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68dc0745 | 1 | =head1 NAME |
2 | ||
fc36a67e | 3 | perlfaq3 - Programming Tools ($Revision: 1.22 $, $Date: 1997/04/24 22:43:42 $) |
68dc0745 | 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. | |
46fc3d4c | 14 | Have you read the appropriate man pages? Here's a brief index: |
68dc0745 | 15 | |
5a964f20 TC |
16 | Basics perldata, perlvar, perlsyn, perlop, perlsub |
17 | Execution perlrun, perldebug | |
18 | Functions perlfunc | |
68dc0745 | 19 | Objects perlref, perlmod, perlobj, perltie |
20 | Data Structures perlref, perllol, perldsc | |
f102b883 | 21 | Modules perlmod, perlmodlib, perlsub |
5a964f20 | 22 | Regexps perlre, perlfunc, perlop, perllocale |
68dc0745 | 23 | Moving to perl5 perltrap, perl |
24 | Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed | |
25 | Various http://www.perl.com/CPAN/doc/FMTEYEWTK/index.html | |
26 | (not a man-page but still useful) | |
27 | ||
46fc3d4c | 28 | L<perltoc> provides a crude table of contents for the perl man page set. |
68dc0745 | 29 | |
30 | =head2 How can I use Perl interactively? | |
31 | ||
32 | The typical approach uses the Perl debugger, described in the | |
46fc3d4c | 33 | perldebug(1) man page, on an "empty" program, like this: |
68dc0745 | 34 | |
35 | perl -de 42 | |
36 | ||
37 | Now just type in any legal Perl code, and it will be immediately | |
38 | evaluated. You can also examine the symbol table, get stack | |
39 | backtraces, check variable values, set breakpoints, and other | |
40 | operations typically found in symbolic debuggers | |
41 | ||
42 | =head2 Is there a Perl shell? | |
43 | ||
44 | In general, no. The Shell.pm module (distributed with perl) makes | |
45 | perl try commands which aren't part of the Perl language as shell | |
46 | commands. perlsh from the source distribution is simplistic and | |
47 | uninteresting, but may still be what you want. | |
48 | ||
49 | =head2 How do I debug my Perl programs? | |
50 | ||
51 | Have you used C<-w>? | |
52 | ||
53 | Have you tried C<use strict>? | |
54 | ||
55 | Did you check the returns of each and every system call? | |
56 | ||
57 | Did you read L<perltrap>? | |
58 | ||
59 | Have you tried the Perl debugger, described in L<perldebug>? | |
60 | ||
61 | =head2 How do I profile my Perl programs? | |
62 | ||
63 | You should get the Devel::DProf module from CPAN, and also use | |
64 | Benchmark.pm from the standard distribution. Benchmark lets you time | |
65 | specific portions of your code, while Devel::DProf gives detailed | |
66 | breakdowns of where your code spends its time. | |
67 | ||
68 | =head2 How do I cross-reference my Perl programs? | |
69 | ||
70 | The B::Xref module, shipped with the new, alpha-release Perl compiler | |
5a964f20 TC |
71 | (not the general distribution prior to the 5.005 release), can be used |
72 | to generate cross-reference reports for Perl programs. | |
68dc0745 | 73 | |
74 | perl -MO=Xref[,OPTIONS] foo.pl | |
75 | ||
76 | =head2 Is there a pretty-printer (formatter) for Perl? | |
77 | ||
78 | There is no program that will reformat Perl as much as indent(1) will | |
79 | do for C. The complex feedback between the scanner and the parser | |
80 | (this feedback is what confuses the vgrind and emacs programs) makes it | |
81 | challenging at best to write a stand-alone Perl parser. | |
82 | ||
83 | Of course, if you simply follow the guidelines in L<perlstyle>, you | |
84 | shouldn't need to reformat. | |
85 | ||
86 | Your editor can and should help you with source formatting. The | |
87 | perl-mode for emacs can provide a remarkable amount of help with most | |
88 | (but not all) code, and even less programmable editors can provide | |
89 | significant assistance. | |
90 | ||
7b8d334a | 91 | If you are used to using vgrind program for printing out nice code to |
68dc0745 | 92 | a laser printer, you can take a stab at this using |
