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1 | =head1 NAME |
2 | |
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3 | perlfaq3 - Programming Tools |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This section of the FAQ answers questions related to programmer tools |
8 | and programming support. |
9 | |
10 | =head2 How do I do (anything)? |
11 | |
12 | Have you looked at CPAN (see L<perlfaq2>)? The chances are that |
13 | someone has already written a module that can solve your problem. |
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14 | Have you read the appropriate manpages? Here's a brief index: |
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15 | |
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16 | Basics perldata, perlvar, perlsyn, perlop, perlsub |
17 | Execution perlrun, perldebug |
18 | Functions perlfunc |
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19 | Objects perlref, perlmod, perlobj, perltie |
20 | Data Structures perlref, perllol, perldsc |
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21 | Modules perlmod, perlmodlib, perlsub |
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22 | Regexes perlre, perlfunc, perlop, perllocale |
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23 | Moving to perl5 perltrap, perl |
24 | Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed |
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25 | Various http://www.cpan.org/misc/olddoc/FMTEYEWTK.tgz |
26 | (not a man-page but still useful, a collection |
27 | of various essays on Perl techniques) |
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28 | |
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29 | A crude table of contents for the Perl manpage set is found in L<perltoc>. |
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30 | |
31 | =head2 How can I use Perl interactively? |
32 | |
33 | The typical approach uses the Perl debugger, described in the |
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34 | C<perldebug(1)> manpage, on an "empty" program, like this: |
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35 | |
36 | perl -de 42 |
37 | |
38 | Now just type in any legal Perl code, and it will be immediately |
39 | evaluated. You can also examine the symbol table, get stack |
40 | backtraces, check variable values, set breakpoints, and other |
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41 | operations typically found in symbolic debuggers. |
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42 | |
43 | =head2 Is there a Perl shell? |
44 | |
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45 | The C<psh> (Perl sh) is currently at version 1.8. The Perl Shell is a shell |
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46 | that combines the interactive nature of a Unix shell with the power of |
47 | Perl. The goal is a full featured shell that behaves as expected for |
48 | normal shell activity and uses Perl syntax and functionality for |
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49 | control-flow statements and other things. You can get C<psh> at |
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50 | http://sourceforge.net/projects/psh/ . |
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51 | |
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52 | C<Zoidberg> is a similar project and provides a shell written in perl, |
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53 | configured in perl and operated in perl. It is intended as a login shell |
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54 | and development environment. It can be found at |
55 | http://pardus-larus.student.utwente.nl/~pardus/projects/zoidberg/ |
f3b9614f |
56 | or your local CPAN mirror. |
57 | |
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58 | The C<Shell.pm> module (distributed with Perl) makes Perl try commands |
59 | which aren't part of the Perl language as shell commands. C<perlsh> from |
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60 | the source distribution is simplistic and uninteresting, but may still |
61 | be what you want. |
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62 | |
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63 | =head2 How do I find which modules are installed on my system? |
64 | |
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65 | From the command line, you can use the C<cpan> command's C<-l> switch: |
66 | |
67 | $ cpan -l |
68 | |
69 | You can also use C<cpan>'s C<-a> switch to create an autobundle file |
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70 | that C<CPAN.pm> understands and can use to re-install every module: |
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71 | |
72 | $ cpan -a |
73 | |
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74 | Inside a Perl program, you can use the C<ExtUtils::Installed> module to |
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75 | show all installed distributions, although it can take awhile to do |
76 | its magic. The standard library which comes with Perl just shows up |
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77 | as "Perl" (although you can get those with C<Module::CoreList>). |
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78 | |
79 | use ExtUtils::Installed; |
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80 | |
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81 | my $inst = ExtUtils::Installed->new(); |
82 | my @modules = $inst->modules(); |
83 | |
84 | If you want a list of all of the Perl module filenames, you |
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85 | can use C<File::Find::Rule>: |
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86 | |
87 | use File::Find::Rule; |
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88 | |
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89 | my @files = File::Find::Rule-> |
90 | extras({follow => 1})-> |
91 | file()-> |
92 | name( '*.pm' )-> |
93 | in( @INC ) |
94 | ; |
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95 | |
96 | If you do not have that module, you can do the same thing |
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97 | with C<File::Find> which is part of the standard library: |
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98 | |
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99 | use File::Find; |
100 | my @files; |
101 | |
102 | find( |
103 | { |
104 | wanted => sub { |
105 | push @files, $File::Find::fullname |
106 | if -f $File::Find::fullname && /\.pm$/ |
107 | }, |
108 | follow => 1, |
109 | follow_skip => 2, |
110 | }, |
111 | @INC |
112 | ); |
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113 | |
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114 | print join "\n", @files; |
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115 | |
