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68dc0745 | 1 | =head1 NAME |
2 | ||
d92eb7b0 | 3 | perlfaq - frequently asked questions about Perl ($Date: 1999/05/23 20:38:02 $) |
68dc0745 | 4 | |
5 | =head1 DESCRIPTION | |
6 | ||
7 | This document is structured into the following sections: | |
8 | ||
9 | =over | |
10 | ||
11 | =item perlfaq: Structural overview of the FAQ. | |
12 | ||
13 | This document. | |
14 | ||
15 | =item L<perlfaq1>: General Questions About Perl | |
16 | ||
17 | Very general, high-level information about Perl. | |
18 | ||
65acb1b1 TC |
19 | =over 4 |
20 | ||
21 | =item * What is Perl? | |
22 | ||
23 | =item * Who supports Perl? Who develops it? Why is it free? | |
24 | ||
25 | =item * Which version of Perl should I use? | |
26 | ||
27 | =item * What are perl4 and perl5? | |
28 | ||
29 | =item * What is perl6? | |
30 | ||
31 | =item * How stable is Perl? | |
32 | ||
33 | =item * Is Perl difficult to learn? | |
34 | ||
35 | =item * How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl? | |
36 | ||
37 | =item * Can I do [task] in Perl? | |
38 | ||
39 | =item * When shouldn't I program in Perl? | |
40 | ||
41 | =item * What's the difference between "perl" and "Perl"? | |
42 | ||
43 | =item * Is it a Perl program or a Perl script? | |
44 | ||
45 | =item * What is a JAPH? | |
46 | ||
47 | =item * Where can I get a list of Larry Wall witticisms? | |
48 | ||
49 | =item * How can I convince my sysadmin/supervisor/employees to use version (5/5.005/Perl instead of some other language)? | |
50 | ||
51 | =back | |
52 | ||
53 | ||
68dc0745 | 54 | =item L<perlfaq2>: Obtaining and Learning about Perl |
55 | ||
92c2ed05 | 56 | Where to find source and documentation to Perl, support, |
68dc0745 | 57 | and related matters. |
58 | ||
65acb1b1 TC |
59 | =over 4 |
60 | ||
61 | =item * What machines support Perl? Where do I get it? | |
62 | ||
63 | =item * How can I get a binary version of Perl? | |
64 | ||
65 | =item * I don't have a C compiler on my system. How can I compile perl? | |
66 | ||
67 | =item * I copied the Perl binary from one machine to another, but scripts don't work. | |
68 | ||
69 | =item * I grabbed the sources and tried to compile but gdbm/dynamic loading/malloc/linking/... failed. How do I make it work? | |
70 | ||
71 | =item * What modules and extensions are available for Perl? What is CPAN? What does CPAN/src/... mean? | |
72 | ||
73 | =item * Is there an ISO or ANSI certified version of Perl? | |
74 | ||
75 | =item * Where can I get information on Perl? | |
76 | ||
77 | =item * What are the Perl newsgroups on USENET? Where do I post questions? | |
78 | ||
79 | =item * Where should I post source code? | |
80 | ||
81 | =item * Perl Books | |
82 | ||
83 | =item * Perl in Magazines | |
84 | ||
85 | =item * Perl on the Net: FTP and WWW Access | |
86 | ||
87 | =item * What mailing lists are there for perl? | |
88 | ||
89 | =item * Archives of comp.lang.perl.misc | |
90 | ||
91 | =item * Where can I buy a commercial version of Perl? | |
92 | ||
93 | =item * Where do I send bug reports? | |
94 | ||
95 | =item * What is perl.com? | |
96 | ||
97 | =back | |
98 | ||
99 | ||
68dc0745 | 100 | =item L<perlfaq3>: Programming Tools |
101 | ||
102 | Programmer tools and programming support. | |
103 | ||
65acb1b1 TC |
104 | =over 4 |
105 | ||
106 | =item * How do I do (anything)? | |
107 | ||
108 | =item * How can I use Perl interactively? | |
109 | ||
110 | =item * Is there a Perl shell? | |
111 | ||
112 | =item * How do I debug my Perl programs? | |
113 | ||
114 | =item * How do I profile my Perl programs? | |
115 | ||
116 | =item * How do I cross-reference my Perl programs? | |
117 | ||
118 | =item * Is there a pretty-printer (formatter) for Perl? | |
119 | ||
120 | =item * Is there a ctags for Perl? | |
121 | ||
122 | =item * Is there an IDE or Windows Perl Editor? | |
123 | ||
124 | =item * Where can I get Perl macros for vi? | |
125 | ||
126 | =item * Where can I get perl-mode for emacs? | |
