654 lines
27 KiB
Plaintext
654 lines
27 KiB
Plaintext
=head1 NAME
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perlfaq3 - Programming Tools ($Revision: 1.33 $, $Date: 1998/12/29 20:12:12 $)
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=head1 DESCRIPTION
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This section of the FAQ answers questions related to programmer tools
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and programming support.
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=head2 How do I do (anything)?
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Have you looked at CPAN (see L<perlfaq2>)? The chances are that
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someone has already written a module that can solve your problem.
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Have you read the appropriate man pages? Here's a brief index:
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Basics perldata, perlvar, perlsyn, perlop, perlsub
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Execution perlrun, perldebug
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Functions perlfunc
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Objects perlref, perlmod, perlobj, perltie
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Data Structures perlref, perllol, perldsc
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Modules perlmod, perlmodlib, perlsub
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Regexps perlre, perlfunc, perlop, perllocale
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Moving to perl5 perltrap, perl
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Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed
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Various http://www.perl.com/CPAN/doc/FMTEYEWTK/index.html
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(not a man-page but still useful)
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L<perltoc> provides a crude table of contents for the perl man page set.
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=head2 How can I use Perl interactively?
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The typical approach uses the Perl debugger, described in the
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perldebug(1) man page, on an ``empty'' program, like this:
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perl -de 42
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Now just type in any legal Perl code, and it will be immediately
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evaluated. You can also examine the symbol table, get stack
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backtraces, check variable values, set breakpoints, and other
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operations typically found in symbolic debuggers.
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=head2 Is there a Perl shell?
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In general, no. The Shell.pm module (distributed with perl) makes
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perl try commands which aren't part of the Perl language as shell
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commands. perlsh from the source distribution is simplistic and
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uninteresting, but may still be what you want.
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=head2 How do I debug my Perl programs?
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Have you used C<-w>? It enables warnings for dubious practices.
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Have you tried C<use strict>? It prevents you from using symbolic
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references, makes you predeclare any subroutines that you call as bare
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words, and (probably most importantly) forces you to predeclare your
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variables with C<my> or C<use vars>.
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Did you check the returns of each and every system call? The operating
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system (and thus Perl) tells you whether they worked or not, and if not
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why.
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open(FH, "> /etc/cantwrite")
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or die "Couldn't write to /etc/cantwrite: $!\n";
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Did you read L<perltrap>? It's full of gotchas for old and new Perl
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programmers, and even has sections for those of you who are upgrading
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from languages like I<awk> and I<C>.
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Have you tried the Perl debugger, described in L<perldebug>? You can
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step through your program and see what it's doing and thus work out
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why what it's doing isn't what it should be doing.
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=head2 How do I profile my Perl programs?
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You should get the Devel::DProf module from CPAN, and also use
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Benchmark.pm from the standard distribution. Benchmark lets you time
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specific portions of your code, while Devel::DProf gives detailed
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breakdowns of where your code spends its time.
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Here's a sample use of Benchmark:
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use Benchmark;
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@junk = `cat /etc/motd`;
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$count = 10_000;
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timethese($count, {
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'map' => sub { my @a = @junk;
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map { s/a/b/ } @a;
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return @a
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},
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'for' => sub { my @a = @junk;
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local $_;
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for (@a) { s/a/b/ };
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return @a },
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});
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This is what it prints (on one machine--your results will be dependent
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on your hardware, operating system, and the load on your machine):
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Benchmark: timing 10000 iterations of for, map...
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for: 4 secs ( 3.97 usr 0.01 sys = 3.98 cpu)
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map: 6 secs ( 4.97 usr 0.00 sys = 4.97 cpu)
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Be aware that a good benchmark is very hard to write. It only tests the
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data you give it, and really proves little about differing complexities
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of contrasting algorithms.
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=head2 How do I cross-reference my Perl programs?
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The B::Xref module, shipped with the new, alpha-release Perl compiler
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(not the general distribution prior to the 5.005 release), can be used
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to generate cross-reference reports for Perl programs.
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perl -MO=Xref[,OPTIONS] scriptname.plx
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=head2 Is there a pretty-printer (formatter) for Perl?
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There is no program that will reformat Perl as much as indent(1) does
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for C. The complex feedback between the scanner and the parser (this
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feedback is what confuses the vgrind and emacs programs) makes it
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challenging at best to write a stand-alone Perl parser.
