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{{mirc title|RegEx}}
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{{mIRC Guide}}
Regular expressions, from here on referred to as '''regex''', can be used to perform complicated pattern matching operations. Users should already be familiar with, and comfortable using, Regular expressions at this point. The [[regular expressions|Regular Expressions]] page contains more detailed information for users who are new to regex but a reminder of the syntax will be provided at the end.
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{{DISPLAYTITLE:RegEx - mIRC}}
 
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Regular expressions, from here on referred to as '''regex''', can be used to perform complicated pattern matching operations. Users should already be familiar with, and comfortable using, Regular expressions at this point. The [[regular expressions|Regular Expressions]] page contains more detailed information for users who are new to regex.
'''Note''': a back reference is the same as a capturing group.
 
  
 
== General Information ==
 
== General Information ==
mIRC uses the 8bits version of [[PCRE library]] to implement regex with the following options enabled:
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mIRC uses the [[PCRE library]] to implement regex with the following options enabled:
  
 
* --enable-utf8
 
* --enable-utf8
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* --with-match-limit-recursion - 999
 
* --with-match-limit-recursion - 999
  
The newline sequence by default is $lf.
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mIRC also has two custom modifiers for regex:
 
 
mIRC has four custom modifiers for regex:
 
 
* S - Strips control codes from the input before matching (not supported by $hfind).
 
* S - Strips control codes from the input before matching (not supported by $hfind).
 
* g - Performs global matches: after one match has been found, mIRC tries to match again from the current position.
 
* g - Performs global matches: after one match has been found, mIRC tries to match again from the current position.
* F - Enable the correct regex behavior: before mIRC 7.44, non participating capturing group were ignored in $regml, see http://forums.mirc.com/ubbthreads.php/topics/260397/Bug_$regmlex#Post260397
 
* u - Enable the (*UCP) option (makes \b and \w works for unicode letters) and the (*UTF8) option (forces the string and pattern to be interpreted as utf8).
 
 
mIRC does not allow you to retrieve the full match. You can access simple captures but you cannot access named capture. Here is an alias which allow you to get the full match (made by jaytea):
 
  
<source lang="mIRC">
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'''Note:''' mIRC remembers up to 50 regex matches. After 50 matches, the first match is overwritten and the backreferences for that match are lost.
;$regexm(input,regex,Nth).pos returns the Nth full match or its position
 
alias regexm {
 
  noop $regex(full, $2, /^(?|m(.)?|(/)|^)(.*?)(?:\1(?!.*\1)(.*)$)?$/usD)
 
  noop $regex(pcre, $regmlex(full, 1, 2), /^((?:(?!\((?:(?:MARK|PRUNE|SKIP|THEN|\*(?=:))(?::[^()]*)?|ACCEPT|COMMIT)\))\(\*.*?\))*)(.*)/us)
 
  if (!$regex( , $+(/, $regmlex(pcre, 1, 1), |, $regmlex(pcre, 1, 2), /))) {
 
    echo -eagc i * $!regexm: Invalid expression ( $+ $regerrstr $+ )
 
    return
 
  }
 
  var %char, %exp
 
  while ($chr($r(2048, 55295)) isin $1) /
 
  %char = $v1
 
  var %exp = $+(m, $regmlex(full, 1, 1), $regmlex(pcre, 1, 1), (?: $+ $regmlex(pcre, 1, 2) $+ \E)(?(R)|\K), $regmlex(full, 1, 1), $regmlex(full, 1, 3))
 
  var %str = $regsubex($1, %exp, %char) .
 
  if (!$pos(%str, %char, $regex($1, $2))) {
 
    noop $regex(check, $regsubex($1, $2, %char), / %char ( %char ?)/gxu)
 
    %str = $regsubex(fix, $left(%str, -2), / %char \K/gxu, $regml(check, \n)) .
 
  }
 
  noop $regex(final, $left(%str, -2), $+(/\Q, $replacecs($regsubex($1, $2, %char), \E, \E\\E\Q, %char, \E(.*?)\Q $+ %char), \E/u))
 
  if ($prop == pos) && ($3. isnum 1- $regml(final, 0)) return $calc(1 + $regml(final, $3).pos - $3)
 
  returnex $regml(final, $3 1)
 
}</source>
 
 
 
 
 
mIRC remembers up to 50 regex matches. After 50 matches, the first match is overwritten and the backreferences for that match are lost.
 
