perlfaq3.pod

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=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