127 | ||
128 | =item * How can I use curses with Perl? | |
129 | ||
130 | =item * How can I use X or Tk with Perl? | |
131 | ||
132 | =item * How can I generate simple menus without using CGI or Tk? | |
133 | ||
134 | =item * What is undump? | |
135 | ||
136 | =item * How can I make my Perl program run faster? | |
137 | ||
138 | =item * How can I make my Perl program take less memory? | |
139 | ||
140 | =item * Is it unsafe to return a pointer to local data? | |
141 | ||
142 | =item * How can I free an array or hash so my program shrinks? | |
143 | ||
144 | =item * How can I make my CGI script more efficient? | |
145 | ||
146 | =item * How can I hide the source for my Perl program? | |
147 | ||
148 | =item * How can I compile my Perl program into byte code or C? | |
149 | ||
150 | =item * How can I compile Perl into Java? | |
151 | ||
152 | =item * How can I get C<#!perl> to work on [MS-DOS,NT,...]? | |
153 | ||
154 | =item * Can I write useful perl programs on the command line? | |
155 | ||
156 | =item * Why don't perl one-liners work on my DOS/Mac/VMS system? | |
157 | ||
158 | =item * Where can I learn about CGI or Web programming in Perl? | |
159 | ||
160 | =item * Where can I learn about object-oriented Perl programming? | |
161 | ||
162 | =item * Where can I learn about linking C with Perl? [h2xs, xsubpp] | |
163 | ||
164 | =item * I've read perlembed, perlguts, etc., but I can't embed perl in | |
165 | my C program, what am I doing wrong? | |
166 | ||
167 | =item * When I tried to run my script, I got this message. What does it | |
168 | mean? | |
169 | ||
170 | =item * What's MakeMaker? | |
171 | ||
172 | =back | |
173 | ||
174 | ||
68dc0745 | 175 | =item L<perlfaq4>: Data Manipulation |
176 | ||
177 | Manipulating numbers, dates, strings, arrays, hashes, and | |
178 | miscellaneous data issues. | |
179 | ||
65acb1b1 TC |
180 | =over 4 |
181 | ||
182 | =item * Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)? | |
183 | ||
184 | =item * Why isn't my octal data interpreted correctly? | |
185 | ||
186 | =item * Does Perl have a round() function? What about ceil() and floor()? Trig functions? | |
187 | ||
188 | =item * How do I convert bits into ints? | |
189 | ||
190 | =item * Why doesn't & work the way I want it to? | |
191 | ||
192 | =item * How do I multiply matrices? | |
193 | ||
194 | =item * How do I perform an operation on a series of integers? | |
195 | ||
196 | =item * How can I output Roman numerals? | |
197 | ||
198 | =item * Why aren't my random numbers random? | |
199 | ||
200 | =item * How do I find the week-of-the-year/day-of-the-year? | |
201 | ||
d92eb7b0 GS |
202 | =item * How do I find the current century or millennium? |
203 | ||
65acb1b1 TC |
204 | =item * How can I compare two dates and find the difference? |
205 | ||
206 | =item * How can I take a string and turn it into epoch seconds? | |
207 | ||
208 | =item * How can I find the Julian Day? | |
209 | ||
210 | =item * How do I find yesterday's date? | |
211 | ||
212 | =item * Does Perl have a year 2000 problem? Is Perl Y2K compliant? | |
213 | ||
214 | =item * How do I validate input? | |
215 | ||
216 | =item * How do I unescape a string? | |
217 | ||
218 | =item * How do I remove consecutive pairs of characters? | |
219 | ||
220 | =item * How do I expand function calls in a string? | |
221 | ||
222 | =item * How do I find matching/nesting anything? | |
223 | ||
224 | =item * How do I reverse a string? | |
225 | ||
226 | =item * How do I expand tabs in a string? | |
227 | ||
228 | =item * How do I reformat a paragraph? | |
229 | ||
230 | =item * How can I access/change the first N letters of a string? | |
231 | ||
232 | =item * How do I change the Nth occurrence of something? | |
233 | ||
234 | =item * How can I count the number of occurrences of a substring within a string? | |
235 | ||
236 | =item * How do I capitalize all the words on one line? | |
237 | ||