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116 | If you simply need to quickly check to see if a module is |
117 | available, you can check for its documentation. If you can |
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118 | read the documentation the module is most likely installed. |
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119 | If you cannot read the documentation, the module might not |
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120 | have any (in rare cases): |
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121 | |
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122 | $ perldoc Module::Name |
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123 | |
124 | You can also try to include the module in a one-liner to see if |
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125 | perl finds it: |
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126 | |
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127 | $ perl -MModule::Name -e1 |
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128 | |
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129 | =head2 How do I debug my Perl programs? |
130 | |
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131 | (contributed by brian d foy) |
132 | |
133 | Before you do anything else, you can help yourself by ensuring that |
134 | you let Perl tell you about problem areas in your code. By turning |
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135 | on warnings and strictures, you can head off many problems before |
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136 | they get too big. You can find out more about these in L<strict> |
137 | and L<warnings>. |
138 | |
139 | #!/usr/bin/perl |
140 | use strict; |
141 | use warnings; |
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142 | |
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143 | Beyond that, the simplest debugger is the C<print> function. Use it |
144 | to look at values as you run your program: |
145 | |
146 | print STDERR "The value is [$value]\n"; |
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147 | |
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148 | The C<Data::Dumper> module can pretty-print Perl data structures: |
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149 | |
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150 | use Data::Dumper qw( Dumper ); |
151 | print STDERR "The hash is " . Dumper( \%hash ) . "\n"; |
152 | |
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153 | Perl comes with an interactive debugger, which you can start with the |
154 | C<-d> switch. It's fully explained in L<perldebug>. |
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155 | |
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156 | If you'd like a graphical user interface and you have C<Tk>, you can use |
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157 | C<ptkdb>. It's on CPAN and available for free. |
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158 | |
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159 | If you need something much more sophisticated and controllable, Leon |
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160 | Brocard's C<Devel::ebug> (which you can call with the C<-D> switch as C<-Debug>) |
500071f4 |
161 | gives you the programmatic hooks into everything you need to write your |
162 | own (without too much pain and suffering). |
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163 | |
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164 | You can also use a commercial debugger such as Affrus (Mac OS X), Komodo |
165 | from Activestate (Windows and Mac OS X), or EPIC (most platforms). |
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166 | |
167 | =head2 How do I profile my Perl programs? |
168 | |
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169 | (contributed by brian d foy, updated Fri Jul 25 12:22:26 PDT 2008) |
170 | |
171 | The C<Devel> namespace has several modules which you can use to |
172 | profile your Perl programs. The C<Devel::DProf> module comes with Perl |
173 | and you can invoke it with the C<-d> switch: |
174 | |
175 | perl -d:DProf program.pl |
176 | |
177 | After running your program under C<DProf>, you'll get a F<tmon.out> file |
178 | with the profile data. To look at the data, you can turn it into a |
179 | human-readable report with the C<dprofpp> program that comes with |
180 | C<Devel::DProf>. |
181 | |
182 | dprofpp |
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183 | |
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184 | You can also do the profiling and reporting in one step with the C<-p> |
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185 | switch to C<dprofpp>: |
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186 | |
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187 | dprofpp -p program.pl |
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188 | |
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189 | The C<Devel::NYTProf> (New York Times Profiler) does both statement |
190 | and subroutine profiling. It's available from CPAN and you also invoke |
191 | it with the C<-d> switch: |
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192 | |
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193 | perl -d:NYTProf some_perl.pl |
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194 | |
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195 | Like C<DProf>, it creates a database of the profile information that you |
196 | can turn into reports. The C<nytprofhtml> command turns the data into |
197 | an HTML report similar to the C<Devel::Cover> report: |
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198 | |
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199 | nytprofhtml |
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200 | |
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201 | CPAN has several other profilers that you can invoke in the same |
202 | fashion. You might also be interested in using the C<Benchmark> to |
203 | measure and compare code snippets. |
204 | |
205 | You can read more about profiling in I<Programming Perl>, chapter 20, |
206 | or I<Mastering Perl>, chapter 5. |
207 | |
208 | L<perldebguts> documents creating a custom debugger if you need to |
209 | create a special sort of profiler. brian d foy describes the process |
210 | in I<The Perl Journal>, "Creating a Perl Debugger", |
211 | http://www.ddj.com/184404522 , and "Profiling in Perl" |
212 | http://www.ddj.com/184404580 . |
213 | |
214 | Perl.com has two interesting articles on profiling: "Profiling Perl", |
215 | by Simon Cozens, http://www.perl.com/lpt/a/850 and "Debugging and |
216 | Profiling mod_perl Applications", by Frank Wiles, |
217 | http://www.perl.com/pub/a/2006/02/09/debug_mod_perl.html . |
218 | |
219 | Randal L. Schwartz writes about profiling in "Speeding up Your Perl |
