Removed unnecessary pointers checks

[perl5.git] / pod / perlfaq2.pod

=head1 NAME

perlfaq2 - Obtaining and Learning about Perl ($Revision: 3606 $)

=head1 DESCRIPTION

This section of the FAQ answers questions about where to find
source and documentation for Perl, support, and
related matters.

=head2 What machines support perl?  Where do I get it?

The standard release of perl (the one maintained by the perl
development team) is distributed only in source code form.  You
can find this at http://www.cpan.org/src/latest.tar.gz , which
is in a standard Internet format (a gzipped archive in POSIX tar format).

Perl builds and runs on a bewildering number of platforms.  Virtually
all known and current Unix derivatives are supported (perl's native
platform), as are other systems like VMS, DOS, OS/2, Windows,
QNX, BeOS, OS X, MPE/iX and the Amiga.

Binary distributions for some proprietary platforms, including
Apple systems, can be found http://www.cpan.org/ports/ directory.
Because these are not part of the standard distribution, they may
and in fact do differ from the base perl port in a variety of ways.
You'll have to check their respective release notes to see just
what the differences are.  These differences can be either positive
(e.g. extensions for the features of the particular platform that
are not supported in the source release of perl) or negative (e.g.
might be based upon a less current source release of perl).

=head2 How can I get a binary version of perl?

If you don't have a C compiler because your vendor for whatever
reasons did not include one with your system, the best thing to do is
grab a binary version of gcc from the net and use that to compile perl
with.  CPAN only has binaries for systems that are terribly hard to
get free compilers for, not for Unix systems.

Some URLs that might help you are:

    http://www.cpan.org/ports/
    http://www.perl.com/pub/language/info/software.html

Someone looking for a perl for Win16 might look to Laszlo Molnar's djgpp
port in http://www.cpan.org/ports/#msdos , which comes with clear
installation instructions.  A simple installation guide for MS-DOS using
Ilya Zakharevich's OS/2 port is available at
http://www.cs.ruu.nl/%7Epiet/perl5dos.html
and similarly for Windows 3.1 at http://www.cs.ruu.nl/%7Epiet/perlwin3.html .

=head2 I don't have a C compiler. How can I build my own Perl interpreter?

Since you don't have a C compiler, you're doomed and your vendor
should be sacrificed to the Sun gods.  But that doesn't help you.

What you need to do is get a binary version of gcc for your system
first.  Consult the Usenet FAQs for your operating system for
information on where to get such a binary version.

=head2 I copied the perl binary from one machine to another, but scripts don't work.

That's probably because you forgot libraries, or library paths differ.
You really should build the whole distribution on the machine it will
eventually live on, and then type C<make install>.  Most other
approaches are doomed to failure.

One simple way to check that things are in the right place is to print out
the hard-coded @INC that perl looks through for libraries:

    % perl -le 'print for @INC'

If this command lists any paths that don't exist on your system, then you
may need to move the appropriate libraries to these locations, or create
symbolic links, aliases, or shortcuts appropriately.  @INC is also printed as
part of the output of

    % perl -V

You might also want to check out
L<perlfaq8/"How do I keep my own module/library directory?">.

=head2 I grabbed the sources and tried to compile but gdbm/dynamic loading/malloc/linking/... failed.  How do I make it work?

Read the F<INSTALL> file, which is part of the source distribution.
It describes in detail how to cope with most idiosyncrasies that the
Configure script can't work around for any given system or
architecture.

=head2 What modules and extensions are available for Perl?  What is CPAN?  What does CPAN/src/... mean?

CPAN stands for Comprehensive Perl Archive Network, a ~1.2Gb archive
replicated on nearly 200 machines all over the world.  CPAN contains
source code, non-native ports, documentation, scripts, and many
third-party modules and extensions, designed for everything from
commercial database interfaces to keyboard/screen control to web
walking and CGI scripts.  The master web site for CPAN is
http://www.cpan.org/ and there is the CPAN Multiplexer at
http://www.cpan.org/CPAN.html which will choose a mirror near you
via DNS.  See http://www.perl.com/CPAN (without a slash at the
end) for how this process works. Also, http://mirror.cpan.org/
has a nice interface to the http://www.cpan.org/MIRRORED.BY
mirror directory.