93 | http://www.perl.com/CPAN/doc/misc/tips/working.vgrind.entry, but the | |
94 | results are not particularly satisfying for sophisticated code. | |
95 | ||
96 | =head2 Is there a ctags for Perl? | |
97 | ||
98 | There's a simple one at | |
99 | http://www.perl.com/CPAN/authors/id/TOMC/scripts/ptags.gz which may do | |
100 | the trick. | |
101 | ||
102 | =head2 Where can I get Perl macros for vi? | |
103 | ||
104 | For a complete version of Tom Christiansen's vi configuration file, | |
5a964f20 TC |
105 | see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc, |
106 | the standard benchmark file for vi emulators. This runs best with nvi, | |
107 | the current version of vi out of Berkeley, which incidentally can be built | |
108 | with an embedded Perl interpreter -- see http://www.perl.com/CPAN/src/misc. | |
68dc0745 | 109 | |
110 | =head2 Where can I get perl-mode for emacs? | |
111 | ||
112 | Since Emacs version 19 patchlevel 22 or so, there have been both a | |
113 | perl-mode.el and support for the perl debugger built in. These should | |
114 | come with the standard Emacs 19 distribution. | |
115 | ||
116 | In the perl source directory, you'll find a directory called "emacs", | |
117 | which contains a cperl-mode that color-codes keywords, provides | |
118 | context-sensitive help, and other nifty things. | |
119 | ||
120 | Note that the perl-mode of emacs will have fits with "main'foo" | |
121 | (single quote), and mess up the indentation and hilighting. You | |
122 | should be using "main::foo", anyway. | |
123 | ||
124 | =head2 How can I use curses with Perl? | |
125 | ||
126 | The Curses module from CPAN provides a dynamically loadable object | |
5a964f20 TC |
127 | module interface to a curses library. A small demo can be found at the |
128 | directory http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/rep; | |
129 | this program repeats a command and updates the screen as needed, rendering | |
130 | B<rep ps axu> similar to B<top>. | |
68dc0745 | 131 | |
132 | =head2 How can I use X or Tk with Perl? | |
133 | ||
5a964f20 TC |
134 | Tk is a completely Perl-based, object-oriented interface to the Tk toolkit |
135 | that doesn't force you to use Tcl just to get at Tk. Sx is an interface | |
136 | to the Athena Widget set. Both are available from CPAN. See the | |
137 | directory http://www.perl.com/CPAN/modules/by-category/08_User_Interfaces/ | |
68dc0745 | 138 | |
139 | =head2 How can I generate simple menus without using CGI or Tk? | |
140 | ||
141 | The http://www.perl.com/CPAN/authors/id/SKUNZ/perlmenu.v4.0.tar.gz | |
142 | module, which is curses-based, can help with this. | |
143 | ||
68dc0745 | 144 | =head2 What is undump? |
145 | ||
146 | See the next questions. | |
147 | ||
148 | =head2 How can I make my Perl program run faster? | |
149 | ||
150 | The best way to do this is to come up with a better algorithm. | |
151 | This can often make a dramatic difference. Chapter 8 in the Camel | |
152 | has some efficiency tips in it you might want to look at. | |
153 | ||
154 | Other approaches include autoloading seldom-used Perl code. See the | |
155 | AutoSplit and AutoLoader modules in the standard distribution for | |
156 | that. Or you could locate the bottleneck and think about writing just | |
157 | that part in C, the way we used to take bottlenecks in C code and | |
158 | write them in assembler. Similar to rewriting in C is the use of | |
159 | modules that have critical sections written in C (for instance, the | |
160 | PDL module from CPAN). | |
161 | ||
162 | In some cases, it may be worth it to use the backend compiler to | |
163 | produce byte code (saving compilation time) or compile into C, which | |
164 | will certainly save compilation time and sometimes a small amount (but | |
165 | not much) execution time. See the question about compiling your Perl | |
166 | programs. | |
