=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.38 $, $Date: 1999/05/23 16:08:30 $)
+perlfaq3 - Programming Tools
=head1 DESCRIPTION
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 man pages? Here's a brief index:
+Have you read the appropriate manpages? Here's a brief index:
Basics perldata, perlvar, perlsyn, perlop, perlsub
Execution perlrun, perldebug
Regexes perlre, perlfunc, perlop, perllocale
Moving to perl5 perltrap, perl
Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed
- Various http://www.perl.com/CPAN/doc/FMTEYEWTK/index.html
- (not a man-page but still useful)
+ 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 man
page set is found in L<perltoc>.
+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) man page, on an ``empty'' program, like this:
+C<perldebug(1)> manpage, on an "empty" program, like this:
perl -de 42
=head2 Is there a Perl shell?
-In general, no. 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.
+The C<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 C<psh> at
+http://sourceforge.net/projects/psh/ .
+
+C<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://pardus-larus.student.utwente.nl/~pardus/projects/zoidberg/
+or your local CPAN mirror.
+
+The C<Shell.pm> module (distributed with Perl) makes Perl try commands
+which aren't part of the Perl language as shell commands. C<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?
+
+From the command line, you can use the C<cpan> command's C<-l> switch:
+
+ $ cpan -l
+
+You can also use C<cpan>'s C<-a> switch to create an autobundle file
+that C<CPAN.pm> understands and can use to re-install every module:
+
+ $ cpan -a
+
+Inside a Perl program, you can use the C<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 C<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 C<File::Find::Rule>:
+
+ use File::Find::Rule;
+
+ my @files = File::Find::Rule->
+ extras({follow => 1})->
+ file()->
+ name( '*.pm' )->
+ in( @INC )
+ ;
+
+If you do not have that module, you can do the same thing
+with C<File::Find> which is part of the standard library:
+
+ use File::Find;
+ my @files;
+
+ find(
+ {
+ wanted => sub {
+ push @files, $File::Find::fullname
+ if -f $File::Find::fullname && /\.pm$/
+ },
+ follow => 1,
+ follow_skip => 2,
+ },
+ @INC
+ );
+
+ print join "\n", @files;
+
+If you simply need to check quickly 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):
+
+ $ 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?
-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:
-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>.
+ print STDERR "The value is [$value]\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.
+The C<Data::Dumper> module can pretty-print Perl data structures:
- open(FH, "> /etc/cantwrite")
- or die "Couldn't write to /etc/cantwrite: $!\n";
+ use Data::Dumper qw( Dumper );
+ print STDERR "The hash is " . Dumper( \%hash ) . "\n";
-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>.
+Perl comes with an interactive debugger, which you can start with the
+C<-d> switch. It's fully explained in L<perldebug>.
-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.
+If you'd like a graphical user interface and you have C<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 C<Devel::ebug> (which you can call with the C<-D> switch as C<-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.
+(contributed by brian d foy, updated Fri Jul 25 12:22:26 PDT 2008)
+
+The C<Devel> namespace has several modules which you can use to
+profile your Perl programs. The C<Devel::DProf> module comes with Perl
+and you can invoke it with the C<-d> switch:
+
+ perl -d:DProf program.pl
-Here's a sample use of Benchmark:
+After running your program under C<DProf>, you'll get a F<tmon.out> file
+with the profile data. To look at the data, you can turn it into a
+human-readable report with the C<dprofpp> program that comes with
+C<Devel::DProf>.
- use Benchmark;
+ dprofpp
- @junk = `cat /etc/motd`;
- $count = 10_000;
+You can also do the profiling and reporting in one step with the C<-p>
+switch to C<dprofpp>:
- timethese($count, {
- 'map' => sub { my @a = @junk;
- map { s/a/b/ } @a;
- return @a
- },
- 'for' => sub { my @a = @junk;
- local $_;
- for (@a) { s/a/b/ };
- return @a },
- });
+ dprofpp -p program.pl
-This is what it prints (on one machine--your results will be dependent
-on your hardware, operating system, and the load on your machine):
+The C<Devel::NYTProf> (New York Times Profiler) does both statement
+and subroutine profiling. It's available from CPAN and you also invoke
+it with the C<-d> switch:
- 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)
+ perl -d:NYTProf some_perl.pl
-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.
+Like C<DProf>, it creates a database of the profile information that you
+can turn into reports. The C<nytprofhtml> command turns the data into
+an HTML report similar to the C<Devel::Cover> report:
+
+ nytprofhtml
+
+CPAN has several other profilers that you can invoke in the same
+fashion. You might also be interested in using the C<Benchmark> to
+measure and compare code snippets.