See the CPAN FAQ at http://www.cpan.org/misc/cpan-faq.html for
answers to the most frequently asked questions about CPAN
including how to become a mirror.

CPAN/path/... is a naming convention for files available on CPAN
sites.  CPAN indicates the base directory of a CPAN mirror, and the
rest of the path is the path from that directory to the file.  For
instance, if you're using ftp://ftp.funet.fi/pub/languages/perl/CPAN
as your CPAN site, the file CPAN/misc/japh is downloadable as
ftp://ftp.funet.fi/pub/languages/perl/CPAN/misc/japh .

Considering that there are close to two thousand existing modules in
the archive, one probably exists to do nearly anything you can think of.
Current categories under CPAN/modules/by-category/ include Perl core
modules; development support; operating system interfaces; networking,
devices, and interprocess communication; data type utilities; database
interfaces; user interfaces; interfaces to other languages; filenames,
file systems, and file locking; internationalization and locale; world
wide web support; server and daemon utilities; archiving and
compression; image manipulation; mail and news; control flow
utilities; filehandle and I/O; Microsoft Windows modules; and
miscellaneous modules.

See http://www.cpan.org/modules/00modlist.long.html or
http://search.cpan.org/ for a more complete list of modules by category.

CPAN is not affiliated with O'Reilly Media.

=head2 Is there an ISO or ANSI certified version of Perl?

Certainly not.  Larry expects that he'll be certified before Perl is.

=head2 Where can I get information on Perl?

The complete Perl documentation is available with the Perl distribution.
If you have Perl installed locally, you probably have the documentation
installed as well: type C<man perl> if you're on a system resembling Unix.
This will lead you to other important man pages, including how to set your
$MANPATH.  If you're not on a Unix system, access to the documentation
will be different; for example, documentation might only be in HTML format.  All
proper perl installations have fully-accessible documentation.

You might also try C<perldoc perl> in case your system doesn't
have a proper man command, or it's been misinstalled.  If that doesn't
work, try looking in /usr/local/lib/perl5/pod for documentation.

If all else fails, consult http://perldoc.perl.org/ which has the
complete documentation in HTML and PDF format.

Many good books have been written about Perl--see the section below
for more details.

Tutorial documents are included in current or upcoming Perl releases
include L<perltoot> for objects or L<perlboot> for a beginner's
approach to objects, L<perlopentut> for file opening semantics,
L<perlreftut> for managing references, L<perlretut> for regular
expressions, L<perlthrtut> for threads, L<perldebtut> for debugging,
and L<perlxstut> for linking C and Perl together.  There may be more
by the time you read this.  These URLs might also be useful:

    http://perldoc.perl.org/
    http://bookmarks.cpan.org/search.cgi?cat=Training%2FTutorials

=head2 What are the Perl newsgroups on Usenet?  Where do I post questions?

Several groups devoted to the Perl language are on Usenet:

    comp.lang.perl.announce 		Moderated announcement group
    comp.lang.perl.misc     		High traffic general Perl discussion
    comp.lang.perl.moderated        Moderated discussion group
    comp.lang.perl.modules  		Use and development of Perl modules
    comp.lang.perl.tk           	Using Tk (and X) from Perl

    comp.infosystems.www.authoring.cgi 	Writing CGI scripts for the Web.

Some years ago, comp.lang.perl was divided into those groups, and
comp.lang.perl itself officially removed.  While that group may still
be found on some news servers, it is unwise to use it, because
postings there will not appear on news servers which honour the
official list of group names.  Use comp.lang.perl.misc for topics
which do not have a more-appropriate specific group.

There is also a Usenet gateway to Perl mailing lists sponsored by
perl.org at nntp://nntp.perl.org , a web interface to the same lists
at http://nntp.perl.org/group/ and these lists are also available
under the C<perl.*> hierarchy at http://groups.google.com . Other
groups are listed at http://lists.perl.org/ ( also known as
http://lists.cpan.org/ ).

A nice place to ask questions is the PerlMonks site,
http://www.perlmonks.org/ , or the Perl Beginners mailing list
http://lists.perl.org/showlist.cgi?name=beginners .