238 | =item * How can I split a [character] delimited string except when inside | |
239 | [character]? (Comma-separated files) | |
240 | ||
241 | =item * How do I strip blank space from the beginning/end of a string? | |
242 | ||
243 | =item * How do I pad a string with blanks or pad a number with zeroes? | |
244 | ||
245 | =item * How do I extract selected columns from a string? | |
246 | ||
247 | =item * How do I find the soundex value of a string? | |
248 | ||
249 | =item * How can I expand variables in text strings? | |
250 | ||
251 | =item * What's wrong with always quoting "$vars"? | |
252 | ||
c47ff5f1 | 253 | =item * Why don't my <<HERE documents work? |
65acb1b1 TC |
254 | |
255 | =item * What is the difference between a list and an array? | |
256 | ||
257 | =item * What is the difference between $array[1] and @array[1]? | |
258 | ||
d92eb7b0 | 259 | =item * How can I remove duplicate elements from a list or array? |
65acb1b1 TC |
260 | |
261 | =item * How can I tell whether a list or array contains a certain element? | |
262 | ||
263 | =item * How do I compute the difference of two arrays? How do I compute the intersection of two arrays? | |
264 | ||
265 | =item * How do I test whether two arrays or hashes are equal? | |
266 | ||
267 | =item * How do I find the first array element for which a condition is true? | |
268 | ||
269 | =item * How do I handle linked lists? | |
270 | ||
271 | =item * How do I handle circular lists? | |
272 | ||
273 | =item * How do I shuffle an array randomly? | |
274 | ||
275 | =item * How do I process/modify each element of an array? | |
276 | ||
277 | =item * How do I select a random element from an array? | |
278 | ||
279 | =item * How do I permute N elements of a list? | |
280 | ||
281 | =item * How do I sort an array by (anything)? | |
282 | ||
283 | =item * How do I manipulate arrays of bits? | |
284 | ||
285 | =item * Why does defined() return true on empty arrays and hashes? | |
286 | ||
287 | =item * How do I process an entire hash? | |
288 | ||
289 | =item * What happens if I add or remove keys from a hash while iterating over it? | |
290 | ||
291 | =item * How do I look up a hash element by value? | |
292 | ||
293 | =item * How can I know how many entries are in a hash? | |
294 | ||
295 | =item * How do I sort a hash (optionally by value instead of key)? | |
296 | ||
297 | =item * How can I always keep my hash sorted? | |
298 | ||
299 | =item * What's the difference between "delete" and "undef" with hashes? | |
300 | ||
301 | =item * Why don't my tied hashes make the defined/exists distinction? | |
302 | ||
303 | =item * How do I reset an each() operation part-way through? | |
304 | ||
305 | =item * How can I get the unique keys from two hashes? | |
306 | ||
307 | =item * How can I store a multidimensional array in a DBM file? | |
308 | ||
309 | =item * How can I make my hash remember the order I put elements into it? | |
310 | ||
311 | =item * Why does passing a subroutine an undefined element in a hash create it? | |
312 | ||
313 | =item * How can I make the Perl equivalent of a C structure/C++ class/hash or array of hashes or arrays? | |
314 | ||
315 | =item * How can I use a reference as a hash key? | |
316 | ||
317 | =item * How do I handle binary data correctly? | |
318 | ||
319 | =item * How do I determine whether a scalar is a number/whole/integer/float? | |
320 | ||
321 | =item * How do I keep persistent data across program calls? | |
322 | ||
323 | =item * How do I print out or copy a recursive data structure? | |
324 | ||
325 | =item * How do I define methods for every class/object? | |
326 | ||
327 | =item * How do I verify a credit card checksum? | |
328 | ||
329 | =item * How do I pack arrays of doubles or floats for XS code? | |
330 | ||
331 | =back | |
332 | ||
333 | ||
68dc0745 | 334 | =item L<perlfaq5>: Files and Formats |
335 | ||
336 | I/O and the "f" issues: filehandles, flushing, formats and footers. | |
337 | ||
65acb1b1 TC |
338 | =over 4 |
339 | ||
