perlunicode.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.

.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  \*(C+ will
.\" give a nicer C++.  Capital omega is used to do unbreakable dashes and
.\" therefore won't be available.  \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.ie \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.el \{\
.    de IX
..
.\}
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "PERLUNICODE 1"
.TH PERLUNICODE 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
perlunicode \- Unicode support in Perl
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
.Sh "Important Caveats"
.IX Subsection "Important Caveats"
Unicode support is an extensive requirement. While Perl does not
implement the Unicode standard or the accompanying technical reports
from cover to cover, Perl does support many Unicode features.
.PP
People who want to learn to use Unicode in Perl, should probably read
the Perl Unicode tutorial before reading this reference
document.
.IP "Input and Output Layers" 4
.IX Item "Input and Output Layers"
Perl knows when a filehandle uses Perl's internal Unicode encodings
(\s-1UTF\-8\s0, or UTF-EBCDIC if in \s-1EBCDIC\s0) if the filehandle is opened with
the \*(L":utf8\*(R" layer.  Other encodings can be converted to Perl's
encoding on input or from Perl's encoding on output by use of the
\&\*(L":encoding(...)\*(R"  layer.  See open.
.Sp
To indicate that Perl source itself is in \s-1UTF\-8\s0, use \f(CW\*(C`use utf8;\*(C'\fR.
.IP "Regular Expressions" 4
.IX Item "Regular Expressions"
The regular expression compiler produces polymorphic opcodes.  That is,
the pattern adapts to the data and automatically switches to the Unicode
character scheme when presented with data that is internally encoded in
\&\s-1UTF\-8\s0 \*(-- or instead uses a traditional byte scheme when presented with
byte data.
.ie n .IP """use utf8"" still needed to enable \s-1UTF\-8/UTF\-EBCDIC\s0 in scripts" 4
.el .IP "\f(CWuse utf8\fR still needed to enable \s-1UTF\-8/UTF\-EBCDIC\s0 in scripts" 4
.IX Item "use utf8 still needed to enable UTF-8/UTF-EBCDIC in scripts"
As a compatibility measure, the \f(CW\*(C`use utf8\*(C'\fR pragma must be explicitly
included to enable recognition of \s-1UTF\-8\s0 in the Perl scripts themselves
(in string or regular expression literals, or in identifier names) on
ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based
machines.  \fBThese are the only times when an explicit \f(CB\*(C`use utf8\*(C'\fB
is needed.\fR  See utf8.
.IP "BOM-marked scripts and \s-1UTF\-16\s0 scripts autodetected" 4
.IX Item "BOM-marked scripts and UTF-16 scripts autodetected"
If a Perl script begins marked with the Unicode \s-1BOM\s0 (\s-1UTF\-16LE\s0, \s-1UTF16\-BE\s0,
or \s-1UTF\-8\s0), or if the script looks like non-BOM-marked \s-1UTF\-16\s0 of either
endianness, Perl will correctly read in the script as Unicode.
(BOMless \s-1UTF\-8\s0 cannot be effectively recognized or differentiated from
\&\s-1ISO\s0 8859\-1 or other eight-bit encodings.)
.ie n .IP """use encoding"" needed to upgrade non\-Latin\-1 byte strings" 4
.el .IP "\f(CWuse encoding\fR needed to upgrade non\-Latin\-1 byte strings" 4
.IX Item "use encoding needed to upgrade non-Latin-1 byte strings"
By default, there is a fundamental asymmetry in Perl's Unicode model:
implicit upgrading from byte strings to Unicode strings assumes that
they were encoded in \fI\s-1ISO\s0 8859\-1 (Latin\-1)\fR, but Unicode strings are
downgraded with \s-1UTF\-8\s0 encoding.  This happens because the first 256
codepoints in Unicode happens to agree with Latin\-1.
.Sp
See \*(L"Byte and Character Semantics\*(R" for more details.
.Sh "Byte and Character Semantics"
.IX Subsection "Byte and Character Semantics"
Beginning with version 5.6, Perl uses logically-wide characters to
represent strings internally.
.PP
In future, Perl-level operations will be expected to work with
characters rather than bytes.
.PP
However, as an interim compatibility measure, Perl aims to
provide a safe migration path from byte semantics to character
semantics for programs.  For operations where Perl can unambiguously
decide that the input data are characters, Perl switches to
character semantics.  For operations where this determination cannot
be made without additional information from the user, Perl decides in
favor of compatibility and chooses to use byte semantics.
.PP
This behavior preserves compatibility with earlier versions of Perl,
which allowed byte semantics in Perl operations only if
none of the program's inputs were marked as being as source of Unicode
character data.  Such data may come from filehandles, from calls to
external programs, from information provided by the system (such as \f(CW%ENV\fR),
or from literals and constants in the source text.
.PP
The \f(CW\*(C`bytes\*(C'\fR pragma will always, regardless of platform, force byte
semantics in a particular lexical scope.  See bytes.
.PP
The \f(CW\*(C`utf8\*(C'\fR pragma is primarily a compatibility device that enables
recognition of \s-1UTF\-\s0(8|EBCDIC) in literals encountered by the parser.
Note that this pragma is only required while Perl defaults to byte
semantics; when character semantics become the default, this pragma
may become a no-op.  See utf8.
.PP
Unless explicitly stated, Perl operators use character semantics
for Unicode data and byte semantics for non-Unicode data.
The decision to use character semantics is made transparently.  If
input data comes from a Unicode source\*(--for example, if a character
encoding layer is added to a filehandle or a literal Unicode
string constant appears in a program\*(--character semantics apply.