  
 
Example:  
 
Example:  
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/(This is) (a ) pattern/
 
/(This is) (a ) pattern/
  
This represent one regular expression (or one pattern) with 2 captured backreferences.
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This represent one regular expression (or one match) with 2 captured backreferences.
 
 
=== Sanitizing the input ===
 
 
 
If you pass value dynamically in a regex pattern, you have to escape any characters in such value that could otherwise be interpreted by the PCRE regex engine.
 
 
 
Instead of escaping a bunch of characters with \, which is supported, PCRE allows for the \Q \E construct to not interpret anything between that construct:
 
 
 
Looking for a match on a nickname such as nick[name], you could use /\b $+ \Q $+ $nick $+ \E\b/
 
 
 
This is good but still has one flaw, if $nick contains \E, it will terminate the escaping sequence and subsequent character would be interpreted by PCRE.
 
 
 
To solve the issue, you have to "escape" all the \E inside the value you're using: /b\Q $+ $replacecs($nick,\E,\E\\E\Q) $+ \E\b/
 
 
 
There's no way to escape a character inside the escaping sequence \Q\E, you have to first terminate the sequence yourself with \E, then you have to match the actual \E from the input with \\E, and then start a new escape sequence with \Q.
 
  
 
== Regex Identifiers ==
 
== Regex Identifiers ==
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If the /g modifier is used, that number can be greater than 1.
 
If the /g modifier is used, that number can be greater than 1.
You may see a negative value being returned if an error occured, the list below is not exhaustive, but the error ommited are the one that can only happen because of a bug in mIRC in the way it uses pcre, which should never happen in practice.
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You may see a negative value being returned if an error occured:
 
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* -8 - you reached the maximum number of backtracks allowed  
* -5 - rare, the compiled pattern has an error in it, could be due to a bug in pcre or because the pattern has been overwritten
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* -21 - you reached an internal recursion limit
* -6 - memory could not be allocated
 
* -7 - memory could not be allocated (specific to retrieving capturing groups)
 
* -8 - you reached the maximum number of backtracks allowed, for example: $regex($str(a,4000),(a+a+)*b)
 
* -14 - mIRC uses this value when compiling the pattern fails but it's a valid value meaning an internal error occured as well. If this error is returned because compiling the pattern failed, {{mIRC|$regerrstr}} is set with an error string, otherwise -14 is the pcre meaning, which is more or less the same as -5 but happens elsewhere in the code.
 
* -21 - you reached an internal recursion limit, for example: $regex($str(a, 1000), (a)+)
 
* -26 - this error is returned when pcre detects a recursion loop within the pattern. Specifically, it means that either the whole pattern or a subpattern has been called recursively for the second time at the same position in the input string. Some simple patterns that might do this are detected and faulted at compile time, but more  complicated cases, in particular mutual recursions between two different subpatterns, cannot be detected until run time. ex: $regex(,((?2))((?3))((?1)))
 
  
 
=== $regml ===
 
=== $regml ===
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Below is an example of a regular expression, using ''name'' as the optional ''[Name]'' property, and then using $regml to reference the match(es):
 
Below is an example of a regular expression, using ''name'' as the optional ''[Name]'' property, and then using $regml to reference the match(es):
<source lang="mIRC">//noop $regex(name, test, /([es])/g) | echo -a $regml(name, 0) : $regml(name, 1) -- $regml(name, 2)</source> would display "2 : e -- s"
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<source lang="mIRC">//noop $regex(name,test,/[es]/g) | echo -a $regml(name,0) : $regml(name,1) -- $regml(name,2)</source>
 
 
'''Note''': $regml is a list of all captures accross all the matches made (/g modifier), which is often enough, but can be a problem in some cases.
 
<source lang="mIRC">//noop $regex(name, teasat, /([es])(a)/g) | echo -a $regml(name, 0) : $regml(name, 1) -- $regml(name, 2) -- $regml(name,3) -- $regml(name,4)</source>would display "4 : e -- a -- s -- a "
 
You can now access the Nth captured group for a given match number with {{mIRC|$regmlex}}.
 