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Of course, if you simply follow the guidelines in L<perlstyle>, you
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shouldn't need to reformat. The habit of formatting your code as you
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write it will help prevent bugs. Your editor can and should help you
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with this. The perl-mode for emacs can provide a remarkable amount of
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help with most (but not all) code, and even less programmable editors
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can provide significant assistance. Tom swears by the following
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settings in vi and its clones:
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set ai sw=4
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map ^O {^M}^[O^T
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Now put that in your F<.exrc> file (replacing the caret characters
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with control characters) and away you go. In insert mode, ^T is
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for indenting, ^D is for undenting, and ^O is for blockdenting --
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as it were. If you haven't used the last one, you're missing
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a lot. A more complete example, with comments, can be found at
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http://www.perl.com/CPAN-local/authors/id/TOMC/scripts/toms.exrc.gz
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If you are used to using the I<vgrind> program for printing out nice code
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to a laser printer, you can take a stab at this using
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http://www.perl.com/CPAN/doc/misc/tips/working.vgrind.entry, but the
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results are not particularly satisfying for sophisticated code.
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The a2ps at http://www.infres.enst.fr/~demaille/a2ps/ does lots of things
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related to generating nicely printed output of documents.
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=head2 Is there a etags/ctags for perl?
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With respect to the source code for the Perl interpreter, yes.
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There has been support for etags in the source for a long time.
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Ctags was introduced in v5.005_54 (and probably 5.005_03).
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After building perl, type 'make etags' or 'make ctags' and both
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sets of tag files will be built.
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Now, if you're looking to build a tag file for perl code, then there's
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a simple one at
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http://www.perl.com/CPAN/authors/id/TOMC/scripts/ptags.gz which may do
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the trick. And if not, it's easy to hack into what you want.
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=head2 Is there an IDE or Windows Perl Editor?
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If you're on Unix, you already have an IDE -- Unix itself.
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You just have to learn the toolbox. If you're not, then you
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probably don't have a toolbox, so may need something else.
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PerlBuilder (XXX URL to follow) is an integrated development
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environment for Windows that supports Perl development. Perl programs
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are just plain text, though, so you could download emacs for Windows
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(XXX) or vim for win32 (http://www.cs.vu.nl/~tmgil/vi.html). If
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you're transferring Windows files to Unix, be sure to transfer in
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ASCII mode so the ends of lines are appropriately converted.
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=head2 Where can I get Perl macros for vi?
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For a complete version of Tom Christiansen's vi configuration file,
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see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc.gz,
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the standard benchmark file for vi emulators. This runs best with nvi,
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the current version of vi out of Berkeley, which incidentally can be built
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with an embedded Perl interpreter -- see http://www.perl.com/CPAN/src/misc.
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=head2 Where can I get perl-mode for emacs?
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Since Emacs version 19 patchlevel 22 or so, there have been both a
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perl-mode.el and support for the perl debugger built in. These should
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come with the standard Emacs 19 distribution.
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In the perl source directory, you'll find a directory called "emacs",
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which contains a cperl-mode that color-codes keywords, provides
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context-sensitive help, and other nifty things.
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Note that the perl-mode of emacs will have fits with C<"main'foo">
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(single quote), and mess up the indentation and hilighting. You
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are probably using C<"main::foo"> in new Perl code anyway, so this
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shouldn't be an issue.
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=head2 How can I use curses with Perl?
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The Curses module from CPAN provides a dynamically loadable object
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module interface to a curses library. A small demo can be found at the
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directory http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/rep;
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this program repeats a command and updates the screen as needed, rendering
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B<rep ps axu> similar to B<top>.
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=head2 How can I use X or Tk with Perl?
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Tk is a completely Perl-based, object-oriented interface to the Tk toolkit
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that doesn't force you to use Tcl just to get at Tk. Sx is an interface
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to the Athena Widget set. Both are available from CPAN. See the
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directory http://www.perl.com/CPAN/modules/by-category/08_User_Interfaces/
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Invaluable for Perl/Tk programming are: the Perl/Tk FAQ at
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http://w4.lns.cornell.edu/~pvhp/ptk/ptkTOC.html , the Perl/Tk Reference
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Guide available at
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http://www.perl.com/CPAN-local/authors/Stephen_O_Lidie/ , and the
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online manpages at
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http://www-users.cs.umn.edu/~amundson/perl/perltk/toc.html .