220 | Programs" for I<Unix Review>, |
221 | http://www.stonehenge.com/merlyn/UnixReview/col49.html , and "Profiling |
222 | in Template Toolkit via Overriding" for I<Linux Magazine>, |
223 | http://www.stonehenge.com/merlyn/LinuxMag/col75.html . |
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224 | |
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225 | =head2 How do I cross-reference my Perl programs? |
226 | |
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227 | The C<B::Xref> module can be used to generate cross-reference reports |
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228 | for Perl programs. |
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229 | |
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230 | perl -MO=Xref[,OPTIONS] scriptname.plx |
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231 | |
232 | =head2 Is there a pretty-printer (formatter) for Perl? |
233 | |
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234 | C<Perltidy> is a Perl script which indents and reformats Perl scripts |
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235 | to make them easier to read by trying to follow the rules of the |
236 | L<perlstyle>. If you write Perl scripts, or spend much time reading |
237 | them, you will probably find it useful. It is available at |
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238 | http://perltidy.sourceforge.net . |
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239 | |
240 | Of course, if you simply follow the guidelines in L<perlstyle>, |
241 | you shouldn't need to reformat. The habit of formatting your code |
242 | as you write it will help prevent bugs. Your editor can and should |
243 | help you with this. The perl-mode or newer cperl-mode for emacs |
244 | can provide remarkable amounts of help with most (but not all) |
245 | code, and even less programmable editors can provide significant |
246 | assistance. Tom Christiansen and many other VI users swear by |
247 | the following settings in vi and its clones: |
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248 | |
249 | set ai sw=4 |
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250 | map! ^O {^M}^[O^T |
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251 | |
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252 | Put that in your F<.exrc> file (replacing the caret characters |
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253 | with control characters) and away you go. In insert mode, ^T is |
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254 | for indenting, ^D is for undenting, and ^O is for blockdenting--as |
255 | it were. A more complete example, with comments, can be found at |
213329dd |
256 | http://www.cpan.org/authors/id/TOMC/scripts/toms.exrc.gz |
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257 | |
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258 | The a2ps http://www-inf.enst.fr/%7Edemaille/a2ps/black+white.ps.gz does |
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259 | lots of things related to generating nicely printed output of |
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260 | documents. |
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261 | |
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262 | =head2 Is there a ctags for Perl? |
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263 | |
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264 | (contributed by brian d foy) |
265 | |
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266 | Ctags uses an index to quickly find things in source code, and many |
267 | popular editors support ctags for several different languages, |
268 | including Perl. |
269 | |
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270 | Exuberent ctags supports Perl: http://ctags.sourceforge.net/ |
bc06af74 |
271 | |
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272 | You might also try pltags: http://www.mscha.com/pltags.zip |
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273 | |
274 | =head2 Is there an IDE or Windows Perl Editor? |
275 | |
6641ed39 |
276 | Perl programs are just plain text, so any editor will do. |
277 | |
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278 | If you're on Unix, you already have an IDE--Unix itself. The Unix |
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279 | philosophy is the philosophy of several small tools that each do one |
280 | thing and do it well. It's like a carpenter's toolbox. |
281 | |
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282 | If you want an IDE, check the following (in alphabetical order, not |
283 | order of preference): |
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284 | |
285 | =over 4 |
286 | |
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287 | =item Eclipse |
288 | |
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289 | http://e-p-i-c.sf.net/ |
290 | |
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291 | The Eclipse Perl Integration Project integrates Perl |
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292 | editing/debugging with Eclipse. |
293 | |
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294 | =item Enginsite |
295 | |
296 | http://www.enginsite.com/ |
297 | |
298 | Perl Editor by EngInSite is a complete integrated development |
299 | environment (IDE) for creating, testing, and debugging Perl scripts; |
300 | the tool runs on Windows 9x/NT/2000/XP or later. |
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301 | |
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302 | =item Komodo |
303 | |
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304 | http://www.ActiveState.com/Products/Komodo/ |
305 | |
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306 | ActiveState's cross-platform (as of October 2004, that's Windows, Linux, |
307 | and Solaris), multi-language IDE has Perl support, including a regular expression |
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308 | debugger and remote debugging. |
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309 | |
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310 | =item Notepad++ |
311 | |
312 | http://notepad-plus.sourceforge.net/ |
313 | |
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314 | =item Open Perl IDE |
315 | |
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316 | http://open-perl-ide.sourceforge.net/ |
317 | |
ac1094a1 |
318 | Open Perl IDE is an integrated development environment for writing |
319 | and debugging Perl scripts with ActiveState's ActivePerl distribution |
320 | under Windows 95/98/NT/2000. |
321 | |
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322 | =item OptiPerl |
323 | |
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324 | http://www.optiperl.com/ |
325 | |
326 | OptiPerl is a Windows IDE with simulated CGI environment, including |
