=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.48 $, $Date: 2005/04/22 19:04:48 $)
+perlfaq3 - Programming Tools ($Revision: 10127 $)
=head1 DESCRIPTION
=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:
+perldebug(1) manpage, on an "empty" program, like this:
perl -de 42
=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://www.focusresearch.com/gregor/psh/ .
+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
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.
+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).
+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;
use File::Find;
my @files;
- find sub { push @files, $File::Find::name if -f _ && /\.pm$/ },
- @INC;
+ find(
+ sub {
+ push @files, $File::Find::name
+ if -f $File::Find::name && /\.pm$/
+ },
+
+ @INC
+ );
print join "\n", @files;
=head2 How do I debug my Perl programs?
-Have you tried C<use warnings> or used C<-w>? They enable warnings
-to detect dubious practices.
+(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:
-Have you tried C<use strict>? It prevents you from using symbolic
-references, makes you predeclare any subroutines that you call as bare
-words, and (probably most importantly) forces you to predeclare your
-variables with C<my>, C<our>, or C<use vars>.
+ use Data::Dumper qw( Dumper );
+ print STDERR "The hash is " . Dumper( \%hash ) . "\n";
-Did you check the return values of each and every system call? The operating
-system (and thus Perl) tells you whether they worked, and if not
-why.
+Perl comes with an interactive debugger, which you can start with the
+C<-d> switch. It's fully explained in L<perldebug>.
- open(FH, "> /etc/cantwrite")
- or die "Couldn't write to /etc/cantwrite: $!\n";
+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.
-Did you read L<perltrap>? It's full of gotchas for old and new Perl
-programmers and even has sections for those of you who are upgrading
-from languages like I<awk> and I<C>.
+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).
-Have you tried the Perl debugger, described in L<perldebug>? You can
-step through your program and see what it's doing and thus work out
-why what it's doing isn't what it should be doing.
+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?
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
+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, as does enscript at http://people.ssh.fi/mtr/genscript/ .
+documents.
=head2 Is there a ctags for Perl?
-Recent versions of ctags do much more than older versions did.
-EXUBERANT CTAGS is available from http://ctags.sourceforge.net/
-and does a good job of making tags files for perl code.
+(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/
-There is also a simple one at
-http://www.cpan.org/authors/id/TOMC/scripts/ptags.gz which may do
-the trick. It can be easy to hack this into what you want.
+You might also try pltags: http://www.mscha.com/pltags.zip
=head2 Is there an IDE or Windows Perl Editor?
=item Eclipse
+http://e-p-i-c.sf.net/
+
The Eclipse Perl Integration Project integrates Perl
editing/debugging with Eclipse.
-The website for the project is http://e-p-i-c.sf.net/
+=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
-( http://www.ActiveState.com/Products/Komodo/ ).
+debugger and remote debugging.
=item Open Perl IDE
-( http://open-perl-ide.sourceforge.net/ )
+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/ ) is a Windows IDE with simulated CGI
-environment, including debugger and syntax highlighting editor.
+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 ) is an integrated development
-environment for Windows that supports Perl development.
+http://www.solutionsoft.com/perl.htm
+
+PerlBuidler is an integrated development environment for Windows that
+supports Perl development.
=item visiPerl+
-( http://helpconsulting.net/visiperl/ )
+http://helpconsulting.net/visiperl/
+
From Help Consulting, for Windows.
=item Visual Perl
-( http://www.activestate.com/Products/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.
+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
There is also a toyedit Text widget based editor written in Perl
that is distributed with the Tk module on CPAN. The ptkdb
-( http://world.std.com/~aep/ptkdb/ ) is a Perl/tk based debugger that
+( 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.
=item Zsh
-ftp://ftp.blarg.net/users/amol/zsh/ , see also http://www.zsh.org/
+http://www.zsh.org/
=back
=item Affrus
-is a full Perl development enivornment with full debugger support
+is a full Perl development environment with full debugger support
( http://www.latenightsw.com ).
=item Alpha
this program repeats a command and updates the screen as needed, rendering
B<rep ps axu> similar to B<top>.
-=head2 How can I use X or Tk with Perl?
+=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
-Tk is a completely Perl-based, object-oriented interface to the Tk toolkit
-that doesn't force you to use Tcl just to get at Tk. Sx is an interface
-to the Athena Widget set. Both are available from CPAN. See the
-directory http://www.cpan.org/modules/by-category/08_User_Interfaces/
+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.
-Invaluable for Perl/Tk programming are the Perl/Tk FAQ at
-http://phaseit.net/claird/comp.lang.perl.tk/ptkFAQ.html , the Perl/Tk Reference
-Guide available at
-http://www.cpan.org/authors/Stephen_O_Lidie/ , and the
-online manpages at
-http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
+=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?
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.
+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
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 judgment, however, because any changes will be propagated
+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.
See http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
-A non-free, commercial product, ``The Velocity Engine for Perl'',
-(http://www.binevolve.com/ or http://www.binevolve.com/velocigen/ )
-might also be worth looking at. It will allow you to increase the
-performance of your Perl programs, running programs up to 25 times
-faster than normal CGI Perl when running in persistent Perl mode or 4
-to 5 times faster without any modification to your existing CGI
-programs. Fully functional evaluation copies are available from the
-web site.
-
=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''.
+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
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 below, but the curious might still be able to de-compile it.
-You can try using the native-code compiler described below, 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).
+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
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.
+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
+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?
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/index.cgi) is
-Perl's analog to Java's JAR. It's freely available and on
-CPAN (http://search.cpan.org/dist/PAR/).
-
-The B::* namespace, often called "the Perl compiler", but is really a
-way for Perl programs to peek at its innards rather than create
-pre-compiled versions of your program. However. the B::Bytecode
-module can turn your script into a bytecode format that could be
-loaded later by the ByteLoader module and executed as a regular Perl
-script.
+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.
+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
+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 compile Perl into Java?
-
-You can also integrate Java and Perl with the
-Perl Resource Kit from O'Reilly Media. See
-http://www.oreilly.com/catalog/prkunix/ .
-
-Perl 5.6 comes with Java Perl Lingo, or JPL. JPL, still in
-development, allows Perl code to be called from Java. See jpl/README
-in the Perl source tree.
+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,...]?
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
+"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).
For example:
- # Unix
+ # Unix (including Mac OS X)
perl -e 'print "Hello world\n"'
# DOS, etc.
perl -e "print \"Hello world\n\""
- # Mac
+ # Mac Classic
print "Hello world\n"
(then Run "Myscript" or Shift-Command-R)
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
+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
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.
-(If you are using really old Perl, you may not have all of these,
-try http://www.perldoc.com/ , but consider upgrading your perl.)
A good book on OO on Perl is the "Object-Oriented Perl"
-by Damian Conway from Manning Publications,
-http://www.manning.com/Conway/index.html
+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? [h2xs, xsubpp]
+=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
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
=head2 What's MakeMaker?
-This module (part of the standard Perl distribution) is designed to
-write a Makefile for an extension module from a Makefile.PL. For more
-information, see L<ExtUtils::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) 1997-2005 Tom Christiansen, Nathan Torkington, and
+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
https://perl5.git.perl.org / perl5.git / blobdiff