Note that none of the above are supposed to write your code for you:
asking questions about particular problems or general advice is fine,
but asking someone to write your code for free is not very cool.

=head2 Where should I post source code?

You should post source code to whichever group is most appropriate, but
feel free to cross-post to comp.lang.perl.misc.  If you want to cross-post
to alt.sources, please make sure it follows their posting standards,
including setting the Followup-To header line to NOT include alt.sources;
see their FAQ ( http://www.faqs.org/faqs/alt-sources-intro/ ) for details.

If you're just looking for software, first use Google
( http://www.google.com ), Google's usenet search interface
( http://groups.google.com ),  and CPAN Search ( http://search.cpan.org ).
This is faster and more productive than just posting a request.

=head2 Perl Books

A number of books on Perl and/or CGI programming are available.  A few
of these are good, some are OK, but many aren't worth your money.
There is a list of these books, some with extensive reviews, at
http://books.perl.org/ . If you don't see your book listed here, you
can write to perlfaq-workers@perl.org .

The incontestably definitive reference book on Perl, written by
the creator of Perl, is Programming Perl:

	Programming Perl (the "Camel Book"):
	by Larry Wall, Tom Christiansen, and Jon Orwant
	ISBN 0-596-00027-8  [3rd edition July 2000]
	http://www.oreilly.com/catalog/pperl3/
	(English, translations to several languages are also available)

The companion volume to the Camel containing thousands
of real-world examples, mini-tutorials, and complete programs is:

	The Perl Cookbook (the "Ram Book"):
	by Tom Christiansen and Nathan Torkington,
	    with Foreword by Larry Wall
	ISBN 0-596-00313-7 [2nd Edition August 2003]
	http://www.oreilly.com/catalog/perlckbk2/

If you're already a seasoned programmer, then the Camel Book might
suffice for you to learn Perl.  If you're not, check out the
Llama book:

	Learning Perl
	by Randal L. Schwartz, Tom Phoenix, and brian d foy
	ISBN 0-596-10105-8 [4th edition July 2005]
	http://www.oreilly.com/catalog/learnperl4/

And for more advanced information on writing larger programs,
presented in the same style as the Llama book, continue your education
with the Alpaca book:

	Learning Perl Objects, References, and Modules (the "Alpaca Book")
	by Randal L. Schwartz, with Tom Phoenix (foreword by Damian Conway)
	ISBN 0-596-00478-8 [1st edition June 2003]
	http://www.oreilly.com/catalog/lrnperlorm/

If you're not an accidental programmer, but a more serious and
possibly even degreed computer scientist who doesn't need as much
hand-holding as we try to provide in the Llama, please check out the
delightful book

	Perl: The Programmer's Companion
	by Nigel Chapman
	ISBN 0-471-97563-X [1997, 3rd printing Spring 1998]
	http://www.wiley.com/compbooks/catalog/97563-X.htm
	http://www.wiley.com/compbooks/chapman/perl/perltpc.html (errata etc)

If you are more at home in Windows the following is available
(though unfortunately rather dated).

	Learning Perl on Win32 Systems (the "Gecko Book")
	by Randal L. Schwartz, Erik Olson, and Tom Christiansen,
	    with foreword by Larry Wall
	ISBN 1-56592-324-3 [1st edition August 1997]
	http://www.oreilly.com/catalog/lperlwin/

Addison-Wesley ( http://www.awlonline.com/ ) and Manning
( http://www.manning.com/ ) are also publishers of some fine Perl books
such as I<Object Oriented Programming with Perl> by Damian Conway and
I<Network Programming with Perl> by Lincoln Stein.

An excellent technical book discounter is Bookpool at
http://www.bookpool.com/ where a 30% discount or more is not unusual.

What follows is a list of the books that the FAQ authors found personally
useful.  Your mileage may (but, we hope, probably won't) vary.

Recommended books on (or mostly on) Perl follow.