+
+You can read more about profiling in I<Programming Perl>, chapter 20,
+or I<Mastering Perl>, chapter 5.
+
+L<perldebguts> documents creating a custom debugger if you need to
+create a special sort of profiler. brian d foy describes the process
+in I<The Perl Journal>, "Creating a Perl Debugger",
+http://www.ddj.com/184404522 , and "Profiling in Perl"
+http://www.ddj.com/184404580 .
+
+Perl.com has two interesting articles on profiling: "Profiling Perl",
+by Simon Cozens, http://www.perl.com/lpt/a/850 and "Debugging and
+Profiling mod_perl Applications", by Frank Wiles,
+http://www.perl.com/pub/a/2006/02/09/debug_mod_perl.html .
+
+Randal L. Schwartz writes about profiling in "Speeding up Your Perl
+Programs" for I<Unix Review>,
+http://www.stonehenge.com/merlyn/UnixReview/col49.html , and "Profiling
+in Template Toolkit via Overriding" for I<Linux Magazine>,
+http://www.stonehenge.com/merlyn/LinuxMag/col75.html .
=head2 How do I cross-reference my Perl programs?
-The B::Xref module, shipped with the new, alpha-release Perl compiler
-(not the general distribution prior to the 5.005 release), can be used
-to generate cross-reference reports for Perl programs.
+The C<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?
-There is no program that will reformat Perl as much as indent(1) does
-for C. The complex feedback between the scanner and the parser (this
-feedback is what confuses the vgrind and emacs programs) makes it
-challenging at best to write a stand-alone Perl parser.
-
-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 swears
-by the following settings in vi and its clones:
+C<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
-Now put that in your F<.exrc> file (replacing the caret characters
+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. If you haven't used the last one, you're missing
-a lot. A more complete example, with comments, can be found at
-http://www.perl.com/CPAN-local/authors/id/TOMC/scripts/toms.exrc.gz
+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
-If you are used to using the I<vgrind> program for printing out nice code
-to a laser printer, you can take a stab at this using
-http://www.perl.com/CPAN/doc/misc/tips/working.vgrind.entry, but the
-results are not particularly satisfying for sophisticated code.
-
-The a2ps at http://www.infres.enst.fr/%7Edemaille/a2ps/ does lots of things
-related to generating nicely printed output of documents.
+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?
-There's a simple one at
-http://www.perl.com/CPAN/authors/id/TOMC/scripts/ptags.gz which may do
-the trick. And if not, it's easy to hack into what you want.
+(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.
+
+Exuberant 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
+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 a Windows IDE, check the following:
+If you want an IDE, check the following (in alphabetical order, not
+order of preference):
=over 4
-=item CodeMagicCD
+=item Eclipse
+
+http://e-p-i-c.sf.net/
+
+The Eclipse Perl Integration Project integrates Perl
+editing/debugging with Eclipse.
+
+=item Enginsite
-http://www.codemagiccd.com/
+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
-ActiveState's cross-platform, multi-language IDE has Perl support,
-including a regular expression debugger and remote debugging
-(http://www.ActiveState.com/Products/Komodo/index.html).
-(Visual Perl, a Visual Studio.NET plug-in is currently (early 2001)
-in beta (http://www.ActiveState.com/Products/VisualPerl/index.html)).
+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 Notepad++
+
+http://notepad-plus.sourceforge.net/
-=item The Object System
+=item Open Perl IDE
-(http://www.castlelink.co.uk/object_system/) is a Perl web
-applications development IDE.
+http://open-perl-ide.sourceforge.net/
-=item Perl code magic
+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.
-(http://www.petes-place.com/codemagic.html).
+=item OptiPerl
+
+http://www.optiperl.com/
+
+OptiPerl is a Windows IDE with simulated CGI environment, including
+debugger and syntax-highlighting editor.
+
+=item Padre
+
+http://padre.perlide.org/
+
+Padre is cross-platform IDE for Perl written in Perl using wxWidgets to provide
+a native look and feel. It's open source under the Artistic License.
+
+=item PerlBuilder
+
+http://www.solutionsoft.com/perl.htm
+
+PerlBuilder is an integrated development environment for Windows that
+supports Perl development.
=item visiPerl+
-http://helpconsulting.net/visiperl/, from Help Consulting.
+http://helpconsulting.net/visiperl/
-=back
+From Help Consulting, for Windows.
-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.