340 | =item * How do I flush/unbuffer an output filehandle? Why must I do this? | |
341 | ||
342 | =item * How do I change one line in a file/delete a line in a file/insert a line in the middle of a file/append to the beginning of a file? | |
343 | ||
344 | =item * How do I count the number of lines in a file? | |
345 | ||
346 | =item * How do I make a temporary file name? | |
347 | ||
348 | =item * How can I manipulate fixed-record-length files? | |
349 | ||
350 | =item * How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles? | |
351 | ||
352 | =item * How can I use a filehandle indirectly? | |
353 | ||
354 | =item * How can I set up a footer format to be used with write()? | |
355 | ||
356 | =item * How can I write() into a string? | |
357 | ||
358 | =item * How can I output my numbers with commas added? | |
359 | ||
360 | =item * How can I translate tildes (~) in a filename? | |
361 | ||
362 | =item * How come when I open a file read-write it wipes it out? | |
363 | ||
c47ff5f1 | 364 | =item * Why do I sometimes get an "Argument list too long" when I use <*>? |
65acb1b1 TC |
365 | |
366 | =item * Is there a leak/bug in glob()? | |
367 | ||
c47ff5f1 | 368 | =item * How can I open a file with a leading ">" or trailing blanks? |
65acb1b1 TC |
369 | |
370 | =item * How can I reliably rename a file? | |
371 | ||
372 | =item * How can I lock a file? | |
373 | ||
374 | =item * Why can't I just open(FH, ">file.lock")? | |
375 | ||
376 | =item * I still don't get locking. I just want to increment the number in the file. How can I do this? | |
377 | ||
378 | =item * How do I randomly update a binary file? | |
379 | ||
380 | =item * How do I get a file's timestamp in perl? | |
381 | ||
382 | =item * How do I set a file's timestamp in perl? | |
383 | ||
384 | =item * How do I print to more than one file at once? | |
385 | ||
d92eb7b0 GS |
386 | =item * How can I read in an entire file all at once? |
387 | ||
65acb1b1 TC |
388 | =item * How can I read in a file by paragraphs? |
389 | ||
390 | =item * How can I read a single character from a file? From the keyboard? | |
391 | ||
392 | =item * How can I tell whether there's a character waiting on a filehandle? | |
393 | ||
394 | =item * How do I do a C<tail -f> in perl? | |
395 | ||
396 | =item * How do I dup() a filehandle in Perl? | |
397 | ||
398 | =item * How do I close a file descriptor by number? | |
399 | ||
400 | =item * Why can't I use "C:\temp\foo" in DOS paths? What doesn't `C:\temp\foo.exe` work? | |
401 | ||
402 | =item * Why doesn't glob("*.*") get all the files? | |
403 | ||
404 | =item * Why does Perl let me delete read-only files? Why does C<-i> clobber protected files? Isn't this a bug in Perl? | |
405 | ||
406 | =item * How do I select a random line from a file? | |
407 | ||
408 | =item * Why do I get weird spaces when I print an array of lines? | |
409 | ||
410 | =back | |
411 | ||
412 | ||
68dc0745 | 413 | =item L<perlfaq6>: Regexps |
414 | ||
415 | Pattern matching and regular expressions. | |
416 | ||
65acb1b1 TC |
417 | =over 4 |
418 | ||
419 | =item * How can I hope to use regular expressions without creating illegible and unmaintainable code? | |
420 | ||
421 | =item * I'm having trouble matching over more than one line. What's wrong? | |
422 | ||
423 | =item * How can I pull out lines between two patterns that are themselves on different lines? | |
424 | ||
425 | =item * I put a regular expression into $/ but it didn't work. What's wrong? | |
426 | ||
427 | =item * How do I substitute case insensitively on the LHS, but preserving case on the RHS? | |
428 | ||
429 | =item * How can I make C<\w> match national character sets? | |
430 | ||
431 | =item * How can I match a locale-smart version of C</[a-zA-Z]/>? | |
432 | ||
d92eb7b0 | 433 | =item * How can I quote a variable to use in a regex? |
65acb1b1 TC |
434 | |
435 | =item * What is C</o> really for? | |
436 | ||
437 | =item * How do I use a regular expression to strip C style comments from a file? | |
