perlfaq3.1

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
There are two popular ways to avoid this overhead.  One solution
involves running the Apache \s-1HTTP\s0 server (available from
http://www.apache.org/ ) with either of the mod_perl or mod_fastcgi
plugin modules.
.PP
With mod_perl and the Apache::Registry module (distributed with
mod_perl), httpd will run with an embedded Perl interpreter which
pre-compiles your script and then executes it within the same address
space without forking.  The Apache extension also gives Perl access to
the internal server \s-1API\s0, so modules written in Perl can do just about
anything a module written in C can.  For more on mod_perl, see
http://perl.apache.org/
.PP
With the \s-1FCGI\s0 module (from \s-1CPAN\s0) and the mod_fastcgi
module (available from http://www.fastcgi.com/ ) each of your Perl
programs becomes a permanent \s-1CGI\s0 daemon process.
.PP
Both of these solutions can have far-reaching effects on your system
and on the way you write your \s-1CGI\s0 programs, so investigate them with
care.
.PP
See http://www.cpan.org/modules/by\-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
.Sh "How can I hide the source for my Perl program?"
.IX Subsection "How can I hide the source for my Perl program?"
Delete it. :\-) Seriously, there are a number of (mostly
unsatisfactory) solutions with varying levels of \*(L"security\*(R".
.PP
First of all, however, you \fIcan't\fR take away read permission, because
the source code has to be readable in order to be compiled and
interpreted.  (That doesn't mean that a \s-1CGI\s0 script's source is
readable by people on the web, though\*(--only by people with access to
the filesystem.)  So you have to leave the permissions at the socially
friendly 0755 level.
.PP
Some people regard this as a security problem.  If your program does
insecure things and relies on people not knowing how to exploit those
insecurities, it is not secure.  It is often possible for someone to
determine the insecure things and exploit them without viewing the
source.  Security through obscurity, the name for hiding your bugs
instead of fixing them, is little security indeed.
.PP
You can try using encryption via source filters (Starting from Perl
5.8 the Filter::Simple and Filter::Util::Call modules are included in
the standard distribution), but any decent programmer will be able to
decrypt it.  You can try using the byte code compiler and interpreter
described later in perlfaq3, but the curious might still be able to
de-compile it. You can try using the native-code compiler described
later, but crackers might be able to disassemble it.  These pose
varying degrees of difficulty to people wanting to get at your code,
but none can definitively conceal it (true of every language, not just
Perl).
.PP
It is very easy to recover the source of Perl programs.  You simply
feed the program to the perl interpreter and use the modules in
the B:: hierarchy.  The B::Deparse module should be able to
defeat most attempts to hide source.  Again, this is not
unique to Perl.
.PP
If you're concerned about people profiting from your code, then the
bottom line is that nothing but a restrictive license will give you
legal security.  License your software and pepper it with threatening
statements like \*(L"This is unpublished proprietary software of \s-1XYZ\s0 Corp.
Your access to it does not give you permission to use it blah blah
blah.\*(R"  We are not lawyers, of course, so you should see a lawyer if
you want to be sure your license's wording will stand up in court.
.Sh "How can I compile my Perl program into byte code or C?"
.IX Subsection "How can I compile my Perl program into byte code or C?"
(contributed by brian d foy)
.PP
In general, you can't do this.  There are some things that may work
for your situation though.  People usually ask this question
because they want to distribute their works without giving away
the source code, and most solutions trade disk space for convenience.
You probably won't see much of a speed increase either, since most
solutions simply bundle a Perl interpreter in the final product
(but see \*(L"How can I make my Perl program run faster?\*(R").
.PP
The Perl Archive Toolkit ( http://par.perl.org/ ) is Perl's
analog to Java's \s-1JAR\s0.  It's freely available and on \s-1CPAN\s0 (
http://search.cpan.org/dist/PAR/ ).
.PP
There are also some commercial products that may work for you, although
you have to buy a license for them.
.PP
The Perl Dev Kit ( http://www.activestate.com/Products/Perl_Dev_Kit/ )
from ActiveState can \*(L"Turn your Perl programs into ready-to-run
executables for HP-UX, Linux, Solaris and Windows.\*(R"
.PP
Perl2Exe ( http://www.indigostar.com/perl2exe.htm ) is a command line
program for converting perl scripts to executable files.  It targets both
Windows and unix platforms.
.ie n .Sh "How can I get ""#!perl"" to work on [\s-1MS\-DOS\s0,NT,...]?"
.el .Sh "How can I get \f(CW#!perl\fP to work on [\s-1MS\-DOS\s0,NT,...]?"
.IX Subsection "How can I get #!perl to work on [MS-DOS,NT,...]?"