+=item Visual Perl
-For Windows editors: you can download an Emacs
+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 MicroEMACS
-http://members.nbci.com/uemacs/
+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
=item Vile
-http://vile.cx/
+http://dickey.his.com/vile/vile.html
=item Vim
http://www.vim.org/
-win32: http://www.cs.vu.nl/%7Etmgil/vi.html
-
=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
+ 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
+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:
+The following are Win32 multilanguage editor/IDEs that support Perl:
=over 4
=item Codewright
-http://www.starbase.com/
+http://www.borland.com/codewright/
=item MultiEdit
http://www.slickedit.com/
+=item ConTEXT
+
+http://www.contexteditor.org/
+
=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://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/vperl.html) is an IDE for Perl/Tk
+( 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
=item Bash
-from the Cygwin package (http://sources.redhat.com/cygwin/)
+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/)
+from the MKS Toolkit ( http://www.mkssoftware.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
+ftp://ftp.astron.com/pub/tcsh/ , see also
http://www.primate.wisc.edu/software/csh-tcsh-book/
=item Zsh
-ftp://ftp.blarg.net/users/amol/zsh/, see also http://www.zsh.org/
+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.
+research purposes), Cygwin is covered by the GNU General 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
=over 4
-=item BBEdit and BBEdit Lite
+=item Affrus
-are text editors for Mac OS that have a Perl sensitivity mode
-(http://web.barebones.com/).
+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://alpha.olm.net/).
+built-in support for several popular markup and programming languages,
+including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ).
-=back
+=item BBEdit and BBEdit Lite
+
+are text editors for Mac OS that have a Perl sensitivity mode
+( http://web.barebones.com/ ).
-Pepper and Pe are programming language sensitive text editors for Mac
-OS X and BeOS respectively (http://www.hekkelman.com/).
+=back
=head2 Where can I get Perl macros for vi?
For a complete version of Tom Christiansen's vi configuration file,
-see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc.gz ,
+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.perl.com/CPAN/src/misc.
+with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ .
-=head2 Where can I get perl-mode for emacs?
+=head2 Where can I get perl-mode or cperl-mode for emacs?
+X<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.
+For CPerlMode, see http://www.emacswiki.org/cgi-bin/wiki/CPerlMode
+
=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.perl.com/CPAN/authors/Tom_Christiansen/scripts/rep;
+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 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
+
+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.
-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.perl.com/CPAN/modules/by-category/08_User_Interfaces/
+=item Wx
-Invaluable for Perl/Tk programming are the Perl/Tk FAQ at
-http://w4.lns.cornell.edu/%7Epvhp/ptk/ptkTOC.html , the Perl/Tk Reference
-Guide available at
-http://www.perl.com/CPAN-local/authors/Stephen_O_Lidie/ , and the
-online manpages at
-http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
+This is a Perl binding for the cross-platform wxWidgets toolkit
+( 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.
-=head2 How can I generate simple menus without using CGI or Tk?
+=item Gtk and Gtk2
-The http://www.perl.com/CPAN/authors/id/SKUNZ/perlmenu.v4.0.tar.gz
-module, which is curses-based, can help with this.
+These are Perl bindings for the Gtk toolkit ( 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 platform: 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.
-=head2 What is undump?
+=item Win32::GUI
-See the next question on ``How can I make my Perl program run faster?''
+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 ( 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
-``Programming Pearls'' (that's not a misspelling!) has some good tips
+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.
+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).
-
-In some cases, it may be worth it to use the backend compiler to
-produce byte code (saving compilation time) or compile into C, which
-will certainly save compilation time and sometimes a small amount (but
-not much) execution time. See the question about compiling your Perl
-programs for more on the compiler--the wins aren't as obvious as you'd
-hope.
-
-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.
-
-Unsubstantiated reports allege that Perl interpreters that use sfio
-outperform those that don't (for I/O intensive applications). To try
-this, see the F<INSTALL> file in the source distribution, especially
-the ``Selecting File I/O mechanisms'' section.
-
-The undump program was an old attempt to speed up your 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.
+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?
distribution. You can find out whether you are using perl's malloc by
typing C<perl -V:usemymalloc>.
-=head2 Is it unsafe to return a pointer to local data?
+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.
-No, Perl's garbage collection system takes care of this.
+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 $i ( 1 .. 10 ) {
+ for ( 1 .. 10 ) {
push @many, makeone();
}
=head2 How can I free an array or hash so my program shrinks?
-You can't. On most operating systems, memory allocated to a program
-can never be returned to the system. That's why long-running programs
-sometimes re-exec themselves. Some operating systems (notably,
-FreeBSD and Linux) allegedly reclaim large chunks of memory that is no
-longer used, but it doesn't appear to happen with Perl (yet). The Mac
-appears to be the only platform that will reliably (albeit, slowly)
-return memory to the OS.
