=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.38 $, $Date: 1999/05/23 16:08:30 $)
+perlfaq3 - Programming Tools ($Revision: 1.10 $, $Date: 2001/11/19 17:09:37 $)
=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
+ Various http://www.cpan.org/doc/FMTEYEWTK/index.html
(not a man-page but still useful)
-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:
+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.
+In general, not yet. There is psh available at
+
+ http://www.focusresearch.com/gregor/psh
+
+Which includes the following description:
+
+ The Perl Shell is a shell that combines the interactive nature
+ of a Unix shell with the power of Perl. The goal is to eventually
+ have a full featured shell that behaves as expected for normal
+ shell activity. But, the Perl Shell will use Perl syntax and
+ functionality for control-flow statements and other things.
+
+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 debug my Perl programs?
=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:
+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
+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
+http://www.cpan.org/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
=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.
+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.
+
+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.
=head2 Is there an IDE or Windows Perl Editor?
-If you're on Unix, you already have an IDE--Unix itself. This powerful
-IDE derives from its interoperability, flexibility, and configurability.
-If you really want to get a feel for Unix-qua-IDE, the best thing to do
-is to find some high-powered programmer whose native language is Unix.
-Find someone who has been at this for many years, and just sit back
-and watch them at work. They have created their own IDE, one that
-suits their own tastes and aptitudes. Quietly observe them edit files,
-move them around, compile them, debug them, test them, etc. The entire
-development *is* integrated, like a top-of-the-line German sports car:
-functional, powerful, and elegant. You will be absolutely astonished
-at the speed and ease exhibited by the native speaker of Unix in his
-home territory. The art and skill of a virtuoso can only be seen to be
-believed. That is the path to mastery--all these cobbled little IDEs
-are expensive toys designed to sell a flashy demo using cheap tricks,
-and being optimized for immediate but shallow understanding rather than
-enduring use, are but a dim palimpsest of real tools.
-
-In short, you just have to learn the toolbox. However, if you're not
-on Unix, then your vendor probably didn't bother to provide you with
-a proper toolbox on the so-called complete system that you forked out
-your hard-earned cash for.
-
-PerlBuilder (http://www.solutionsoft.com/perl.htm) is an integrated
-development environment for Windows that supports Perl development.
-PerlDevKit (http://www.activestate.com/Products/Perl_Dev_Kit/index.html)
-is an IDE from ActiveState supporting the ActivePerl. (VisualPerl,
-a Visual Studio (or Studio.NET, in time) component is currently
-(late 2000) in beta). The visiPerl+ IDE is available from Help
-Consulting (http://helpconsulting.net/visiperl/). Perl code magic is
-another IDE (http://www.petes-place.com/codemagic.html). CodeMagicCD
-(http://www.codemagiccd.com/) is a commercial IDE. The Object System
+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:
+
+=over 4
+
+=item Komodo
+
+ActiveState's cross-platform (as of April 2001 Windows and Linux),
+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)).
+
+=item The Object System
+
(http://www.castlelink.co.uk/object_system/) is a Perl web
-applications development IDE. Starbase's Codewright
-(http://www.starbase.com/) is yet another multilanguage editor/IDE.
-
-Perl programs are just plain text, though, so you could download GNU
-Emacs or XEmacs
-(http://www.gnu.org/software/emacs/windows/ntemacs.html)
-(http://www.xemacs.org/Download/index.html), or a vi clone such as nvi
-(available from CPAN in src/misc/) or vim (http://www.vim.org/). Vim
-runs on win32 (http://www.cs.vu.nl/%7Etmgil/vi.html). Vile is another
-widely ported vi clone that has a Perl language sensitivity module
-(http://www.clark.net/pub/dickey/vile/vile.html). SlickEdit
-(http://www.slickedit.com/) is a full featured commercial editor that
-has a modular architecture: it can emulate several other common
-editors and it can help with programming language sensitivity modules
-for a variety of programming languages including Perl. MultiEdit
-(http://www.MultiEdit.com) has a user extendable interface and
-good Perl support.
-
-If you're transferring Windows text files to Unix be sure to transfer
-them in ASCII mode so the ends of lines are appropriately mangled.
