perlreref.1

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

.PP
For Titlecase, see \*(L"Titlecase\*(R".
.PP
This one works differently from normal strings:
.PP
.Vb 1
\&   \eb  An assertion, not backspace, except in a character class
.Ve
.Sh "\s-1CHARACTER\s0 \s-1CLASSES\s0"
.IX Subsection "CHARACTER CLASSES"
.Vb 4
\&   [amy]    Match \*(Aqa\*(Aq, \*(Aqm\*(Aq or \*(Aqy\*(Aq
\&   [f\-j]    Dash specifies "range"
\&   [f\-j\-]   Dash escaped or at start or end means \*(Aqdash\*(Aq
\&   [^f\-j]   Caret indicates "match any character _except_ these"
.Ve
.PP
The following sequences work within or without a character class.
The first six are locale aware, all are Unicode aware. See perllocale
and perlunicode for details.
.PP
.Vb 11
\&   \ed      A digit
\&   \eD      A nondigit
\&   \ew      A word character
\&   \eW      A non\-word character
\&   \es      A whitespace character
\&   \eS      A non\-whitespace character
\&   \eh      An horizontal white space
\&   \eH      A non horizontal white space
\&   \ev      A vertical white space
\&   \eV      A non vertical white space
\&   \eR      A generic newline           (?>\ev|\ex0D\ex0A)
\&
\&   \eC      Match a byte (with Unicode, \*(Aq.\*(Aq matches a character)
\&   \epP     Match P\-named (Unicode) property
\&   \ep{...} Match Unicode property with long name
\&   \ePP     Match non\-P
\&   \eP{...} Match lack of Unicode property with long name
\&   \eX      Match extended Unicode combining character sequence
.Ve
.PP
\&\s-1POSIX\s0 character classes and their Unicode and Perl equivalents:
.PP
.Vb 10
\&   alnum   IsAlnum              Alphanumeric
\&   alpha   IsAlpha              Alphabetic
\&   ascii   IsASCII              Any ASCII char
\&   blank   IsSpace  [ \et]       Horizontal whitespace (GNU extension)
\&   cntrl   IsCntrl              Control characters
\&   digit   IsDigit  \ed          Digits
\&   graph   IsGraph              Alphanumeric and punctuation
\&   lower   IsLower              Lowercase chars (locale and Unicode aware)
\&   print   IsPrint              Alphanumeric, punct, and space
\&   punct   IsPunct              Punctuation
\&   space   IsSpace  [\es\eck]     Whitespace
\&           IsSpacePerl   \es     Perl\*(Aqs whitespace definition
\&   upper   IsUpper              Uppercase chars (locale and Unicode aware)
\&   word    IsWord   \ew          Alphanumeric plus _ (Perl extension)
\&   xdigit  IsXDigit [0\-9A\-Fa\-f] Hexadecimal digit
.Ve
.PP
Within a character class:
.PP
.Vb 3
\&    POSIX       traditional   Unicode
\&    [:digit:]       \ed        \ep{IsDigit}
\&    [:^digit:]      \eD        \eP{IsDigit}
.Ve
.Sh "\s-1ANCHORS\s0"
.IX Subsection "ANCHORS"
All are zero-width assertions.
.PP
.Vb 8
\&   ^  Match string start (or line, if /m is used)
\&   $  Match string end (or line, if /m is used) or before newline
\&   \eb Match word boundary (between \ew and \eW)
\&   \eB Match except at word boundary (between \ew and \ew or \eW and \eW)
\&   \eA Match string start (regardless of /m)
\&   \eZ Match string end (before optional newline)
\&   \ez Match absolute string end
\&   \eG Match where previous m//g left off
\&
\&   \eK Keep the stuff left of the \eK, don\*(Aqt include it in $&
.Ve
.Sh "\s-1QUANTIFIERS\s0"
.IX Subsection "QUANTIFIERS"
Quantifiers are greedy by default \*(-- match the \fBlongest\fR leftmost.
.PP
.Vb 9
\&   Maximal Minimal Possessive Allowed range
\&   \-\-\-\-\-\-\- \-\-\-\-\-\-\- \-\-\-\-\-\-\-\-\-\- \-\-\-\-\-\-\-\-\-\-\-\-\-
\&   {n,m}   {n,m}?  {n,m}+     Must occur at least n times
\&                              but no more than m times
\&   {n,}    {n,}?   {n,}+      Must occur at least n times
\&   {n}     {n}?    {n}+       Must occur exactly n times
\&   *       *?      *+         0 or more times (same as {0,})
\&   +       +?      ++         1 or more times (same as {1,})
\&   ?       ??      ?+         0 or 1 time (same as {0,1})
.Ve
.PP
The possessive forms (new in Perl 5.10) prevent backtracking: what gets
matched by a pattern with a possessive quantifier will not be backtracked
into, even if that causes the whole match to fail.
.PP
There is no quantifier {,n} \*(-- that gets understood as a literal string.