For \s-1OS/2\s0 just use
.PP
.Vb 1
\&    extproc perl \-S \-your_switches
.Ve
.PP
as the first line in \f(CW\*(C`*.cmd\*(C'\fR file (\f(CW\*(C`\-S\*(C'\fR due to a bug in cmd.exe's
\&\*(L"extproc\*(R" handling).  For \s-1DOS\s0 one should first invent a corresponding
batch file and codify it in \f(CW\*(C`ALTERNATE_SHEBANG\*(C'\fR (see the
\&\fIdosish.h\fR file in the source distribution for more information).
.PP
The Win95/NT installation, when using the ActiveState port of Perl,
will modify the Registry to associate the \f(CW\*(C`.pl\*(C'\fR extension with the
perl interpreter.  If you install another port, perhaps even building
your own Win95/NT Perl from the standard sources by using a Windows port
of gcc (e.g., with cygwin or mingw32), then you'll have to modify
the Registry yourself.  In addition to associating \f(CW\*(C`.pl\*(C'\fR with the
interpreter, \s-1NT\s0 people can use: \f(CW\*(C`SET PATHEXT=%PATHEXT%;.PL\*(C'\fR to let them
run the program \f(CW\*(C`install\-linux.pl\*(C'\fR merely by typing \f(CW\*(C`install\-linux\*(C'\fR.
.PP
Under \*(L"Classic\*(R" MacOS, a perl program will have the appropriate Creator and
Type, so that double-clicking them will invoke the MacPerl application.
Under Mac \s-1OS\s0 X, clickable apps can be made from any \f(CW\*(C`#!\*(C'\fR script using Wil
Sanchez' DropScript utility: http://www.wsanchez.net/software/ .
.PP
\&\fI\s-1IMPORTANT\s0!\fR: Whatever you do, \s-1PLEASE\s0 don't get frustrated, and just
throw the perl interpreter into your cgi-bin directory, in order to
get your programs working for a web server.  This is an \s-1EXTREMELY\s0 big
security risk.  Take the time to figure out how to do it correctly.
.Sh "Can I write useful Perl programs on the command line?"
.IX Subsection "Can I write useful Perl programs on the command line?"
Yes.  Read perlrun for more information.  Some examples follow.
(These assume standard Unix shell quoting rules.)
.PP
.Vb 2
\&    # sum first and last fields
\&    perl \-lane \*(Aqprint $F[0] + $F[\-1]\*(Aq *
\&
\&    # identify text files
\&    perl \-le \*(Aqfor(@ARGV) {print if \-f && \-T _}\*(Aq *
\&
\&    # remove (most) comments from C program
\&    perl \-0777 \-pe \*(Aqs{/\e*.*?\e*/}{}gs\*(Aq foo.c
\&
\&    # make file a month younger than today, defeating reaper daemons
\&    perl \-e \*(Aq$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)\*(Aq *
\&
\&    # find first unused uid
\&    perl \-le \*(Aq$i++ while getpwuid($i); print $i\*(Aq
\&
\&    # display reasonable manpath
\&    echo $PATH | perl \-nl \-072 \-e \*(Aq
\&        s![^/+]*$!man!&&\-d&&!$s{$_}++&&push@m,$_;END{print"@m"}\*(Aq
.Ve
.PP
\&\s-1OK\s0, the last one was actually an Obfuscated Perl Contest entry. :\-)
.Sh "Why don't Perl one-liners work on my DOS/Mac/VMS system?"
.IX Subsection "Why don't Perl one-liners work on my DOS/Mac/VMS system?"
The problem is usually that the command interpreters on those systems
have rather different ideas about quoting than the Unix shells under
which the one-liners were created.  On some systems, you may have to
change single-quotes to double ones, which you must \fI\s-1NOT\s0\fR do on Unix
or Plan9 systems.  You might also have to change a single % to a %%.
.PP
For example:
.PP
.Vb 2
\&    # Unix (including Mac OS X)
\&    perl \-e \*(Aqprint "Hello world\en"\*(Aq
\&
\&    # DOS, etc.
\&    perl \-e "print \e"Hello world\en\e""
\&
\&    # Mac Classic
\&    print "Hello world\en"
\&     (then Run "Myscript" or Shift\-Command\-R)
\&
\&    # MPW
\&    perl \-e \*(Aqprint "Hello world\en"\*(Aq
\&
\&    # VMS
\&    perl \-e "print ""Hello world\en"""
.Ve
.PP
The problem is that none of these examples are reliable: they depend on the
command interpreter.  Under Unix, the first two often work. Under \s-1DOS\s0,
it's entirely possible that neither works.  If 4DOS was the command shell,
you'd probably have better luck like this:
.PP
.Vb 1
\&  perl \-e "print <Ctrl\-x>"Hello world\en<Ctrl\-x>""
.Ve
.PP
Under the Mac, it depends which environment you are using.  The MacPerl
shell, or \s-1MPW\s0, is much like Unix shells in its support for several
quoting variants, except that it makes free use of the Mac's non-ASCII
characters as control characters.
