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diff --git a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlfaq3.pod b/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlfaq3.pod deleted file mode 100644 index 7b58df85af6..00000000000 --- a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlfaq3.pod +++ /dev/null @@ -1,1054 +0,0 @@ -=head1 NAME - -perlfaq3 - Programming Tools ($Revision: 10127 $) - -=head1 DESCRIPTION - -This section of the FAQ answers questions related to programmer tools -and programming support. - -=head2 How do I do (anything)? - -Have you looked at CPAN (see L<perlfaq2>)? The chances are that -someone has already written a module that can solve your problem. -Have you read the appropriate manpages? Here's a brief index: - - Basics perldata, perlvar, perlsyn, perlop, perlsub - Execution perlrun, perldebug - Functions perlfunc - Objects perlref, perlmod, perlobj, perltie - Data Structures perlref, perllol, perldsc - Modules perlmod, perlmodlib, perlsub - Regexes perlre, perlfunc, perlop, perllocale - Moving to perl5 perltrap, perl - Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed - Various http://www.cpan.org/misc/olddoc/FMTEYEWTK.tgz - (not a man-page but still useful, a collection - of various essays on Perl techniques) - -A crude table of contents for the Perl manpage set is found in L<perltoc>. - -=head2 How can I use Perl interactively? - -The typical approach uses the Perl debugger, described in the -perldebug(1) manpage, on an "empty" program, like this: - - perl -de 42 - -Now just type in any legal Perl code, and it will be immediately -evaluated. You can also examine the symbol table, get stack -backtraces, check variable values, set breakpoints, and other -operations typically found in symbolic debuggers. - -=head2 Is there a Perl shell? - -The psh (Perl sh) is currently at version 1.8. The Perl Shell is a shell -that combines the interactive nature of a Unix shell with the power of -Perl. The goal is a full featured shell that behaves as expected for -normal shell activity and uses Perl syntax and functionality for -control-flow statements and other things. You can get psh at -http://sourceforge.net/projects/psh/ . - -Zoidberg is a similar project and provides a shell written in perl, -configured in perl and operated in perl. It is intended as a login shell -and development environment. It can be found at http://zoidberg.sf.net/ -or your local CPAN mirror. - -The Shell.pm module (distributed with Perl) makes Perl try commands -which aren't part of the Perl language as shell commands. perlsh from -the source distribution is simplistic and uninteresting, but may still -be what you want. - -=head2 How do I find which modules are installed on my system? - -You can use the ExtUtils::Installed module to show all installed -distributions, although it can take awhile to do its magic. The -standard library which comes with Perl just shows up as "Perl" (although -you can get those with Module::CoreList). - - use ExtUtils::Installed; - - my $inst = ExtUtils::Installed->new(); - my @modules = $inst->modules(); - -If you want a list of all of the Perl module filenames, you -can use File::Find::Rule. - - use File::Find::Rule; - - my @files = File::Find::Rule->file()->name( '*.pm' )->in( @INC ); - -If you do not have that module, you can do the same thing -with File::Find which is part of the standard library. - - use File::Find; - my @files; - - find( - sub { - push @files, $File::Find::name - if -f $File::Find::name && /\.pm$/ - }, - - @INC - ); - - print join "\n", @files; - -If you simply need to quickly check to see if a module is -available, you can check for its documentation. If you can -read the documentation the module is most likely installed. -If you cannot read the documentation, the module might not -have any (in rare cases). - - prompt% perldoc Module::Name - -You can also try to include the module in a one-liner to see if -perl finds it. - - perl -MModule::Name -e1 - -=head2 How do I debug my Perl programs? - -(contributed by brian d foy) - -Before you do anything else, you can help yourself by ensuring that -you let Perl tell you about problem areas in your code. By turning -on warnings and strictures, you can head off many problems before -they get too big. You can find out more about these in L<strict> -and L<warnings>. - - #!