 
 
=== $regmlex ===
 
<source lang=mIRC>$regmlex([name],M,N)</source>
 
 
 
 
 
As stated above for $regml, when /g is used, $regml can be inconvenient: you cannot get all the captured group for a given match number for sure when you don't know about the pattern or input string in advance, this identifier allows you to retrieve these captured groups (backreferences). M is the Mth match and N is the Nth capturing group, N default to 1 if not specified. It supports the same properties as $regml.
 
 
 
  
 
=== $regsub ===
 
=== $regsub ===
<source lang="mIRC">$regsub([name], <input>, <regex>, <subtext>, <%varname>)</source>
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<source lang="mIRC">$regsub([name],<input>,<regex>,<subtext>,<%varname>)</source>
 
Performs a regular expression match, like $regex, and then performs a substitution using <subtext>. Returns the number of substitution made and fills <%varname> with the resulting text
 
Performs a regular expression match, like $regex, and then performs a substitution using <subtext>. Returns the number of substitution made and fills <%varname> with the resulting text
  
<source lang="mIRC">//var %res | noop $regsub(name,test,/([es])/g,t,%res) | echo -a $regml(name,0) : $regml(name,1) -- $regml(name,2) : %res</source>
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<source lang="mIRC">//noop $regsub(name,test,/([es])/g,t) | echo -a $regml(name,0) : $regml(name,1) -- $regml(name,2)</source>
  
 
=== $regsubex ===
 
=== $regsubex ===
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$regsubex is a more modern version of $regsub, in that it performs the match, then the substitution, and finally returns the result of the substitution.
 
$regsubex is a more modern version of $regsub, in that it performs the match, then the substitution, and finally returns the result of the substitution.
  
This time, <subtext> is evaluated during substitution so you can use %variables and $identifiers there, they will be evaluated.
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This time, <subtext> is evaluated during substitution so you can use %variables and $identifiers there, they will be evaluated
 
 
'''Note''': You can now use $regsubex the same way as $regsub to get it to return the number of match and filling a %variable with the result, the name is required, both also supports output to a binvar: $regsubex(name,<input>,<regex>,<subtext>,%var|&binvar)
 
  
 
==== Markers, $1- and Nested $regsubex calls ====
 
==== Markers, $1- and Nested $regsubex calls ====
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Special markers can be used inside the <subtext> parameter of $regsubex:
 
Special markers can be used inside the <subtext> parameter of $regsubex:
  
* \0 - Returns the number of captures.
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* \0 - Returns the number of matches.
 
* \n - Returns the current match number.
 
* \n - Returns the current match number.
 
* \t - Returns the current match text (same as $regml(\n)).
 
* \t - Returns the current match text (same as $regml(\n)).
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* \2 is 'f'
 
* \2 is 'f'
 
* \n is 2 because it's the second match.
 
* \n is 2 because it's the second match.
* \t is the current matchtext (same as $regml(\n)), which is 'c' and not 'e' (\n is 2), it is important to note that when you have more than one backreference and more than one match (because of the /g modifier), \t is a bit meaningless.
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* \t is the current matchtext (same as $regml(\n)), which is 'c' and not 'e' (\n is 2), it is important to note that when you have more than one backreference and more than one match, \t is a bit meaningless.
 
* \a is "e f" while \A is "ef"
 
* \a is "e f" while \A is "ef"
  
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<source lang="mIRC">\t \t \1 \n</source>
 
<source lang="mIRC">\t \t \1 \n</source>
 
mIRC assigns the value of \t to ''$1'' & ''$2'', \1 is assigned to ''$3'' and finally, \n is assigned to ''$4''.
 
mIRC assigns the value of \t to ''$1'' & ''$2'', \1 is assigned to ''$3'' and finally, \n is assigned to ''$4''.
 
Then each marker is replaced with their corresponding values, the subtext becomes:
 
<source lang="mIRC">$1 $2 $3 $4</source>
 
And now mIRC evaluates that for each match and use it as a replacement.
 
  
 
'''Note''': If the form '''\N''' is used in the subtext, where N is a positive number greater-than or equal to 1 (such as '''\1'''), and there is no such back-reference number in the pattern, mIRC will use the value of '''$regml(\n + N - 1)'''.
 