=over 4

=item References

	Programming Perl
	by Larry Wall, Tom Christiansen, and Jon Orwant
	ISBN 0-596-00027-8 [3rd edition July 2000]
	http://www.oreilly.com/catalog/pperl3/

	Perl 5 Pocket Reference
	by Johan Vromans
	ISBN 0-596-00032-4 [3rd edition May 2000]
	http://www.oreilly.com/catalog/perlpr3/

=item Tutorials

	Beginning Perl
	by James Lee
	ISBN 1-59059-391-X [2nd edition August 2004]
	http://apress.com/book/bookDisplay.html?bID=344

	Elements of Programming with Perl
	by Andrew L. Johnson
	ISBN 1-884777-80-5 [1st edition October 1999]
	http://www.manning.com/Johnson/

	Learning Perl
	by Randal L. Schwartz, Tom Phoenix, and brian d foy
	ISBN 0-596-10105-8 [4th edition July 2005]
	http://www.oreilly.com/catalog/learnperl4/

	Learning Perl Objects, References, and Modules
	by Randal L. Schwartz, with Tom Phoenix (foreword by Damian Conway)
	ISBN 0-596-00478-8 [1st edition June 2003]
	http://www.oreilly.com/catalog/lrnperlorm/

=item Task-Oriented

	Writing Perl Modules for CPAN
	by Sam Tregar
	ISBN 1-59059-018-X [1st edition Aug 2002]
	http://apress.com/book/bookDisplay.html?bID=14

	The Perl Cookbook
	by Tom Christiansen and Nathan Torkington
	    with foreword by Larry Wall
	ISBN 1-56592-243-3 [1st edition August 1998]
	http://www.oreilly.com/catalog/cookbook/

	Effective Perl Programming
	by Joseph Hall
	ISBN 0-201-41975-0 [1st edition 1998]
	http://www.awl.com/

	Real World SQL Server Administration with Perl
	by Linchi Shea
	ISBN 1-59059-097-X [1st edition July 2003]
	http://apress.com/book/bookDisplay.html?bID=171

=item Special Topics

	Perl Best Practices
	by Damian Conway
	ISBN: 0-596-00173-8 [1st edition July 2005]
	http://www.oreilly.com/catalog/perlbp/

	Higher Order Perl
	by Mark-Jason Dominus
	ISBN: 1558607013 [1st edition March 2005]
	http://hop.perl.plover.com/

	Perl 6 Now: The Core Ideas Illustrated with Perl 5
	by Scott Walters
	ISBN 1-59059-395-2 [1st edition December 2004]
	http://apress.com/book/bookDisplay.html?bID=355

	Mastering Regular Expressions
	by Jeffrey E. F. Friedl
	ISBN 0-596-00289-0 [2nd edition July 2002]
	http://www.oreilly.com/catalog/regex2/

	Network Programming with Perl
	by Lincoln Stein
	ISBN 0-201-61571-1 [1st edition 2001]
	http://www.awlonline.com/

	Object Oriented Perl
	Damian Conway
	    with foreword by Randal L. Schwartz
	ISBN 1-884777-79-1 [1st edition August 1999]
	http://www.manning.com/Conway/

	Data Munging with Perl
	Dave Cross
	ISBN 1-930110-00-6 [1st edition 2001]
	http://www.manning.com/cross

	Mastering Perl/Tk
	by Steve Lidie and Nancy Walsh
	ISBN 1-56592-716-8 [1st edition January 2002]
	http://www.oreilly.com/catalog/mastperltk/

	Extending and Embedding Perl
	by Tim Jenness and Simon Cozens
	ISBN 1-930110-82-0 [1st edition August 2002]
	http://www.manning.com/jenness

	Perl Debugger Pocket Reference
	by Richard Foley
	ISBN 0-596-00503-2 [1st edition January 2004]
	http://www.oreilly.com/catalog/perldebugpr/

=back

=head2 Which magazines have Perl content?