327 | debugger and syntax highlighting editor. |
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328 | |
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329 | =item Padre |
330 | |
331 | http://padre.perlide.org/ |
332 | |
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333 | Padre is cross-platform IDE for Perl written in Perl using wxWidgets to provide |
334 | a native look and feel. It's open source under the Artistic License. |
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335 | |
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336 | =item PerlBuilder |
337 | |
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338 | http://www.solutionsoft.com/perl.htm |
339 | |
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340 | PerlBuilder is an integrated development environment for Windows that |
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341 | supports Perl development. |
8782d048 |
342 | |
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343 | =item visiPerl+ |
344 | |
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345 | http://helpconsulting.net/visiperl/ |
346 | |
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347 | From Help Consulting, for Windows. |
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348 | |
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349 | =item Visual Perl |
350 | |
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351 | http://www.activestate.com/Products/Visual_Perl/ |
352 | |
28b41a80 |
353 | Visual Perl is a Visual Studio.NET plug-in from ActiveState. |
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354 | |
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355 | =item Zeus |
356 | |
357 | http://www.zeusedit.com/lookmain.html |
358 | |
359 | Zeus for Window is another Win32 multi-language editor/IDE |
360 | that comes with support for Perl: |
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361 | |
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362 | =back |
363 | |
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364 | For editors: if you're on Unix you probably have vi or a vi clone |
365 | already, and possibly an emacs too, so you may not need to download |
366 | anything. In any emacs the cperl-mode (M-x cperl-mode) gives you |
367 | perhaps the best available Perl editing mode in any editor. |
368 | |
369 | If you are using Windows, you can use any editor that lets you work |
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370 | with plain text, such as NotePad or WordPad. Word processors, such as |
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371 | Microsoft Word or WordPerfect, typically do not work since they insert |
372 | all sorts of behind-the-scenes information, although some allow you to |
589a5df2 |
373 | save files as "Text Only". You can also download text editors designed |
374 | specifically for programming, such as Textpad ( |
375 | http://www.textpad.com/ ) and UltraEdit ( http://www.ultraedit.com/ ), |
376 | among others. |
377 | |
378 | If you are using MacOS, the same concerns apply. MacPerl (for Classic |
379 | environments) comes with a simple editor. Popular external editors are |
380 | BBEdit ( http://www.bbedit.com/ ) or Alpha ( |
381 | http://www.his.com/~jguyer/Alpha/Alpha8.html ). MacOS X users can use |
382 | Unix editors as well. |
383 | |
384 | =over 4 |
385 | |
386 | =item GNU Emacs |
387 | |
388 | http://www.gnu.org/software/emacs/windows/ntemacs.html |
389 | |
390 | =item MicroEMACS |
391 | |
392 | http://www.microemacs.de/ |
393 | |
394 | =item XEmacs |
395 | |
396 | http://www.xemacs.org/Download/index.html |
397 | |
398 | =item Jed |
399 | |
400 | http://space.mit.edu/~davis/jed/ |
401 | |
402 | =back |
403 | |
404 | or a vi clone such as |
405 | |
406 | =over 4 |
407 | |
408 | =item Elvis |
409 | |
410 | ftp://ftp.cs.pdx.edu/pub/elvis/ http://www.fh-wedel.de/elvis/ |
411 | |
412 | =item Vile |
413 | |
414 | http://dickey.his.com/vile/vile.html |
415 | |
416 | =item Vim |
417 | |
418 | http://www.vim.org/ |
419 | |
420 | =back |
421 | |
422 | For vi lovers in general, Windows or elsewhere: |
423 | |
424 | http://www.thomer.com/thomer/vi/vi.html |
425 | |
426 | nvi ( http://www.bostic.com/vi/ , available from CPAN in src/misc/) is |
427 | yet another vi clone, unfortunately not available for Windows, but in |
23bec515 |
428 | Unix platforms you might be interested in trying it out, firstly because |
589a5df2 |
429 | strictly speaking it is not a vi clone, it is the real vi, or the new |
430 | incarnation of it, and secondly because you can embed Perl inside it |
431 | to use Perl as the scripting language. nvi is not alone in this, |
432 | though: at least also vim and vile offer an embedded Perl. |
433 | |
434 | The following are Win32 multilanguage editor/IDEs that support Perl: |
435 | |
436 | =over 4 |
437 | |
438 | =item Codewright |
439 | |
440 | http://www.borland.com/codewright/ |
441 | |
442 | =item MultiEdit |
443 | |
444 | http://www.MultiEdit.com/ |
445 | |
446 | =item SlickEdit |
447 | |
448 | http://www.slickedit.com/ |
449 | |
450 | =item ConTEXT |
451 | |
452 | http://www.contexteditor.org/ |
453 | |
454 | =back |
455 | |
456 | There is also a toyedit Text widget based editor written in Perl |
457 | that is distributed with the Tk module on CPAN. The ptkdb |
458 | ( http://ptkdb.sourceforge.net/ ) is a Perl/tk based debugger that |
459 | acts as a development environment of sorts. Perl Composer |
460 | ( http://perlcomposer.sourceforge.net/ ) is an IDE for Perl/Tk |
461 | GUI creation. |
462 | |
463 | In addition to an editor/IDE you might be interested in a more |
464 | powerful shell environment for Win32. Your options include |
465 | |
466 | =over 4 |
467 | |
468 | =item Bash |
469 | |
470 | from the Cygwin package ( http://sources.redhat.com/cygwin/ ) |
471 | |
472 | =item Ksh |
473 | |
474 | from the MKS Toolkit ( http://www.mkssoftware.com/ ), or the Bourne shell of |
475 | the U/WIN environment ( http://www.research.att.com/sw/tools/uwin/ ) |
476 | |
477 | =item Tcsh |
478 | |
479 | ftp://ftp.astron.com/pub/tcsh/ , see also |
480 | http://www.primate.wisc.edu/software/csh-tcsh-book/ |
481 | |
482 | =item Zsh |
483 | |
484 | http://www.zsh.org/ |
485 | |
486 | =back |
487 | |
488 | MKS and U/WIN are commercial (U/WIN is free for educational and |
489 | research purposes), Cygwin is covered by the GNU General Public |
490 | License (but that shouldn't matter for Perl use). The Cygwin, MKS, |
491 | and U/WIN all contain (in addition to the shells) a comprehensive set |
23bec515 |
492 | of standard Unix toolkit utilities. |
589a5df2 |
493 | |
494 | If you're transferring text files between Unix and Windows using FTP |
495 | be sure to transfer them in ASCII mode so the ends of lines are |
496 | appropriately converted. |
497 | |