'''Note''': If the form '''\N''' is used in the subtext, where N is a positive number greater-than or equal to 1 (such as '''\1'''), and there is no such back-reference number in the pattern, mIRC will use the value of '''$regml(\n + N - 1)'''.
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* When ''a'' is matched, '''\n''' is ''1'', and only one marker is used. Therefore, '''$1''' (used to represent \6) is filled with ''$regml(1 + 6 -1) = $regml(6)'', which is '''f'''
 
* When ''a'' is matched, '''\n''' is ''1'', and only one marker is used. Therefore, '''$1''' (used to represent \6) is filled with ''$regml(1 + 6 -1) = $regml(6)'', which is '''f'''
 
* When ''b'' is matched, '''\n''' is ''2'', '''$1''' is then filled with ''$regml(2 + 6 - 1) = $regml(7)'', which is '''g'''
 
* When ''b'' is matched, '''\n''' is ''2'', '''$1''' is then filled with ''$regml(2 + 6 - 1) = $regml(7)'', which is '''g'''
* And so on until '''\n + N - 1''' is greater than the total number of back-references, which at this point, '''$null''' is used.
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* And so on until '''\n + N - 1''' is greater than the number of back-references, which at this point, '''$null''' is used.
  
 
==== Nested calls ====
 
==== Nested calls ====
 
Nested '''$regsubex''' calls are possible, but caution must be taken with markers.
 
Nested '''$regsubex''' calls are possible, but caution must be taken with markers.
  
First of all, if you use the /g modifier in either the outer or the inner $regsubex call and you need to use the different backreferences made in either of them, you must give a name to either one or both of them, otherwise, the call of the inner $regsubex will overwrite the backreferences of the outer $regsubex (if you don't use a name, mIRC use a default name, which would be the same here).
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First of all, if you use the /g modifier in the outer $regsubex and you need to use the different backreferences made inside the inner $regsubex, you must give a name to either the outer or inner $regsubex (ot both), otherwise, the call of the inner $regsubex will overwrite the backreferences of the outer $regsubex (if you don't use a name, mIRC use a default name, which would be the same here).
  
 
When mIRC replaces the markers, it will do so on the whole subtext parameter, consider:
 
When mIRC replaces the markers, it will do so on the whole subtext parameter, consider:
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The example above conveys how only the '''[[ ]]''' has changed. Remember '''$+''' was not evaluated because the subtext parameter of $regsubex is not evaluated until the regex match is performed.
 
The example above conveys how only the '''[[ ]]''' has changed. Remember '''$+''' was not evaluated because the subtext parameter of $regsubex is not evaluated until the regex match is performed.
  
Now, the outer '''$regsubex''' is evaluated, it gets its parameters (without evaluating the subtext), makes the regex match, and calls the subtext for each match, the subtext is:
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Now, the outer '''$regsubex''' is evaluated, [ \ $+ t ] produces \t right before the $regsubex gets its parameters, makes the regex match, and calls the subtext for each match:
<source lang="mIRC">$regsubex(<value of \t from the outer $regsubex>,/(.)/g,$upper( [ \ $+ t ] ))</source>
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<source lang="mIRC">$regsubex(<value of \t from the outer $regsubex>,/(.)/g,$upper( \t ))</source>
 
 
And when this $regsubex evaluates (for each replacement of the outer $regsubex) [ \ $+ t ] will first produce \t, and everything works as we wanted.
 
 
 
The more nested $regsubex you have, the more you have to make sure each subtext has the correct number of [[ ]].
 
  
Obviously, you can make this cleaner by calling a custom alias as the subtext with the markers passed as parameters and doing the nested $regsubex call here, but this is possible.
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The more nested $regsubex you have, the more you have to makes sure each subtext has the correct number of [[ ]]. You can make this cleaner by calling a custom alias as the subtext with the markers passed as parameters and doing the nested $regsubex call here.
  
 
==== No Marker ====
 
==== No Marker ====
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So how do you use the value of the marker of the outer $regsubex inside the subtext of the inner $regsubex?
 
So how do you use the value of the marker of the outer $regsubex inside the subtext of the inner $regsubex?
  