/usr/bin/perl - use strict; - use warnings; - -Beyond that, the simplest debugger is the C<print> function. Use it -to look at values as you run your program: - - print STDERR "The value is [$value]\n"; - -The C<Data::Dumper> module can pretty-print Perl data structures: - - use Data::Dumper qw( Dumper ); - print STDERR "The hash is " . Dumper( \%hash ) . "\n"; - -Perl comes with an interactive debugger, which you can start with the -C<-d> switch. It's fully explained in L<perldebug>. - -If you'd like a graphical user interface and you have Tk, you can use -C<ptkdb>. It's on CPAN and available for free. - -If you need something much more sophisticated and controllable, Leon -Brocard's Devel::ebug (which you can call with the -D switch as -Debug) -gives you the programmatic hooks into everything you need to write your -own (without too much pain and suffering). - -You can also use a commercial debugger such as Affrus (Mac OS X), Komodo -from Activestate (Windows and Mac OS X), or EPIC (most platforms). - -=head2 How do I profile my Perl programs? - -You should get the Devel::DProf module from the standard distribution -(or separately on CPAN) and also use Benchmark.pm from the standard -distribution. The Benchmark module lets you time specific portions of -your code, while Devel::DProf gives detailed breakdowns of where your -code spends its time. - -Here's a sample use of Benchmark: - - use Benchmark; - - @junk = `cat /etc/motd`; - $count = 10_000; - - timethese($count, { - 'map' => sub { my @a = @junk; - map { s/a/b/ } @a; - return @a }, - 'for' => sub { my @a = @junk; - for (@a) { s/a/b/ }; - return @a }, - }); - -This is what it prints (on one machine--your results will be dependent -on your hardware, operating system, and the load on your machine): - - Benchmark: timing 10000 iterations of for, map... - for: 4 secs ( 3.97 usr 0.01 sys = 3.98 cpu) - map: 6 secs ( 4.97 usr 0.00 sys = 4.97 cpu) - -Be aware that a good benchmark is very hard to write. It only tests the -data you give it and proves little about the differing complexities -of contrasting algorithms. - -=head2 How do I cross-reference my Perl programs? - -The B::Xref module can be used to generate cross-reference reports -for Perl programs. - - perl -MO=Xref[,OPTIONS] scriptname.plx - -=head2 Is there a pretty-printer (formatter) for Perl? - -Perltidy is a Perl script which indents and reformats Perl scripts -to make them easier to read by trying to follow the rules of the -L<perlstyle>. If you write Perl scripts, or spend much time reading -them, you will probably find it useful. It is available at -http://perltidy.sourceforge.net - -Of course, if you simply follow the guidelines in L<perlstyle>, -you shouldn't need to reformat. The habit of formatting your code -as you write it will help prevent bugs. Your editor can and should -help you with this. The perl-mode or newer cperl-mode for emacs -can provide remarkable amounts of help with most (but not all) -code, and even less programmable editors can provide significant -assistance. Tom Christiansen and many other VI users swear by -the following settings in vi and its clones: - - set ai sw=4 - map! ^O {^M}^[O^T - -Put that in your F<.exrc> file (replacing the caret characters -with control characters) and away you go. In insert mode, ^T is -for indenting, ^D is for undenting, and ^O is for blockdenting--as -it were. A more complete example, with comments, can be found at -http://www.cpan.org/authors/id/TOMC/scripts/toms.exrc.gz - -The a2ps http://www-inf.enst.fr/%7Edemaille/a2ps/black+white.ps.gz does -lots of things related to generating nicely printed output of -documents. - -=head2 Is there a ctags for Perl? - -(contributed by brian d foy) - -Ctags uses an index to quickly find things in source code, and many -popular editors support ctags for several different languages, -including Perl. - -Exuberent ctags supports Perl: http://ctags.sourceforge.net/ - -You might also try pltags: http://www.mscha.com/pltags.zip - -=head2 Is there an IDE or Windows Perl Editor? - -Perl programs are just plain text, so any editor will do. - -If you're on Unix, you already have an IDE--Unix itself. The