Commit | Line | Data |
a0d0e21e |
1 | =head1 NAME |
2 | |
3 | perlmod - Perl modules (packages) |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | =head2 Packages |
8 | |
748a9306 |
9 | Perl provides a mechanism for alternative namespaces to protect packages |
d0c42abe |
10 | from stomping on each other's variables. In fact, apart from certain |
cb1a09d0 |
11 | magical variables, there's really no such thing as a global variable in |
12 | Perl. The package statement declares the compilation unit as being in the |
13 | given namespace. The scope of the package declaration is from the |
14 | declaration itself through the end of the enclosing block (the same scope |
15 | as the local() operator). All further unqualified dynamic identifiers |
5f05dabc |
16 | will be in this namespace. A package statement affects only dynamic |
cb1a09d0 |
17 | variables--including those you've used local() on--but I<not> lexical |
18 | variables created with my(). Typically it would be the first declaration |
19 | in a file to be included by the C<require> or C<use> operator. You can |
5f05dabc |
20 | switch into a package in more than one place; it influences merely which |
a0d0e21e |
21 | symbol table is used by the compiler for the rest of that block. You can |
22 | refer to variables and filehandles in other packages by prefixing the |
23 | identifier with the package name and a double colon: |
24 | C<$Package::Variable>. If the package name is null, the C<main> package |
d0c42abe |
25 | is assumed. That is, C<$::sail> is equivalent to C<$main::sail>. |
a0d0e21e |
26 | |
27 | (The old package delimiter was a single quote, but double colon |
28 | is now the preferred delimiter, in part because it's more readable |
29 | to humans, and in part because it's more readable to B<emacs> macros. |
30 | It also makes C++ programmers feel like they know what's going on.) |
31 | |
32 | Packages may be nested inside other packages: C<$OUTER::INNER::var>. This |
33 | implies nothing about the order of name lookups, however. All symbols |
34 | are either local to the current package, or must be fully qualified |
35 | from the outer package name down. For instance, there is nowhere |
36 | within package C<OUTER> that C<$INNER::var> refers to C<$OUTER::INNER::var>. |
37 | It would treat package C<INNER> as a totally separate global package. |
38 | |
39 | Only identifiers starting with letters (or underscore) are stored in a |
cb1a09d0 |
40 | package's symbol table. All other symbols are kept in package C<main>, |
41 | including all of the punctuation variables like $_. In addition, the |
5f05dabc |
42 | identifiers STDIN, STDOUT, STDERR, ARGV, ARGVOUT, ENV, INC, and SIG are |
cb1a09d0 |
43 | forced to be in package C<main>, even when used for other purposes than |
44 | their built-in one. Note also that, if you have a package called C<m>, |
5f05dabc |
45 | C<s>, or C<y>, then you can't use the qualified form of an identifier |
cb1a09d0 |
46 | because it will be interpreted instead as a pattern match, a substitution, |
47 | or a translation. |
a0d0e21e |
48 | |
49 | (Variables beginning with underscore used to be forced into package |
50 | main, but we decided it was more useful for package writers to be able |
cb1a09d0 |
51 | to use leading underscore to indicate private variables and method names. |
52 | $_ is still global though.) |
a0d0e21e |
53 | |
54 | Eval()ed strings are compiled in the package in which the eval() was |
55 | compiled. (Assignments to C<$SIG{}>, however, assume the signal |
748a9306 |
56 | handler specified is in the C<main> package. Qualify the signal handler |
a0d0e21e |
57 | name if you wish to have a signal handler in a package.) For an |
58 | example, examine F<perldb.pl> in the Perl library. It initially switches |
59 | to the C<DB> package so that the debugger doesn't interfere with variables |
60 | in the script you are trying to debug. At various points, however, it |
61 | temporarily switches back to the C<main> package to evaluate various |
62 | expressions in the context of the C<main> package (or wherever you came |
63 | from). See L<perldebug>. |
64 | |
5f05dabc |
65 | See L<perlsub> for other scoping issues related to my() and local(), |
cb1a09d0 |
66 | or L<perlref> regarding closures. |
67 | |
a0d0e21e |
68 | =head2 Symbol Tables |
69 | |
aa689395 |
70 | The symbol table for a package happens to be stored in the hash of that |
71 | name with two colons appended. The main symbol table's name is thus |
72 | C<%main::>, or C<%::> for short. Likewise symbol table for the nested |
73 | package mentioned earlier is named C<%OUTER::INNER::>. |
74 | |
75 | The value in each entry of the hash is what you are referring to when you |
76 | use the C<*name> typeglob notation. In fact, the following have the same |
77 | effect, though the first is more efficient because it does the symbol |
78 | table lookups at compile time: |
a0d0e21e |
79 | |
80 | local(*main::foo) = *main::bar; local($main::{'foo'}) = |
81 | $main::{'bar'}; |
82 | |
83 | You can use this to print out all the variables in a package, for |
84 | instance. Here is F<dumpvar.pl> from the Perl library: |
85 | |
86 | package dumpvar; |
87 | sub main::dumpvar { |
88 | ($package) = @_; |
89 | local(*stab) = eval("*${package}::"); |
90 | while (($key,$val) = each(%stab)) { |
91 | local(*entry) = $val; |
92 | if (defined $entry) { |
93 | print "\$$key = '$entry'\n"; |
94 | } |
95 | |
96 | if (defined @entry) { |
97 | print "\@$key = (\n"; |
98 | foreach $num ($[ .. $#entry) { |
99 | print " $num\t'",$entry[$num],"'\n"; |
100 | } |
101 | print ")\n"; |
102 | } |
103 | |
104 | if ($key ne "${package}::" && defined %entry) { |
105 | print "\%$key = (\n"; |
106 | foreach $key (sort keys(%entry)) { |
107 | print " $key\t'",$entry{$key},"'\n"; |
108 | } |
109 | print ")\n"; |
110 | } |
111 | } |
112 | } |
113 | |
114 | Note that even though the subroutine is compiled in package C<dumpvar>, |
115 | the name of the subroutine is qualified so that its name is inserted |
116 | into package C<main>. |
117 | |
cb1a09d0 |
118 | Assignment to a typeglob performs an aliasing operation, i.e., |
a0d0e21e |
119 | |
120 | *dick = *richard; |
121 | |
5f05dabc |
122 | causes variables, subroutines, and file handles accessible via the |
d0c42abe |
123 | identifier C<richard> to also be accessible via the identifier C<dick>. If |
5f05dabc |
124 | you want to alias only a particular variable or subroutine, you can |
a0d0e21e |
125 | assign a reference instead: |
126 | |
127 | *dick = \$richard; |
128 | |
129 | makes $richard and $dick the same variable, but leaves |
130 | @richard and @dick as separate arrays. Tricky, eh? |
131 | |
cb1a09d0 |
132 | This mechanism may be used to pass and return cheap references |