498 | On Mac OS the MacPerl Application comes with a simple 32k text editor |
499 | that behaves like a rudimentary IDE. In contrast to the MacPerl Application |
500 | the MPW Perl tool can make use of the MPW Shell itself as an editor (with |
501 | no 32k limit). |
502 | |
503 | =over 4 |
504 | |
505 | =item Affrus |
506 | |
507 | is a full Perl development environment with full debugger support |
508 | ( http://www.latenightsw.com ). |
509 | |
510 | =item Alpha |
511 | |
512 | is an editor, written and extensible in Tcl, that nonetheless has |
513 | built in support for several popular markup and programming languages |
514 | including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ). |
515 | |
516 | =item BBEdit and BBEdit Lite |
517 | |
518 | are text editors for Mac OS that have a Perl sensitivity mode |
519 | ( http://web.barebones.com/ ). |
520 | |
521 | =back |
522 | |
523 | =head2 Where can I get Perl macros for vi? |
524 | |
525 | For a complete version of Tom Christiansen's vi configuration file, |
526 | see http://www.cpan.org/authors/Tom_Christiansen/scripts/toms.exrc.gz , |
527 | the standard benchmark file for vi emulators. The file runs best with nvi, |
528 | the current version of vi out of Berkeley, which incidentally can be built |
529 | with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ . |
530 | |
d12d61cf |
531 | =head2 Where can I get perl-mode or cperl-mode for emacs? |
532 | X<emacs> |
589a5df2 |
533 | |
534 | Since Emacs version 19 patchlevel 22 or so, there have been both a |
535 | perl-mode.el and support for the Perl debugger built in. These should |
536 | come with the standard Emacs 19 distribution. |
537 | |
589a5df2 |
538 | Note that the perl-mode of emacs will have fits with C<"main'foo"> |
539 | (single quote), and mess up the indentation and highlighting. You |
540 | are probably using C<"main::foo"> in new Perl code anyway, so this |
541 | shouldn't be an issue. |
542 | |
d12d61cf |
543 | For CPerlMode, see http://www.emacswiki.org/cgi-bin/wiki/CPerlMode |
544 | |
589a5df2 |
545 | =head2 How can I use curses with Perl? |
546 | |
547 | The Curses module from CPAN provides a dynamically loadable object |
548 | module interface to a curses library. A small demo can be found at the |
549 | directory http://www.cpan.org/authors/Tom_Christiansen/scripts/rep.gz ; |
550 | this program repeats a command and updates the screen as needed, rendering |
551 | B<rep ps axu> similar to B<top>. |
552 | |
553 | =head2 How can I write a GUI (X, Tk, Gtk, etc.) in Perl? |
554 | X<GUI> X<Tk> X<Wx> X<WxWidgets> X<Gtk> X<Gtk2> X<CamelBones> X<Qt> |
555 | |
556 | (contributed by Ben Morrow) |
557 | |
558 | There are a number of modules which let you write GUIs in Perl. Most |
559 | GUI toolkits have a perl interface: an incomplete list follows. |
560 | |
561 | =over 4 |
562 | |
563 | =item Tk |
564 | |
565 | This works under Unix and Windows, and the current version doesn't |
566 | look half as bad under Windows as it used to. Some of the gui elements |
567 | still don't 'feel' quite right, though. The interface is very natural |
568 | and 'perlish', making it easy to use in small scripts that just need a |
569 | simple gui. It hasn't been updated in a while. |
570 | |
571 | =item Wx |
572 | |
573 | This is a Perl binding for the cross-platform wxWidgets toolkit |
574 | ( http://www.wxwidgets.org ). It works under Unix, Win32 and Mac OS X, |
575 | using native widgets (Gtk under Unix). The interface follows the C++ |
576 | interface closely, but the documentation is a little sparse for someone |
577 | who doesn't know the library, mostly just referring you to the C++ |
578 | documentation. |
579 | |
580 | =item Gtk and Gtk2 |
581 | |
582 | These are Perl bindings for the Gtk toolkit ( http://www.gtk.org ). The |
583 | interface changed significantly between versions 1 and 2 so they have |
584 | separate Perl modules. It runs under Unix, Win32 and Mac OS X (currently |
585 | it requires an X server on Mac OS, but a 'native' port is underway), and |
586 | the widgets look the same on every plaform: i.e., they don't match the |
587 | native widgets. As with Wx, the Perl bindings follow the C API closely, |
588 | and the documentation requires you to read the C documentation to |
589 | understand it. |
590 | |
591 | =item Win32::GUI |
592 | |
593 | This provides access to most of the Win32 GUI widgets from Perl. |
594 | Obviously, it only runs under Win32, and uses native widgets. The Perl |
595 | interface doesn't really follow the C interface: it's been made more |
596 | Perlish, and the documentation is pretty good. More advanced stuff may |
597 | require familiarity with the C Win32 APIs, or reference to MSDN. |
598 | |
599 | =item CamelBones |
600 | |
601 | CamelBones ( http://camelbones.sourceforge.net ) is a Perl interface to |
602 | Mac OS X's Cocoa GUI toolkit, and as such can be used to produce native |
603 | GUIs on Mac OS X. It's not on CPAN, as it requires frameworks that |
604 | CPAN.pm doesn't know how to install, but installation is via the |
605 | standard OSX package installer. The Perl API is, again, very close to |
606 | the ObjC API it's wrapping, and the documentation just tells you how to |
607 | translate from one to the other. |
608 | |
609 | =item Qt |
610 | |
611 | There is a Perl interface to TrollTech's Qt toolkit, but it does not |
612 | appear to be maintained. |
613 | |
614 | =item Athena |
615 | |
616 | Sx is an interface to the Athena widget set which comes with X, but |
617 | again it appears not to be much used nowadays. |
618 | |
619 | =back |
620 | |
621 | =head2 How can I make my Perl program run faster? |
622 | |
623 | The best way to do this is to come up with a better algorithm. This |
624 | can often make a dramatic difference. Jon Bentley's book |
625 | I<Programming Pearls> (that's not a misspelling!) has some good tips |
626 | on optimization, too. Advice on benchmarking boils down to: benchmark |
627 | and profile to make sure you're optimizing the right part, look for |
628 | better algorithms instead of microtuning your code, and when all else |
629 | fails consider just buying faster hardware. You will probably want to |
630 | read the answer to the earlier question "How do I profile my Perl |
631 | programs?" if you haven't done so already. |
632 | |
633 | A different approach is to autoload seldom-used Perl code. See the |
634 | AutoSplit and AutoLoader modules in the standard distribution for |
635 | that. Or you could locate the bottleneck and think about writing just |
636 | that part in C, the way we used to take bottlenecks in C code and |
637 | write them in assembler. Similar to rewriting in C, modules that have |
638 | critical sections can be written in C (for instance, the PDL module |
639 | from CPAN). |
640 | |
641 | If you're currently linking your perl executable to a shared |
642 | I<libc.so>, you can often gain a 10-25% performance benefit by |