UNIX -philosophy is the philosophy of several small tools that each do one -thing and do it well. It's like a carpenter's toolbox. - -If you want an IDE, check the following (in alphabetical order, not -order of preference): - -=over 4 - -=item Eclipse - -http://e-p-i-c.sf.net/ - -The Eclipse Perl Integration Project integrates Perl -editing/debugging with Eclipse. - -=item Enginsite - -http://www.enginsite.com/ - -Perl Editor by EngInSite is a complete integrated development -environment (IDE) for creating, testing, and debugging Perl scripts; -the tool runs on Windows 9x/NT/2000/XP or later. - -=item Komodo - -http://www.ActiveState.com/Products/Komodo/ - -ActiveState's cross-platform (as of October 2004, that's Windows, Linux, -and Solaris), multi-language IDE has Perl support, including a regular expression -debugger and remote debugging. - -=item Open Perl IDE - -http://open-perl-ide.sourceforge.net/ - -Open Perl IDE is an integrated development environment for writing -and debugging Perl scripts with ActiveState's ActivePerl distribution -under Windows 95/98/NT/2000. - -=item OptiPerl - -http://www.optiperl.com/ - -OptiPerl is a Windows IDE with simulated CGI environment, including -debugger and syntax highlighting editor. - -=item PerlBuilder - -http://www.solutionsoft.com/perl.htm - -PerlBuidler is an integrated development environment for Windows that -supports Perl development. - -=item visiPerl+ - -http://helpconsulting.net/visiperl/ - -From Help Consulting, for Windows. - -=item Visual Perl - -http://www.activestate.com/Products/Visual_Perl/ - -Visual Perl is a Visual Studio.NET plug-in from ActiveState. - -=item Zeus - -http://www.zeusedit.com/lookmain.html - -Zeus for Window is another Win32 multi-language editor/IDE -that comes with support for Perl: - -=back - -For editors: if you're on Unix you probably have vi or a vi clone -already, and possibly an emacs too, so you may not need to download -anything. In any emacs the cperl-mode (M-x cperl-mode) gives you -perhaps the best available Perl editing mode in any editor. - -If you are using Windows, you can use any editor that lets you work -with plain text, such as NotePad or WordPad. Word processors, such as -Microsoft Word or WordPerfect, typically do not work since they insert -all sorts of behind-the-scenes information, although some allow you to -save files as "Text Only". You can also download text editors designed -specifically for programming, such as Textpad ( -http://www.textpad.com/ ) and UltraEdit ( http://www.ultraedit.com/ ), -among others. - -If you are using MacOS, the same concerns apply. MacPerl (for Classic -environments) comes with a simple editor. Popular external editors are -BBEdit ( http://www.bbedit.com/ ) or Alpha ( -http://www.his.com/~jguyer/Alpha/Alpha8.html ). MacOS X users can use -Unix editors as well. - -=over 4 - -=item GNU Emacs - -http://www.gnu.org/software/emacs/windows/ntemacs.html - -=item MicroEMACS - -http://www.microemacs.de/ - -=item XEmacs - -http://www.xemacs.org/Download/index.html - -=item Jed - -http://space.mit.edu/~davis/jed/ - -=back - -or a vi clone such as - -=over 4 - -=item Elvis - -ftp://ftp.cs.pdx.edu/pub/elvis/ http://www.fh-wedel.de/elvis/ - -=item Vile - -http://dickey.his.com/vile/vile.html - -=item Vim - -http://www.vim.org/ - -=back - -For vi lovers in general, Windows or elsewhere: - - http://www.thomer.com/thomer/vi/vi.html - -nvi ( http://www.bostic.com/vi/ , available from CPAN in src/misc/) is -yet another vi clone, unfortunately not available for Windows, but in -UNIX platforms you might be interested in trying it out, firstly because -strictly speaking it is not a vi clone, it is the real vi, or the new -incarnation of it, and secondly because you can embed Perl inside it -to use Perl as the scripting language. nvi is not alone in this, -though: at least also vim and vile offer an embedded Perl. - -The following are Win32 multilanguage editor/IDESs that support Perl: - -=over 4 - -=item Codewright - -http://www.borland.com/codewright/ - -=item MultiEdit - -http://www.MultiEdit.com/ - -=item SlickEdit - -http://www.slickedit.com/ - -=back - -There is also a toyedit Text widget based editor written in Perl -that is distributed with the Tk module on CPAN. The