133 | into or from subroutines if you won't want to copy the whole |
134 | thing. |
135 | |
136 | %some_hash = (); |
137 | *some_hash = fn( \%another_hash ); |
138 | sub fn { |
139 | local *hashsym = shift; |
140 | # now use %hashsym normally, and you |
141 | # will affect the caller's %another_hash |
142 | my %nhash = (); # do what you want |
5f05dabc |
143 | return \%nhash; |
cb1a09d0 |
144 | } |
145 | |
5f05dabc |
146 | On return, the reference will overwrite the hash slot in the |
cb1a09d0 |
147 | symbol table specified by the *some_hash typeglob. This |
c36e9b62 |
148 | is a somewhat tricky way of passing around references cheaply |
cb1a09d0 |
149 | when you won't want to have to remember to dereference variables |
150 | explicitly. |
151 | |
152 | Another use of symbol tables is for making "constant" scalars. |
153 | |
154 | *PI = \3.14159265358979; |
155 | |
156 | Now you cannot alter $PI, which is probably a good thing all in all. |
157 | |
55497cff |
158 | You can say C<*foo{PACKAGE}> and C<*foo{NAME}> to find out what name and |
159 | package the *foo symbol table entry comes from. This may be useful |
160 | in a subroutine which is passed typeglobs as arguments |
161 | |
162 | sub identify_typeglob { |
163 | my $glob = shift; |
164 | print 'You gave me ', *{$glob}{PACKAGE}, '::', *{$glob}{NAME}, "\n"; |
165 | } |
166 | identify_typeglob *foo; |
167 | identify_typeglob *bar::baz; |
168 | |
169 | This prints |
170 | |
171 | You gave me main::foo |
172 | You gave me bar::baz |
173 | |
174 | The *foo{THING} notation can also be used to obtain references to the |
175 | individual elements of *foo, see L<perlref>. |
176 | |
a0d0e21e |
177 | =head2 Package Constructors and Destructors |
178 | |
179 | There are two special subroutine definitions that function as package |
180 | constructors and destructors. These are the C<BEGIN> and C<END> |
181 | routines. The C<sub> is optional for these routines. |
182 | |
183 | A C<BEGIN> subroutine is executed as soon as possible, that is, the |
184 | moment it is completely defined, even before the rest of the containing |
185 | file is parsed. You may have multiple C<BEGIN> blocks within a |
186 | file--they will execute in order of definition. Because a C<BEGIN> |
187 | block executes immediately, it can pull in definitions of subroutines |
188 | and such from other files in time to be visible to the rest of the |
189 | file. |
190 | |
191 | An C<END> subroutine is executed as late as possible, that is, when the |
192 | interpreter is being exited, even if it is exiting as a result of a |
193 | die() function. (But not if it's is being blown out of the water by a |
194 | signal--you have to trap that yourself (if you can).) You may have |
748a9306 |
195 | multiple C<END> blocks within a file--they will execute in reverse |
a0d0e21e |
196 | order of definition; that is: last in, first out (LIFO). |
197 | |
c36e9b62 |
198 | Inside an C<END> subroutine C<$?> contains the value that the script is |
199 | going to pass to C<exit()>. You can modify C<$?> to change the exit |
5f05dabc |
200 | value of the script. Beware of changing C<$?> by accident (e.g.,, by |
c36e9b62 |
201 | running something via C<system>). |
202 | |
a0d0e21e |
203 | Note that when you use the B<-n> and B<-p> switches to Perl, C<BEGIN> |
204 | and C<END> work just as they do in B<awk>, as a degenerate case. |
205 | |
206 | =head2 Perl Classes |
207 | |
4633a7c4 |
208 | There is no special class syntax in Perl, but a package may function |
a0d0e21e |
209 | as a class if it provides subroutines that function as methods. Such a |
210 | package may also derive some of its methods from another class package |
5f05dabc |
211 | by listing the other package name in its @ISA array. |
4633a7c4 |
212 | |
213 | For more on this, see L<perlobj>. |
a0d0e21e |
214 | |
215 | =head2 Perl Modules |
216 | |
c07a80fd |
217 | A module is just a package that is defined in a library file of |
a0d0e21e |
218 | the same name, and is designed to be reusable. It may do this by |
219 | providing a mechanism for exporting some of its symbols into the symbol |
220 | table of any package using it. Or it may function as a class |
221 | definition and make its semantics available implicitly through method |
222 | calls on the class and its objects, without explicit exportation of any |
223 | symbols. Or it can do a little of both. |
224 | |
4633a7c4 |
225 | For example, to start a normal module called Fred, create |
226 | a file called Fred.pm and put this at the start of it: |
227 | |
5f05dabc |
228 | package Fred; |
229 | use strict; |
230 | use Exporter (); |
231 | use vars qw(@ISA @EXPORT @EXPORT_OK); |
4633a7c4 |
232 | @ISA = qw(Exporter); |
5f05dabc |
233 | @EXPORT = qw(&func1 &func2); |
234 | @EXPORT_OK = qw($sally @listabob %harry &func3); |
235 | use vars qw($sally @listabob %harry); |
4633a7c4 |
236 | |
237 | Then go on to declare and use your variables in functions |
238 | without any qualifications. |
5f05dabc |
239 | See L<Exporter> and the I<Perl Modules File> for details on |
4633a7c4 |
240 | mechanics and style issues in module creation. |
241 | |
242 | Perl modules are included into your program by saying |
a0d0e21e |
243 | |
244 | use Module; |
245 | |
246 | or |
247 | |
248 | use Module LIST; |
249 | |
250 | This is exactly equivalent to |
251 | |
252 | BEGIN { require "Module.pm"; import Module; } |
253 | |
254 | or |
255 | |
256 | BEGIN { require "Module.pm"; import Module LIST; } |
257 | |
cb1a09d0 |
258 | As a special case |
259 | |
260 | use Module (); |
261 | |
262 | is exactly equivalent to |
263 | |
264 | BEGIN { require "Module.pm"; } |
265 | |
a0d0e21e |
266 | All Perl module files have the extension F<.pm>. C<use> assumes this so |
267 | that you don't have to spell out "F<Module.pm>" in quotes. This also |
268 | helps to differentiate new modules from old F<.pl> and F<.ph> files. |
269 | Module names are also capitalized unless they're functioning as pragmas, |
270 | "Pragmas" are in effect compiler directives, and are sometimes called |
271 | "pragmatic modules" (or even "pragmata" if you're a classicist). |
272 | |
273 | Because the C<use> statement implies a C<BEGIN> block, the importation |
274 | of semantics happens at the moment the C<use> statement is compiled, |
275 | before the rest of the file is compiled. This is how it is able |
276 | to function as a pragma mechanism, and also how modules are able to |
277 | declare subroutines that are then visible as list operators for |
278 | the rest of the current file. This will not work if you use C<require> |
cb1a09d0 |
279 | instead of C<use>. With require you can get into this problem: |
a0d0e21e |
280 | |
281 | require Cwd; # make Cwd:: accessible |
282 | $here = Cwd::getcwd(); |
