=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 8539 $)
+perlfaq3 - Programming Tools
=head1 DESCRIPTION
=head2 How can I use Perl interactively?
The typical approach uses the Perl debugger, described in the
-perldebug(1) manpage, on an "empty" program, like this:
+C<perldebug(1)> manpage, on an "empty" program, like this:
perl -de 42
=head2 Is there a Perl shell?
-The psh (Perl sh) is currently at version 1.8. The Perl Shell is a shell
+The C<psh> (Perl sh) is currently at version 1.8. The Perl Shell is a shell
that combines the interactive nature of a Unix shell with the power of
-Perl. The goal is a full featured shell that behaves as expected for
+Perl. The goal is a full-featured shell that behaves as expected for
normal shell activity and uses Perl syntax and functionality for
-control-flow statements and other things. You can get psh at
+control-flow statements and other things. You can get C<psh> at
http://sourceforge.net/projects/psh/ .
-Zoidberg is a similar project and provides a shell written in perl,
+C<Zoidberg> is a similar project and provides a shell written in perl,
configured in perl and operated in perl. It is intended as a login shell
-and development environment. It can be found at http://zoidberg.sf.net/
+and development environment. It can be found at
+http://pardus-larus.student.utwente.nl/~pardus/projects/zoidberg/
or your local CPAN mirror.
-The Shell.pm module (distributed with Perl) makes Perl try commands
-which aren't part of the Perl language as shell commands. perlsh from
+The C<Shell.pm> module (distributed with Perl) makes Perl try commands
+which aren't part of the Perl language as shell commands. C<perlsh> from
the source distribution is simplistic and uninteresting, but may still
be what you want.
=head2 How do I find which modules are installed on my system?
-You can use the ExtUtils::Installed module to show all installed
-distributions, although it can take awhile to do its magic. The
-standard library which comes with Perl just shows up as "Perl" (although
-you can get those with Module::CoreList).
+From the command line, you can use the C<cpan> command's C<-l> switch:
+
+ $ cpan -l
+
+You can also use C<cpan>'s C<-a> switch to create an autobundle file
+that C<CPAN.pm> understands and can use to re-install every module:
+
+ $ cpan -a
+
+Inside a Perl program, you can use the C<ExtUtils::Installed> module to
+show all installed distributions, although it can take awhile to do
+its magic. The standard library which comes with Perl just shows up
+as "Perl" (although you can get those with C<Module::CoreList>).
use ExtUtils::Installed;
my @modules = $inst->modules();
If you want a list of all of the Perl module filenames, you
-can use File::Find::Rule.
+can use C<File::Find::Rule>:
use File::Find::Rule;
- my @files = File::Find::Rule->file()->name( '*.pm' )->in( @INC );
+ my @files = File::Find::Rule->
+ extras({follow => 1})->
+ file()->
+ name( '*.pm' )->
+ in( @INC )
+ ;
If you do not have that module, you can do the same thing
-with File::Find which is part of the standard library.
-
- use File::Find;
- my @files;
-
- find(
- sub {
- push @files, $File::Find::name
- if -f $File::Find::name && /\.pm$/
- },
-
- @INC
- );
+with C<File::Find> which is part of the standard library:
+
+ use File::Find;
+ my @files;
+
+ find(
+ {
+ wanted => sub {
+ push @files, $File::Find::fullname
+ if -f $File::Find::fullname && /\.pm$/
+ },
+ follow => 1,
+ follow_skip => 2,
+ },
+ @INC
+ );
print join "\n", @files;
-If you simply need to quickly check to see if a module is
+If you simply need to check quickly to see if a module is
available, you can check for its documentation. If you can
read the documentation the module is most likely installed.
If you cannot read the documentation, the module might not
-have any (in rare cases).
+have any (in rare cases):
- prompt% perldoc Module::Name
+ $ perldoc Module::Name
You can also try to include the module in a one-liner to see if
-perl finds it.
+perl finds it:
- perl -MModule::Name -e1
+ $ perl -MModule::Name -e1
=head2 How do I debug my Perl programs?
Perl comes with an interactive debugger, which you can start with the
C<-d> switch. It's fully explained in L<perldebug>.
-If you'd like a graphical user interface and you have Tk, you can use
+If you'd like a graphical user interface and you have C<Tk>, you can use
C<ptkdb>. It's on CPAN and available for free.