167 | ||
168 | If you're currently linking your perl executable to a shared libc.so, | |
169 | you can often gain a 10-25% performance benefit by rebuilding it to | |
170 | link with a static libc.a instead. This will make a bigger perl | |
171 | executable, but your Perl programs (and programmers) may thank you for | |
172 | it. See the F<INSTALL> file in the source distribution for more | |
173 | information. | |
174 | ||
175 | Unsubstantiated reports allege that Perl interpreters that use sfio | |
176 | outperform those that don't (for IO intensive applications). To try | |
177 | this, see the F<INSTALL> file in the source distribution, especially | |
178 | the "Selecting File IO mechanisms" section. | |
179 | ||
180 | The undump program was an old attempt to speed up your Perl program | |
181 | by storing the already-compiled form to disk. This is no longer | |
182 | a viable option, as it only worked on a few architectures, and | |
183 | wasn't a good solution anyway. | |
184 | ||
185 | =head2 How can I make my Perl program take less memory? | |
186 | ||
187 | When it comes to time-space tradeoffs, Perl nearly always prefers to | |
188 | throw memory at a problem. Scalars in Perl use more memory than | |
189 | strings in C, arrays take more that, and hashes use even more. While | |
190 | there's still a lot to be done, recent releases have been addressing | |
191 | these issues. For example, as of 5.004, duplicate hash keys are | |
192 | shared amongst all hashes using them, so require no reallocation. | |
193 | ||
194 | In some cases, using substr() or vec() to simulate arrays can be | |
195 | highly beneficial. For example, an array of a thousand booleans will | |
196 | take at least 20,000 bytes of space, but it can be turned into one | |
197 | 125-byte bit vector for a considerable memory savings. The standard | |
198 | Tie::SubstrHash module can also help for certain types of data | |
199 | structure. If you're working with specialist data structures | |
200 | (matrices, for instance) modules that implement these in C may use | |
201 | less memory than equivalent Perl modules. | |
202 | ||
203 | Another thing to try is learning whether your Perl was compiled with | |
54310121 | 204 | the system malloc or with Perl's builtin malloc. Whichever one it |
68dc0745 | 205 | is, try using the other one and see whether this makes a difference. |
206 | Information about malloc is in the F<INSTALL> file in the source | |
207 | distribution. You can find out whether you are using perl's malloc by | |
208 | typing C<perl -V:usemymalloc>. | |
209 | ||
210 | =head2 Is it unsafe to return a pointer to local data? | |
211 | ||
212 | No, Perl's garbage collection system takes care of this. | |
213 | ||
214 | sub makeone { | |
215 | my @a = ( 1 .. 10 ); | |
216 | return \@a; | |
217 | } | |
218 | ||
219 | for $i ( 1 .. 10 ) { | |
220 | push @many, makeone(); | |
221 | } | |
222 | ||
223 | print $many[4][5], "\n"; | |
224 | ||
225 | print "@many\n"; | |
226 | ||
227 | =head2 How can I free an array or hash so my program shrinks? | |
228 | ||
5a964f20 TC |
229 | You can't. Memory the system allocates to a program will in practice |
230 | never be returned to the system. That's why long-running programs | |
231 | sometimes re-exec themselves. | |
68dc0745 | 232 | |
233 | However, judicious use of my() on your variables will help make sure | |
234 | that they go out of scope so that Perl can free up their storage for | |
235 | use in other parts of your program. (NB: my() variables also execute | |
236 | about 10% faster than globals.) A global variable, of course, never | |
237 | goes out of scope, so you can't get its space automatically reclaimed, | |
238 | although undef()ing and/or delete()ing it will achieve the same effect. | |
46fc3d4c | 239 | In general, memory allocation and de-allocation isn't something you can |