283 | |
5f05dabc |
284 | use Cwd; # import names from Cwd:: |
a0d0e21e |
285 | $here = getcwd(); |
286 | |
287 | require Cwd; # make Cwd:: accessible |
288 | $here = getcwd(); # oops! no main::getcwd() |
289 | |
cb1a09d0 |
290 | In general C<use Module ();> is recommended over C<require Module;>. |
291 | |
a0d0e21e |
292 | Perl packages may be nested inside other package names, so we can have |
293 | package names containing C<::>. But if we used that package name |
294 | directly as a filename it would makes for unwieldy or impossible |
295 | filenames on some systems. Therefore, if a module's name is, say, |
296 | C<Text::Soundex>, then its definition is actually found in the library |
297 | file F<Text/Soundex.pm>. |
298 | |
299 | Perl modules always have a F<.pm> file, but there may also be dynamically |
300 | linked executables or autoloaded subroutine definitions associated with |
301 | the module. If so, these will be entirely transparent to the user of |
302 | the module. It is the responsibility of the F<.pm> file to load (or |
303 | arrange to autoload) any additional functionality. The POSIX module |
304 | happens to do both dynamic loading and autoloading, but the user can |
5f05dabc |
305 | say just C<use POSIX> to get it all. |
a0d0e21e |
306 | |
8e07c86e |
307 | For more information on writing extension modules, see L<perlxs> |
a0d0e21e |
308 | and L<perlguts>. |
309 | |
310 | =head1 NOTE |
311 | |
312 | Perl does not enforce private and public parts of its modules as you may |
313 | have been used to in other languages like C++, Ada, or Modula-17. Perl |
314 | doesn't have an infatuation with enforced privacy. It would prefer |
315 | that you stayed out of its living room because you weren't invited, not |
316 | because it has a shotgun. |
317 | |
318 | The module and its user have a contract, part of which is common law, |
319 | and part of which is "written". Part of the common law contract is |
320 | that a module doesn't pollute any namespace it wasn't asked to. The |
5f05dabc |
321 | written contract for the module (A.K.A. documentation) may make other |
a0d0e21e |
322 | provisions. But then you know when you C<use RedefineTheWorld> that |
323 | you're redefining the world and willing to take the consequences. |
324 | |
325 | =head1 THE PERL MODULE LIBRARY |
326 | |
5f05dabc |
327 | A number of modules are included the Perl distribution. These are |
328 | described below, and all end in F<.pm>. You may also discover files in |
a0d0e21e |
329 | the library directory that end in either F<.pl> or F<.ph>. These are old |
748a9306 |
330 | libraries supplied so that old programs that use them still run. The |
a0d0e21e |
331 | F<.pl> files will all eventually be converted into standard modules, and |
332 | the F<.ph> files made by B<h2ph> will probably end up as extension modules |
333 | made by B<h2xs>. (Some F<.ph> values may already be available through the |
334 | POSIX module.) The B<pl2pm> file in the distribution may help in your |
4fdae800 |
335 | conversion, but it's just a mechanical process and therefore far from |
336 | bulletproof. |
a0d0e21e |
337 | |
338 | =head2 Pragmatic Modules |
339 | |
340 | They work somewhat like pragmas in that they tend to affect the compilation of |
5f05dabc |
341 | your program, and thus will usually work well only when used within a |
55497cff |
342 | C<use>, or C<no>. Most of these are locally scoped, so an inner BLOCK |
343 | may countermand any of these by saying: |
a0d0e21e |
344 | |
345 | no integer; |
346 | no strict 'refs'; |
347 | |
348 | which lasts until the end of that BLOCK. |
349 | |
5f05dabc |
350 | Unlike the pragmas that effect the C<$^H> hints variable, the C<use |
55497cff |
351 | vars> and C<use subs> declarations are not BLOCK-scoped. They allow |
352 | you to pre-declare a variables or subroutines within a particular |
4fdae800 |
353 | I<file> rather than just a block. Such declarations are effective |
55497cff |
354 | for the entire file for which they were declared. You cannot rescind |
355 | them with C<no vars> or C<no subs>. |
356 | |
357 | The following pragmas are defined (and have their own documentation). |
a0d0e21e |
358 | |
359 | =over 12 |
360 | |
5f05dabc |
361 | =item blib |
362 | |
363 | manipulate @INC at compile time to use MakeMaker's uninstalled version |
364 | of a package |
365 | |
cb1a09d0 |
366 | =item diagnostics |
4633a7c4 |
367 | |
55497cff |
368 | force verbose warning diagnostics |
4633a7c4 |
369 | |
cb1a09d0 |
370 | =item integer |
a0d0e21e |
371 | |
55497cff |
372 | compute arithmetic in integer instead of double |
a0d0e21e |
373 | |
cb1a09d0 |
374 | =item less |
a0d0e21e |
375 | |
55497cff |
376 | request less of something from the compiler |
377 | |
378 | =item lib |
379 | |
380 | manipulate @INC at compile time |
a0d0e21e |
381 | |
5f05dabc |
382 | =item locale |
383 | |
71be2cbc |
384 | use or ignore current locale for built-in operations (see L<perllocale>) |
5f05dabc |
385 | |
d0c42abe |
386 | =item ops |
387 | |
5f05dabc |
388 | restrict named opcodes when compiling or running Perl code |
d0c42abe |
389 | |
cb1a09d0 |
390 | =item overload |
391 | |
5f05dabc |
392 | overload basic Perl operations |
cb1a09d0 |
393 | |
394 | =item sigtrap |
a0d0e21e |
395 | |
55497cff |
396 | enable simple signal handling |
a0d0e21e |
397 | |
cb1a09d0 |
398 | =item strict |
a0d0e21e |
399 | |
55497cff |
400 | restrict unsafe constructs |
a0d0e21e |
401 | |
cb1a09d0 |
402 | =item subs |
a0d0e21e |
403 | |
5f05dabc |
404 | pre-declare sub names |
a0d0e21e |
405 | |
ff0cee69 |
406 | =item vmsish |
407 | |
408 | adopt certain VMS-specific behaviors |
409 | |
d0c42abe |
410 | =item vars |
411 | |
5f05dabc |
412 | pre-declare global variable names |
d0c42abe |
413 | |
a0d0e21e |
414 | =back |
415 | |
416 | =head2 Standard Modules |
417 | |
4633a7c4 |
418 | Standard, bundled modules are all expected to behave in a well-defined |
a0d0e21e |
419 | manner with respect to namespace pollution because they use the |
4633a7c4 |
420 | Exporter module. See their own documentation for details. |
a0d0e21e |
421 | |
cb1a09d0 |
422 | =over 12 |
423 | |
424 | =item AnyDBM_File |
425 | |
426 | provide framework for multiple DBMs |
427 | |
428 | =item AutoLoader |
429 | |
430 | load functions only on demand |
431 | |
432 | =item AutoSplit |
433 | |
434 | split a package for autoloading |
435 | |
436 | =item Benchmark |
437 | |
438 | benchmark running times of code |
439 | |
71be2cbc |
440 | =item CPAN |
441 | |
442 | interface to Comprehensive Perl Archive Network |
443 | |
444 | =item CPAN::FirstTime |
445 | |
446 | create a CPAN configuration file |
447 | |
448 | =item CPAN::Nox |
449 | |
450 | run CPAN while avoiding compiled extensions |
451 | |
cb1a09d0 |
