=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.28 $, $Date: 1998/07/16 22:08:49 $)
+perlfaq3 - Programming Tools ($Revision: 1.38 $, $Date: 1999/05/23 16:08:30 $)
=head1 DESCRIPTION
Objects perlref, perlmod, perlobj, perltie
Data Structures perlref, perllol, perldsc
Modules perlmod, perlmodlib, perlsub
- Regexps perlre, perlfunc, perlop, perllocale
+ 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)
-L<perltoc> provides a crude table of contents for the perl man page set.
+A crude table of contents for the Perl man page set is found in L<perltoc>.
=head2 How can I use Perl interactively?
=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
+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.
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> or C<use vars>.
+variables with C<my> or C<our> or C<use vars>.
Did you check the returns of each and every system call? The operating
system (and thus Perl) tells you whether they worked or not, and if not
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 really proves little about differing complexities
+of contrasting algorithms.
+
=head2 How do I cross-reference my Perl programs?
The B::Xref module, shipped with the new, alpha-release Perl compiler
write it will help prevent bugs. Your editor can and should help you
with this. The perl-mode for emacs can provide a remarkable amount of
help with most (but not all) code, and even less programmable editors
-can provide significant assistance.
+can provide significant assistance. Tom swears 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
+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
-If you are used to using I<vgrind> program for printing out nice code
+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.
+
=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.
+the trick. And if not, it's easy to hack 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 on.
+
+PerlBuilder (XXX URL to follow) is an integrated development environment
+for Windows that supports Perl development. Perl programs are just plain
+text, though, so you could download emacs for Windows (???) or a vi clone
+(vim) which runs on for win32 (http://www.cs.vu.nl/%7Etmgil/vi.html).
+If you're transferring Windows files to Unix, be sure to transfer in
+ASCII mode so the ends of lines are appropriately mangled.
=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,
+see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc.gz,
the standard benchmark file for vi emulators. This 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.
=head2 Where can I get perl-mode for 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
+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",
+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 hilighting. You
-should be using C<"main::foo"> in new Perl code anyway, so this
+(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.
=head2 How can I use curses with Perl?
directory http://www.perl.com/CPAN/modules/by-category/08_User_Interfaces/
Invaluable for Perl/Tk programming are: the Perl/Tk FAQ at
-http://w4.lns.cornell.edu/~pvhp/ptk/ptkTOC.html , the Perl/Tk Reference
+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/~amundson/perl/perltk/toc.html .
+http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
=head2 How can I generate simple menus without using CGI or Tk?
information.
Unsubstantiated reports allege that Perl interpreters that use sfio
-outperform those that don't (for IO intensive applications). To try
+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 IO mechanisms'' section.
+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
When it comes to time-space tradeoffs, Perl nearly always prefers to
throw memory at a problem. Scalars in Perl use more memory than
-strings in C, arrays take more that, and hashes use even more. While
+strings in C, arrays take more than that, and hashes use even more. While
there's still a lot to be done, recent releases have been addressing
these issues. For example, as of 5.004, duplicate hash keys are
shared amongst all hashes using them, so require no reallocation.
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)
-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.
+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 their storage for
anything a module written in C can. For more on mod_perl, see
http://perl.apache.org/
-With the FCGI module (from CPAN), a Perl executable compiled with sfio
-(see the F<INSTALL> file in the distribution) and the mod_fastcgi
-module (available from http://www.fastcgi.com/) each of your perl
-scripts becomes a permanent CGI daemon process.
+With the FCGI module (from CPAN) and the mod_fastcgi
+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 scripts, so investigate them with
+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, commerical product, ``The Velocity Engine for Perl'',
-(http://www.binevolve.com/ or http://www.binevolve.com/bine/vep) might
+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 scripts, upto 25 times faster than normal CGI perl by
-running in persistent perl mode, or 4 to 5 times faster without any
-modification to your existing CGI scripts. Fully functional evaluation
+of your Perl programs, up to 25 times faster than normal CGI Perl by
+running in persistent Perl mode, or 4 to 5 times faster without any
+modification to your existing CGI programs. Fully functional evaluation
copies are available from the web site.
=head2 How can I hide the source for my Perl program?
instead of fixing them, is little security indeed.
You can try using encryption via source filters (Filter::* from CPAN),
-but crackers might be able to decrypt it. You can try using the byte
-code compiler and interpreter described below, but crackers might 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 (this is true of every
+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 (this is 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 licence will give you
+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.