68dc0745 | 240 | or should be worrying about much in Perl, but even this capability |
241 | (preallocation of data types) is in the works. | |
242 | ||
243 | =head2 How can I make my CGI script more efficient? | |
244 | ||
245 | Beyond the normal measures described to make general Perl programs | |
246 | faster or smaller, a CGI program has additional issues. It may be run | |
247 | several times per second. Given that each time it runs it will need | |
46fc3d4c | 248 | to be re-compiled and will often allocate a megabyte or more of system |
68dc0745 | 249 | memory, this can be a killer. Compiling into C B<isn't going to help |
46fc3d4c | 250 | you> because the process start-up overhead is where the bottleneck is. |
68dc0745 | 251 | |
252 | There are at least two popular ways to avoid this overhead. One | |
253 | solution involves running the Apache HTTP server (available from | |
254 | http://www.apache.org/) with either of the mod_perl or mod_fastcgi | |
255 | plugin modules. With mod_perl and the Apache::* modules (from CPAN), | |
46fc3d4c | 256 | httpd will run with an embedded Perl interpreter which pre-compiles |
68dc0745 | 257 | your script and then executes it within the same address space without |
258 | forking. The Apache extension also gives Perl access to the internal | |
259 | server API, so modules written in Perl can do just about anything a | |
260 | module written in C can. With the FCGI module (from CPAN), a Perl | |
261 | executable compiled with sfio (see the F<INSTALL> file in the | |
262 | distribution) and the mod_fastcgi module (available from | |
263 | http://www.fastcgi.com/) each of your perl scripts becomes a permanent | |
7b8d334a | 264 | CGI daemon process. |
68dc0745 | 265 | |
266 | Both of these solutions can have far-reaching effects on your system | |
267 | and on the way you write your CGI scripts, so investigate them with | |
268 | care. | |
269 | ||
5a964f20 TC |
270 | See http://www.perl.com/CPAN/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/. |
271 | ||
68dc0745 | 272 | =head2 How can I hide the source for my Perl program? |
273 | ||
274 | Delete it. :-) Seriously, there are a number of (mostly | |
275 | unsatisfactory) solutions with varying levels of "security". | |
276 | ||
277 | First of all, however, you I<can't> take away read permission, because | |
278 | the source code has to be readable in order to be compiled and | |
279 | interpreted. (That doesn't mean that a CGI script's source is | |
280 | readable by people on the web, though.) So you have to leave the | |
281 | permissions at the socially friendly 0755 level. | |
282 | ||
283 | Some people regard this as a security problem. If your program does | |
284 | insecure things, and relies on people not knowing how to exploit those | |
285 | insecurities, it is not secure. It is often possible for someone to | |
286 | determine the insecure things and exploit them without viewing the | |
287 | source. Security through obscurity, the name for hiding your bugs | |
288 | instead of fixing them, is little security indeed. | |
289 | ||
290 | You can try using encryption via source filters (Filter::* from CPAN). | |
fc36a67e | 291 | But crackers might be able to decrypt it. You can try using the byte |
292 | code compiler and interpreter described below, but crackers might be | |
293 | able to de-compile it. You can try using the native-code compiler | |
68dc0745 | 294 | described below, but crackers might be able to disassemble it. These |
295 | pose varying degrees of difficulty to people wanting to get at your | |
296 | code, but none can definitively conceal it (this is true of every | |
297 | language, not just Perl). | |
298 | ||
299 | If you're concerned about people profiting from your code, then the | |
300 | bottom line is that nothing but a restrictive licence will give you | |
301 | legal security. License your software and pepper it with threatening | |