452 | =item Carp |
453 | |
454 | warn of errors (from perspective of caller) |
455 | |
5f05dabc |
456 | =item Class::Template |
457 | |
458 | struct/member template builder |
459 | |
cb1a09d0 |
460 | =item Config |
461 | |
55497cff |
462 | access Perl configuration information |
cb1a09d0 |
463 | |
464 | =item Cwd |
465 | |
466 | get pathname of current working directory |
467 | |
468 | =item DB_File |
469 | |
55497cff |
470 | access to Berkeley DB |
cb1a09d0 |
471 | |
472 | =item Devel::SelfStubber |
473 | |
474 | generate stubs for a SelfLoading module |
475 | |
55497cff |
476 | =item DirHandle |
477 | |
478 | supply object methods for directory handles |
479 | |
cb1a09d0 |
480 | =item DynaLoader |
481 | |
5f05dabc |
482 | dynamically load C libraries into Perl code |
cb1a09d0 |
483 | |
484 | =item English |
485 | |
55497cff |
486 | use nice English (or awk) names for ugly punctuation variables |
cb1a09d0 |
487 | |
488 | =item Env |
489 | |
55497cff |
490 | import environment variables |
cb1a09d0 |
491 | |
492 | =item Exporter |
493 | |
55497cff |
494 | implements default import method for modules |
495 | |
496 | =item ExtUtils::Embed |
497 | |
5f05dabc |
498 | utilities for embedding Perl in C/C++ applications |
55497cff |
499 | |
500 | =item ExtUtils::Install |
501 | |
502 | install files from here to there |
cb1a09d0 |
503 | |
504 | =item ExtUtils::Liblist |
505 | |
506 | determine libraries to use and how to use them |
507 | |
5f05dabc |
508 | =item ExtUtils::MM_OS2 |
509 | |
510 | methods to override UN*X behaviour in ExtUtils::MakeMaker |
511 | |
512 | =item ExtUtils::MM_Unix |
513 | |
514 | methods used by ExtUtils::MakeMaker |
515 | |
516 | =item ExtUtils::MM_VMS |
517 | |
518 | methods to override UN*X behaviour in ExtUtils::MakeMaker |
519 | |
cb1a09d0 |
520 | =item ExtUtils::MakeMaker |
521 | |
522 | create an extension Makefile |
523 | |
524 | =item ExtUtils::Manifest |
525 | |
526 | utilities to write and check a MANIFEST file |
527 | |
528 | =item ExtUtils::Mkbootstrap |
529 | |
530 | make a bootstrap file for use by DynaLoader |
531 | |
55497cff |
532 | =item ExtUtils::Mksymlists |
533 | |
534 | write linker options files for dynamic extension |
535 | |
5f05dabc |
536 | =item ExtUtils::testlib |
55497cff |
537 | |
5f05dabc |
538 | add blib/* directories to @INC |
55497cff |
539 | |
cb1a09d0 |
540 | =item Fcntl |
541 | |
542 | load the C Fcntl.h defines |
543 | |
544 | =item File::Basename |
545 | |
5f05dabc |
546 | split a pathname into pieces |
55497cff |
547 | |
cb1a09d0 |
548 | =item File::CheckTree |
549 | |
550 | run many filetest checks on a tree |
551 | |
5f05dabc |
552 | =item File::Compare |
553 | |
554 | compare files or filehandles |
555 | |
55497cff |
556 | =item File::Copy |
557 | |
5f05dabc |
558 | copy files or filehandles |
55497cff |
559 | |
cb1a09d0 |
560 | =item File::Find |
561 | |
562 | traverse a file tree |
563 | |
cb1a09d0 |
564 | =item File::Path |
565 | |
566 | create or remove a series of directories |
567 | |
5f05dabc |
568 | =item File::stat |
569 | |
570 | by-name interface to Perl's built-in stat() functions |
571 | |
572 | =item FileCache |
573 | |
574 | keep more files open than the system permits |
575 | |
576 | =item FileHandle |
577 | |
578 | supply object methods for filehandles |
579 | |
55497cff |
580 | =item FindBin |
581 | |
582 | locate directory of original perl script |
583 | |
584 | =item GDBM_File |
585 | |
5f05dabc |
586 | access to the gdbm library |
55497cff |
587 | |
cb1a09d0 |
588 | =item Getopt::Long |
589 | |
55497cff |
590 | extended processing of command line options |
cb1a09d0 |
591 | |
592 | =item Getopt::Std |
593 | |
55497cff |
594 | process single-character switches with switch clustering |
cb1a09d0 |
595 | |
596 | =item I18N::Collate |
597 | |
598 | compare 8-bit scalar data according to the current locale |
599 | |
55497cff |
600 | =item IO |
601 | |
602 | load various IO modules |
603 | |
604 | =item IO::File |
605 | |
606 | supply object methods for filehandles |
607 | |
608 | =item IO::Handle |
609 | |
610 | supply object methods for I/O handles |
611 | |
612 | =item IO::Pipe |
613 | |
614 | supply object methods for pipes |
615 | |
616 | =item IO::Seekable |
617 | |
618 | supply seek based methods for I/O objects |
619 | |
620 | =item IO::Select |
621 | |
622 | OO interface to the select system call |
623 | |
624 | =item IO::Socket |
625 | |
626 | object interface to socket communications |
627 | |
cb1a09d0 |
628 | =item IPC::Open2 |
629 | |
55497cff |
630 | open a process for both reading and writing |
cb1a09d0 |
631 | |
632 | =item IPC::Open3 |
633 | |
634 | open a process for reading, writing, and error handling |
635 | |
55497cff |
636 | =item Math::BigFloat |
637 | |
638 | arbitrary length float math package |
639 | |
640 | =item Math::BigInt |
641 | |
642 | arbitrary size integer math package |
643 | |
644 | =item Math::Complex |
645 | |
646 | complex numbers and associated mathematical functions |
647 | |
648 | =item NDBM_File |
649 | |
650 | tied access to ndbm files |
651 | |
7e1af8bc |
652 | =item Net::Ping |
653 | |
654 | Hello, anybody home? |
655 | |
5f05dabc |
656 | =item Net::hostent |
657 | |
658 | by-name interface to Perl's built-in gethost*() functions |
659 | |
660 | =item Net::netent |
661 | |
662 | by-name interface to Perl's built-in getnet*() functions |
663 | |
664 | =item Net::protoent |
665 | |
666 | by-name interface to Perl's built-in getproto*() functions |
667 | |
668 | =item Net::servent |
669 | |
670 | by-name interface to Perl's built-in getserv*() functions |
671 | |
55497cff |
672 | =item Opcode |
673 | |
5f05dabc |
674 | disable named opcodes when compiling or running perl code |
55497cff |
675 | |
676 | =item Pod::Text |
677 | |
678 | convert POD data to formatted ASCII text |
679 | |
cb1a09d0 |
680 | =item POSIX |
681 | |
5f05dabc |
682 | interface to IEEE Standard 1003.1 |
55497cff |
683 | |
684 | =item SDBM_File |
685 | |
686 | tied access to sdbm files |
687 | |
5f05dabc |
688 | =item Safe |
689 | |
690 | compile and execute code in restricted compartments |
691 | |
55497cff |
692 | =item Search::Dict |
693 | |
694 | search for key in dictionary file |
695 | |
696 | =item SelectSaver |
697 | |
698 | save and restore selected file handle |
cb1a09d0 |
699 | |
700 | =item SelfLoader |
701 | |
702 | load functions only on demand |
703 | |
55497cff |
704 | =item Shell |
a2927560 |
705 | |
55497cff |
706 | run shell commands transparently within perl |
a2927560 |
707 | |
cb1a09d0 |
708 | =item Socket |
709 | |
710 | load the C socket.h defines and structure manipulators |
711 | |
55497cff |
712 | =item Symbol |
713 | |
714 | manipulate Perl symbols and their names |
715 | |
716 | =item Sys::Hostname |
717 | |
