scan for matches

-> [RegexMatchFlags]

matchOptions: match options

-> m (Bool, MatchInfo)

Returns: 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 regexMatchAllFull.

A MatchInfo structure, used to get information on the match, is stored in matchInfo if not Nothing. Note that if matchInfo is not Nothing 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 MatchInfo internally. If you use any MatchInfo method (except matchInfoFree) after freeing or modifying string then the behaviour is undefined.

Since: 2.14

matchAllFull

regexMatchAllFull

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure from regexNew

-> [Text]

string: the string to scan for matches

-> Int32

startPosition: starting index of the string to match, in bytes

-> [RegexMatchFlags]

matchOptions: match options

-> m MatchInfo

(Can throw GError)

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 matchInfoGetMatchCount. To obtain the matched strings and their position you can use, respectively, matchInfoFetch and matchInfoFetchPos. 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 startPosition 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".

A MatchInfo structure, used to get information on the match, is stored in matchInfo if not Nothing. Note that if matchInfo is not Nothing 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 MatchInfo internally. If you use any MatchInfo method (except matchInfoFree) after freeing or modifying string then the behaviour is undefined.

Since: 2.14

matchFull

regexMatchFull

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure from regexNew

-> [Text]

string: the string to scan for matches

-> Int32

startPosition: starting index of the string to match, in bytes

-> [RegexMatchFlags]

matchOptions: match options

-> m MatchInfo

(Can throw GError)

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

Setting startPosition 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".

A MatchInfo structure, used to get information on the match, is stored in matchInfo if not Nothing. Note that if matchInfo is not Nothing 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 MatchInfo internally. If you use any MatchInfo method (except matchInfoFree) 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 matchInfoNext.

C code

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);
    }
}

Since: 2.14

matchSimple

regexMatchSimple

Arguments

:: (HasCallStack, MonadIO m)

=> Text

pattern: the regular expression

-> Text

string: the string to scan for matches

-> [RegexCompileFlags]

compileOptions: compile options for the regular expression, or 0

-> [RegexMatchFlags]

matchOptions: match options, or 0

-> m Bool

Returns: True if the string matched, False otherwise

Scans for a match in string for pattern.

This function is equivalent to regexMatch but it does not require to compile the pattern with regexNew, 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 regexNew and then use regexMatch.

Since: 2.14

new

regexNew

Arguments

:: (HasCallStack, MonadIO m)

=> Text

pattern: the regular expression

-> [RegexCompileFlags]

compileOptions: compile options for the regular expression, or 0

-> [RegexMatchFlags]

matchOptions: match options for the regular expression, or 0

-> m (Maybe Regex)

Returns: a Regex structure or Nothing if an error occured. Call regexUnref when you are done with it (Can throw GError)

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

Since: 2.14

ref

regexRef

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m Regex

Returns: regex

Increases reference count of regex by 1.

Since: 2.14

replace

regexReplace

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> [Text]

string: the string to perform matches against

-> Int32

startPosition: starting index of the string to match, in bytes

-> Text

replacement: text to replace each match with

-> [RegexMatchFlags]

matchOptions: options for the match

-> m Text

Returns: a newly allocated string containing the replacements (Can throw GError)

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 regexReplaceLiteral.

The replacement string must be UTF-8 encoded even if G_REGEX_RAW was passed to regexNew. If you want to use not UTF-8 encoded stings you can use regexReplaceLiteral.

Setting startPosition 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".

Since: 2.14

replaceLiteral

regexReplaceLiteral

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> [Text]

string: the string to perform matches against

-> Int32

startPosition: starting index of the string to match, in bytes

-> Text

replacement: text to replace each match with

-> [RegexMatchFlags]

matchOptions: options for the match

-> m Text

Returns: a newly allocated string containing the replacements (Can throw GError)

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

Setting startPosition 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".

Since: 2.14

split

regexSplit

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> Text

string: the string to split with the pattern

-> [RegexMatchFlags]

matchOptions: match time option flags

-> m [Text]

Returns: a Nothing-terminated gchar ** array. Free it using 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 a 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".

Since: 2.14

splitFull

regexSplitFull

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex structure

-> [Text]

string: the string to split with the pattern

-> Int32

startPosition: starting index of the string to match, in bytes

-> [RegexMatchFlags]

matchOptions: match time option flags

-> Int32

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

-> m [Text]

Returns: a Nothing-terminated gchar ** array. Free it using strfreev (Can throw GError)

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 a 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 startPosition 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".

Since: 2.14

splitSimple

regexSplitSimple

Arguments

:: (HasCallStack, MonadIO m)

=> Text

pattern: the regular expression

-> Text

string: the string to scan for matches

-> [RegexCompileFlags]

compileOptions: compile options for the regular expression, or 0

-> [RegexMatchFlags]

matchOptions: match options, or 0

-> m [Text]

Returns: a Nothing-terminated array of strings. Free it using 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.

This function is equivalent to regexSplit but it does not require to compile the pattern with regexNew, 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 regexNew and then use regexSplit.

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 a 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".

Since: 2.14

unref

regexUnref

Arguments

:: (HasCallStack, MonadIO m)

=> Regex

regex: a Regex

-> m ()

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