.Sh "\s-1EXTENDED\s0 \s-1CONSTRUCTS\s0"
.IX Subsection "EXTENDED CONSTRUCTS"
.Vb 10
\&   (?#text)          A comment
\&   (?:...)           Groups subexpressions without capturing (cluster)
\&   (?pimsx\-imsx:...) Enable/disable option (as per m// modifiers)
\&   (?=...)           Zero\-width positive lookahead assertion
\&   (?!...)           Zero\-width negative lookahead assertion
\&   (?<=...)          Zero\-width positive lookbehind assertion
\&   (?<!...)          Zero\-width negative lookbehind assertion
\&   (?>...)           Grab what we can, prohibit backtracking
\&   (?|...)           Branch reset
\&   (?<name>...)      Named capture
\&   (?\*(Aqname\*(Aq...)      Named capture
\&   (?P<name>...)     Named capture (python syntax)
\&   (?{ code })       Embedded code, return value becomes $^R
\&   (??{ code })      Dynamic regex, return value used as regex
\&   (?N)              Recurse into subpattern number N
\&   (?\-N), (?+N)      Recurse into Nth previous/next subpattern
\&   (?R), (?0)        Recurse at the beginning of the whole pattern
\&   (?&name)          Recurse into a named subpattern
\&   (?P>name)         Recurse into a named subpattern (python syntax)
\&   (?(cond)yes|no)
\&   (?(cond)yes)      Conditional expression, where "cond" can be:
\&                     (N)       subpattern N has matched something
\&                     (<name>)  named subpattern has matched something
\&                     (\*(Aqname\*(Aq)  named subpattern has matched something
\&                     (?{code}) code condition
\&                     (R)       true if recursing
\&                     (RN)      true if recursing into Nth subpattern
\&                     (R&name)  true if recursing into named subpattern
\&                     (DEFINE)  always false, no no\-pattern allowed
.Ve
.Sh "\s-1VARIABLES\s0"
.IX Subsection "VARIABLES"
.Vb 1
\&   $_    Default variable for operators to use
\&
\&   $\`    Everything prior to matched string
\&   $&    Entire matched string
\&   $\*(Aq    Everything after to matched string
\&
\&   ${^PREMATCH}   Everything prior to matched string
\&   ${^MATCH}      Entire matched string
\&   ${^POSTMATCH}  Everything after to matched string
.Ve
.PP
The use of \f(CW\*(C`$\`\*(C'\fR, \f(CW$&\fR or \f(CW\*(C`$\*(Aq\*(C'\fR will slow down \fBall\fR regex use
within your program. Consult perlvar for \f(CW\*(C`@\-\*(C'\fR
to see equivalent expressions that won't cause slow down.
See also Devel::SawAmpersand. Starting with Perl 5.10, you
can also use the equivalent variables \f(CW\*(C`${^PREMATCH}\*(C'\fR, \f(CW\*(C`${^MATCH}\*(C'\fR
and \f(CW\*(C`${^POSTMATCH}\*(C'\fR, but for them to be defined, you have to
specify the \f(CW\*(C`/p\*(C'\fR (preserve) modifier on your regular expression.
.PP
.Vb 8
\&   $1, $2 ...  hold the Xth captured expr
\&   $+    Last parenthesized pattern match
\&   $^N   Holds the most recently closed capture
\&   $^R   Holds the result of the last (?{...}) expr
\&   @\-    Offsets of starts of groups. $\-[0] holds start of whole match
\&   @+    Offsets of ends of groups. $+[0] holds end of whole match
\&   %+    Named capture buffers
\&   %\-    Named capture buffers, as array refs
.Ve
.PP
Captured groups are numbered according to their \fIopening\fR paren.
.Sh "\s-1FUNCTIONS\s0"
.IX Subsection "FUNCTIONS"
.Vb 4
\&   lc          Lowercase a string
\&   lcfirst     Lowercase first char of a string
\&   uc          Uppercase a string
\&   ucfirst     Titlecase first char of a string
\&
\&   pos         Return or set current match position
\&   quotemeta   Quote metacharacters
\&   reset       Reset ?pattern? status
\&   study       Analyze string for optimizing matching
\&
\&   split       Use a regex to split a string into parts
.Ve
.PP
The first four of these are like the escape sequences \f(CW\*(C`\eL\*(C'\fR, \f(CW\*(C`\el\*(C'\fR,
\&\f(CW\*(C`\eU\*(C'\fR, and \f(CW\*(C`\eu\*(C'\fR.  For Titlecase, see \*(L"Titlecase\*(R".
.Sh "\s-1TERMINOLOGY\s0"
.IX Subsection "TERMINOLOGY"
\fITitlecase\fR
.IX Subsection "Titlecase"
.PP
Unicode concept which most often is equal to uppercase, but for
certain characters like the German \*(L"sharp s\*(R" there is a difference.
.SH "AUTHOR"
.IX Header "AUTHOR"
Iain Truskett. Updated by the Perl 5 Porters.
.PP
This document may be distributed under the same terms as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "\(bu" 4
perlretut for a tutorial on regular expressions.
.IP "\(bu" 4
perlrequick for a rapid tutorial.
.IP "\(bu" 4
perlre for more details.
.IP "\(bu" 4
perlvar for details on the variables.
.IP "\(bu" 4
perlop for details on the operators.
.IP "\(bu" 4
perlfunc for details on the functions.
.IP "\(bu" 4
perlfaq6 for FAQs on regular expressions.
.IP "\(bu" 4
perlrebackslash for a reference on backslash sequences.
.IP "\(bu" 4
perlrecharclass for a reference on character classes.
.IP "\(bu" 4
The re module to alter behaviour and aid
debugging.
.IP "\(bu" 4
\&\*(L"Debugging regular expressions\*(R" in perldebug
.IP "\(bu" 4
perluniintro, perlunicode, charnames and perllocale
for details on regexes and internationalisation.
.IP "\(bu" 4
\&\fIMastering Regular Expressions\fR by Jeffrey Friedl
(\fIhttp://regex.info/\fR) for a thorough grounding and
reference on the topic.
.SH "THANKS"
.IX Header "THANKS"
David P.C. Wollmann,
Richard Soderberg,
Sean M. Burke,
Tom Christiansen,
Jim Cromie,
and
Jeffrey Goff
for useful advice.