718 | try every conceivable way to get hostname |
719 | |
720 | =item Sys::Syslog |
721 | |
722 | interface to the UNIX syslog(3) calls |
723 | |
724 | =item Term::Cap |
725 | |
5f05dabc |
726 | termcap interface |
55497cff |
727 | |
728 | =item Term::Complete |
729 | |
730 | word completion module |
731 | |
732 | =item Term::ReadLine |
733 | |
5f05dabc |
734 | interface to various C<readline> packages |
55497cff |
735 | |
cb1a09d0 |
736 | =item Test::Harness |
737 | |
738 | run perl standard test scripts with statistics |
739 | |
740 | =item Text::Abbrev |
741 | |
c36e9b62 |
742 | create an abbreviation table from a list |
cb1a09d0 |
743 | |
55497cff |
744 | =item Text::ParseWords |
745 | |
746 | parse text into an array of tokens |
747 | |
748 | =item Text::Soundex |
749 | |
5f05dabc |
750 | implementation of the Soundex Algorithm as described by Knuth |
55497cff |
751 | |
752 | =item Text::Tabs |
753 | |
754 | expand and unexpand tabs per the unix expand(1) and unexpand(1) |
755 | |
756 | =item Text::Wrap |
757 | |
758 | line wrapping to form simple paragraphs |
759 | |
760 | =item Tie::Hash |
761 | |
762 | base class definitions for tied hashes |
763 | |
5f05dabc |
764 | =item Tie::RefHash |
765 | |
766 | base class definitions for tied hashes with references as keys |
767 | |
55497cff |
768 | =item Tie::Scalar |
769 | |
770 | base class definitions for tied scalars |
771 | |
772 | =item Tie::SubstrHash |
773 | |
774 | fixed-table-size, fixed-key-length hashing |
775 | |
776 | =item Time::Local |
777 | |
778 | efficiently compute time from local and GMT time |
779 | |
5f05dabc |
780 | =item Time::gmtime |
781 | |
782 | by-name interface to Perl's built-in gmtime() function |
783 | |
784 | =item Time::localtime |
785 | |
786 | by-name interface to Perl's built-in localtime() function |
787 | |
788 | =item Time::tm |
789 | |
790 | internal object used by Time::gmtime and Time::localtime |
791 | |
55497cff |
792 | =item UNIVERSAL |
793 | |
794 | base class for ALL classes (blessed references) |
795 | |
5f05dabc |
796 | =item User::grent |
797 | |
798 | by-name interface to Perl's built-in getgr*() functions |
799 | |
800 | =item User::pwent |
801 | |
802 | by-name interface to Perl's built-in getpw*() functions |
803 | |
cb1a09d0 |
804 | =back |
805 | |
806 | To find out I<all> the modules installed on your system, including |
807 | those without documentation or outside the standard release, do this: |
a0d0e21e |
808 | |
4633a7c4 |
809 | find `perl -e 'print "@INC"'` -name '*.pm' -print |
a0d0e21e |
810 | |
4633a7c4 |
811 | They should all have their own documentation installed and accessible via |
812 | your system man(1) command. If that fails, try the I<perldoc> program. |
a0d0e21e |
813 | |
4633a7c4 |
814 | =head2 Extension Modules |
a0d0e21e |
815 | |
4633a7c4 |
816 | Extension modules are written in C (or a mix of Perl and C) and get |
817 | dynamically loaded into Perl if and when you need them. Supported |
818 | extension modules include the Socket, Fcntl, and POSIX modules. |
a0d0e21e |
819 | |
cb1a09d0 |
820 | Many popular C extension modules do not come bundled (at least, not |
5f05dabc |
821 | completely) due to their sizes, volatility, or simply lack of time for |
cb1a09d0 |
822 | adequate testing and configuration across the multitude of platforms on |
823 | which Perl was beta-tested. You are encouraged to look for them in |
824 | archie(1L), the Perl FAQ or Meta-FAQ, the WWW page, and even with their |
825 | authors before randomly posting asking for their present condition and |
826 | disposition. |
a0d0e21e |
827 | |
cb1a09d0 |
828 | =head1 CPAN |
a0d0e21e |
829 | |
4633a7c4 |
830 | CPAN stands for the Comprehensive Perl Archive Network. This is a globally |
5f05dabc |
831 | replicated collection of all known Perl materials, including hundreds |
c36e9b62 |
832 | of unbundled modules. Here are the major categories of modules: |
a0d0e21e |
833 | |
4633a7c4 |
834 | =over |
a0d0e21e |
835 | |
4633a7c4 |
836 | =item * |
5f05dabc |
837 | Language Extensions and Documentation Tools |
a0d0e21e |
838 | |
4633a7c4 |
839 | =item * |
840 | Development Support |
a0d0e21e |
841 | |
4633a7c4 |
842 | =item * |
843 | Operating System Interfaces |
a0d0e21e |
844 | |
4633a7c4 |
845 | =item * |
846 | Networking, Device Control (modems) and InterProcess Communication |
a0d0e21e |
847 | |
4633a7c4 |
848 | =item * |
849 | Data Types and Data Type Utilities |
a0d0e21e |
850 | |
4633a7c4 |
851 | =item * |
852 | Database Interfaces |
a0d0e21e |
853 | |
4633a7c4 |
854 | =item * |
855 | User Interfaces |
a0d0e21e |
856 | |
4633a7c4 |
857 | =item * |
858 | Interfaces to / Emulations of Other Programming Languages |
a0d0e21e |
859 | |
4633a7c4 |
860 | =item * |
861 | File Names, File Systems and File Locking (see also File Handles) |
a0d0e21e |
862 | |
4633a7c4 |
863 | =item * |
5f05dabc |
864 | String Processing, Language Text Processing, Parsing, and Searching |
a0d0e21e |
865 | |
4633a7c4 |
866 | =item * |
5f05dabc |
867 | Option, Argument, Parameter, and Configuration File Processing |
a0d0e21e |
868 | |
4633a7c4 |
869 | =item * |
870 | Internationalization and Locale |
a0d0e21e |
871 | |
4633a7c4 |
872 | =item * |
5f05dabc |
873 | Authentication, Security, and Encryption |
a0d0e21e |
874 | |
4633a7c4 |
875 | =item * |
876 | World Wide Web, HTML, HTTP, CGI, MIME |
a0d0e21e |
877 | |
4633a7c4 |
878 | =item * |
879 | Server and Daemon Utilities |
a0d0e21e |
880 | |
4633a7c4 |
881 | =item * |
882 | Archiving and Compression |
a0d0e21e |
883 | |
4633a7c4 |
884 | =item * |
5f05dabc |
885 | Images, Pixmap and Bitmap Manipulation, Drawing, and Graphing |
a0d0e21e |
886 | |
4633a7c4 |
887 | =item * |
888 | Mail and Usenet News |
a0d0e21e |
889 | |
4633a7c4 |
890 | =item * |
891 | Control Flow Utilities (callbacks and exceptions etc) |
a0d0e21e |
892 | |
4633a7c4 |
893 | =item * |
894 | File Handle and Input/Output Stream Utilities |
a0d0e21e |
895 | |
4633a7c4 |
896 | =item * |
897 | Miscellaneous Modules |
a0d0e21e |
898 | |
4633a7c4 |
899 | =back |
a0d0e21e |
900 | |
d0c42abe |
901 | The registered CPAN sites as of this writing include the following. |
4633a7c4 |
902 | You should try to choose one close to you: |
a0d0e21e |
903 | |
4633a7c4 |
904 | =over |
a0d0e21e |
905 | |
4633a7c4 |
906 | =item * |
907 | ftp://ftp.sterling.com/programming/languages/perl/ |
a0d0e21e |
908 | |
4633a7c4 |
909 | =item * |
910 | ftp://ftp.sedl.org/pub/mirrors/CPAN/ |
a0d0e21e |
911 | |
4633a7c4 |
912 | =item * |
913 | ftp://ftp.uoknor.edu/mirrors/CPAN/ |
a0d0e21e |
914 | |
4633a7c4 |
915 | =item * |
916 | ftp://ftp.delphi.com/pub/mirrors/packages/perl/CPAN/ |
a0d0e21e |
917 | |
4633a7c4 |
918 | =item * |
919 | ftp://uiarchive.cso.uiuc.edu/pub/lang/perl/CPAN/ |
a0d0e21e |
920 | |
4633a7c4 |