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=head2 How can I generate simple menus without using CGI or Tk?
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The http://www.perl.com/CPAN/authors/id/SKUNZ/perlmenu.v4.0.tar.gz
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module, which is curses-based, can help with this.
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=head2 What is undump?
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See the next questions.
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=head2 How can I make my Perl program run faster?
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The best way to do this is to come up with a better algorithm. This
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can often make a dramatic difference. Chapter 8 in the Camel has some
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efficiency tips in it you might want to look at. Jon Bentley's book
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``Programming Pearls'' (that's not a misspelling!) has some good tips
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on optimization, too. Advice on benchmarking boils down to: benchmark
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and profile to make sure you're optimizing the right part, look for
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better algorithms instead of microtuning your code, and when all else
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fails consider just buying faster hardware.
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A different approach is to autoload seldom-used Perl code. See the
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AutoSplit and AutoLoader modules in the standard distribution for
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that. Or you could locate the bottleneck and think about writing just
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that part in C, the way we used to take bottlenecks in C code and
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write them in assembler. Similar to rewriting in C is the use of
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modules that have critical sections written in C (for instance, the
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PDL module from CPAN).
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In some cases, it may be worth it to use the backend compiler to
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produce byte code (saving compilation time) or compile into C, which
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will certainly save compilation time and sometimes a small amount (but
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not much) execution time. See the question about compiling your Perl
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programs for more on the compiler--the wins aren't as obvious as you'd
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hope.
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If you're currently linking your perl executable to a shared I<libc.so>,
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you can often gain a 10-25% performance benefit by rebuilding it to
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link with a static libc.a instead. This will make a bigger perl
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executable, but your Perl programs (and programmers) may thank you for
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it. See the F<INSTALL> file in the source distribution for more
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information.
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Unsubstantiated reports allege that Perl interpreters that use sfio
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outperform those that don't (for IO intensive applications). To try
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this, see the F<INSTALL> file in the source distribution, especially
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the ``Selecting File IO mechanisms'' section.
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The undump program was an old attempt to speed up your Perl program
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by storing the already-compiled form to disk. This is no longer
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a viable option, as it only worked on a few architectures, and
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wasn't a good solution anyway.
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=head2 How can I make my Perl program take less memory?
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When it comes to time-space tradeoffs, Perl nearly always prefers to
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throw memory at a problem. Scalars in Perl use more memory than
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strings in C, arrays take more than that, and hashes use even more. While
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there's still a lot to be done, recent releases have been addressing
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these issues. For example, as of 5.004, duplicate hash keys are
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shared amongst all hashes using them, so require no reallocation.
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In some cases, using substr() or vec() to simulate arrays can be
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highly beneficial. For example, an array of a thousand booleans will
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take at least 20,000 bytes of space, but it can be turned into one
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125-byte bit vector for a considerable memory savings. The standard
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Tie::SubstrHash module can also help for certain types of data
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structure. If you're working with specialist data structures
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(matrices, for instance) modules that implement these in C may use
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less memory than equivalent Perl modules.
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Another thing to try is learning whether your Perl was compiled with
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the system malloc or with Perl's builtin malloc. Whichever one it
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is, try using the other one and see whether this makes a difference.
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Information about malloc is in the F<INSTALL> file in the source
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distribution. You can find out whether you are using perl's malloc by
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typing C<perl -V:usemymalloc>.
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=head2 Is it unsafe to return a pointer to local data?
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No, Perl's garbage collection system takes care of this.
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sub makeone {
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my @a = ( 1 .. 10 );
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return \@a;
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}
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for $i ( 1 .. 10 ) {
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push @many, makeone();
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}
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print $many[4][5], "\n";
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print "@many\n";
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=head2 How can I free an array or hash so my program shrinks?
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You can't. On most operating systems, memory allocated to a program
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can never be returned to the system. That's why long-running programs
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sometimes re-exec themselves. Some operating systems (notably,
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FreeBSD and Linux) allegedly reclaim large chunks of memory that is no
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longer used, but it doesn't appear to happen with Perl (yet). The Mac
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appears to be the only platform that will reliably (albeit, slowly)
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return memory to the OS.