.PP
Using \fIqq()\fR, q(), and \fIqx()\fR, instead of \*(L"double quotes\*(R", 'single
quotes', and `backticks`, may make one-liners easier to write.
.PP
There is no general solution to all of this.  It is a mess.
.PP
[Some of this answer was contributed by Kenneth Albanowski.]
.Sh "Where can I learn about \s-1CGI\s0 or Web programming in Perl?"
.IX Subsection "Where can I learn about CGI or Web programming in Perl?"
For modules, get the \s-1CGI\s0 or \s-1LWP\s0 modules from \s-1CPAN\s0.  For textbooks,
see the two especially dedicated to web stuff in the question on
books.  For problems and questions related to the web, like \*(L"Why
do I get 500 Errors\*(R" or \*(L"Why doesn't it run from the browser right
when it runs fine on the command line\*(R", see the troubleshooting
guides and references in perlfaq9 or in the \s-1CGI\s0 MetaFAQ:
.PP
.Vb 1
\&        http://www.perl.org/CGI_MetaFAQ.html
.Ve
.Sh "Where can I learn about object-oriented Perl programming?"
.IX Subsection "Where can I learn about object-oriented Perl programming?"
A good place to start is perltoot, and you can use perlobj,
perlboot, perltoot, perltooc, and perlbot for reference.
.PP
A good book on \s-1OO\s0 on Perl is the \*(L"Object-Oriented Perl\*(R"
by Damian Conway from Manning Publications, or \*(L"Intermediate Perl\*(R"
by Randal Schwartz, brian d foy, and Tom Phoenix from O'Reilly Media.
.Sh "Where can I learn about linking C with Perl?"
.IX Subsection "Where can I learn about linking C with Perl?"
If you want to call C from Perl, start with perlxstut,
moving on to perlxs, xsubpp, and perlguts.  If you want to
call Perl from C, then read perlembed, perlcall, and
perlguts.  Don't forget that you can learn a lot from looking at
how the authors of existing extension modules wrote their code and
solved their problems.
.PP
You might not need all the power of \s-1XS\s0. The Inline::C module lets
you put C code directly in your Perl source. It handles all the
magic to make it work. You still have to learn at least some of
the perl \s-1API\s0 but you won't have to deal with the complexity of the
\&\s-1XS\s0 support files.
.Sh "I've read perlembed, perlguts, etc., but I can't embed perl in my C program; what am I doing wrong?"
.IX Subsection "I've read perlembed, perlguts, etc., but I can't embed perl in my C program; what am I doing wrong?"
Download the ExtUtils::Embed kit from \s-1CPAN\s0 and run `make test'.  If
the tests pass, read the pods again and again and again.  If they
fail, see perlbug and send a bug report with the output of
\&\f(CW\*(C`make test TEST_VERBOSE=1\*(C'\fR along with \f(CW\*(C`perl \-V\*(C'\fR.
.Sh "When I tried to run my script, I got this message. What does it mean?"
.IX Subsection "When I tried to run my script, I got this message. What does it mean?"
A complete list of Perl's error messages and warnings with explanatory
text can be found in perldiag. You can also use the splain program
(distributed with Perl) to explain the error messages:
.PP
.Vb 2
\&    perl program 2>diag.out
\&    splain [\-v] [\-p] diag.out
.Ve
.PP
or change your program to explain the messages for you:
.PP
.Vb 1
\&    use diagnostics;
.Ve
.PP
or
.PP
.Vb 1
\&    use diagnostics \-verbose;
.Ve
.Sh "What's MakeMaker?"
.IX Subsection "What's MakeMaker?"
(contributed by brian d foy)
.PP
The \f(CW\*(C`ExtUtils::MakeMaker\*(C'\fR module, better known simply as \*(L"MakeMaker\*(R",
turns a Perl script, typically called \f(CW\*(C`Makefile.PL\*(C'\fR, into a Makefile.
The unix tool \f(CW\*(C`make\*(C'\fR uses this file to manage dependencies and actions
to process and install a Perl distribution.
.SH "REVISION"
.IX Header "REVISION"
Revision: \f(CW$Revision:\fR 10127 $
.PP
Date: \f(CW$Date:\fR 2007\-10\-27 21:40:20 +0200 (Sat, 27 Oct 2007) $
.PP
See perlfaq for source control details and availability.
.SH "AUTHOR AND COPYRIGHT"
.IX Header "AUTHOR AND COPYRIGHT"
Copyright (c) 1997\-2007 Tom Christiansen, Nathan Torkington, and
other authors as noted. All rights reserved.
.PP
This documentation is free; you can redistribute it and/or modify it
under the same terms as Perl itself.
.PP
Irrespective of its distribution, all code examples here are in the public
domain.  You are permitted and encouraged to use this code and any
derivatives thereof in your own programs for fun or for profit as you
see fit.  A simple comment in the code giving credit to the \s-1FAQ\s0 would
be courteous but is not required.