921 | =item * |
922 | ftp://ftp.cis.ufl.edu/pub/perl/CPAN/ |
a0d0e21e |
923 | |
4633a7c4 |
924 | =item * |
925 | ftp://ftp.switch.ch/mirror/CPAN/ |
a0d0e21e |
926 | |
4633a7c4 |
927 | =item * |
928 | ftp://ftp.sunet.se/pub/lang/perl/CPAN/ |
a0d0e21e |
929 | |
4633a7c4 |
930 | =item * |
931 | ftp://ftp.ci.uminho.pt/pub/lang/perl/ |
a0d0e21e |
932 | |
4633a7c4 |
933 | =item * |
934 | ftp://ftp.cs.ruu.nl/pub/PERL/CPAN/ |
a0d0e21e |
935 | |
4633a7c4 |
936 | =item * |
937 | ftp://ftp.demon.co.uk/pub/mirrors/perl/CPAN/ |
a0d0e21e |
938 | |
4633a7c4 |
939 | =item * |
940 | ftp://ftp.rz.ruhr-uni-bochum.de/pub/programming/languages/perl/CPAN/ |
a0d0e21e |
941 | |
4633a7c4 |
942 | =item * |
943 | ftp://ftp.leo.org/pub/comp/programming/languages/perl/CPAN/ |
a0d0e21e |
944 | |
4633a7c4 |
945 | =item * |
946 | ftp://ftp.pasteur.fr/pub/computing/unix/perl/CPAN/ |
a0d0e21e |
947 | |
4633a7c4 |
948 | =item * |
949 | ftp://ftp.ibp.fr/pub/perl/CPAN/ |
a0d0e21e |
950 | |
4633a7c4 |
951 | =item * |
952 | ftp://ftp.funet.fi/pub/languages/perl/CPAN/ |
a0d0e21e |
953 | |
4633a7c4 |
954 | =item * |
955 | ftp://ftp.tekotago.ac.nz/pub/perl/CPAN/ |
a0d0e21e |
956 | |
4633a7c4 |
957 | =item * |
958 | ftp://ftp.mame.mu.oz.au/pub/perl/CPAN/ |
a0d0e21e |
959 | |
4633a7c4 |
960 | =item * |
961 | ftp://coombs.anu.edu.au/pub/perl/ |
a0d0e21e |
962 | |
4633a7c4 |
963 | =item * |
964 | ftp://dongpo.math.ncu.edu.tw/perl/CPAN/ |
a0d0e21e |
965 | |
4633a7c4 |
966 | =item * |
967 | ftp://ftp.lab.kdd.co.jp/lang/perl/CPAN/ |
a0d0e21e |
968 | |
4633a7c4 |
969 | =item * |
970 | ftp://ftp.is.co.za/programming/perl/CPAN/ |
a0d0e21e |
971 | |
972 | =back |
4633a7c4 |
973 | |
5f05dabc |
974 | For an up-to-date listing of CPAN sites, |
d0c42abe |
975 | see F<http://www.perl.com/perl/CPAN> or F<ftp://ftp.perl.com/perl/>. |
cb1a09d0 |
976 | |
5f05dabc |
977 | =head1 Modules: Creation, Use, and Abuse |
cb1a09d0 |
978 | |
979 | (The following section is borrowed directly from Tim Bunce's modules |
980 | file, available at your nearest CPAN site.) |
981 | |
5f05dabc |
982 | Perl implements a class using a package, but the presence of a |
cb1a09d0 |
983 | package doesn't imply the presence of a class. A package is just a |
984 | namespace. A class is a package that provides subroutines that can be |
985 | used as methods. A method is just a subroutine that expects, as its |
986 | first argument, either the name of a package (for "static" methods), |
987 | or a reference to something (for "virtual" methods). |
988 | |
989 | A module is a file that (by convention) provides a class of the same |
990 | name (sans the .pm), plus an import method in that class that can be |
991 | called to fetch exported symbols. This module may implement some of |
992 | its methods by loading dynamic C or C++ objects, but that should be |
993 | totally transparent to the user of the module. Likewise, the module |
994 | might set up an AUTOLOAD function to slurp in subroutine definitions on |
995 | demand, but this is also transparent. Only the .pm file is required to |
996 | exist. |
997 | |
998 | =head2 Guidelines for Module Creation |
999 | |
1000 | =over 4 |
1001 | |
1002 | =item Do similar modules already exist in some form? |
1003 | |
1004 | If so, please try to reuse the existing modules either in whole or |
1005 | by inheriting useful features into a new class. If this is not |
1006 | practical try to get together with the module authors to work on |
1007 | extending or enhancing the functionality of the existing modules. |
1008 | A perfect example is the plethora of packages in perl4 for dealing |
1009 | with command line options. |
1010 | |
1011 | If you are writing a module to expand an already existing set of |
1012 | modules, please coordinate with the author of the package. It |
1013 | helps if you follow the same naming scheme and module interaction |
1014 | scheme as the original author. |
1015 | |
1016 | =item Try to design the new module to be easy to extend and reuse. |
1017 | |
1018 | Use blessed references. Use the two argument form of bless to bless |
1019 | into the class name given as the first parameter of the constructor, |
5f05dabc |
1020 | e.g.,: |
cb1a09d0 |
1021 | |
5f05dabc |
1022 | sub new { |
cb1a09d0 |
1023 | my $class = shift; |
1024 | return bless {}, $class; |
1025 | } |
1026 | |
1027 | or even this if you'd like it to be used as either a static |
1028 | or a virtual method. |
1029 | |
5f05dabc |
1030 | sub new { |
cb1a09d0 |
1031 | my $self = shift; |
1032 | my $class = ref($self) || $self; |
1033 | return bless {}, $class; |
1034 | } |
1035 | |
1036 | Pass arrays as references so more parameters can be added later |
1037 | (it's also faster). Convert functions into methods where |
1038 | appropriate. Split large methods into smaller more flexible ones. |
1039 | Inherit methods from other modules if appropriate. |
1040 | |
c36e9b62 |
1041 | Avoid class name tests like: C<die "Invalid" unless ref $ref eq 'FOO'>. |
1042 | Generally you can delete the "C<eq 'FOO'>" part with no harm at all. |
cb1a09d0 |
1043 | Let the objects look after themselves! Generally, avoid hardwired |
1044 | class names as far as possible. |
1045 | |
c36e9b62 |
1046 | Avoid C<$r-E<gt>Class::func()> where using C<@ISA=qw(... Class ...)> and |
1047 | C<$r-E<gt>func()> would work (see L<perlbot> for more details). |
cb1a09d0 |
1048 | |
1049 | Use autosplit so little used or newly added functions won't be a |
1050 | burden to programs which don't use them. Add test functions to |
1051 | the module after __END__ either using AutoSplit or by saying: |
1052 | |
1053 | eval join('',<main::DATA>) || die $@ unless caller(); |
1054 | |
1055 | Does your module pass the 'empty sub-class' test? If you say |
c36e9b62 |
1056 | "C<@SUBCLASS::ISA = qw(YOURCLASS);>" your applications should be able |
cb1a09d0 |
1057 | to use SUBCLASS in exactly the same way as YOURCLASS. For example, |
c36e9b62 |
1058 | does your application still work if you change: C<$obj = new YOURCLASS;> |
1059 | into: C<$obj = new SUBCLASS;> ? |
cb1a09d0 |
1060 | |
1061 | Avoid keeping any state information in your packages. It makes it |
1062 | difficult for multiple other packages to use yours. Keep state |
1063 | information in objects. |
1064 | |
c36e9b62 |
1065 | Always use B<-w>. Try to C<use strict;> (or C<use strict qw(...);>). |
cb1a09d0 |
1066 | Remember that you can add C<no strict qw(...);> to individual blocks |
c36e9b62 |
1067 | of code which need less strictness. Always use B<-w>. Always use B<-w>! |
cb1a09d0 |
1068 | Follow the guidelines in the perlstyle(1) manual. |
1069 | |
1070 | =item Some simple style guidelines |
1071 | |
1072 | The perlstyle manual supplied with perl has many helpful points. |
1073 | |