-If you need something much more sophisicated and controllable, Leon
-Brocard's Devel::ebug (which you can call with the -D switch as -Debug)
+If you need something much more sophisticated and controllable, Leon
+Brocard's C<Devel::ebug> (which you can call with the C<-D> switch as C<-Debug>)
gives you the programmatic hooks into everything you need to write your
own (without too much pain and suffering).
=head2 How do I profile my Perl programs?
-You should get the Devel::DProf module from the standard distribution
-(or separately on CPAN) and also use Benchmark.pm from the standard
-distribution. The Benchmark module lets you time specific portions of
-your code, while Devel::DProf gives detailed breakdowns of where your
-code spends its time.
+(contributed by brian d foy, updated Fri Jul 25 12:22:26 PDT 2008)
+
+The C<Devel> namespace has several modules which you can use to
+profile your Perl programs. The C<Devel::DProf> module comes with Perl
+and you can invoke it with the C<-d> switch:
+
+ perl -d:DProf program.pl
+
+After running your program under C<DProf>, you'll get a F<tmon.out> file
+with the profile data. To look at the data, you can turn it into a
+human-readable report with the C<dprofpp> program that comes with
+C<Devel::DProf>.
+
+ dprofpp
+
+You can also do the profiling and reporting in one step with the C<-p>
+switch to C<dprofpp>:
+
+ dprofpp -p program.pl
-Here's a sample use of Benchmark:
+The C<Devel::NYTProf> (New York Times Profiler) does both statement
+and subroutine profiling. It's available from CPAN and you also invoke
+it with the C<-d> switch:
- use Benchmark;
+ perl -d:NYTProf some_perl.pl
- @junk = `cat /etc/motd`;
- $count = 10_000;
+Like C<DProf>, it creates a database of the profile information that you
+can turn into reports. The C<nytprofhtml> command turns the data into
+an HTML report similar to the C<Devel::Cover> report:
- timethese($count, {
- 'map' => sub { my @a = @junk;
- map { s/a/b/ } @a;
- return @a },
- 'for' => sub { my @a = @junk;
- for (@a) { s/a/b/ };
- return @a },
- });
+ nytprofhtml
-This is what it prints (on one machine--your results will be dependent
-on your hardware, operating system, and the load on your machine):
+CPAN has several other profilers that you can invoke in the same
+fashion. You might also be interested in using the C<Benchmark> to
+measure and compare code snippets.
- Benchmark: timing 10000 iterations of for, map...
- for: 4 secs ( 3.97 usr 0.01 sys = 3.98 cpu)
- map: 6 secs ( 4.97 usr 0.00 sys = 4.97 cpu)
+You can read more about profiling in I<Programming Perl>, chapter 20,
+or I<Mastering Perl>, chapter 5.
-Be aware that a good benchmark is very hard to write. It only tests the
-data you give it and proves little about the differing complexities
-of contrasting algorithms.
+L<perldebguts> documents creating a custom debugger if you need to
+create a special sort of profiler. brian d foy describes the process
+in I<The Perl Journal>, "Creating a Perl Debugger",
+http://www.ddj.com/184404522 , and "Profiling in Perl"
+http://www.ddj.com/184404580 .
+
+Perl.com has two interesting articles on profiling: "Profiling Perl",
+by Simon Cozens, http://www.perl.com/lpt/a/850 and "Debugging and
+Profiling mod_perl Applications", by Frank Wiles,
+http://www.perl.com/pub/a/2006/02/09/debug_mod_perl.html .
+
+Randal L. Schwartz writes about profiling in "Speeding up Your Perl
+Programs" for I<Unix Review>,
+http://www.stonehenge.com/merlyn/UnixReview/col49.html , and "Profiling
+in Template Toolkit via Overriding" for I<Linux Magazine>,
+http://www.stonehenge.com/merlyn/LinuxMag/col75.html .
=head2 How do I cross-reference my Perl programs?
-The B::Xref module can be used to generate cross-reference reports
+The C<B::Xref> module can be used to generate cross-reference reports
for Perl programs.
perl -MO=Xref[,OPTIONS] scriptname.plx
=head2 Is there a pretty-printer (formatter) for Perl?
-Perltidy is a Perl script which indents and reformats Perl scripts
+C<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
+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
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
+assistance. Tom Christiansen and many other VI users swear by
the following settings in vi and its clones:
set ai sw=4
The a2ps http://www-inf.enst.fr/%7Edemaille/a2ps/black+white.ps.gz does
lots of things related to generating nicely printed output of
-documents, as does enscript at http://people.ssh.fi/mtr/genscript/ .