ptkdb -( http://ptkdb.sourceforge.net/ ) is a Perl/tk based debugger that -acts as a development environment of sorts. Perl Composer -( http://perlcomposer.sourceforge.net/ ) is an IDE for Perl/Tk -GUI creation. - -In addition to an editor/IDE you might be interested in a more -powerful shell environment for Win32. Your options include - -=over 4 - -=item Bash - -from the Cygwin package ( http://sources.redhat.com/cygwin/ ) - -=item Ksh - -from the MKS Toolkit ( http://www.mks.com/ ), or the Bourne shell of -the U/WIN environment ( http://www.research.att.com/sw/tools/uwin/ ) - -=item Tcsh - -ftp://ftp.astron.com/pub/tcsh/ , see also -http://www.primate.wisc.edu/software/csh-tcsh-book/ - -=item Zsh - -http://www.zsh.org/ - -=back - -MKS and U/WIN are commercial (U/WIN is free for educational and -research purposes), Cygwin is covered by the GNU Public License (but -that shouldn't matter for Perl use). The Cygwin, MKS, and U/WIN all -contain (in addition to the shells) a comprehensive set of standard -UNIX toolkit utilities. - -If you're transferring text files between Unix and Windows using FTP -be sure to transfer them in ASCII mode so the ends of lines are -appropriately converted. - -On Mac OS the MacPerl Application comes with a simple 32k text editor -that behaves like a rudimentary IDE. In contrast to the MacPerl Application -the MPW Perl tool can make use of the MPW Shell itself as an editor (with -no 32k limit). - -=over 4 - -=item Affrus - -is a full Perl development environment with full debugger support -( http://www.latenightsw.com ). - -=item Alpha - -is an editor, written and extensible in Tcl, that nonetheless has -built in support for several popular markup and programming languages -including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ). - -=item BBEdit and BBEdit Lite - -are text editors for Mac OS that have a Perl sensitivity mode -( http://web.barebones.com/ ). - - -=back - -Pepper and Pe are programming language sensitive text editors for Mac -OS X and BeOS respectively ( http://www.hekkelman.com/ ). - -=head2 Where can I get Perl macros for vi? - -For a complete version of Tom Christiansen's vi configuration file, -see http://www.cpan.org/authors/Tom_Christiansen/scripts/toms.exrc.gz , -the standard benchmark file for vi emulators. The file runs best with nvi, -the current version of vi out of Berkeley, which incidentally can be built -with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ . - -=head2 Where can I get perl-mode for emacs? - -Since Emacs version 19 patchlevel 22 or so, there have been both a -perl-mode.el and support for the Perl debugger built in. These should -come with the standard Emacs 19 distribution. - -In the Perl source directory, you'll find a directory called "emacs", -which contains a cperl-mode that color-codes keywords, provides -context-sensitive help, and other nifty things. - -Note that the perl-mode of emacs will have fits with C<"main'foo"> -(single quote), and mess up the indentation and highlighting. You -are probably using C<"main::foo"> in new Perl code anyway, so this -shouldn't be an issue. - -=head2 How can I use curses with Perl? - -The Curses module from CPAN provides a dynamically loadable object -module interface to a curses library. A small demo can be found at the -directory http://www.cpan.org/authors/Tom_Christiansen/scripts/rep.gz ; -this program repeats a command and updates the screen as needed, rendering -B<rep ps axu> similar to B<top>. - -=head2 How can I write a GUI (X, Tk, Gtk, etc.) in Perl? -X<GUI> X<Tk> X<Wx> X<WxWidgets> X<Gtk> X<Gtk2> X<CamelBones> X<Qt> - -(contributed by Ben Morrow) - -There are a number of modules which let you write GUIs in Perl. Most -GUI toolkits have a perl interface: an incomplete list follows. - -=over 4 - -=item Tk - -This works under Unix and Windows, and the current version doesn't -look half as bad under Windows as it used to. Some of the gui elements -still don't 'feel' quite right, though. The interface is very natural -and 'perlish', making it easy to use in small scripts that just need a -simple gui. It hasn't been updated in a while. - -=item Wx - -This is a Perl binding for the cross-platform wxWidgets toolkit -L<http://www.wxwidgets.org>. It works under