1074 | Coding style is a matter of personal taste. Many people evolve their |
1075 | style over several years as they learn what helps them write and |
1076 | maintain good code. Here's one set of assorted suggestions that |
1077 | seem to be widely used by experienced developers: |
1078 | |
1079 | Use underscores to separate words. It is generally easier to read |
1080 | $var_names_like_this than $VarNamesLikeThis, especially for |
1081 | non-native speakers of English. It's also a simple rule that works |
1082 | consistently with VAR_NAMES_LIKE_THIS. |
1083 | |
1084 | Package/Module names are an exception to this rule. Perl informally |
1085 | reserves lowercase module names for 'pragma' modules like integer |
1086 | and strict. Other modules normally begin with a capital letter and |
1087 | use mixed case with no underscores (need to be short and portable). |
1088 | |
1089 | You may find it helpful to use letter case to indicate the scope |
1090 | or nature of a variable. For example: |
1091 | |
1092 | $ALL_CAPS_HERE constants only (beware clashes with perl vars) |
1093 | $Some_Caps_Here package-wide global/static |
1094 | $no_caps_here function scope my() or local() variables |
1095 | |
1096 | Function and method names seem to work best as all lowercase. |
5f05dabc |
1097 | e.g.,, C<$obj-E<gt>as_string()>. |
cb1a09d0 |
1098 | |
1099 | You can use a leading underscore to indicate that a variable or |
1100 | function should not be used outside the package that defined it. |
1101 | |
1102 | =item Select what to export. |
1103 | |
1104 | Do NOT export method names! |
1105 | |
1106 | Do NOT export anything else by default without a good reason! |
1107 | |
1108 | Exports pollute the namespace of the module user. If you must |
1109 | export try to use @EXPORT_OK in preference to @EXPORT and avoid |
1110 | short or common names to reduce the risk of name clashes. |
1111 | |
1112 | Generally anything not exported is still accessible from outside the |
c36e9b62 |
1113 | module using the ModuleName::item_name (or C<$blessed_ref-E<gt>method>) |
cb1a09d0 |
1114 | syntax. By convention you can use a leading underscore on names to |
5f05dabc |
1115 | indicate informally that they are 'internal' and not for public use. |
cb1a09d0 |
1116 | |
1117 | (It is actually possible to get private functions by saying: |
c36e9b62 |
1118 | C<my $subref = sub { ... }; &$subref;>. But there's no way to call that |
5f05dabc |
1119 | directly as a method, because a method must have a name in the symbol |
cb1a09d0 |
1120 | table.) |
1121 | |
1122 | As a general rule, if the module is trying to be object oriented |
1123 | then export nothing. If it's just a collection of functions then |
1124 | @EXPORT_OK anything but use @EXPORT with caution. |
1125 | |
1126 | =item Select a name for the module. |
1127 | |
5f05dabc |
1128 | This name should be as descriptive, accurate, and complete as |
cb1a09d0 |
1129 | possible. Avoid any risk of ambiguity. Always try to use two or |
1130 | more whole words. Generally the name should reflect what is special |
1131 | about what the module does rather than how it does it. Please use |
5f05dabc |
1132 | nested module names to group informally or categorize a module. |
1133 | There should be a very good reason for a module not to have a nested name. |
cb1a09d0 |
1134 | Module names should begin with a capital letter. |
1135 | |
1136 | Having 57 modules all called Sort will not make life easy for anyone |
1137 | (though having 23 called Sort::Quick is only marginally better :-). |
1138 | Imagine someone trying to install your module alongside many others. |
1139 | If in any doubt ask for suggestions in comp.lang.perl.misc. |
1140 | |
1141 | If you are developing a suite of related modules/classes it's good |
1142 | practice to use nested classes with a common prefix as this will |
1143 | avoid namespace clashes. For example: Xyz::Control, Xyz::View, |
1144 | Xyz::Model etc. Use the modules in this list as a naming guide. |
1145 | |
1146 | If adding a new module to a set, follow the original author's |
1147 | standards for naming modules and the interface to methods in |
1148 | those modules. |
1149 | |
1150 | To be portable each component of a module name should be limited to |
1151 | 11 characters. If it might be used on DOS then try to ensure each is |
1152 | unique in the first 8 characters. Nested modules make this easier. |
1153 | |
1154 | =item Have you got it right? |
1155 | |
1156 | How do you know that you've made the right decisions? Have you |
1157 | picked an interface design that will cause problems later? Have |
1158 | you picked the most appropriate name? Do you have any questions? |
1159 | |
1160 | The best way to know for sure, and pick up many helpful suggestions, |
1161 | is to ask someone who knows. Comp.lang.perl.misc is read by just about |
1162 | all the people who develop modules and it's the best place to ask. |
1163 | |
1164 | All you need to do is post a short summary of the module, its |
1165 | purpose and interfaces. A few lines on each of the main methods is |
1166 | probably enough. (If you post the whole module it might be ignored |
1167 | by busy people - generally the very people you want to read it!) |
1168 | |
1169 | Don't worry about posting if you can't say when the module will be |
1170 | ready - just say so in the message. It might be worth inviting |
1171 | others to help you, they may be able to complete it for you! |
1172 | |
1173 | =item README and other Additional Files. |
1174 | |
1175 | It's well known that software developers usually fully document the |
1176 | software they write. If, however, the world is in urgent need of |
1177 | your software and there is not enough time to write the full |
1178 | documentation please at least provide a README file containing: |
1179 | |
1180 | =over 10 |
1181 | |
1182 | =item * |
1183 | A description of the module/package/extension etc. |
1184 | |
1185 | =item * |
1186 | A copyright notice - see below. |
1187 | |
1188 | =item * |
1189 | Prerequisites - what else you may need to have. |
1190 | |
1191 | =item * |
1192 | How to build it - possible changes to Makefile.PL etc. |
1193 | |
1194 | =item * |
1195 | How to install it. |
1196 | |
1197 | =item * |
1198 | Recent changes in this release, especially incompatibilities |
1199 | |
1200 | =item * |
1201 | Changes / enhancements you plan to make in the future. |
1202 | |
1203 | =back |
1204 | |
1205 | If the README file seems to be getting too large you may wish to |
1206 | split out some of the sections into separate files: INSTALL, |
1207 | Copying, ToDo etc. |
1208 | |
d0c42abe |
1209 | =over 4 |
1210 | |
cb1a09d0 |
1211 | =item Adding a Copyright Notice. |
1212 | |
5f05dabc |
1213 | How you choose to license your work is a personal decision. |
