perlpodspec.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.

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.\" ========================================================================
.\"
.IX Title "PERLPODSPEC 1"
.TH PERLPODSPEC 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.
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.SH "NAME"
perlpodspec \- Plain Old Documentation: format specification and notes
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This document is detailed notes on the Pod markup language.  Most
people will only have to read perlpod to know how to write
in Pod, but this document may answer some incidental questions to do
with parsing and rendering Pod.
.PP
In this document, \*(L"must\*(R" / \*(L"must not\*(R", \*(L"should\*(R" /
\&\*(L"should not\*(R", and \*(L"may\*(R" have their conventional (cf. \s-1RFC\s0 2119)
meanings: \*(L"X must do Y\*(R" means that if X doesn't do Y, it's against
this specification, and should really be fixed.  \*(L"X should do Y\*(R"
means that it's recommended, but X may fail to do Y, if there's a
good reason.  \*(L"X may do Y\*(R" is merely a note that X can do Y at
will (although it is up to the reader to detect any connotation of
"and I think it would be \fInice\fR if X did Y\*(L" versus \*(R"it wouldn't
really \fIbother\fR me if X did Y").
.PP
Notably, when I say \*(L"the parser should do Y\*(R", the
parser may fail to do Y, if the calling application explicitly
requests that the parser \fInot\fR do Y.  I often phrase this as
\&\*(L"the parser should, by default, do Y.\*(R"  This doesn't \fIrequire\fR
the parser to provide an option for turning off whatever
feature Y is (like expanding tabs in verbatim paragraphs), although
it implicates that such an option \fImay\fR be provided.
.SH "Pod Definitions"
.IX Header "Pod Definitions"
Pod is embedded in files, typically Perl source files \*(-- although you
can write a file that's nothing but Pod.
.PP
A \fBline\fR in a file consists of zero or more non-newline characters,
terminated by either a newline or the end of the file.
.PP
A \fBnewline sequence\fR is usually a platform-dependent concept, but
Pod parsers should understand it to mean any of \s-1CR\s0 (\s-1ASCII\s0 13), \s-1LF\s0
(\s-1ASCII\s0 10), or a \s-1CRLF\s0 (\s-1ASCII\s0 13 followed immediately by \s-1ASCII\s0 10), in
addition to any other system-specific meaning.  The first \s-1CR/CRLF/LF\s0
sequence in the file may be used as the basis for identifying the
newline sequence for parsing the rest of the file.
.PP
A \fBblank line\fR is a line consisting entirely of zero or more spaces
(\s-1ASCII\s0 32) or tabs (\s-1ASCII\s0 9), and terminated by a newline or end-of-file.
A \fBnon-blank line\fR is a line containing one or more characters other
than space or tab (and terminated by a newline or end-of-file).
.PP
(\fINote:\fR Many older Pod parsers did not accept a line consisting of
spaces/tabs and then a newline as a blank line \*(-- the only lines they
considered blank were lines consisting of \fIno characters at all\fR,
terminated by a newline.)
.PP
\&\fBWhitespace\fR is used in this document as a blanket term for spaces,
tabs, and newline sequences.  (By itself, this term usually refers
to literal whitespace.  That is, sequences of whitespace characters
in Pod source, as opposed to \*(L"E<32>\*(R", which is a formatting
code that \fIdenotes\fR a whitespace character.)
.PP
A \fBPod parser\fR is a module meant for parsing Pod (regardless of
whether this involves calling callbacks or building a parse tree or
directly formatting it).  A \fBPod formatter\fR (or \fBPod translator\fR)
is a module or program that converts Pod to some other format (\s-1HTML\s0,
plaintext, TeX, PostScript, \s-1RTF\s0).  A \fBPod processor\fR might be a
formatter or translator, or might be a program that does something
else with the Pod (like counting words, scanning for index points,
etc.).
.PP
Pod content is contained in \fBPod blocks\fR.  A Pod block starts with a
line that matches <m/\eA=[a\-zA\-Z]/>, and continues up to the next line
that matches \f(CW\*(C`m/\eA=cut/\*(C'\fR \*(-- or up to the end of the file, if there is
no \f(CW\*(C`m/\eA=cut/\*(C'\fR line.
.PP
Within a Pod block, there are \fBPod paragraphs\fR.  A Pod paragraph
consists of non-blank lines of text, separated by one or more blank
lines.