643 | rebuilding it to link with a static libc.a instead. This will make a |
644 | bigger perl executable, but your Perl programs (and programmers) may |
645 | thank you for it. See the F<INSTALL> file in the source distribution |
646 | for more information. |
647 | |
648 | The undump program was an ancient attempt to speed up Perl program by |
649 | storing the already-compiled form to disk. This is no longer a viable |
650 | option, as it only worked on a few architectures, and wasn't a good |
651 | solution anyway. |
652 | |
653 | =head2 How can I make my Perl program take less memory? |
654 | |
655 | When it comes to time-space tradeoffs, Perl nearly always prefers to |
656 | throw memory at a problem. Scalars in Perl use more memory than |
657 | strings in C, arrays take more than that, and hashes use even more. While |
658 | there's still a lot to be done, recent releases have been addressing |
659 | these issues. For example, as of 5.004, duplicate hash keys are |
660 | shared amongst all hashes using them, so require no reallocation. |
661 | |
662 | In some cases, using substr() or vec() to simulate arrays can be |
663 | highly beneficial. For example, an array of a thousand booleans will |
664 | take at least 20,000 bytes of space, but it can be turned into one |
665 | 125-byte bit vector--a considerable memory savings. The standard |
666 | Tie::SubstrHash module can also help for certain types of data |
667 | structure. If you're working with specialist data structures |
668 | (matrices, for instance) modules that implement these in C may use |
669 | less memory than equivalent Perl modules. |
670 | |
671 | Another thing to try is learning whether your Perl was compiled with |
672 | the system malloc or with Perl's builtin malloc. Whichever one it |
673 | is, try using the other one and see whether this makes a difference. |
674 | Information about malloc is in the F<INSTALL> file in the source |
675 | distribution. You can find out whether you are using perl's malloc by |
676 | typing C<perl -V:usemymalloc>. |
677 | |
678 | Of course, the best way to save memory is to not do anything to waste |
679 | it in the first place. Good programming practices can go a long way |
680 | toward this: |
681 | |
682 | =over 4 |
683 | |
684 | =item * Don't slurp! |
685 | |
686 | Don't read an entire file into memory if you can process it line |
687 | by line. Or more concretely, use a loop like this: |
688 | |
689 | # |
690 | # Good Idea |
691 | # |
692 | while (<FILE>) { |
693 | # ... |
694 | } |
695 | |
696 | instead of this: |
697 | |
698 | # |
699 | # Bad Idea |
700 | # |
701 | @data = <FILE>; |
702 | foreach (@data) { |
703 | # ... |
704 | } |
705 | |
706 | When the files you're processing are small, it doesn't much matter which |
707 | way you do it, but it makes a huge difference when they start getting |
708 | larger. |
709 | |
710 | =item * Use map and grep selectively |
711 | |
712 | Remember that both map and grep expect a LIST argument, so doing this: |
713 | |
714 | @wanted = grep {/pattern/} <FILE>; |
715 | |
716 | will cause the entire file to be slurped. For large files, it's better |
717 | to loop: |
718 | |
719 | while (<FILE>) { |
720 | push(@wanted, $_) if /pattern/; |
721 | } |
722 | |
723 | =item * Avoid unnecessary quotes and stringification |
724 | |
725 | Don't quote large strings unless absolutely necessary: |
726 | |
727 | my $copy = "$large_string"; |
728 | |
729 | makes 2 copies of $large_string (one for $copy and another for the |
730 | quotes), whereas |
731 | |
732 | my $copy = $large_string; |
733 | |
734 | only makes one copy. |
735 | |
736 | Ditto for stringifying large arrays: |
737 | |
738 | { |
739 | local $, = "\n"; |
740 | print @big_array; |
741 | } |
742 | |
743 | is much more memory-efficient than either |
744 | |
745 | print join "\n", @big_array; |
746 | |
747 | or |
748 | |
749 | { |
750 | local $" = "\n"; |
751 | print "@big_array"; |
752 | } |
753 | |
754 | |
755 | =item * Pass by reference |
756 | |
757 | Pass arrays and hashes by reference, not by value. For one thing, it's |
758 | the only way to pass multiple lists or hashes (or both) in a single |
759 | call/return. It also avoids creating a copy of all the contents. This |
760 | requires some judgement, however, because any changes will be propagated |
761 | back to the original data. If you really want to mangle (er, modify) a |
762 | copy, you'll have to sacrifice the memory needed to make one. |
763 | |
764 | =item * Tie large variables to disk. |
765 | |
766 | For "big" data stores (i.e. ones that exceed available memory) consider |
767 | using one of the DB modules to store it on disk instead of in RAM. This |
768 | will incur a penalty in access time, but that's probably better than |
769 | causing your hard disk to thrash due to massive swapping. |
770 | |
771 | =back |
772 | |
773 | =head2 Is it safe to return a reference to local or lexical data? |
774 | |
775 | Yes. Perl's garbage collection system takes care of this so |
776 | everything works out right. |
777 | |
778 | sub makeone { |
779 | my @a = ( 1 .. 10 ); |
780 | return \@a; |
781 | } |
782 | |
783 | for ( 1 .. 10 ) { |
784 | push @many, makeone(); |
785 | } |
786 | |
787 | print $many[4][5], "\n"; |
788 | |
789 | print "@many\n"; |
790 | |
791 | =head2 How can I free an array or hash so my program shrinks? |
792 | |
793 | (contributed by Michael Carman) |
794 | |
795 | You usually can't. Memory allocated to lexicals (i.e. my() variables) |
796 | cannot be reclaimed or reused even if they go out of scope. It is |
797 | reserved in case the variables come back into scope. Memory allocated |
798 | to global variables can be reused (within your program) by using |
799 | undef() and/or delete(). |
800 | |
801 | On most operating systems, memory allocated to a program can never be |
802 | returned to the system. That's why long-running programs sometimes re- |
803 | exec themselves. Some operating systems (notably, systems that use |
804 | mmap(2) for allocating large chunks of memory) can reclaim memory that |
805 | is no longer used, but on such systems, perl must be configured and |
806 | compiled to use the OS's malloc, not perl's. |
807 | |
808 | In general, memory allocation and de-allocation isn't something you can |
809 | or should be worrying about much in Perl. |
810 | |
811 | See also "How can I make my Perl program take less memory?" |
812 | |
813 | =head2 How can I make my CGI script more efficient? |
814 | |
815 | Beyond the normal measures described to make general Perl programs |
816 | faster or smaller, a CGI program has additional issues. It may be run |
817 | several times per second. Given that each time it runs it will need |
818 | to be re-compiled and will often allocate a megabyte or more of system |
819 | memory, this can be a killer. Compiling into C B<isn't going to help |