Otherwise, byte semantics are in effect.  The \f(CW\*(C`bytes\*(C'\fR pragma should
be used to force byte semantics on Unicode data.
.PP
If strings operating under byte semantics and strings with Unicode
character data are concatenated, the new string will be created by
decoding the byte strings as \fI\s-1ISO\s0 8859\-1 (Latin\-1)\fR, even if the
old Unicode string used \s-1EBCDIC\s0.  This translation is done without
regard to the system's native 8\-bit encoding.
.PP
Under character semantics, many operations that formerly operated on
bytes now operate on characters. A character in Perl is
logically just a number ranging from 0 to 2**31 or so. Larger
characters may encode into longer sequences of bytes internally, but
this internal detail is mostly hidden for Perl code.
See perluniintro for more.
.Sh "Effects of Character Semantics"
.IX Subsection "Effects of Character Semantics"
Character semantics have the following effects:
.IP "\(bu" 4
Strings\*(--including hash keys\*(--and regular expression patterns may
contain characters that have an ordinal value larger than 255.
.Sp
If you use a Unicode editor to edit your program, Unicode characters may
occur directly within the literal strings in \s-1UTF\-8\s0 encoding, or \s-1UTF\-16\s0.
(The former requires a \s-1BOM\s0 or \f(CW\*(C`use utf8\*(C'\fR, the latter requires a \s-1BOM\s0.)
.Sp
Unicode characters can also be added to a string by using the \f(CW\*(C`\ex{...}\*(C'\fR
notation.  The Unicode code for the desired character, in hexadecimal,
should be placed in the braces. For instance, a smiley face is
\&\f(CW\*(C`\ex{263A}\*(C'\fR.  This encoding scheme only works for all characters, but
for characters under 0x100, note that Perl may use an 8 bit encoding
internally, for optimization and/or backward compatibility.
.Sp
Additionally, if you
.Sp
.Vb 1
\&   use charnames \*(Aq:full\*(Aq;
.Ve
.Sp
you can use the \f(CW\*(C`\eN{...}\*(C'\fR notation and put the official Unicode
character name within the braces, such as \f(CW\*(C`\eN{WHITE SMILING FACE}\*(C'\fR.
.IP "\(bu" 4
If an appropriate encoding is specified, identifiers within the
Perl script may contain Unicode alphanumeric characters, including
ideographs.  Perl does not currently attempt to canonicalize variable
names.
.IP "\(bu" 4
Regular expressions match characters instead of bytes.  \*(L".\*(R" matches
a character instead of a byte.
.IP "\(bu" 4
Character classes in regular expressions match characters instead of
bytes and match against the character properties specified in the
Unicode properties database.  \f(CW\*(C`\ew\*(C'\fR can be used to match a Japanese
ideograph, for instance.
.IP "\(bu" 4
Named Unicode properties, scripts, and block ranges may be used like
character classes via the \f(CW\*(C`\ep{}\*(C'\fR \*(L"matches property\*(R" construct and
the \f(CW\*(C`\eP{}\*(C'\fR negation, \*(L"doesn't match property\*(R".
.Sp
See \*(L"Unicode Character Properties\*(R" for more details.
.Sp
You can define your own character properties and use them
in the regular expression with the \f(CW\*(C`\ep{}\*(C'\fR or \f(CW\*(C`\eP{}\*(C'\fR construct.
.Sp
See \*(L"User-Defined Character Properties\*(R" for more details.
.IP "\(bu" 4
The special pattern \f(CW\*(C`\eX\*(C'\fR matches any extended Unicode
sequence\-\-\*(L"a combining character sequence\*(R" in Standardese\*(--where the
first character is a base character and subsequent characters are mark
characters that apply to the base character.  \f(CW\*(C`\eX\*(C'\fR is equivalent to
\&\f(CW\*(C`(?:\ePM\epM*)\*(C'\fR.
.IP "\(bu" 4
The \f(CW\*(C`tr///\*(C'\fR operator translates characters instead of bytes.  Note
that the \f(CW\*(C`tr///CU\*(C'\fR functionality has been removed.  For similar
functionality see pack('U0', ...) and pack('C0', ...).
.IP "\(bu" 4
Case translation operators use the Unicode case translation tables
when character input is provided.  Note that \f(CW\*(C`uc()\*(C'\fR, or \f(CW\*(C`\eU\*(C'\fR in
interpolated strings, translates to uppercase, while \f(CW\*(C`ucfirst\*(C'\fR,
or \f(CW\*(C`\eu\*(C'\fR in interpolated strings, translates to titlecase in languages
that make the distinction.
.IP "\(bu" 4
Most operators that deal with positions or lengths in a string will
automatically switch to using character positions, including
\&\f(CW\*(C`chop()\*(C'\fR, \f(CW\*(C`chomp()\*(C'\fR, \f(CW\*(C`substr()\*(C'\fR, \f(CW\*(C`pos()\*(C'\fR, \f(CW\*(C`index()\*(C'\fR, \f(CW\*(C`rindex()\*(C'\fR,
\&\f(CW\*(C`sprintf()\*(C'\fR, \f(CW\*(C`write()\*(C'\fR, and \f(CW\*(C`length()\*(C'\fR.  An operator that
specifically does not switch is \f(CW\*(C`vec()\*(C'\fR.  Operators that really don't 
care include operators that treat strings as a bucket of bits such as 
\&\f(CW\*(C`sort()\*(C'\fR, and operators dealing with filenames.