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We've had reports that on Linux (Redhat 5.1) on Intel, C<undef
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$scalar> will return memory to the system, while on Solaris 2.6 it
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won't. In general, try it yourself and see.
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However, judicious use of my() on your variables will help make sure
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that they go out of scope so that Perl can free up their storage for
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use in other parts of your program. A global variable, of course, never
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goes out of scope, so you can't get its space automatically reclaimed,
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although undef()ing and/or delete()ing it will achieve the same effect.
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In general, memory allocation and de-allocation isn't something you can
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or should be worrying about much in Perl, but even this capability
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(preallocation of data types) is in the works.
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=head2 How can I make my CGI script more efficient?
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Beyond the normal measures described to make general Perl programs
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faster or smaller, a CGI program has additional issues. It may be run
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several times per second. Given that each time it runs it will need
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to be re-compiled and will often allocate a megabyte or more of system
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memory, this can be a killer. Compiling into C B<isn't going to help
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you> because the process start-up overhead is where the bottleneck is.
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There are two popular ways to avoid this overhead. One solution
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involves running the Apache HTTP server (available from
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http://www.apache.org/) with either of the mod_perl or mod_fastcgi
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plugin modules.
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With mod_perl and the Apache::Registry module (distributed with
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mod_perl), httpd will run with an embedded Perl interpreter which
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pre-compiles your script and then executes it within the same address
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space without forking. The Apache extension also gives Perl access to
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the internal server API, so modules written in Perl can do just about
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anything a module written in C can. For more on mod_perl, see
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http://perl.apache.org/
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With the FCGI module (from CPAN) and the mod_fastcgi
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module (available from http://www.fastcgi.com/) each of your perl
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scripts becomes a permanent CGI daemon process.
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Both of these solutions can have far-reaching effects on your system
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and on the way you write your CGI scripts, so investigate them with
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care.
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See http://www.perl.com/CPAN/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
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A non-free, commercial product, ``The Velocity Engine for Perl'',
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(http://www.binevolve.com/ or
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also be worth looking at. It will allow you to increase the performance
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of your perl scripts, upto 25 times faster than normal CGI perl by
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running in persistent perl mode, or 4 to 5 times faster without any
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modification to your existing CGI scripts. Fully functional evaluation
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copies are available from the web site.
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=head2 How can I hide the source for my Perl program?
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Delete it. :-) Seriously, there are a number of (mostly
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unsatisfactory) solutions with varying levels of ``security''.
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First of all, however, you I<can't> take away read permission, because
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the source code has to be readable in order to be compiled and
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interpreted. (That doesn't mean that a CGI script's source is
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readable by people on the web, though, only by people with access to
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the filesystem) So you have to leave the permissions at the socially
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friendly 0755 level.
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Some people regard this as a security problem. If your program does
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insecure things, and relies on people not knowing how to exploit those
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insecurities, it is not secure. It is often possible for someone to
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determine the insecure things and exploit them without viewing the
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source. Security through obscurity, the name for hiding your bugs
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instead of fixing them, is little security indeed.
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You can try using encryption via source filters (Filter::* from CPAN),
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but any decent programmer will be able to decrypt it. You can try using
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the byte code compiler and interpreter described below, but the curious
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might still be able to de-compile it. You can try using the native-code
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compiler described below, but crackers might be able to disassemble it.
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These pose varying degrees of difficulty to people wanting to get at
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your code, but none can definitively conceal it (this is true of every
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language, not just Perl).
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If you're concerned about people profiting from your code, then the
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bottom line is that nothing but a restrictive licence will give you
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legal security. License your software and pepper it with threatening
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statements like ``This is unpublished proprietary software of XYZ Corp.
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Your access to it does not give you permission to use it blah blah
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blah.'' We are not lawyers, of course, so you should see a lawyer if
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you want to be sure your licence's wording will stand up in court.
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=head2 How can I compile my Perl program into byte code or C?
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Malcolm Beattie has written a multifunction backend compiler,
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available from CPAN, that can do both these things. It is included
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in the perl5.005 release, but is still considered experimental.
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This means it's fun to play with if you're a programmer but not
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really for people looking for turn-key solutions.