The solution is to use '''<nowiki>[[ \t ]]</nowiki>''':
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The solution is to use <nowiki>[[ \t ]]</nowiki>:
  
 
<source lang="mIRC">$regsubex(name,abcdefcdab,/(cd)/g,$regsubex(\t,/(.)/g,$upper( [[ \t ]] )))</source>
 
<source lang="mIRC">$regsubex(name,abcdefcdab,/(cd)/g,$regsubex(\t,/(.)/g,$upper( [[ \t ]] )))</source>
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<source lang="mIRC">$regsubex($1,/(.)/g,$upper( [ $+ $2 $+ ] )))</source>
 
<source lang="mIRC">$regsubex($1,/(.)/g,$upper( [ $+ $2 $+ ] )))</source>
  
The difference is that you now have a pair of bracket, which are processed first, forcing the evaluation of $2, which has the correct value at this point.
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The difference is that you now have a pair of bracket, which are processed first before mIRC loops on the result and evaluate, forcing the evaluation of $2, which has the correct value at this point.
  
 
'''Note''': the more you are nesting, the more you need to get mIRC to see the correct things, which easily gets ugly, calling an alias in the subtext to do the replacement is recommended.
 
'''Note''': the more you are nesting, the more you need to get mIRC to see the correct things, which easily gets ugly, calling an alias in the subtext to do the replacement is recommended.
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== $hfind ==
 
== $hfind ==
'''$hfind''' can be used along with '''regex'''. However, '''$hfind''' does not support the custom '''S''' modifier.
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'''$hfind''' can be used along with '''$regex'''. However, '''$hfind''' does not support the custom '''S''' modifier.
  
 
== /write, $read, $fline, etc ==
 
== /write, $read, $fline, etc ==
 
These, and many more, are various places where [[regular expression|Regular Expression]] can be used.
 
These, and many more, are various places where [[regular expression|Regular Expression]] can be used.
 
== Syntax ==
 
 
This part is meant to document all the different features of PCRE that work with mIRC, and to explain a bit of regular expression works.
 
 
A regular expression is a pattern that is matched against a subject string from left to right. Most characters stand for themselves in a pattern, and match the corresponding characters in the subject.
 
 
As a trivial example, the pattern "The quick brown fox" matches a portion of a subject string that is identical to itself.
 
 
The power of regular expressions comes from the ability to include alternatives and repetitions in the pattern.
 
 
These are encoded in the pattern by the use of metacharacters, which do not stand for themselves but instead are interpreted in some special way.
 
 
There are two different sets of metacharacters: those that are recognized anywhere in the pattern except within square brackets, and those that are recognized within square brackets.
 
 
=== Outside square brackets ===
 
 
The metacharacters are as follows:
 
 
\  general escape character with several uses
 
^  assert start of string (or line, in multiline mode)
 
$  assert end of string (or line, in multiline mode)
 
.  match any character except newline (by default)
 
[  start character class definition
 
|  start of alternative branch
 
(  start subpattern
 
)  end subpattern
 
?  extends the meaning of '(', also 0 or 1 quantifier, also "quantifier minimizer"
 
*  0 or more quantifier
 
+  1 or more quantifier, also "possessive quantifier"
 
{  start min/max quantifier
 
 
=== Inside a character class ===
 
 
Part  of  a  pattern  that is in square brackets is called a "character class".
 
 
In a character class the only metacharacters are:
 
 
\  general escape character
 
^  negate the class, but only if the first character
 
-  indicates character range
 
[  POSIX character class (only if followed by POSIX syntax)
 
]  terminates the character class
 
 
=== The Backslash \ ===
 
 
The backslash character has several uses. Firstly, if it is followed by a character that is not a number or a letter, it takes away any special meaning that character may have.
 
 
This use of backslash as an escape character applies both inside and outside character classes.
 
 
Another usage of the backslash is to represent non printable character, they can all be used inside a character class:
 
 
\a        Bel character, ascii 07
 
\cx        where x is any ascii character. The  precise effect of \cx on ASCII characters is as follows: if x is a lower case letter, it is converted to upper case. Then bit 6  of  the character (hex 40) is inverted. Thus \cA to \cZ become hex 01 to hex 1A (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and  \c;  becomes hex  7B (; is 3B). If the data item (byte or 16-bit value) following \c has a value greater than 127, a compile-time error occurs.  This locks out non-ASCII characters.
 