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
-you want to be sure your licence's wording will stand up in court.
+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 as of
-Jul-1998 in late alpha release, which means it's fun to play with if
-you're a programmer but not really for people looking for turn-key
-solutions.
+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
rare programs actually benefit significantly (like several times
faster), but this takes some tweaking of your code.
-The 5.005 release of Perl itself, whose main goal is merging the various
-non-Unix ports back into the one Perl source, will also have preliminary
-(strictly beta) support for Malcolm's compiler and his light-weight
-processes (sometimes called ``threads'').
-
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 miniscule.
+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!
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 anywayt.
+Perl install anyway.
+
+=head2 How can I compile Perl into Java?
+
+You can't. Not yet, anyway. You can integrate Java and Perl with the
+Perl Resource Kit from O'Reilly and Associates. See
+http://www.oreilly.com/catalog/prkunix/ for more information.
+The Java interface will be supported in the core 5.6 release
+of Perl.
=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
The Win95/NT installation, when using the ActiveState port of Perl,
will modify the Registry to associate the C<.pl> extension with the
-perl interpreter. If you install another port (Gurusaramy Sarathy's
-is the recommended Win95/NT port), or (eventually) build your own
-Win95/NT Perl using WinGCC, then you'll have to modify the Registry
-yourself.
+perl interpreter. If you install another port, perhaps even building
+your own Win95/NT Perl from the standard sources by using a Windows port
+of gcc (e.g., with cygwin or mingw32), then you'll have to modify
+the Registry yourself. In addition to associating C<.pl> 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 scripts will have the the appropriate Creator and
-Type, so that double-clicking them will invoke the perl application.
+Macintosh Perl programs will have the appropriate Creator and
+Type, so that double-clicking them will invoke the Perl application.
I<IMPORTANT!>: Whatever you do, PLEASE don't get frustrated, and just
throw the perl interpreter into your cgi-bin directory, in order to
-get your scripts working for a web server. This is an EXTREMELY big
+get your programs working for a web server. This is an EXTREMELY big
security risk. Take the time to figure out how to do it correctly.
-=head2 Can I write useful perl programs on the command line?
+=head2 Can I write useful Perl programs on the command line?
Yes. Read L<perlrun> for more information. Some examples follow.
(These assume standard Unix shell quoting rules.)
echo $PATH | perl -nl -072 -e '
s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}'
-Ok, the last one was actually an obfuscated perl entry. :-)
+OK, the last one was actually an Obfuscated Perl Contest entry. :-)
-=head2 Why don't perl one-liners work on my DOS/Mac/VMS system?
+=head2 Why don't Perl one-liners work on my DOS/Mac/VMS system?
The problem is usually that the command interpreters on those systems
have rather different ideas about quoting than the Unix shells under
quoting variants, except that it makes free use of the Mac's non-ASCII
characters as control characters.
+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? :-)
http://www.boutell.com/faq/
CGI FAQ
- http://www.webthing.com/page.cgi/cgifaq
+ http://www.webthing.com/tutorials/cgifaq.html
HTTP Spec
http://www.w3.org/pub/WWW/Protocols/HTTP/
=head2 Where can I learn about object-oriented Perl programming?
-
L<perltoot> is a good place to start, and you can use L<perlobj> and
+
A good place to start is L<perltoot>, and you can use L<perlobj> and
L<perlbot> for reference. Perltoot didn't come out until the 5.004
release, but you can get a copy (in pod, html, or postscript) from
http://www.perl.com/CPAN/doc/FMTEYEWTK/ .
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 bugreport with the output of
+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?
-L<perldiag> has a complete list of perl's error messages and warnings,
-with explanatory text. You can also use the splain program (distributed
-with perl) to explain the error messages:
+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
+(distributed with Perl) to explain the error messages:
perl program 2>diag.out
splain [-v] [-p] diag.out
=head2 What's MakeMaker?
-This module (part of the standard perl distribution) is designed to
+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>.
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997, 1998 Tom Christiansen and Nathan Torkington.
+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 Licence. For separate distributions of
+covered under Perl's Artistic License. For separate distributions of
all or part of this FAQ outside of that, see L<perlfaq>.
-Irrespective of its distribution, all code examples here are public
+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
https://perl5.git.perl.org / perl5.git / blobdiff