438 | ||
439 | =item * Can I use Perl regular expressions to match balanced text? | |
440 | ||
d92eb7b0 | 441 | =item * What does it mean that regexes are greedy? How can I get around it? |
65acb1b1 TC |
442 | |
443 | =item * How do I process each word on each line? | |
444 | ||
445 | =item * How can I print out a word-frequency or line-frequency summary? | |
446 | ||
447 | =item * How can I do approximate matching? | |
448 | ||
449 | =item * How do I efficiently match many regular expressions at once? | |
450 | ||
451 | =item * Why don't word-boundary searches with C<\b> work for me? | |
452 | ||
453 | =item * Why does using $&, $`, or $' slow my program down? | |
454 | ||
455 | =item * What good is C<\G> in a regular expression? | |
456 | ||
d92eb7b0 | 457 | =item * Are Perl regexes DFAs or NFAs? Are they POSIX compliant? |
65acb1b1 TC |
458 | |
459 | =item * What's wrong with using grep or map in a void context? | |
460 | ||
461 | =item * How can I match strings with multibyte characters? | |
462 | ||
463 | =item * How do I match a pattern that is supplied by the user? | |
464 | ||
465 | =back | |
466 | ||
467 | ||
68dc0745 | 468 | =item L<perlfaq7>: General Perl Language Issues |
469 | ||
470 | General Perl language issues that don't clearly fit into any of the | |
471 | other sections. | |
472 | ||
65acb1b1 TC |
473 | =over 4 |
474 | ||
475 | =item * Can I get a BNF/yacc/RE for the Perl language? | |
476 | ||
d92eb7b0 | 477 | =item * What are all these $@%&* punctuation signs, and how do I know when to use them? |
65acb1b1 TC |
478 | |
479 | =item * Do I always/never have to quote my strings or use semicolons and commas? | |
480 | ||
481 | =item * How do I skip some return values? | |
482 | ||
483 | =item * How do I temporarily block warnings? | |
484 | ||
485 | =item * What's an extension? | |
486 | ||
487 | =item * Why do Perl operators have different precedence than C operators? | |
488 | ||
489 | =item * How do I declare/create a structure? | |
490 | ||
491 | =item * How do I create a module? | |
492 | ||
493 | =item * How do I create a class? | |
494 | ||
495 | =item * How can I tell if a variable is tainted? | |
496 | ||
497 | =item * What's a closure? | |
498 | ||
499 | =item * What is variable suicide and how can I prevent it? | |
500 | ||
d92eb7b0 | 501 | =item * How can I pass/return a {Function, FileHandle, Array, Hash, Method, Regex}? |
65acb1b1 TC |
502 | |
503 | =item * How do I create a static variable? | |
504 | ||
505 | =item * What's the difference between dynamic and lexical (static) scoping? Between local() and my()? | |
506 | ||
507 | =item * How can I access a dynamic variable while a similarly named lexical is in scope? | |
508 | ||
509 | =item * What's the difference between deep and shallow binding? | |
510 | ||
c47ff5f1 | 511 | =item * Why doesn't "my($foo) = <FILE>;" work right? |
65acb1b1 TC |
512 | |
513 | =item * How do I redefine a builtin function, operator, or method? | |
514 | ||
515 | =item * What's the difference between calling a function as &foo and foo()? | |
516 | ||
517 | =item * How do I create a switch or case statement? | |
518 | ||
519 | =item * How can I catch accesses to undefined variables/functions/methods? | |
520 | ||
521 | =item * Why can't a method included in this same file be found? | |
522 | ||
523 | =item * How can I find out my current package? | |
524 | ||
525 | =item * How can I comment out a large block of perl code? | |
526 | ||
527 | =item * How do I clear a package? | |
528 | ||
d92eb7b0 GS |
529 | =item * How can I use a variable as a variable name? |
530 | ||
65acb1b1 TC |
531 | =back |
532 | ||
533 | ||
68dc0745 | 534 | =item L<perlfaq8>: System Interaction |
535 | ||
536 | Interprocess communication (IPC), control over the user-interface | |
537 | (keyboard, screen and pointing devices). | |
538 | ||
65acb1b1 TC |
539 | =over 4 |
540 | ||
541 | =item * How do I find out which operating system I'm running under? | |