820 | you> because the process start-up overhead is where the bottleneck is. |
821 | |
822 | There are two popular ways to avoid this overhead. One solution |
823 | involves running the Apache HTTP server (available from |
824 | http://www.apache.org/ ) with either of the mod_perl or mod_fastcgi |
825 | plugin modules. |
826 | |
827 | With mod_perl and the Apache::Registry module (distributed with |
828 | mod_perl), httpd will run with an embedded Perl interpreter which |
829 | pre-compiles your script and then executes it within the same address |
830 | space without forking. The Apache extension also gives Perl access to |
831 | the internal server API, so modules written in Perl can do just about |
832 | anything a module written in C can. For more on mod_perl, see |
833 | http://perl.apache.org/ |
834 | |
835 | With the FCGI module (from CPAN) and the mod_fastcgi |
836 | module (available from http://www.fastcgi.com/ ) each of your Perl |
837 | programs becomes a permanent CGI daemon process. |
838 | |
839 | Both of these solutions can have far-reaching effects on your system |
840 | and on the way you write your CGI programs, so investigate them with |
841 | care. |
842 | |
843 | See http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ . |
844 | |
845 | =head2 How can I hide the source for my Perl program? |
846 | |
847 | Delete it. :-) Seriously, there are a number of (mostly |
848 | unsatisfactory) solutions with varying levels of "security". |
849 | |
850 | First of all, however, you I<can't> take away read permission, because |
851 | the source code has to be readable in order to be compiled and |
852 | interpreted. (That doesn't mean that a CGI script's source is |
853 | readable by people on the web, though--only by people with access to |
854 | the filesystem.) So you have to leave the permissions at the socially |
855 | friendly 0755 level. |
856 | |
857 | Some people regard this as a security problem. If your program does |
858 | insecure things and relies on people not knowing how to exploit those |
859 | insecurities, it is not secure. It is often possible for someone to |
860 | determine the insecure things and exploit them without viewing the |
861 | source. Security through obscurity, the name for hiding your bugs |
862 | instead of fixing them, is little security indeed. |
863 | |
864 | You can try using encryption via source filters (Starting from Perl |
865 | 5.8 the Filter::Simple and Filter::Util::Call modules are included in |
866 | the standard distribution), but any decent programmer will be able to |
867 | decrypt it. You can try using the byte code compiler and interpreter |
868 | described later in L<perlfaq3>, but the curious might still be able to |
869 | de-compile it. You can try using the native-code compiler described |
870 | later, but crackers might be able to disassemble it. These pose |
871 | varying degrees of difficulty to people wanting to get at your code, |
872 | but none can definitively conceal it (true of every language, not just |
873 | Perl). |
874 | |
875 | It is very easy to recover the source of Perl programs. You simply |
876 | feed the program to the perl interpreter and use the modules in |
877 | the B:: hierarchy. The B::Deparse module should be able to |
878 | defeat most attempts to hide source. Again, this is not |
879 | unique to Perl. |
880 | |
881 | If you're concerned about people profiting from your code, then the |
882 | bottom line is that nothing but a restrictive license will give you |
883 | legal security. License your software and pepper it with threatening |
884 | statements like "This is unpublished proprietary software of XYZ Corp. |
885 | Your access to it does not give you permission to use it blah blah |
886 | blah." We are not lawyers, of course, so you should see a lawyer if |
887 | you want to be sure your license's wording will stand up in court. |
888 | |
889 | =head2 How can I compile my Perl program into byte code or C? |
890 | |
891 | (contributed by brian d foy) |
892 | |
893 | In general, you can't do this. There are some things that may work |
894 | for your situation though. People usually ask this question |
895 | because they want to distribute their works without giving away |
896 | the source code, and most solutions trade disk space for convenience. |
897 | You probably won't see much of a speed increase either, since most |
898 | solutions simply bundle a Perl interpreter in the final product |
899 | (but see L<How can I make my Perl program run faster?>). |
900 | |
901 | The Perl Archive Toolkit ( http://par.perl.org/ ) is Perl's |
902 | analog to Java's JAR. It's freely available and on CPAN ( |
903 | http://search.cpan.org/dist/PAR/ ). |
904 | |
905 | There are also some commercial products that may work for you, although |
906 | you have to buy a license for them. |
907 | |
908 | The Perl Dev Kit ( http://www.activestate.com/Products/Perl_Dev_Kit/ ) |
909 | from ActiveState can "Turn your Perl programs into ready-to-run |
910 | executables for HP-UX, Linux, Solaris and Windows." |
911 | |
912 | Perl2Exe ( http://www.indigostar.com/perl2exe.htm ) is a command line |
913 | program for converting perl scripts to executable files. It targets both |
23bec515 |
914 | Windows and Unix platforms. |
589a5df2 |
915 | |
916 | =head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]? |
917 | |
918 | For OS/2 just use |
919 | |
920 | extproc perl -S -your_switches |
921 | |
922 | as the first line in C<*.cmd> file (C<-S> due to a bug in cmd.exe's |
923 | "extproc" handling). For DOS one should first invent a corresponding |
924 | batch file and codify it in C<ALTERNATE_SHEBANG> (see the |
925 | F<dosish.h> file in the source distribution for more information). |
926 | |
927 | The Win95/NT installation, when using the ActiveState port of Perl, |
928 | will modify the Registry to associate the C<.pl> extension with the |
929 | perl interpreter. If you install another port, perhaps even building |
930 | your own Win95/NT Perl from the standard sources by using a Windows port |
931 | of gcc (e.g., with cygwin or mingw32), then you'll have to modify |
932 | the Registry yourself. In addition to associating C<.pl> with the |
933 | interpreter, NT people can use: C<SET PATHEXT=%PATHEXT%;.PL> to let them |
934 | run the program C<install-linux.pl> merely by typing C<install-linux>. |
935 | |
936 | Under "Classic" MacOS, a perl program will have the appropriate Creator and |
937 | Type, so that double-clicking them will invoke the MacPerl application. |
938 | Under Mac OS X, clickable apps can be made from any C<#!> script using Wil |
939 | Sanchez' DropScript utility: http://www.wsanchez.net/software/ . |
940 | |
941 | I<IMPORTANT!>: Whatever you do, PLEASE don't get frustrated, and just |
942 | throw the perl interpreter into your cgi-bin directory, in order to |
943 | get your programs working for a web server. This is an EXTREMELY big |