+documents.
=head2 Is there a ctags for Perl?
popular editors support ctags for several different languages,
including Perl.
-Exuberent ctags supports Perl: http://ctags.sourceforge.net/
+Exuberant ctags supports Perl: http://ctags.sourceforge.net/
You might also try pltags: http://www.mscha.com/pltags.zip
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
+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.
and Solaris), multi-language IDE has Perl support, including a regular expression
debugger and remote debugging.
+=item Notepad++
+
+http://notepad-plus.sourceforge.net/
+
=item Open Perl IDE
http://open-perl-ide.sourceforge.net/
http://www.optiperl.com/
OptiPerl is a Windows IDE with simulated CGI environment, including
-debugger and syntax highlighting editor.
+debugger and syntax-highlighting editor.
+
+=item Padre
+
+http://padre.perlide.org/
+
+Padre is cross-platform IDE for Perl written in Perl using wxWidgets to provide
+a native look and feel. It's open source under the Artistic License.
=item PerlBuilder
http://www.solutionsoft.com/perl.htm
-PerlBuidler is an integrated development environment for Windows that
+PerlBuilder is an integrated development environment for Windows that
supports Perl development.
=item visiPerl+
http://www.zeusedit.com/lookmain.html
Zeus for Window is another Win32 multi-language editor/IDE
-that comes with support for Perl:
+that comes with support for Perl.
=back
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
+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
http://www.textpad.com/ ) and UltraEdit ( http://www.ultraedit.com/ ),
among others.
-If you are using MacOS, the same concerns apply. MacPerl (for Classic
+If you are using MacOS, the same concerns apply. MacPerl (for Classic
environments) comes with a simple editor. Popular external editors are
BBEdit ( http://www.bbedit.com/ ) or Alpha (
http://www.his.com/~jguyer/Alpha/Alpha8.html ). MacOS X users can use
-Unix editors as well. Neil Bowers (the man behind Geekcruises) has a
-list of Mac editors that can handle Perl (
-http://www.neilbowers.org/macperleditors.html ).
+Unix editors as well.
=over 4
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
+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:
+The following are Win32 multilanguage editor/IDEs that support Perl:
=over 4
http://www.slickedit.com/
+=item ConTEXT
+
+http://www.contexteditor.org/
+
=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
+( http://ptkdb.sourceforge.net/ ) is a Perl/Tk-based debugger that
acts as a development environment of sorts. Perl Composer
( http://perlcomposer.sourceforge.net/ ) is an IDE for Perl/Tk
GUI creation.
=item Ksh
-from the MKS Toolkit ( http://www.mks.com/ ), or the Bourne shell of
+from the MKS Toolkit ( http://www.mkssoftware.com/ ), or the Bourne shell of
the U/WIN environment ( http://www.research.att.com/sw/tools/uwin/ )
=item Tcsh
=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.
+research purposes), Cygwin is covered by the GNU General 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
=item Alpha
is an editor, written and extensible in Tcl, that nonetheless has
-built in support for several popular markup and programming languages
+built-in support for several popular markup and programming languages,
including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ).
=item BBEdit and BBEdit Lite
are text editors for Mac OS that have a Perl sensitivity mode
( http://web.barebones.com/ ).
-
=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,
the current version of vi out of Berkeley, which incidentally can be built
with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ .
-=head2 Where can I get perl-mode for emacs?
+=head2 Where can I get perl-mode or cperl-mode for emacs?
+X<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
come with the standard Emacs 19 distribution.
-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 highlighting. You
are probably using C<"main::foo"> in new Perl code anyway, so this
shouldn't be an issue.
+For CPerlMode, see http://www.emacswiki.org/cgi-bin/wiki/CPerlMode
+
=head2 How can I use curses with Perl?
The Curses module from CPAN provides a dynamically loadable object
this program repeats a command and updates the screen as needed, rendering
B<rep ps axu> similar to B<top>.
-=head2 How can I use X or Tk with Perl?
+=head2 How can I write a GUI (X, Tk, Gtk, etc.) in Perl?
+X<GUI> X<Tk> X<Wx> X<WxWidgets> X<Gtk> X<Gtk2> X<CamelBones> X<Qt>
-The Tk.pm module 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.cpan.org/modules/by-category/08_User_Interfaces/
+(contributed by Ben Morrow)
-Invaluable for Perl/Tk programming are the Perl/Tk FAQ at
-http://phaseit.net/claird/comp.lang.perl.tk/ptkFAQ.html , the Perl/Tk Reference
-Guide available at
-http://www.cpan.org/authors/Stephen_O_Lidie/ , and the
-online manpages at
-http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
+There are a number of modules which let you write GUIs in Perl. Most
+GUI toolkits have a perl interface: an incomplete list follows.