542 | ||
543 | =item * How come exec() doesn't return? | |
544 | ||
545 | =item * How do I do fancy stuff with the keyboard/screen/mouse? | |
546 | ||
547 | =item * How do I print something out in color? | |
548 | ||
549 | =item * How do I read just one key without waiting for a return key? | |
550 | ||
551 | =item * How do I check whether input is ready on the keyboard? | |
552 | ||
553 | =item * How do I clear the screen? | |
554 | ||
555 | =item * How do I get the screen size? | |
556 | ||
557 | =item * How do I ask the user for a password? | |
558 | ||
559 | =item * How do I read and write the serial port? | |
560 | ||
561 | =item * How do I decode encrypted password files? | |
562 | ||
563 | =item * How do I start a process in the background? | |
564 | ||
565 | =item * How do I trap control characters/signals? | |
566 | ||
567 | =item * How do I modify the shadow password file on a Unix system? | |
568 | ||
569 | =item * How do I set the time and date? | |
570 | ||
571 | =item * How can I sleep() or alarm() for under a second? | |
572 | ||
573 | =item * How can I measure time under a second? | |
574 | ||
575 | =item * How can I do an atexit() or setjmp()/longjmp()? (Exception handling) | |
576 | ||
577 | =item * Why doesn't my sockets program work under System V (Solaris)? What does the error message "Protocol not supported" mean? | |
578 | ||
579 | =item * How can I call my system's unique C functions from Perl? | |
580 | ||
581 | =item * Where do I get the include files to do ioctl() or syscall()? | |
582 | ||
583 | =item * Why do setuid perl scripts complain about kernel problems? | |
584 | ||
585 | =item * How can I open a pipe both to and from a command? | |
586 | ||
587 | =item * Why can't I get the output of a command with system()? | |
588 | ||
589 | =item * How can I capture STDERR from an external command? | |
590 | ||
591 | =item * Why doesn't open() return an error when a pipe open fails? | |
592 | ||
593 | =item * What's wrong with using backticks in a void context? | |
594 | ||
595 | =item * How can I call backticks without shell processing? | |
596 | ||
597 | =item * Why can't my script read from STDIN after I gave it EOF (^D on Unix, ^Z on MS-DOS)? | |
598 | ||
599 | =item * How can I convert my shell script to perl? | |
600 | ||
601 | =item * Can I use perl to run a telnet or ftp session? | |
602 | ||
603 | =item * How can I write expect in Perl? | |
604 | ||
605 | =item * Is there a way to hide perl's command line from programs such as "ps"? | |
606 | ||
607 | =item * I {changed directory, modified my environment} in a perl script. How come the change disappeared when I exited the script? How do I get my changes to be visible? | |
608 | ||
609 | =item * How do I close a process's filehandle without waiting for it to complete? | |
610 | ||
611 | =item * How do I fork a daemon process? | |
612 | ||
613 | =item * How do I make my program run with sh and csh? | |
614 | ||
615 | =item * How do I find out if I'm running interactively or not? | |
616 | ||
617 | =item * How do I timeout a slow event? | |
618 | ||
619 | =item * How do I set CPU limits? | |
620 | ||
621 | =item * How do I avoid zombies on a Unix system? | |
622 | ||
623 | =item * How do I use an SQL database? | |
624 | ||
625 | =item * How do I make a system() exit on control-C? | |
626 | ||
627 | =item * How do I open a file without blocking? | |
628 | ||
d92eb7b0 | 629 | =item * How do I install a module from CPAN? |
65acb1b1 TC |
630 | |
631 | =item * What's the difference between require and use? | |
632 | ||
633 | =item * How do I keep my own module/library directory? | |
634 | ||
635 | =item * How do I add the directory my program lives in to the module/library search path? | |
636 | ||
637 | =item * How do I add a directory to my include path at runtime? | |
638 | ||
639 | =item * What is socket.ph and where do I get it? | |
640 | ||
641 | =back | |
642 | ||
643 | ||