The first (and for a long time, only) periodical devoted to All Things Perl,
I<The Perl Journal> contains tutorials, demonstrations, case studies,
announcements, contests, and much more.  I<TPJ> has columns on web
development, databases, Win32 Perl, graphical programming, regular
expressions, and networking, and sponsors the Obfuscated Perl Contest
and the Perl Poetry Contests.  Beginning in November 2002, TPJ moved to a
reader-supported monthly e-zine format in which subscribers can download
issues as PDF documents. For more details on TPJ, see http://www.tpj.com/

Beyond this, magazines that frequently carry quality articles on
Perl are I<The Perl Review> ( http://www.theperlreview.com ),
I<Unix Review> ( http://www.unixreview.com/ ),
I<Linux Magazine> ( http://www.linuxmagazine.com/ ),
and Usenix's newsletter/magazine to its members, I<login:>
( http://www.usenix.org/ )

The Perl columns of Randal L. Schwartz are available on the web at
http://www.stonehenge.com/merlyn/WebTechniques/ ,
http://www.stonehenge.com/merlyn/UnixReview/ , and
http://www.stonehenge.com/merlyn/LinuxMag/ .

=head2 What mailing lists are there for Perl?

Most of the major modules (Tk, CGI, libwww-perl) have their own
mailing lists.  Consult the documentation that came with the module for
subscription information.

A comprehensive list of Perl related mailing lists can be found at:

	http://lists.perl.org/

=head2 Where are the archives for comp.lang.perl.misc?

The Google search engine now carries archived and searchable newsgroup
content.

http://groups.google.com/groups?group=comp.lang.perl.misc

If you have a question, you can be sure someone has already asked the
same question at some point on c.l.p.m. It requires some time and patience
to sift through all the content but often you will find the answer you
seek.

=head2 Where can I buy a commercial version of perl?

In a real sense, perl already I<is> commercial software: it has a license
that you can grab and carefully read to your manager. It is distributed
in releases and comes in well-defined packages. There is a very large
user community and an extensive literature.  The comp.lang.perl.*
newsgroups and several of the mailing lists provide free answers to your
questions in near real-time.  Perl has traditionally been supported by
Larry, scores of software designers and developers, and myriad
programmers, all working for free to create a useful thing to make life
better for everyone.

However, these answers may not suffice for managers who require a
purchase order from a company whom they can sue should anything go awry.
Or maybe they need very serious hand-holding and contractual obligations.
Shrink-wrapped CDs with perl on them are available from several sources if
that will help.  For example, many Perl books include a distribution of perl,
as do the O'Reilly Perl Resource Kits (in both the Unix flavor
and in the proprietary Microsoft flavor); the free Unix distributions
also all come with perl.

=head2 Where do I send bug reports?

If you are reporting a bug in the perl interpreter or the modules
shipped with Perl, use the I<perlbug> program in the Perl distribution or
mail your report to perlbug@perl.org or at http://rt.perl.org/perlbug/ .

For Perl modules, you can submit bug reports to the Request Tracker set
up at http://rt.cpan.org .

If you are posting a bug with a non-standard port (see the answer to
"What platforms is perl available for?"), a binary distribution, or a
non-standard module (such as Tk, CGI, etc), then please see the
documentation that came with it to determine the correct place to post
bugs.

Read the perlbug(1) man page (perl5.004 or later) for more information.

=head2 What is perl.com? Perl Mongers? pm.org? perl.org? cpan.org?

Perl.com at http://www.perl.com/ is part of the O'Reilly Network, a
subsidiary of O'Reilly Media.

The Perl Foundation is an advocacy organization for the Perl language
which maintains the web site http://www.perl.org/ as a general
advocacy site for the Perl language. It uses the domain to provide
general support services to the Perl community, including the hosting
of mailing lists, web sites, and other services.  The web site
http://www.perl.org/ is a general advocacy site for the Perl language,
and there are many other sub-domains for special topics, such as

	http://learn.perl.org/
	http://use.perl.org/
	http://jobs.perl.org/
	http://lists.perl.org/

Perl Mongers uses the pm.org domain for services related to Perl user
groups, including the hosting of mailing lists and web sites.  See the
Perl user group web site at http://www.pm.org/ for more information about
joining, starting, or requesting services for a Perl user group.

http://www.cpan.org/ is the Comprehensive Perl Archive Network,
a replicated worldwide repository of Perl software, see
the I<What is CPAN?> question earlier in this document.

=head1 REVISION

Revision: $Revision: 3606 $

Date: $Date: 2006-03-06 12:05:47 +0100 (lun, 06 mar 2006) $

See L<perlfaq> for source control details and availability.

=head1 AUTHOR AND COPYRIGHT

Copyright (c) 1997-2006 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.