Unix, Win32 and Mac OS X, -using native widgets (Gtk under Unix). The interface follows the C++ -interface closely, but the documentation is a little sparse for someone -who doesn't know the library, mostly just referring you to the C++ -documentation. - -=item Gtk and Gtk2 - -These are Perl bindings for the Gtk toolkit L<http://www.gtk.org>. The -interface changed significantly between versions 1 and 2 so they have -separate Perl modules. It runs under Unix, Win32 and Mac OS X (currently -it requires an X server on Mac OS, but a 'native' port is underway), and -the widgets look the same on every plaform: i.e., they don't match the -native widgets. As with Wx, the Perl bindings follow the C API closely, -and the documentation requires you to read the C documentation to -understand it. - -=item Win32::GUI - -This provides access to most of the Win32 GUI widgets from Perl. -Obviously, it only runs under Win32, and uses native widgets. The Perl -interface doesn't really follow the C interface: it's been made more -Perlish, and the documentation is pretty good. More advanced stuff may -require familiarity with the C Win32 APIs, or reference to MSDN. - -=item CamelBones - -CamelBones L<http://camelbones.sourceforge.net> is a Perl interface to -Mac OS X's Cocoa GUI toolkit, and as such can be used to produce native -GUIs on Mac OS X. It's not on CPAN, as it requires frameworks that -CPAN.pm doesn't know how to install, but installation is via the -standard OSX package installer. The Perl API is, again, very close to -the ObjC API it's wrapping, and the documentation just tells you how to -translate from one to the other. - -=item Qt - -There is a Perl interface to TrollTech's Qt toolkit, but it does not -appear to be maintained. - -=item Athena - -Sx is an interface to the Athena widget set which comes with X, but -again it appears not to be much used nowadays. - -=back - -=head2 How can I make my Perl program run faster? - -The best way to do this is to come up with a better algorithm. This -can often make a dramatic difference. Jon Bentley's book -I<Programming Pearls> (that's not a misspelling!) has some good tips -on optimization, too. Advice on benchmarking boils down to: benchmark -and profile to make sure you're optimizing the right part, look for -better algorithms instead of microtuning your code, and when all else -fails consider just buying faster hardware. You will probably want to -read the answer to the earlier question "How do I profile my Perl -programs?" if you haven't done so already. - -A different approach is to autoload seldom-used Perl code. See the -AutoSplit and AutoLoader modules in the standard distribution for -that. Or you could locate the bottleneck and think about writing just -that part in C, the way we used to take bottlenecks in C code and -write them in assembler. Similar to rewriting in C, modules that have -critical sections can be written in C (for instance, the PDL module -from CPAN). - -If you're currently linking your perl executable to a shared -I<libc.so>, you can often gain a 10-25% performance benefit by -rebuilding it to link with a static libc.a instead. This will make a -bigger perl executable, but your Perl programs (and programmers) may -thank you for it. See the F<INSTALL> file in the source distribution -for more information. - -The undump program was an ancient attempt to speed up Perl program by -storing the already-compiled form to disk. This is no longer a viable -option, as it only worked on a few architectures, and wasn't a good -solution anyway. - -=head2 How can I make my Perl program take less memory? - -When it comes to time-space tradeoffs, Perl nearly always prefers to -throw memory at a problem. Scalars in Perl use more memory than -strings in C, arrays take more than that, and hashes use even more. While -there's still a lot to be done, recent releases have been addressing -these issues. For example, as of 5.004, duplicate hash keys are -shared amongst all hashes using them, so require no reallocation. - -In some cases, using substr() or vec() to simulate arrays can be -highly beneficial. For example, an array of a thousand booleans will -take at least 20,000 bytes of space, but it can be turned into one -125-byte bit vector--a