.PP
For purposes of Pod processing, there are four types of paragraphs in
a Pod block:
.IP "\(bu" 4
A command paragraph (also called a \*(L"directive\*(R").  The first line of
this paragraph must match \f(CW\*(C`m/\eA=[a\-zA\-Z]/\*(C'\fR.  Command paragraphs are
typically one line, as in:
.Sp
.Vb 1
\&  =head1 NOTES
\&
\&  =item *
.Ve
.Sp
But they may span several (non-blank) lines:
.Sp
.Vb 3
\&  =for comment
\&  Hm, I wonder what it would look like if
\&  you tried to write a BNF for Pod from this.
\&
\&  =head3 Dr. Strangelove, or: How I Learned to
\&  Stop Worrying and Love the Bomb
.Ve
.Sp
\&\fISome\fR command paragraphs allow formatting codes in their content
(i.e., after the part that matches \f(CW\*(C`m/\eA=[a\-zA\-Z]\eS*\es*/\*(C'\fR), as in:
.Sp
.Vb 1
\&  =head1 Did You Remember to C<use strict;>?
.Ve
.Sp
In other words, the Pod processing handler for \*(L"head1\*(R" will apply the
same processing to \*(L"Did You Remember to C<use strict;>?\*(R" that it
would to an ordinary paragraph \*(-- i.e., formatting codes (like
\&\*(L"C<...>\*(R") are parsed and presumably formatted appropriately, and
whitespace in the form of literal spaces and/or tabs is not
significant.
.IP "\(bu" 4
A \fBverbatim paragraph\fR.  The first line of this paragraph must be a
literal space or tab, and this paragraph must not be inside a "=begin
\&\fIidentifier\fR\*(L", ... \*(R"=end \fIidentifier\fR\*(L" sequence unless
\&\*(R"\fIidentifier\fR\*(L" begins with a colon (\*(R":").  That is, if a paragraph
starts with a literal space or tab, but \fIis\fR inside a
"=begin \fIidentifier\fR\*(L", ... \*(R"=end \fIidentifier\fR\*(L" region, then it's
a data paragraph, unless \*(R"\fIidentifier\fR" begins with a colon.
.Sp
Whitespace \fIis\fR significant in verbatim paragraphs (although, in
processing, tabs are probably expanded).
.IP "\(bu" 4
An \fBordinary paragraph\fR.  A paragraph is an ordinary paragraph
if its first line matches neither \f(CW\*(C`m/\eA=[a\-zA\-Z]/\*(C'\fR nor
\&\f(CW\*(C`m/\eA[ \et]/\*(C'\fR, \fIand\fR if it's not inside a "=begin \fIidentifier\fR\*(L",
\&... \*(R"=end \fIidentifier\fR\*(L" sequence unless \*(R"\fIidentifier\fR\*(L" begins with
a colon (\*(R":").
.IP "\(bu" 4
A \fBdata paragraph\fR.  This is a paragraph that \fIis\fR inside a "=begin
\&\fIidentifier\fR\*(L" ... \*(R"=end \fIidentifier\fR\*(L" sequence where
\&\*(R"\fIidentifier\fR" does \fInot\fR begin with a literal colon (\*(L":\*(R").  In
some sense, a data paragraph is not part of Pod at all (i.e.,
effectively it's \*(L"out-of-band\*(R"), since it's not subject to most kinds
of Pod parsing; but it is specified here, since Pod
parsers need to be able to call an event for it, or store it in some
form in a parse tree, or at least just parse \fIaround\fR it.
.PP
For example: consider the following paragraphs:
.PP
.Vb 1
\&  # <\- that\*(Aqs the 0th column
\&
\&  =head1 Foo
\&
\&  Stuff
\&
\&    $foo\->bar
\&
\&  =cut
.Ve
.PP
Here, \*(L"=head1 Foo\*(R" and \*(L"=cut\*(R" are command paragraphs because the first
line of each matches \f(CW\*(C`m/\eA=[a\-zA\-Z]/\*(C'\fR.  "\fI[space][space]\fR\f(CW$foo\fR\->bar\*(L"
is a verbatim paragraph, because its first line starts with a literal
whitespace character (and there's no \*(R"=begin\*(L"...\*(R"=end" region around).
.PP
The "=begin \fIidentifier\fR\*(L" ... \*(R"=end \fIidentifier\fR" commands stop