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[;1m compile(Regexp)[0m
The same as [;;4mcompile(Regexp,[])[0m
[;1m compile(Regexp, Options)[0m
Compiles a regular expression, with the syntax described below,
into an internal format to be used later as a parameter to [;;4mrun/2[0m
and [;;4mrun/3[0m.
Compiling the regular expression before matching is useful if the
same expression is to be used in matching against multiple
subjects during the lifetime of the program. Compiling once and
executing many times is far more efficient than compiling each
time one wants to match.
When option [;;4municode[0m is specified, the regular expression is to
be specified as a valid Unicode [;;4mcharlist()[0m, otherwise as any
valid [;;4miodata/0[0m.
Options:
• [;;4municode[0m - The regular expression is specified as a Unicode [;;4m[0m
[;;4mcharlist()[0m and the resulting regular expression code is to
be run against a valid Unicode [;;4mcharlist()[0m subject. Also
consider option [;;4mucp[0m when using Unicode characters.
• [;;4manchored[0m - The pattern is forced to be "anchored", that is,
it is constrained to match only at the first matching point
in the string that is searched (the "subject string"). This
effect can also be achieved by appropriate constructs in the
pattern itself.
• [;;4mcaseless[0m - Letters in the pattern match both uppercase and
lowercase letters. It is equivalent to Perl option [;;4m/i[0m and
can be changed within a pattern by a [;;4m(?i)[0m option setting.
Uppercase and lowercase letters are defined as in the ISO
8859-1 character set.
• [;;4mdollar_endonly[0m - A dollar metacharacter in the pattern
matches only at the end of the subject string. Without this
option, a dollar also matches immediately before a newline
at the end of the string (but not before any other
newlines). This option is ignored if option [;;4mmultiline[0m is
specified. There is no equivalent option in Perl, and it
cannot be set within a pattern.
• [;;4mdotall[0m - A dot in the pattern matches all characters,
including those indicating newline. Without it, a dot does
not match when the current position is at a newline. This
option is equivalent to Perl option [;;4m/s[0m and it can be
changed within a pattern by a [;;4m(?s)[0m option setting. A
negative class, such as [;;4m[^a][0m, always matches newline
characters, independent of the setting of this option.
• [;;4mextended[0m - If this option is set, most white space
characters in the pattern are totally ignored except when
escaped or inside a character class. However, white space is
not allowed within sequences such as [;;4m(?>[0m that introduce
various parenthesized subpatterns, nor within a numerical
quantifier such as [;;4m{1,3}[0m. However, ignorable white space
is permitted between an item and a following quantifier and
between a quantifier and a following + that indicates
possessiveness.
White space did not used to include the VT character (code
11), because Perl did not treat this character as white
space. However, Perl changed at release 5.18, so PCRE
followed at release 8.34, and VT is now treated as white
space.
This also causes characters between an unescaped # outside a
character class and the next newline, inclusive, to be
ignored. This is equivalent to Perl's [;;4m/x[0m option, and it
can be changed within a pattern by a [;;4m(?x)[0m option setting.
With this option, comments inside complicated patterns can
be included. However, notice that this applies only to data
characters. Whitespace characters can never appear within
special character sequences in a pattern, for example within
sequence [;;4m(?([0m that introduces a conditional subpattern.
• [;;4mfirstline[0m - An unanchored pattern is required to match
before or at the first newline in the subject string,
although the matched text can continue over the newline.
• [;;4mmultiline[0m - By default, PCRE treats the subject string as
consisting of a single line of characters (even if it
contains newlines). The "start of line" metacharacter ([;;4m^[0m)
matches only at the start of the string, while the "end of
line" metacharacter ([;;4m$[0m) matches only at the end of the
string, or before a terminating newline (unless option [;;4m[0m
[;;4mdollar_endonly[0m is specified). This is the same as in Perl.
When this option is specified, the "start of line" and "end
of line" constructs match immediately following or
immediately before internal newlines in the subject string,
respectively, as well as at the very start and end. This is
equivalent to Perl option [;;4m/m[0m and can be changed within a
pattern by a [;;4m(?m)[0m option setting. If there are no newlines
in a subject string, or no occurrences of [;;4m^[0m or [;;4m$[0m in a
pattern, setting [;;4mmultiline[0m has no effect.
• [;;4mno_auto_capture[0m - Disables the use of numbered capturing
parentheses in the pattern. Any opening parenthesis that is
not followed by [;;4m?[0m behaves as if it is followed by [;;4m?:[0m.
Named parentheses can still be used for capturing (and they
acquire numbers in the usual way). There is no equivalent
option in Perl.
• [;;4mdupnames[0m - Names used to identify capturing subpatterns
need not be unique. This can be helpful for certain types of
pattern when it is known that only one instance of the named
subpattern can ever be matched. More details of named
subpatterns are provided below.
• [;;4mungreedy[0m - Inverts the "greediness" of the quantifiers so
that they are not greedy by default, but become greedy if
followed by "?". It is not compatible with Perl. It can also
be set by a [;;4m(?U)[0m option setting within the pattern.
• [;;4m{newline, NLSpec}[0m - Overrides the default definition of a
newline in the subject string, which is LF (ASCII 10) in
Erlang.
￮ [;;4mcr[0m - Newline is indicated by a single character [;;4mcr[0m
(ASCII 13).
￮ [;;4mlf[0m - Newline is indicated by a single character LF
(ASCII 10), the default.
￮ [;;4mcrlf[0m - Newline is indicated by the two-character CRLF
(ASCII 13 followed by ASCII 10) sequence.
￮ [;;4manycrlf[0m - Any of the three preceding sequences is to
be recognized.
￮ [;;4many[0m - Any of the newline sequences above, and the
Unicode sequences VT (vertical tab, U+000B), FF
(formfeed, U+000C), NEL (next line, U+0085), LS (line
separator, U+2028), and PS (paragraph separator,
U+2029).
• [;;4mbsr_anycrlf[0m - Specifies specifically that \R is to match
only the CR, LF, or CRLF sequences, not the Unicode-specific
newline characters.
• [;;4mbsr_unicode[0m - Specifies specifically that \R is to match
all the Unicode newline characters (including CRLF, and so
on, the default).
• [;;4mno_start_optimize[0m - Disables optimization that can
malfunction if "Special start-of-pattern items" are present
in the regular expression. A typical example would be when
matching "DEFABC" against "(COMMIT)ABC", where the start
optimization of PCRE would skip the subject up to "A" and
never realize that the (COMMIT) instruction is to have made
the matching fail. This option is only relevant if you use
"start-of-pattern items", as discussed in section PCRE
Regular Expression Details.
• [;;4mucp[0m - Specifies that Unicode character properties are to be
used when resolving \B, \b, \D, \d, \S, \s, \W and \w.
Without this flag, only ISO Latin-1 properties are used.
Using Unicode properties hurts performance, but is
semantically correct when working with Unicode characters
beyond the ISO Latin-1 range.
• [;;4mnever_utf[0m - Specifies that the (UTF) and/or (UTF8)
"start-of-pattern items" are forbidden. This flag cannot be
combined with option [;;4municode[0m. Useful if ISO Latin-1
patterns from an external source are to be compiled.
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