considerable memory savings. The standard -Tie::SubstrHash module can also help for certain types of data -structure. If you're working with specialist data structures -(matrices, for instance) modules that implement these in C may use -less memory than equivalent Perl modules. - -Another thing to try is learning whether your Perl was compiled with -the system malloc or with Perl's builtin malloc. Whichever one it -is, try using the other one and see whether this makes a difference. -Information about malloc is in the F<INSTALL> file in the source -distribution. You can find out whether you are using perl's malloc by -typing C<perl -V:usemymalloc>. - -Of course, the best way to save memory is to not do anything to waste -it in the first place. Good programming practices can go a long way -toward this: - -=over 4 - -=item * Don't slurp! - -Don't read an entire file into memory if you can process it line -by line. Or more concretely, use a loop like this: - - # - # Good Idea - # - while (<FILE>) { - # ... - } - -instead of this: - - # - # Bad Idea - # - @data = <FILE>; - foreach (@data) { - # ... - } - -When the files you're processing are small, it doesn't much matter which -way you do it, but it makes a huge difference when they start getting -larger. - -=item * Use map and grep selectively - -Remember that both map and grep expect a LIST argument, so doing this: - - @wanted = grep {/pattern/} <FILE>; - -will cause the entire file to be slurped. For large files, it's better -to loop: - - while (<FILE>) { - push(@wanted, $_) if /pattern/; - } - -=item * Avoid unnecessary quotes and stringification - -Don't quote large strings unless absolutely necessary: - - my $copy = "$large_string"; - -makes 2 copies of $large_string (one for $copy and another for the -quotes), whereas - - my $copy = $large_string; - -only makes one copy. - -Ditto for stringifying large arrays: - - { - local $, = "\n"; - print @big_array; - } - -is much more memory-efficient than either - - print join "\n", @big_array; - -or - - { - local $" = "\n"; - print "@big_array"; - } - - -=item * Pass by reference - -Pass arrays and hashes by reference, not by value. For one thing, it's -the only way to pass multiple lists or hashes (or both) in a single -call/return. It also avoids creating a copy of all the contents. This -requires some judgement, however, because any changes will be propagated -back to the original data. If you really want to mangle (er, modify) a -copy, you'll have to sacrifice the memory needed to make one. - -=item * Tie large variables to disk. - -For "big" data stores (i.e. ones that exceed available memory) consider -using one of the DB modules to store it on disk instead of in RAM. This -will incur a penalty in access time, but that's probably better than -causing your hard disk to thrash due to massive swapping. - -=back - -=head2 Is it safe to return a reference to local or lexical data? - -Yes. Perl's garbage collection system takes care of this so -everything works out right. - - sub makeone { - my @a = ( 1 .. 10 ); - return \@a; - } - - for ( 1 .. 10 ) { - push @many, makeone(); - } - - print $many[4][5], "\n"; - - print "@many\n"; - -=head2 How can I free an array or hash so my program shrinks? - -(contributed by Michael Carman) - -You usually can't. Memory allocated to lexicals (i.e. my() variables) -cannot be reclaimed or reused even if they go out of scope. It is -reserved in case the variables come back into scope. Memory allocated -to global variables can be reused (within your program) by using -undef()ing and/or delete(). - -On most operating systems, memory allocated to a program can never be -returned to the system. That's why long-running programs sometimes re- -exec themselves. Some operating systems (notably, systems that use -mmap(2) for allocating large chunks of memory) can reclaim memory that -is no longer used, but on such systems, perl must be configured and -compiled to use the OS's malloc, not perl's. - -In general, memory allocation and de-allocation isn't something you can -or should be worrying about much in Perl. - -See also "How can I make my Perl program take less memory?" - -=head2 How can I make my CGI script more efficient? - -Beyond the normal measures described to make general