-
-There is also a toyedit Text widget based editor written in Perl that
-is distributed with the Tk module on CPAN. The ptkdb
+applications development IDE, apparently for any platform
+that runs Perl.
+
+=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 PerlBuilder
+
+(http://www.solutionsoft.com/perl.htm) is an integrated development
+environment for Windows that supports Perl development.
+
+=item visiPerl+
+
+( http://helpconsulting.net/visiperl/ )
+From Help Consulting, for Windows.
+
+=back
+
+For Windows there's also the
+
+=over 4
+
+=item CodeMagicCD
+
+( http://www.codemagiccd.com/ ) Collection of various programming
+tools for Windows: Perl (5.005_03), TclTk, Python, GNU programming
+tools, REBOL, wxWindows toolkit, the MinGW GNU C/C++ compiler, DJGPP
+GNU C/C++ compiler, Cint C interpreter, YaBasic.
+
+=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://alpha.olm.net/). 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://members.nbci.com/uemacs/
+
+=item XEmacs
+
+http://www.xemacs.org/Download/index.html
+
+=back
+
+or a vi clone such as
+
+=over 4
+
+=item Elvis
+
+ftp://ftp.cs.pdx.edu/pub/elvis/ http://www.fh-wedel.de/elvis/
+
+=item Vile
+
+http://vile.cx/
+
+=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
+yet another vi clone, unfortunately not available for Windows, but in
+UNIX platforms you might be interested in trying it out, firstly because
+strictly speaking it is not a vi clone, it is the real vi, or the new
+incarnation of it, and secondly because you can embed Perl inside it
+to use Perl as the scripting language. nvi is not alone in this,
+though: at least also vim and vile offer an embedded Perl.
+
+The following are Win32 multilanguage editor/IDESs that support Perl:
+
+=over 4
+
+=item Codewright
+
+http://www.starbase.com/
+
+=item MultiEdit
+
+http://www.MultiEdit.com/
+
+=item SlickEdit
+
+http://www.slickedit.com/
+
+=back
+
+There is also a toyedit Text widget based editor written in Perl
+that is distributed with the Tk module on CPAN. The ptkdb
(http://world.std.com/~aep/ptkdb/) 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
GUI creation.
In addition to an editor/IDE you might be interested in a more
-powerful shell environment for Win32. Your options include the Bash
-from the Cygwin package (http://sources.redhat.com/cygwin/), or the
-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/), or
-or the Zsh (ftp://ftp.blarg.net/users/amol/zsh/, see also
-http://www.zsh.org/). MKS and U/WIN are commercial (U/WIN is free for
-educational and research purposes), Cygwin is GPL (but that shouldn't
-matter for Perl use). All the above except for the Zsh (which is just
-the shell) also include a comprehensive set of standard UNIX toolkit
-utilities.
+powerful shell environment for Win32. Your options include
+
+=over 4
+
+=item Bash
+
+from the Cygwin package (http://sources.redhat.com/cygwin/)
+
+=item Ksh
+
+from the MKS Toolkit (http://www.mks.com/), or the Bourne shell of
+the U/WIN environment (http://www.research.att.com/sw/tools/uwin/)
+
+=item Tcsh
+
+ftp://ftp.astron.com/pub/tcsh/, see also
+http://www.primate.wisc.edu/software/csh-tcsh-book/
+
+=item Zsh
+
+ftp://ftp.blarg.net/users/amol/zsh/, see also http://www.zsh.org/
+
+=back
+
+MKS and U/WIN are commercial (U/WIN is free for educational and
+research purposes), Cygwin is covered by the GNU Public License (but
+that shouldn't matter for Perl use). The Cygwin, MKS, and U/WIN all
+contain (in addition to the shells) a comprehensive set of standard
+UNIX toolkit utilities.
+
+If you're transferring text files between Unix and Windows using FTP
+be sure to transfer them in ASCII mode so the ends of lines are
+appropriately converted.
On Mac OS the MacPerl Application comes with a simple 32k text editor
that behaves like a rudimentary IDE. In contrast to the MacPerl Application
the MPW Perl tool can make use of the MPW Shell itself as an editor (with
-no 32k limit). BBEdit and BBEdit Lite are text editors for Mac OS
-that have a Perl sensitivity mode (http://web.barebones.com/).