cb1a09d0 |
1214 | The general mechanism is to assert your Copyright and then make |
1215 | a declaration of how others may copy/use/modify your work. |
1216 | |
c36e9b62 |
1217 | Perl, for example, is supplied with two types of license: The GNU |
5f05dabc |
1218 | GPL and The Artistic License (see the files README, Copying, and |
cb1a09d0 |
1219 | Artistic). Larry has good reasons for NOT just using the GNU GPL. |
1220 | |
5f05dabc |
1221 | My personal recommendation, out of respect for Larry, Perl, and the |
1222 | perl community at large is to state something simply like: |
cb1a09d0 |
1223 | |
1224 | Copyright (c) 1995 Your Name. All rights reserved. |
1225 | This program is free software; you can redistribute it and/or |
1226 | modify it under the same terms as Perl itself. |
1227 | |
1228 | This statement should at least appear in the README file. You may |
1229 | also wish to include it in a Copying file and your source files. |
1230 | Remember to include the other words in addition to the Copyright. |
1231 | |
1232 | =item Give the module a version/issue/release number. |
1233 | |
1234 | To be fully compatible with the Exporter and MakeMaker modules you |
1235 | should store your module's version number in a non-my package |
5f05dabc |
1236 | variable called $VERSION. This should be a floating point |
1237 | number with at least two digits after the decimal (i.e., hundredths, |
c36e9b62 |
1238 | e.g, C<$VERSION = "0.01">). Don't use a "1.3.2" style version. |
cb1a09d0 |
1239 | See Exporter.pm in Perl5.001m or later for details. |
1240 | |
1241 | It may be handy to add a function or method to retrieve the number. |
1242 | Use the number in announcements and archive file names when |
1243 | releasing the module (ModuleName-1.02.tar.Z). |
1244 | See perldoc ExtUtils::MakeMaker.pm for details. |
1245 | |
1246 | =item How to release and distribute a module. |
1247 | |
1248 | It's good idea to post an announcement of the availability of your |
1249 | module (or the module itself if small) to the comp.lang.perl.announce |
1250 | Usenet newsgroup. This will at least ensure very wide once-off |
1251 | distribution. |
1252 | |
1253 | If possible you should place the module into a major ftp archive and |
5f05dabc |
1254 | include details of its location in your announcement. |
cb1a09d0 |
1255 | |
1256 | Some notes about ftp archives: Please use a long descriptive file |
1257 | name which includes the version number. Most incoming directories |
1258 | will not be readable/listable, i.e., you won't be able to see your |
1259 | file after uploading it. Remember to send your email notification |
1260 | message as soon as possible after uploading else your file may get |
1261 | deleted automatically. Allow time for the file to be processed |
1262 | and/or check the file has been processed before announcing its |
1263 | location. |
1264 | |
1265 | FTP Archives for Perl Modules: |
1266 | |
1267 | Follow the instructions and links on |
1268 | |
1269 | http://franz.ww.tu-berlin.de/modulelist |
1270 | |
5f05dabc |
1271 | or upload to one of these sites: |
cb1a09d0 |
1272 | |
1273 | ftp://franz.ww.tu-berlin.de/incoming |
5f05dabc |
1274 | ftp://ftp.cis.ufl.edu/incoming |
cb1a09d0 |
1275 | |
1276 | and notify upload@franz.ww.tu-berlin.de. |
1277 | |
1278 | By using the WWW interface you can ask the Upload Server to mirror |
1279 | your modules from your ftp or WWW site into your own directory on |
1280 | CPAN! |
1281 | |
1282 | Please remember to send me an updated entry for the Module list! |
1283 | |
1284 | =item Take care when changing a released module. |
1285 | |
1286 | Always strive to remain compatible with previous released versions |
1287 | (see 2.2 above) Otherwise try to add a mechanism to revert to the |
1288 | old behaviour if people rely on it. Document incompatible changes. |
1289 | |
1290 | =back |
1291 | |
d0c42abe |
1292 | =back |
1293 | |
cb1a09d0 |
1294 | =head2 Guidelines for Converting Perl 4 Library Scripts into Modules |
1295 | |
1296 | =over 4 |
1297 | |
1298 | =item There is no requirement to convert anything. |
1299 | |
1300 | If it ain't broke, don't fix it! Perl 4 library scripts should |
1301 | continue to work with no problems. You may need to make some minor |
1302 | changes (like escaping non-array @'s in double quoted strings) but |
1303 | there is no need to convert a .pl file into a Module for just that. |
1304 | |
1305 | =item Consider the implications. |
1306 | |
1307 | All the perl applications which make use of the script will need to |
1308 | be changed (slightly) if the script is converted into a module. Is |
1309 | it worth it unless you plan to make other changes at the same time? |
1310 | |
1311 | =item Make the most of the opportunity. |
1312 | |
1313 | If you are going to convert the script to a module you can use the |
1314 | opportunity to redesign the interface. The 'Guidelines for Module |
1315 | Creation' above include many of the issues you should consider. |
1316 | |
1317 | =item The pl2pm utility will get you started. |
1318 | |
1319 | This utility will read *.pl files (given as parameters) and write |
1320 | corresponding *.pm files. The pl2pm utilities does the following: |
1321 | |
1322 | =over 10 |
1323 | |
1324 | =item * |
1325 | Adds the standard Module prologue lines |
1326 | |
1327 | =item * |
1328 | Converts package specifiers from ' to :: |
1329 | |
1330 | =item * |
1331 | Converts die(...) to croak(...) |
1332 | |
1333 | =item * |
1334 | Several other minor changes |
1335 | |
1336 | =back |
1337 | |
1338 | Being a mechanical process pl2pm is not bullet proof. The converted |
1339 | code will need careful checking, especially any package statements. |
1340 | Don't delete the original .pl file till the new .pm one works! |
1341 | |
1342 | =back |
1343 | |
1344 | =head2 Guidelines for Reusing Application Code |
1345 | |
1346 | =over 4 |
1347 | |
1348 | =item Complete applications rarely belong in the Perl Module Library. |
1349 | |
1350 | =item Many applications contain some perl code which could be reused. |
1351 | |
1352 | Help save the world! Share your code in a form that makes it easy |
1353 | to reuse. |
1354 | |
1355 | =item Break-out the reusable code into one or more separate module files. |
1356 | |
1357 | =item Take the opportunity to reconsider and redesign the interfaces. |
1358 | |
1359 | =item In some cases the 'application' can then be reduced to a small |
1360 | |
1361 | fragment of code built on top of the reusable modules. In these cases |
1362 | the application could invoked as: |
1363 | |
1364 | perl -e 'use Module::Name; method(@ARGV)' ... |
5f05dabc |
1365 | or |
d0c42abe |
1366 | perl -mModule::Name ... (in perl5.002) |
cb1a09d0 |
1367 | |
1368 | =back |