Perl programs -faster or smaller, a CGI program has additional issues. It may be run -several times per second. Given that each time it runs it will need -to be re-compiled and will often allocate a megabyte or more of system -memory, this can be a killer. Compiling into C B<isn't going to help -you> because the process start-up overhead is where the bottleneck is. - -There are two popular ways to avoid this overhead. One solution -involves running the Apache HTTP server (available from -http://www.apache.org/ ) with either of the mod_perl or mod_fastcgi -plugin modules. - -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 API, 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/ - -With the FCGI module (from CPAN) and the mod_fastcgi -module (available from http://www.fastcgi.com/ ) each of your Perl -programs becomes a permanent CGI daemon process. - -Both of these solutions can have far-reaching effects on your system -and on the way you write your CGI programs, so investigate them with -care. - -See http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ . - -=head2 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 "security". - -First of all, however, you I<can't> 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 CGI 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. - -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. - -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 L<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). - -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. - -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 "This is unpublished proprietary software of XYZ Corp. -Your access to it does not give you permission to use it blah blah -blah." 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. - -=head2 How can I compile my Perl program into byte code or C? - -(contributed by brian d foy) - -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?>). - -The Perl Archive Toolkit ( http://par.perl.org/ ) is Perl's -analog to Java's JAR. It's freely available and on CPAN ( -http://search.cpan.org/dist/PAR/ ). - -There are also some commercial products that may work for you, although -you have to buy a license for them. - -The Perl Dev Kit ( http://www.activestate.com/Products/Perl_Dev_Kit/ ) -from ActiveState can "Turn your Perl programs into ready-to-run -executables for HP-UX, Linux, Solaris and Windows." - -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. - -=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]? - -For OS/2 just use - - extproc perl -S -your_switches - -as the first line in C<*.cmd> file (C<-S> due to a bug in cmd.exe's -"extproc" handling). For DOS one should first invent a corresponding -batch file and codify it in C<ALTERNATE_SHEBANG> (see the -F<dosish.h> file in the source distribution for more information). - -The Win95/NT installation, when using the ActiveState port of Perl, -will modify the Registry to associate the C<.pl> 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 C<.pl> with the -interpreter, NT people can use: C<SET PATHEXT=%PATHEXT%;.PL> to let them -run the program C<install-linux.pl> merely by typing C<install-linux>. - -Under "Classic" MacOS, a perl program will have the appropriate Creator and -Type, so that double-clicking them will invoke the MacPerl application. -Under Mac OS X, clickable apps can be made from any C<#!> script using Wil -Sanchez' DropScript utility: http://www.wsanchez.net/software/ . - -I<IMPORTANT!>: Whatever you do, PLEASE 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 EXTREMELY big -security risk. Take the time to figure out how to do it correctly. - -=head2 Can I write useful Perl programs on the command line? - -Yes. Read L<perlrun> for more information. Some examples follow. -(These assume standard Unix shell quoting rules.) - - # sum first and last fields - perl -lane 'print $F[0] + $F[-1]' * - - # identify text files - perl -le 'for(@ARGV) {print if -f && -T _}' * - - # remove (most) comments from C program - perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c - - # make file a month younger than today, defeating reaper daemons - perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' * - - # find first unused uid - perl -le '$i++ while getpwuid($i); print $i' - - # display reasonable manpath - echo $PATH | perl -nl -072 -e ' - s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}' - -OK, the last one was actually an Obfuscated Perl Contest entry. :-) - -=head2 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 I<NOT> do on Unix -or Plan9 systems. You might also have to change a single % to a %%. - -For example: - - # Unix (including Mac OS X) - perl -e 'print "Hello world\n"' - - # DOS, etc. - perl -e "print \"Hello world\n\"" - - # Mac Classic - print "Hello world\n" - (then Run "Myscript" or Shift-Command-R) - - # MPW - perl -e 'print "Hello world\n"' - - # VMS - perl -e "print ""Hello world\n""" - -The problem is that none of these examples are reliable: they depend on the -command interpreter. Under Unix, the first two often work. Under DOS, -it's entirely possible that neither works. If 4DOS was the command shell, -you'd probably have better luck like this: - - perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>"" - -Under the Mac, it depends which environment you are using. The MacPerl -shell, or MPW, 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. - -Using qq(), q(), and qx(), instead of "double quotes", 'single -quotes', and `backticks`, may make one-liners easier to write. - -There is no general solution to all of this. It is a mess. - -[Some of this answer was contributed by Kenneth Albanowski.] - -=head2 Where can I learn about CGI or Web programming in Perl? - -For modules, get the CGI or LWP modules from CPAN. For textbooks, -see the two especially dedicated to web stuff in the question on -books. For problems and questions related to the web, like "Why -do I get 500 Errors" or "Why doesn't it run from the browser right -when it runs fine on the command line", see the troubleshooting -guides and references in L<perlfaq9> or in the CGI MetaFAQ: - - http://www.perl.org/CGI_MetaFAQ.html - -=head2 Where can I learn about object-oriented Perl programming? - -A good place to start is L<perltoot>, and you can use L<perlobj>, -L<perlboot>, L<perltoot>, L<perltooc>, and L<perlbot> for reference. - -A good book on OO on Perl is the "Object-Oriented Perl" -by Damian Conway from Manning Publications, or "Intermediate Perl" -by Randal Schwartz, brian d foy, and Tom Phoenix from O'Reilly Media. - -=head2 Where can I learn about linking C with Perl? - -If you want to call C from Perl, start with L<perlxstut>, -moving on to L<perlxs>, L<xsubpp>, and L<perlguts>. If you want to -call Perl from C, then read L<perlembed>, L<perlcall>, and -L<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. - -You might not need all the power of XS. 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 API but you won't have to deal with the complexity of the -XS support files. - -=head2 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 CPAN and run `make test'. If -the tests pass, read the pods again and again and again. If they -fail, see L<perlbug> and send a bug report with the output of -C<make test TEST_VERBOSE=1> along with C<perl -V>. - -=head2 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 L<perldiag>. You can also use the splain program -(distributed with Perl) to explain the error messages: - - perl program 2>diag.out - splain [-v] [-p] diag.out - -or change your program to explain the messages for you: - - use diagnostics; - -or - - use diagnostics -verbose; - -=head2 What's MakeMaker? - -(contributed by brian d foy) - -The C<ExtUtils::MakeMaker> module, better known simply as "MakeMaker", -turns a Perl script, typically called C<Makefile.PL>, into a Makefile. -The unix tool C<make> uses this file to manage dependencies and actions -to process and install a Perl distribution. - -=head1 REVISION - -Revision: $Revision: 10127 $ - -Date: $Date: 2007-10-27 21:40:20 +0200 (Sat, 27 Oct 2007) $ - -See L<perlfaq> for source control details and availability. - -=head1 AUTHOR AND COPYRIGHT - -Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and -other authors as noted. All rights reserved. - -This documentation is free; you can redistribute it and/or modify it -under the same terms as Perl itself. - -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 FAQ would -be courteous but is not required. |