-
-We've had reports that on Linux (Redhat 5.1) on Intel, C<undef
-$scalar> will return memory to the system, while on Solaris 2.6 it
-won't. In general, try it yourself and see.
-
-However, judicious use of my() on your variables will help make sure
-that they go out of scope so that Perl can free up that space for
-use in other parts of your program. A global variable, of course, never
-goes out of scope, so you can't get its space automatically reclaimed,
-although undef()ing and/or delete()ing it will achieve the same effect.
+(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() 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, but even this capability
-(preallocation of data types) is in the works.
+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?
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
+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
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
+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.perl.com/CPAN/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.
+See also
+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''.
+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
+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.
+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?
-Malcolm Beattie has written a multifunction backend compiler,
-available from CPAN, that can do both these things. It is included
-in the perl5.005 release, but is still considered experimental.
-This means it's fun to play with if you're a programmer but not
-really for people looking for turn-key solutions.
-
-Merely compiling into C does not in and of itself guarantee that your
-code will run very much faster. That's because except for lucky cases
-where a lot of native type inferencing is possible, the normal Perl
-run-time system is still present and so your program will take just as
-long to run and be just as big. Most programs save little more than
-compilation time, leaving execution no more than 10-30% faster. A few
-rare programs actually benefit significantly (even running several times
-faster), but this takes some tweaking of your code.
-
-You'll probably be astonished to learn that the current version of the
-compiler generates a compiled form of your script whose executable is
-just as big as the original perl executable, and then some. That's
-because as currently written, all programs are prepared for a full
-eval() statement. You can tremendously reduce this cost by building a
-shared I<libperl.so> library and linking against that. See the
-F<INSTALL> podfile in the Perl source distribution for details. If
-you link your main perl binary with this, it will make it minuscule.
-For example, on one author's system, F</usr/bin/perl> is only 11k in
-size!
-
-In general, the compiler will do nothing to make a Perl program smaller,
-faster, more portable, or more secure. In fact, it can make your
-situation worse. The executable will be bigger, your VM system may take
-longer to load the whole thing, the binary is fragile and hard to fix,
-and compilation never stopped software piracy in the form of crackers,
-viruses, or bootleggers. The real advantage of the compiler is merely
-packaging, and once you see the size of what it makes (well, unless
-you use a shared I<libperl.so>), you'll probably want a complete
-Perl install anyway.
-
-=head2 How can I compile Perl into Java?
-
-You can also integrate Java and Perl with the
-Perl Resource Kit from O'Reilly and Associates. 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.
+(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,...]?
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<ALTERNATIVE_SHEBANG> (see the
-F<INSTALL> file in the source distribution for more information).
+"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
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>.
-Macintosh Perl programs will have the appropriate Creator and
-Type, so that double-clicking them will invoke the Perl application.
+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
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)
+ # MPW
+ perl -e 'print "Hello world\n"'
+
# VMS
perl -e "print ""Hello world\n"""
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, pure and
-simple. Sucks to be away from Unix, huh? :-)
+There is no general solution to all of this. It is a mess.
[Some of this answer was contributed by Kenneth Albanowski.]
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 these sources:
+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:
- WWW Security FAQ
- http://www.w3.org/Security/Faq/
-
- Web FAQ
- http://www.boutell.com/faq/
-
- CGI FAQ
- http://www.webthing.com/tutorials/cgifaq.html
-
- HTTP Spec
- http://www.w3.org/pub/WWW/Protocols/HTTP/
-
- HTML Spec
- http://www.w3.org/TR/REC-html40/
- http://www.w3.org/pub/WWW/MarkUp/
-
- CGI Spec
- http://www.w3.org/CGI/
-
- CGI Security FAQ
- http://www.go2net.com/people/paulp/cgi-security/safe-cgi.txt
+ 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>, and L<perlbot> for reference. Perltoot didn't come out
-until the 5.004 release; you can get a copy (in pod, html, or
-postscript) from http://www.perl.com/CPAN/doc/FMTEYEWTK/ .
+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? [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.
-=head2 I've read perlembed, perlguts, etc., but I can't embed perl in
-my C program; what am I doing wrong?
+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?
+=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
=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 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
-All rights reserved.
+Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and
+other authors as noted. All rights reserved.
-When included as an integrated part of the Standard Distribution
-of Perl or of its documentation (printed or otherwise), this works is
-covered under Perl's Artistic License. For separate distributions of
-all or part of this FAQ outside of that, see L<perlfaq>.
+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
https://perl5.git.perl.org / perl5.git / blobdiff