+
+=over 4
+
+=item Tk
+
+This works under Unix and Windows, and the current version doesn't
+look half as bad under Windows as it used to. Some of the gui elements
+still don't 'feel' quite right, though. The interface is very natural
+and 'perlish', making it easy to use in small scripts that just need a
+simple gui. It hasn't been updated in a while.
+
+=item Wx
+
+This is a Perl binding for the cross-platform wxWidgets toolkit
+( http://www.wxwidgets.org ). It works under Unix, Win32 and Mac OS X,
+using native widgets (Gtk under Unix). The interface follows the C++
+interface closely, but the documentation is a little sparse for someone
+who doesn't know the library, mostly just referring you to the C++
+documentation.
+
+=item Gtk and Gtk2
+
+These are Perl bindings for the Gtk toolkit ( http://www.gtk.org ). The
+interface changed significantly between versions 1 and 2 so they have
+separate Perl modules. It runs under Unix, Win32 and Mac OS X (currently
+it requires an X server on Mac OS, but a 'native' port is underway), and
+the widgets look the same on every platform: i.e., they don't match the
+native widgets. As with Wx, the Perl bindings follow the C API closely,
+and the documentation requires you to read the C documentation to
+understand it.
+
+=item Win32::GUI
+
+This provides access to most of the Win32 GUI widgets from Perl.
+Obviously, it only runs under Win32, and uses native widgets. The Perl
+interface doesn't really follow the C interface: it's been made more
+Perlish, and the documentation is pretty good. More advanced stuff may
+require familiarity with the C Win32 APIs, or reference to MSDN.
+
+=item CamelBones
+
+CamelBones ( http://camelbones.sourceforge.net ) is a Perl interface to
+Mac OS X's Cocoa GUI toolkit, and as such can be used to produce native
+GUIs on Mac OS X. It's not on CPAN, as it requires frameworks that
+CPAN.pm doesn't know how to install, but installation is via the
+standard OSX package installer. The Perl API is, again, very close to
+the ObjC API it's wrapping, and the documentation just tells you how to
+translate from one to the other.
+
+=item Qt
+
+There is a Perl interface to TrollTech's Qt toolkit, but it does not
+appear to be maintained.
+
+=item Athena
+
+Sx is an interface to the Athena widget set which comes with X, but
+again it appears not to be much used nowadays.
+
+=back
=head2 How can I make my Perl program run faster?
Ditto for stringifying large arrays:
- {
- local $, = "\n";
- print @big_array;
- }
+ {
+ local $, = "\n";
+ print @big_array;
+ }
is much more memory-efficient than either
- print join "\n", @big_array;
+ print join "\n", @big_array;
or
- {
- local $" = "\n";
- print "@big_array";
- }
+ {
+ 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
+requires some judgement, 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.
+=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
cannot be reclaimed or reused even if they go out of scope. It is
reserved in case the variables come back into scope. Memory allocated
to global variables can be reused (within your program) by using
-undef()ing and/or delete().
+undef() and/or delete().
On most operating systems, memory allocated to a program can never be
returned to the system. That's why long-running programs sometimes re-
and on the way you write your CGI programs, so investigate them with
care.
-See http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
+See also
+http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
=head2 How can I hide the source for my Perl program?
Perl2Exe ( http://www.indigostar.com/perl2exe.htm ) is a command line
program for converting perl scripts to executable files. It targets both
-Windows and unix platforms.
+Windows and Unix platforms.
=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
The C<ExtUtils::MakeMaker> module, better known simply as "MakeMaker",
turns a Perl script, typically called C<Makefile.PL>, into a Makefile.
-The unix tool C<make> uses this file to manage dependencies and actions
+The Unix tool C<make> uses this file to manage dependencies and actions
to process and install a Perl distribution.
-=head1 REVISION
-
-Revision: $Revision: 8539 $
-
-Date: $Date: 2007-01-11 00:07:14 +0100 (Thu, 11 Jan 2007) $
-
-See L<perlfaq> for source control details and availability.
-
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and
+Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and
other authors as noted. All rights reserved.
This documentation is free; you can redistribute it and/or modify it
https://perl5.git.perl.org / perl5.git / blobdiff