302 | statements like "This is unpublished proprietary software of XYZ Corp. | |
303 | Your access to it does not give you permission to use it blah blah | |
304 | blah." We are not lawyers, of course, so you should see a lawyer if | |
305 | you want to be sure your licence's wording will stand up in court. | |
306 | ||
54310121 | 307 | =head2 How can I compile my Perl program into byte code or C? |
68dc0745 | 308 | |
309 | Malcolm Beattie has written a multifunction backend compiler, | |
310 | available from CPAN, that can do both these things. It is as of | |
311 | Feb-1997 in late alpha release, which means it's fun to play with if | |
46fc3d4c | 312 | you're a programmer but not really for people looking for turn-key |
68dc0745 | 313 | solutions. |
314 | ||
315 | I<Please> understand that merely compiling into C does not in and of | |
316 | itself guarantee that your code will run very much faster. That's | |
317 | because except for lucky cases where a lot of native type inferencing | |
318 | is possible, the normal Perl run time system is still present and thus | |
319 | will still take just as long to run and be just as big. Most programs | |
320 | save little more than compilation time, leaving execution no more than | |
321 | 10-30% faster. A few rare programs actually benefit significantly | |
322 | (like several times faster), but this takes some tweaking of your | |
323 | code. | |
324 | ||
5a964f20 TC |
325 | The 5.005 release of Perl itself, whose main goal is merging the various |
326 | non-Unix ports back into the one Perl source, will also have preliminary | |
327 | (strictly beta) support for Malcolm's compiler and his light-weight | |
328 | processes (sometimes called "threads"). | |
68dc0745 | 329 | |
330 | You'll probably be astonished to learn that the current version of the | |
331 | compiler generates a compiled form of your script whose executable is | |
332 | just as big as the original perl executable, and then some. That's | |
333 | because as currently written, all programs are prepared for a full | |
334 | eval() statement. You can tremendously reduce this cost by building a | |
335 | shared libperl.so library and linking against that. See the | |
336 | F<INSTALL> podfile in the perl source distribution for details. If | |
337 | you link your main perl binary with this, it will make it miniscule. | |
338 | For example, on one author's system, /usr/bin/perl is only 11k in | |
339 | size! | |
340 | ||
5a964f20 TC |
341 | In general, the compiler will do nothing to make a Perl program smaller, |
342 | faster, more portable, or more secure. In fact, it will usually hurt | |
343 | all of those. The executable will be bigger, your VM system may take | |
344 | longer to load the whole thing, the binary is fragile and hard to fix, | |
345 | and compilation never stopped software piracy in the form of crackers, | |
346 | viruses, or bootleggers. The real advantage of the compiler is merely | |
347 | packaging, and once you see the size of what it makes (well, unless | |
348 | you use a shared I<libperl.so>), you'll probably want a complete | |
349 | Perl install anywayt. | |
350 | ||
46fc3d4c | 351 | =head2 How can I get '#!perl' to work on [MS-DOS,NT,...]? |
68dc0745 | 352 | |
353 | For OS/2 just use | |
354 | ||
355 | extproc perl -S -your_switches | |
356 | ||
357 | as the first line in C<*.cmd> file (C<-S> due to a bug in cmd.exe's | |
46fc3d4c | 358 | `extproc' handling). For DOS one should first invent a corresponding |
68dc0745 | 359 | batch file, and codify it in C<ALTERNATIVE_SHEBANG> (see the |
360 | F<INSTALL> file in the source distribution for more information). | |
361 | ||
362 | The Win95/NT installation, when using the Activeware port of Perl, | |
363 | will modify the Registry to associate the .pl extension with the perl | |