\e escape character, ascii 27
 
\f        form feed character, ascii 12
 
\n        linefeed character, ascii 10
 
\r        carriage return character, ascii 13
 
\t        tab character, ascii 09
 
\0dd      character with octal code 0dd. After \0, up to two further octal digits are read. If there are fewer than two digits, just those that are present are used. Thus the sequence \0\x\015 specifies two binary zeros followed by a CR character. Make sure you supply two digits after the initial zero if the pattern character that follows is itself an octal digit.
 
\ddd      character with octal code ddd, or back reference
 
\o{ddd..} character with octal code ddd..  The escape \o must be followed by a sequence of octal digits, enclosed in braces. An error occurs if this is not the case. This escape is an addition to Perl; it provides way of specifying character code points as octal numbers greater than 0777, and it also allows octal numbers and back references to be unambiguously specified.
 
\xhh      character with hex code hh
 
\x{hhh..} character with hex code hhh..
 
 
For greater clarity and unambiguity, it is best to avoid following \ by a digit greater than zero. Instead, use \o{} or \x{} to specify character numbers, and \g{} to specify back references. The  following  paragraphs describe the old, ambiguous syntax.
 
 
The handling of a backslash followed by a digit other than 0 is complicated, and Perl has changed in recent releases, causing PCRE also to change.
 
 
Outside a character class, PCRE reads the digit and any following digits as a decimal number.
 
If the number is less than 8, or if there  have been at least that many previous capturing left parentheses in the expression, the entire sequence is taken as a back reference.
 
 
Inside a character class, or if the decimal number following \ is greater than 7 and there have not been that many capturing subpatterns, PCRE handles \8 and \9 as the literal characters "8" and "9", and otherwise re-reads up to three octal digits following the backslash, using them to generate a data character. Any subsequent digits  stand for themselves.
 
 
For example:
 
 
        \040  is another way of writing an ASCII space
 
        \40    is the same, provided there are fewer than 40 previous capturing subpatterns
 
        \7    is always a back reference
 
        \11    might be a back reference, or another way of writing a tab
 
        \011  is always a tab
 
        \0113  is a tab followed by the character "3"
 
        \113  might be a back reference, otherwise the character with octal code 113
 
        \377  might be a back reference, otherwise the value 255 (decimal)
 
        \81    is either a back reference, or the two characters "8" and "1"
 
 
Note that octal values of 100 or greater that are specified using this syntax must not be introduced by a leading zero, because no more than three octal digits are ever read.
 
 
By  default, after \x that is not followed by {, from zero to two hexadecimal digits are read (letters can be in upper or lower  case).
 
Any number of hexadecimal digits may appear between \x{ and }. If a character other than a hexadecimal digit appears between \x{  and  }, or if there is no terminating }, an error occurs.
 
 
Characters that are specified using octal or hexadecimal numbers are limited to certain values, less than 0x10ffff and a valid codepoint.
 
     
 
Invalid Unicode codepoints are the range  0xd800  to  0xdfff  (the  so called "surrogate" codepoints), and 0xffef.
 
 
All the sequences that define a single character value can be used both inside and outside character classes. In addition, inside a character class, \b is interpreted as the backspace character (ascii 08).
 
 
\N matches a non newline character, (same as the dot '.' without single line mode (/s modifier), it is not allowed inside a character class.
 
 
\g+N or \g-N is a relative back reference, it matches the value of the capturing group that can be found by counting as many opening parentheses of named or numbered capturing groups as specified by the number from right to left starting at the backreference. (a)(b)(c)(d)\g<-3> matches abcdb.
 
 
Another use of backslash is for specifying generic character types:
 
 
        \d    any decimal digit
 
        \D    any character that is not a decimal digit
 
        \h    any horizontal white space character
 
        \H    any character that is not a horizontal white space character
 
        \s    any white space character
 
        \S    any character that is not a white space character
 
        \v    any vertical white space character
 
        \V    any character that is not a vertical white space character
 
        \w    any "word" character
 
        \W    any "non-word" character
 
[[Category:mIRC|regex]]
 

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