-Alpha is an editor, written and extensible in Tcl, that nonetheless has
+no 32k limit).
+
+=over 4
+
+=item BBEdit and BBEdit Lite
+
+are text editors for Mac OS that have a Perl sensitivity mode
+(http://web.barebones.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/).
+=back
+
+Pepper and Pe are programming language sensitive text editors for Mac
+OS X and BeOS respectively (http://www.hekkelman.com/).
+
=head2 Where can I get Perl macros for vi?
For a complete version of Tom Christiansen's vi configuration file,
-see http://www.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?
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;
this program repeats a command and updates the screen as needed, rendering
B<rep ps axu> similar to B<top>.
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/
+directory http://www.cpan.org/modules/by-category/08_User_Interfaces/
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
+http://www.cpan.org/authors/Stephen_O_Lidie/ , and the
online manpages at
http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
=head2 How can I generate simple menus without using CGI or Tk?
-The http://www.perl.com/CPAN/authors/id/SKUNZ/perlmenu.v4.0.tar.gz
+The http://www.cpan.org/authors/id/SKUNZ/perlmenu.v4.0.tar.gz
module, which is curses-based, can help with this.
-=head2 What is undump?
-
-See the next question on ``How can I make my Perl program run faster?''
-
=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
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
distribution. You can find out whether you are using perl's malloc by
typing C<perl -V:usemymalloc>.
+Of course, the best way to save memory is to not do anything to waste
+it in the first place. Good programming practices can go a long way
+toward this:
+
+=over 4
+
+=item * Don't slurp!
+
+Don't read an entire file into memory if you can process it line
+by line. Or more concretely, use a loop like this:
+
+ #
+ # Good Idea
+ #
+ while (<FILE>) {
+ # ...
+ }
+
+instead of this:
+
+ #
+ # Bad Idea
+ #
+ @data = <FILE>;
+ foreach (@data) {
+ # ...
+ }
+
+When the files you're processing are small, it doesn't much matter which
+way you do it, but it makes a huge difference when they start getting
+larger.
+
+=item * Use map and grep selectively
+
+Remember that both map and grep expect a LIST argument, so doing this:
+
+ @wanted = grep {/pattern/} <FILE>;
+
+will cause the entire file to be slurped. For large files, it's better
+to loop:
+
+ while (<FILE>) {
+ push(@wanted, $_) if /pattern/;
+ }
+
+=item * Avoid unnecessary quotes and stringification
+
+Don't quote large strings unless absolutely necessary:
+
+ my $copy = "$large_string";
+
+makes 2 copies of $large_string (one for $copy and another for the
+quotes), whereas
+
+ my $copy = $large_string;
+
+only makes one copy.
+
+Ditto for stringifying large arrays:
+
+ {
+ local $, = "\n";
+ print @big_array;
+ }
+
+is much more memory-efficient than either
+
+ print join "\n", @big_array;
+
+or
+
+ {
+ local $" = "\n";
+ print "@big_array";
+ }
+
+
+=item * Pass by reference
+
+Pass arrays and hashes by reference, not by value. For one thing, it's
+the only way to pass multiple lists or hashes (or both) in a single
+call/return. It also avoids creating a copy of all the contents. This
+requires some judgment, 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 that
+causing your hard disk to thrash due to massive swapping.
+
+=back
+
=head2 Is it unsafe to return a pointer to local data?
No, Perl's garbage collection system takes care of this.
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/ .
+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/ )
source. Security through obscurity, the name for hiding your bugs
instead of fixing them, is little security indeed.
-You can try using encryption via source filters (Filter::* from CPAN),
-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).
+You can try using encryption via source filters (Starting from Perl
+5.8 the Filter::Simple and Filter::Util::Call modules are included in
+the standard distribution), but any decent programmer will be able to
+decrypt it. You can try using the byte code compiler and interpreter
+described 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).
If you're concerned about people profiting from your code, then the
bottom line is that nothing but a restrictive license will give you
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:
-
- 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/
+when it runs fine on the command line'', see the troubleshooting
+guides and references in L<perlfaq9> or in the CGI MetaFAQ:
- 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/ .
+postscript) from http://www.cpan.org/doc/FMTEYEWTK/ .
=head2 Where can I learn about linking C with Perl? [h2xs, xsubpp]
Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
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