364 | interpreter. If you install another port, or (eventually) build your | |
365 | own Win95/NT Perl using WinGCC, then you'll have to modify the | |
366 | Registry yourself. | |
367 | ||
46fc3d4c | 368 | Macintosh perl scripts will have the the appropriate Creator and |
68dc0745 | 369 | Type, so that double-clicking them will invoke the perl application. |
370 | ||
371 | I<IMPORTANT!>: Whatever you do, PLEASE don't get frustrated, and just | |
372 | throw the perl interpreter into your cgi-bin directory, in order to | |
373 | get your scripts working for a web server. This is an EXTREMELY big | |
374 | security risk. Take the time to figure out how to do it correctly. | |
375 | ||
376 | =head2 Can I write useful perl programs on the command line? | |
377 | ||
378 | Yes. Read L<perlrun> for more information. Some examples follow. | |
379 | (These assume standard Unix shell quoting rules.) | |
380 | ||
381 | # sum first and last fields | |
5a964f20 | 382 | perl -lane 'print $F[0] + $F[-1]' * |
68dc0745 | 383 | |
384 | # identify text files | |
385 | perl -le 'for(@ARGV) {print if -f && -T _}' * | |
386 | ||
5a964f20 | 387 | # remove (most) comments from C program |
68dc0745 | 388 | perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c |
389 | ||
390 | # make file a month younger than today, defeating reaper daemons | |
391 | perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' * | |
392 | ||
393 | # find first unused uid | |
394 | perl -le '$i++ while getpwuid($i); print $i' | |
395 | ||
396 | # display reasonable manpath | |
397 | echo $PATH | perl -nl -072 -e ' | |
398 | s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}' | |
399 | ||
400 | Ok, the last one was actually an obfuscated perl entry. :-) | |
401 | ||
46fc3d4c | 402 | =head2 Why don't perl one-liners work on my DOS/Mac/VMS system? |
68dc0745 | 403 | |
404 | The problem is usually that the command interpreters on those systems | |
405 | have rather different ideas about quoting than the Unix shells under | |
406 | which the one-liners were created. On some systems, you may have to | |
407 | change single-quotes to double ones, which you must I<NOT> do on Unix | |
408 | or Plan9 systems. You might also have to change a single % to a %%. | |
409 | ||
410 | For example: | |
411 | ||
412 | # Unix | |
413 | perl -e 'print "Hello world\n"' | |
414 | ||
46fc3d4c | 415 | # DOS, etc. |
68dc0745 | 416 | perl -e "print \"Hello world\n\"" |
417 | ||
46fc3d4c | 418 | # Mac |
68dc0745 | 419 | print "Hello world\n" |
420 | (then Run "Myscript" or Shift-Command-R) | |
421 | ||
422 | # VMS | |
423 | perl -e "print ""Hello world\n""" | |
424 | ||
425 | The problem is that none of this is reliable: it depends on the command | |
46fc3d4c | 426 | interpreter. Under Unix, the first two often work. Under DOS, it's |
68dc0745 | 427 | entirely possible neither works. If 4DOS was the command shell, I'd |
428 | probably have better luck like this: | |
429 | ||
430 | perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>"" | |
431 | ||
46fc3d4c | 432 | Under the Mac, it depends which environment you are using. The MacPerl |
68dc0745 | 433 | shell, or MPW, is much like Unix shells in its support for several |
46fc3d4c | 434 | quoting variants, except that it makes free use of the Mac's non-ASCII |
68dc0745 | 435 | characters as control characters. |
436 | ||
437 | I'm afraid that there is no general solution to all of this. It is a | |
438 | mess, pure and simple. | |
439 | ||
440 | [Some of this answer was contributed by Kenneth Albanowski.] | |
441 | ||
442 | =head2 Where can I learn about CGI or Web programming in Perl? | |
443 | ||
444 | For modules, get the CGI or LWP modules from CPAN. For textbooks, | |
445 | see the two especially dedicated to web stuff in the question on | |
446 | books. For problems and questions related to the web, like "Why | |
447 | do I get 500 Errors" or "Why doesn't it run from the browser right | |