68dc0745 | 644 | =item L<perlfaq9>: Networking |
645 | ||
646 | Networking, the Internet, and a few on the web. | |
647 | ||
65acb1b1 TC |
648 | =over 4 |
649 | ||
650 | =item * My CGI script runs from the command line but not the browser. (500 Server Error) | |
651 | ||
652 | =item * How can I get better error messages from a CGI program? | |
653 | ||
654 | =item * How do I remove HTML from a string? | |
655 | ||
656 | =item * How do I extract URLs? | |
657 | ||
658 | =item * How do I download a file from the user's machine? How do I open a file on another machine? | |
659 | ||
660 | =item * How do I make a pop-up menu in HTML? | |
661 | ||
662 | =item * How do I fetch an HTML file? | |
663 | ||
664 | =item * How do I automate an HTML form submission? | |
665 | ||
666 | =item * How do I decode or create those %-encodings on the web? | |
667 | ||
668 | =item * How do I redirect to another page? | |
669 | ||
670 | =item * How do I put a password on my web pages? | |
671 | ||
672 | =item * How do I edit my .htpasswd and .htgroup files with Perl? | |
673 | ||
674 | =item * How do I make sure users can't enter values into a form that cause my CGI script to do bad things? | |
675 | ||
676 | =item * How do I parse a mail header? | |
677 | ||
678 | =item * How do I decode a CGI form? | |
679 | ||
680 | =item * How do I check a valid mail address? | |
681 | ||
682 | =item * How do I decode a MIME/BASE64 string? | |
683 | ||
684 | =item * How do I return the user's mail address? | |
685 | ||
686 | =item * How do I send mail? | |
687 | ||
688 | =item * How do I read mail? | |
689 | ||
690 | =item * How do I find out my hostname/domainname/IP address? | |
691 | ||
692 | =item * How do I fetch a news article or the active newsgroups? | |
693 | ||
694 | =item * How do I fetch/put an FTP file? | |
695 | ||
696 | =item * How can I do RPC in Perl? | |
697 | ||
698 | =back | |
699 | ||
700 | ||
68dc0745 | 701 | =back |
702 | ||
703 | =head2 Where to get this document | |
704 | ||
705 | This document is posted regularly to comp.lang.perl.announce and | |
706 | several other related newsgroups. It is available in a variety of | |
707 | formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web | |
708 | at http://www.perl.com/perl/faq/ . | |
709 | ||
710 | =head2 How to contribute to this document | |
711 | ||
712 | You may mail corrections, additions, and suggestions to | |
c8db1d39 TC |
713 | perlfaq-suggestions@perl.com . This alias should not be |
714 | used to I<ask> FAQs. It's for fixing the current FAQ. | |
65acb1b1 | 715 | Send questions to the comp.lang.perl.misc newsgroup. |
68dc0745 | 716 | |
717 | =head2 What will happen if you mail your Perl programming problems to the authors | |
718 | ||
719 | Your questions will probably go unread, unless they're suggestions of | |
720 | new questions to add to the FAQ, in which case they should have gone | |
721 | to the perlfaq-suggestions@perl.com instead. | |
722 | ||
723 | You should have read section 2 of this faq. There you would have | |
724 | learned that comp.lang.perl.misc is the appropriate place to go for | |
725 | free advice. If your question is really important and you require a | |
726 | prompt and correct answer, you should hire a consultant. | |
727 | ||
728 | =head1 Credits | |
729 | ||
730 | When I first began the Perl FAQ in the late 80s, I never realized it | |
731 | would have grown to over a hundred pages, nor that Perl would ever become | |
732 | so popular and widespread. This document could not have been written | |
733 | without the tremendous help provided by Larry Wall and the rest of the | |
734 | Perl Porters. | |
735 | ||
736 | =head1 Author and Copyright Information | |
737 | ||
65acb1b1 | 738 | Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington. |
68dc0745 | 739 | All rights reserved. |
740 | ||
c8db1d39 | 741 | =head2 Bundled Distributions |
68dc0745 | 742 | |
c8db1d39 TC |
743 | When included as part of the Standard Version of Perl, or as part of |