944 | security risk. Take the time to figure out how to do it correctly. |
945 | |
946 | =head2 Can I write useful Perl programs on the command line? |
947 | |
948 | Yes. Read L<perlrun> for more information. Some examples follow. |
949 | (These assume standard Unix shell quoting rules.) |
950 | |
951 | # sum first and last fields |
952 | perl -lane 'print $F[0] + $F[-1]' * |
953 | |
954 | # identify text files |
955 | perl -le 'for(@ARGV) {print if -f && -T _}' * |
956 | |
957 | # remove (most) comments from C program |
958 | perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c |
959 | |
960 | # make file a month younger than today, defeating reaper daemons |
961 | perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' * |
962 | |
963 | # find first unused uid |
964 | perl -le '$i++ while getpwuid($i); print $i' |
965 | |
966 | # display reasonable manpath |
967 | echo $PATH | perl -nl -072 -e ' |
968 | s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}' |
969 | |
970 | OK, the last one was actually an Obfuscated Perl Contest entry. :-) |
971 | |
972 | =head2 Why don't Perl one-liners work on my DOS/Mac/VMS system? |
973 | |
974 | The problem is usually that the command interpreters on those systems |
975 | have rather different ideas about quoting than the Unix shells under |
976 | which the one-liners were created. On some systems, you may have to |
977 | change single-quotes to double ones, which you must I<NOT> do on Unix |
978 | or Plan9 systems. You might also have to change a single % to a %%. |
979 | |
980 | For example: |
981 | |
982 | # Unix (including Mac OS X) |
983 | perl -e 'print "Hello world\n"' |
984 | |
985 | # DOS, etc. |
986 | perl -e "print \"Hello world\n\"" |
987 | |
988 | # Mac Classic |
989 | print "Hello world\n" |
990 | (then Run "Myscript" or Shift-Command-R) |
991 | |
992 | # MPW |
993 | perl -e 'print "Hello world\n"' |
994 | |
995 | # VMS |
996 | perl -e "print ""Hello world\n""" |
997 | |
998 | The problem is that none of these examples are reliable: they depend on the |
999 | command interpreter. Under Unix, the first two often work. Under DOS, |
1000 | it's entirely possible that neither works. If 4DOS was the command shell, |
1001 | you'd probably have better luck like this: |
1002 | |
1003 | perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>"" |
1004 | |
1005 | Under the Mac, it depends which environment you are using. The MacPerl |
1006 | shell, or MPW, is much like Unix shells in its support for several |
1007 | quoting variants, except that it makes free use of the Mac's non-ASCII |
1008 | characters as control characters. |
1009 | |
1010 | Using qq(), q(), and qx(), instead of "double quotes", 'single |
1011 | quotes', and `backticks`, may make one-liners easier to write. |
1012 | |
1013 | There is no general solution to all of this. It is a mess. |
1014 | |
1015 | [Some of this answer was contributed by Kenneth Albanowski.] |
1016 | |
1017 | =head2 Where can I learn about CGI or Web programming in Perl? |
1018 | |
1019 | For modules, get the CGI or LWP modules from CPAN. For textbooks, |
1020 | see the two especially dedicated to web stuff in the question on |
1021 | books. For problems and questions related to the web, like "Why |
1022 | do I get 500 Errors" or "Why doesn't it run from the browser right |
1023 | when it runs fine on the command line", see the troubleshooting |
1024 | guides and references in L<perlfaq9> or in the CGI MetaFAQ: |
1025 | |
1026 | http://www.perl.org/CGI_MetaFAQ.html |
1027 | |
1028 | =head2 Where can I learn about object-oriented Perl programming? |
1029 | |
1030 | A good place to start is L<perltoot>, and you can use L<perlobj>, |
1031 | L<perlboot>, L<perltoot>, L<perltooc>, and L<perlbot> for reference. |
1032 | |
1033 | A good book on OO on Perl is the "Object-Oriented Perl" |
1034 | by Damian Conway from Manning Publications, or "Intermediate Perl" |
1035 | by Randal Schwartz, brian d foy, and Tom Phoenix from O'Reilly Media. |
1036 | |
1037 | =head2 Where can I learn about linking C with Perl? |
1038 | |
1039 | If you want to call C from Perl, start with L<perlxstut>, |
1040 | moving on to L<perlxs>, L<xsubpp>, and L<perlguts>. If you want to |
1041 | call Perl from C, then read L<perlembed>, L<perlcall>, and |
1042 | L<perlguts>. Don't forget that you can learn a lot from looking at |
1043 | how the authors of existing extension modules wrote their code and |
1044 | solved their problems. |
1045 | |
1046 | You might not need all the power of XS. The Inline::C module lets |
1047 | you put C code directly in your Perl source. It handles all the |
1048 | magic to make it work. You still have to learn at least some of |
1049 | the perl API but you won't have to deal with the complexity of the |
1050 | XS support files. |
1051 | |
1052 | =head2 I've read perlembed, perlguts, etc., but I can't embed perl in my C program; what am I doing wrong? |
1053 | |
1054 | Download the ExtUtils::Embed kit from CPAN and run `make test'. If |
1055 | the tests pass, read the pods again and again and again. If they |
1056 | fail, see L<perlbug> and send a bug report with the output of |
1057 | C<make test TEST_VERBOSE=1> along with C<perl -V>. |
1058 | |
1059 | =head2 When I tried to run my script, I got this message. What does it mean? |
1060 | |
1061 | A complete list of Perl's error messages and warnings with explanatory |
1062 | text can be found in L<perldiag>. You can also use the splain program |
1063 | (distributed with Perl) to explain the error messages: |
1064 | |
1065 | perl program 2>diag.out |
1066 | splain [-v] [-p] diag.out |
1067 | |
1068 | or change your program to explain the messages for you: |
1069 | |
1070 | use diagnostics; |
1071 | |
1072 | or |
1073 | |
1074 | use diagnostics -verbose; |
1075 | |
1076 | =head2 What's MakeMaker? |
1077 | |
1078 | (contributed by brian d foy) |
1079 | |
1080 | The C<ExtUtils::MakeMaker> module, better known simply as "MakeMaker", |
1081 | turns a Perl script, typically called C<Makefile.PL>, into a Makefile. |
23bec515 |
1082 | The Unix tool C<make> uses this file to manage dependencies and actions |
589a5df2 |
1083 | to process and install a Perl distribution. |
1084 | |
589a5df2 |
1085 | =head1 AUTHOR AND COPYRIGHT |
1086 | |
8d2e243f |
1087 | Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and |
589a5df2 |
1088 | other authors as noted. All rights reserved. |
1089 | |
1090 | This documentation is free; you can redistribute it and/or modify it |
1091 | under the same terms as Perl itself. |
1092 | |
1093 | Irrespective of its distribution, all code examples here are in the public |
1094 | domain. You are permitted and encouraged to use this code and any |
1095 | derivatives thereof in your own programs for fun or for profit as you |
1096 | see fit. A simple comment in the code giving credit to the FAQ would |
1097 | be courteous but is not required. |