448 | when it runs fine on the command line", see these sources: | |
449 | ||
5a964f20 TC |
450 | WWW Security FAQ |
451 | http://www.w3.org/Security/Faq/ | |
68dc0745 | 452 | |
5a964f20 TC |
453 | Web FAQ |
454 | http://www.boutell.com/faq/ | |
68dc0745 | 455 | |
5a964f20 TC |
456 | CGI FAQ |
457 | http://www.webthing.com/page.cgi/cgifaq | |
68dc0745 | 458 | |
5a964f20 TC |
459 | HTTP Spec |
460 | http://www.w3.org/pub/WWW/Protocols/HTTP/ | |
461 | ||
462 | HTML Spec | |
463 | http://www.w3.org/TR/REC-html40/ | |
464 | http://www.w3.org/pub/WWW/MarkUp/ | |
465 | ||
466 | CGI Spec | |
467 | http://www.w3.org/CGI/ | |
468 | ||
469 | CGI Security FAQ | |
470 | http://www.go2net.com/people/paulp/cgi-security/safe-cgi.txt | |
68dc0745 | 471 | |
68dc0745 | 472 | |
473 | =head2 Where can I learn about object-oriented Perl programming? | |
474 | ||
475 | L<perltoot> is a good place to start, and you can use L<perlobj> and | |
476 | L<perlbot> for reference. Perltoot didn't come out until the 5.004 | |
477 | release, but you can get a copy (in pod, html, or postscript) from | |
478 | http://www.perl.com/CPAN/doc/FMTEYEWTK/ . | |
479 | ||
480 | =head2 Where can I learn about linking C with Perl? [h2xs, xsubpp] | |
481 | ||
482 | If you want to call C from Perl, start with L<perlxstut>, | |
483 | moving on to L<perlxs>, L<xsubpp>, and L<perlguts>. If you want to | |
484 | call Perl from C, then read L<perlembed>, L<perlcall>, and | |
485 | L<perlguts>. Don't forget that you can learn a lot from looking at | |
486 | how the authors of existing extension modules wrote their code and | |
487 | solved their problems. | |
488 | ||
489 | =head2 I've read perlembed, perlguts, etc., but I can't embed perl in | |
490 | my C program, what am I doing wrong? | |
491 | ||
492 | Download the ExtUtils::Embed kit from CPAN and run `make test'. If | |
493 | the tests pass, read the pods again and again and again. If they | |
46fc3d4c | 494 | fail, see L<perlbug> and send a bugreport with the output of |
68dc0745 | 495 | C<make test TEST_VERBOSE=1> along with C<perl -V>. |
496 | ||
497 | =head2 When I tried to run my script, I got this message. What does it | |
498 | mean? | |
499 | ||
500 | L<perldiag> has a complete list of perl's error messages and warnings, | |
501 | with explanatory text. You can also use the splain program (distributed | |
502 | with perl) to explain the error messages: | |
503 | ||
504 | perl program 2>diag.out | |
505 | splain [-v] [-p] diag.out | |
506 | ||
507 | or change your program to explain the messages for you: | |
508 | ||
509 | use diagnostics; | |
510 | ||
511 | or | |
512 | ||
513 | use diagnostics -verbose; | |
514 | ||
515 | =head2 What's MakeMaker? | |
516 | ||
517 | This module (part of the standard perl distribution) is designed to | |
518 | write a Makefile for an extension module from a Makefile.PL. For more | |
519 | information, see L<ExtUtils::MakeMaker>. | |
520 | ||
521 | =head1 AUTHOR AND COPYRIGHT | |
522 | ||
5a964f20 TC |
523 | Copyright (c) 1997, 1998 Tom Christiansen and Nathan Torkington. |
524 | All rights reserved. | |
525 | ||
526 | When included as part of the Standard Version of Perl, or as part of | |
527 | its complete documentation whether printed or otherwise, this work | |
528 | may be distributed only under the terms of Perl's Artistic License. | |
529 | Any distribution of this file or derivatives thereof I<outside> | |
530 | of that package require that special arrangements be made with | |
531 | copyright holder. | |
532 | ||
533 | Irrespective of its distribution, all code examples in this file | |
534 | are hereby placed into the public domain. You are permitted and | |
535 | encouraged to use this code in your own programs for fun | |
536 | or for profit as you see fit. A simple comment in the code giving | |
537 | credit would be courteous but is not required. |