744 | its complete documentation whether printed or otherwise, this work | |
745 | may be distributed only under the terms of Perl's Artistic License. | |
746 | Any distribution of this file or derivatives thereof I<outside> | |
747 | of that package require that special arrangements be made with | |
748 | copyright holder. | |
68dc0745 | 749 | |
c8db1d39 TC |
750 | Irrespective of its distribution, all code examples in these files |
751 | are hereby placed into the public domain. You are permitted and | |
752 | encouraged to use this code in your own programs for fun | |
753 | or for profit as you see fit. A simple comment in the code giving | |
754 | credit would be courteous but is not required. | |
68dc0745 | 755 | |
756 | =head2 Disclaimer | |
757 | ||
758 | This information is offered in good faith and in the hope that it may | |
759 | be of use, but is not guaranteed to be correct, up to date, or suitable | |
760 | for any particular purpose whatsoever. The authors accept no liability | |
761 | in respect of this information or its use. | |
762 | ||
763 | =head1 Changes | |
764 | ||
765 | =over 4 | |
766 | ||
d92eb7b0 GS |
767 | =item 23/May/99 |
768 | ||
87275199 | 769 | Extensive updates from the net in preparation for 5.6 release. |
d92eb7b0 GS |
770 | |
771 | =item 13/April/99 | |
772 | ||
773 | More minor touch-ups. Added new question at the end | |
774 | of perlfaq7 on variable names within variables. | |
775 | ||
65acb1b1 TC |
776 | =item 7/January/99 |
777 | ||
778 | Small touchups here and there. Added all questions in this | |
779 | document as a sort of table of contents. | |
780 | ||
707102d0 | 781 | =item 22/June/98 |
c8db1d39 TC |
782 | |
783 | Significant changes throughout in preparation for the 5.005 | |
784 | release. | |
785 | ||
fc36a67e | 786 | =item 24/April/97 |
787 | ||
788 | Style and whitespace changes from Chip, new question on reading one | |
789 | character at a time from a terminal using POSIX from Tom. | |
790 | ||
46fc3d4c | 791 | =item 23/April/97 |
792 | ||
793 | Added http://www.oasis.leo.org/perl/ to L<perlfaq2>. Style fix to | |
794 | L<perlfaq3>. Added floating point precision, fixed complex number | |
795 | arithmetic, cross-references, caveat for Text::Wrap, alternative | |
796 | answer for initial capitalizing, fixed incorrect regexp, added example | |
797 | of Tie::IxHash to L<perlfaq4>. Added example of passing and storing | |
798 | filehandles, added commify to L<perlfaq5>. Restored variable suicide, | |
799 | and added mass commenting to L<perlfaq7>. Added Net::Telnet, fixed | |
800 | backticks, added reader/writer pair to telnet question, added FindBin, | |
801 | grouped module questions together in L<perlfaq8>. Expanded caveats | |
802 | for the simple URL extractor, gave LWP example, added CGI security | |
5a964f20 | 803 | question, expanded on the mail address answer in L<perlfaq9>. |
46fc3d4c | 804 | |
3fe9a6f1 | 805 | =item 25/March/97 |
806 | ||
807 | Added more info to the binary distribution section of L<perlfaq2>. | |
808 | Added Net::Telnet to L<perlfaq6>. Fixed typos in L<perlfaq8>. Added | |
809 | mail sending example to L<perlfaq9>. Added Merlyn's columns to | |
810 | L<perlfaq2>. | |
811 | ||
46fc3d4c | 812 | =item 18/March/97 |
3fe9a6f1 | 813 | |
814 | Added the DATE to the NAME section, indicating which sections have | |
815 | changed. | |
816 | ||
817 | Mentioned SIGPIPE and L<perlipc> in the forking open answer in | |
818 | L<perlfaq8>. | |
819 | ||
820 | Fixed description of a regular expression in L<perlfaq4>. | |
821 | ||
68dc0745 | 822 | =item 17/March/97 Version |
823 | ||
824 | Various typos fixed throughout. | |
825 | ||
826 | Added new question on Perl BNF on L<perlfaq7>. | |
827 | ||
828 | =item Initial Release: 11/March/97 | |
829 | ||
830 | This is the initial release of version 3 of the FAQ; consequently there | |
831 | have been no changes since its initial release. | |
832 | ||
833 | =back |