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Merely compiling into C does not in and of itself guarantee that your
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code will run very much faster. That's because except for lucky cases
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where a lot of native type inferencing is possible, the normal Perl
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run time system is still present and so your program will take just as
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long to run and be just as big. Most programs save little more than
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compilation time, leaving execution no more than 10-30% faster. A few
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rare programs actually benefit significantly (like several times
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faster), but this takes some tweaking of your code.
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You'll probably be astonished to learn that the current version of the
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compiler generates a compiled form of your script whose executable is
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just as big as the original perl executable, and then some. That's
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because as currently written, all programs are prepared for a full
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eval() statement. You can tremendously reduce this cost by building a
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shared I<libperl.so> library and linking against that. See the
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F<INSTALL> podfile in the perl source distribution for details. If
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you link your main perl binary with this, it will make it miniscule.
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For example, on one author's system, F</usr/bin/perl> is only 11k in
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size!
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In general, the compiler will do nothing to make a Perl program smaller,
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faster, more portable, or more secure. In fact, it will usually hurt
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all of those. The executable will be bigger, your VM system may take
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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'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 5.006 release
|
|
of Perl.
|
|
|
|
=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
|
|
|
|
For OS/2 just use
|
|
|
|
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).
|
|
|
|
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 (Gurusamy Sarathy's is
|
|
the recommended Win95/NT port), or (eventually) build your own
|
|
Win95/NT Perl using a Windows port of gcc (e.g., with cygwin32 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 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
|
|
security risk. Take the time to figure out how to do it correctly.
|
|
|
|
=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.)
|
|
|
|
# sum first and last fields
|
|
perl -lane 'print $F[0] + $F[-1]' *
|
|
|
|
# identify text files
|
|
perl -le 'for(@ARGV) {print if -f && -T _}' *
|
|
|
|
# remove (most) comments from C program
|
|
perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c
|
|
|
|
# make file a month younger than today, defeating reaper daemons
|
|
perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' *
|
|
|
|
# find first unused uid
|
|
perl -le '$i++ while getpwuid($i); print $i'
|
|
|
|
# display reasonable manpath
|
|
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. :-)
|
|
|
|
=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
|
|
which the one-liners were created. On some systems, you may have to
|
|
change single-quotes to double ones, which you must I<NOT> do on Unix
|
|
or Plan9 systems. You might also have to change a single % to a %%.
|
|
|
|
For example:
|
|
|
|
# Unix
|
|
perl -e 'print "Hello world\n"'
|
|
|
|
# DOS, etc.
|
|
perl -e "print \"Hello world\n\""
|
|
|
|
# Mac
|
|
print "Hello world\n"
|
|
(then Run "Myscript" or Shift-Command-R)
|
|
|
|
# VMS
|
|
perl -e "print ""Hello world\n"""
|
|
|
|
The problem is that none of this is reliable: it depends on the
|
|
command interpreter. Under Unix, the first two often work. Under DOS,
|
|
it's entirely possible neither works. If 4DOS was the command shell,
|
|
you'd probably have better luck like this:
|
|
|
|
perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""
|
|
|
|
Under the Mac, it depends which environment you are using. The MacPerl
|
|
shell, or MPW, is much like Unix shells in its support for several
|
|
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? :-)
|
|
|
|
[Some of this answer was contributed by Kenneth Albanowski.]
|
|
|
|
=head2 Where can I learn about CGI or Web programming in Perl?
|
|
|
|
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:
|
|
|
|
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
|
|
|
|
Also take a look at L<perlfaq9>
|
|
|
|
=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
|
|
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/ .
|
|
|
|
=head2 Where can I learn about linking C with Perl? [h2xs, xsubpp]
|
|
|
|
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
|
|
call Perl from C, then read L<perlembed>, L<perlcall>, and
|
|
L<perlguts>. Don't forget that you can learn a lot from looking at
|
|
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?
|
|
|
|
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
|
|
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:
|
|
|
|
perl program 2>diag.out
|
|
splain [-v] [-p] diag.out
|
|
|
|
or change your program to explain the messages for you:
|
|
|
|
use diagnostics;
|
|
|
|
or
|
|
|
|
use diagnostics -verbose;
|
|
|
|
=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>.
|
|
|
|
=head1 AUTHOR AND COPYRIGHT
|
|
|
|
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 work is
|
|
covered under Perl's Artistic Licence. 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
|
|
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.
|
|
|