3 perlport - Writing portable Perl
7 Perl runs on numerous operating systems. While most of them share
8 much in common, they also have their own unique features.
10 This document is meant to help you to find out what constitutes portable
11 Perl code. That way once you make a decision to write portably,
12 you know where the lines are drawn, and you can stay within them.
14 There is a tradeoff between taking full advantage of one particular
15 type of computer and taking advantage of a full range of them.
16 Naturally, as you broaden your range and become more diverse, the
17 common factors drop, and you are left with an increasingly smaller
18 area of common ground in which you can operate to accomplish a
19 particular task. Thus, when you begin attacking a problem, it is
20 important to consider under which part of the tradeoff curve you
21 want to operate. Specifically, you must decide whether it is
22 important that the task that you are coding have the full generality
23 of being portable, or whether to just get the job done right now.
24 This is the hardest choice to be made. The rest is easy, because
25 Perl provides many choices, whichever way you want to approach your
28 Looking at it another way, writing portable code is usually about
29 willfully limiting your available choices. Naturally, it takes
30 discipline and sacrifice to do that. The product of portability
31 and convenience may be a constant. You have been warned.
33 Be aware of two important points:
37 =item Not all Perl programs have to be portable
39 There is no reason you should not use Perl as a language to glue Unix
40 tools together, or to prototype a Macintosh application, or to manage the
41 Windows registry. If it makes no sense to aim for portability for one
42 reason or another in a given program, then don't bother.
44 =item Nearly all of Perl already I<is> portable
46 Don't be fooled into thinking that it is hard to create portable Perl
47 code. It isn't. Perl tries its level-best to bridge the gaps between
48 what's available on different platforms, and all the means available to
49 use those features. Thus almost all Perl code runs on any machine
50 without modification. But there are some significant issues in
51 writing portable code, and this document is entirely about those issues.
55 Here's the general rule: When you approach a task commonly done
56 using a whole range of platforms, think about writing portable
57 code. That way, you don't sacrifice much by way of the implementation
58 choices you can avail yourself of, and at the same time you can give
59 your users lots of platform choices. On the other hand, when you have to
60 take advantage of some unique feature of a particular platform, as is
61 often the case with systems programming (whether for Unix, Windows,
62 S<Mac OS>, VMS, etc.), consider writing platform-specific code.
64 When the code will run on only two or three operating systems, you
65 may need to consider only the differences of those particular systems.
66 The important thing is to decide where the code will run and to be
67 deliberate in your decision.
69 The material below is separated into three main sections: main issues of
70 portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and
71 built-in perl functions that behave differently on various ports
72 (L<"FUNCTION IMPLEMENTATIONS">.
74 This information should not be considered complete; it includes possibly
75 transient information about idiosyncrasies of some of the ports, almost
76 all of which are in a state of constant evolution. Thus, this material
77 should be considered a perpetual work in progress
78 (<IMG SRC="yellow_sign.gif" ALT="Under Construction">).
84 In most operating systems, lines in files are terminated by newlines.
85 Just what is used as a newline may vary from OS to OS. Unix
86 traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>,
87 and S<Mac OS> uses C<\015>.
89 Perl uses C<\n> to represent the "logical" newline, where what is
90 logical may depend on the platform in use. In MacPerl, C<\n> always
91 means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
92 when accessing a file in "text" mode, STDIO translates it to (or
93 from) C<\015\012>, depending on whether you're reading or writing.
94 Unix does the same thing on ttys in canonical mode. C<\015\012>
95 is commonly referred to as CRLF.
97 A common cause of unportable programs is the misuse of chop() to trim
107 You can get away with this on Unix and MacOS (they have a single
108 character end-of-line), but the same program will break under DOSish
109 perls because you're only chop()ing half the end-of-line. Instead,
110 chomp() should be used to trim newlines. The Dunce::Files module can
111 help audit your code for misuses of chop().
113 When dealing with binary files (or text files in binary mode) be sure
114 to explicitly set $/ to the appropriate value for your file format
115 before using chomp().
117 Because of the "text" mode translation, DOSish perls have limitations
118 in using C<seek> and C<tell> on a file accessed in "text" mode.
119 Stick to C<seek>-ing to locations you got from C<tell> (and no
120 others), and you are usually free to use C<seek> and C<tell> even
121 in "text" mode. Using C<seek> or C<tell> or other file operations
122 may be non-portable. If you use C<binmode> on a file, however, you
123 can usually C<seek> and C<tell> with arbitrary values in safety.
125 A common misconception in socket programming is that C<\n> eq C<\012>
126 everywhere. When using protocols such as common Internet protocols,
127 C<\012> and C<\015> are called for specifically, and the values of
128 the logical C<\n> and C<\r> (carriage return) are not reliable.
130 print SOCKET "Hi there, client!\r\n"; # WRONG
131 print SOCKET "Hi there, client!\015\012"; # RIGHT
133 However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
134 and unsightly, as well as confusing to those maintaining the code. As
135 such, the Socket module supplies the Right Thing for those who want it.
137 use Socket qw(:DEFAULT :crlf);
138 print SOCKET "Hi there, client!$CRLF" # RIGHT
140 When reading from a socket, remember that the default input record
141 separator C<$/> is C<\n>, but robust socket code will recognize as
142 either C<\012> or C<\015\012> as end of line:
148 Because both CRLF and LF end in LF, the input record separator can
149 be set to LF and any CR stripped later. Better to write:
151 use Socket qw(:DEFAULT :crlf);
152 local($/) = LF; # not needed if $/ is already \012
155 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
156 # s/\015?\012/\n/; # same thing
159 This example is preferred over the previous one--even for Unix
160 platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
161 (and there was much rejoicing).
163 Similarly, functions that return text data--such as a function that
164 fetches a web page--should sometimes translate newlines before
165 returning the data, if they've not yet been translated to the local
166 newline representation. A single line of code will often suffice:
168 $data =~ s/\015?\012/\n/g;
171 Some of this may be confusing. Here's a handy reference to the ASCII CR
172 and LF characters. You can print it out and stick it in your wallet.
174 LF == \012 == \x0A == \cJ == ASCII 10
175 CR == \015 == \x0D == \cM == ASCII 13
178 ---------------------------
181 \n * | LF | CRLF | CR |
182 \r * | CR | CR | LF |
183 ---------------------------
186 The Unix column assumes that you are not accessing a serial line
187 (like a tty) in canonical mode. If you are, then CR on input becomes
188 "\n", and "\n" on output becomes CRLF.
190 These are just the most common definitions of C<\n> and C<\r> in Perl.
191 There may well be others.
193 =head2 Numbers endianness and Width
195 Different CPUs store integers and floating point numbers in different
196 orders (called I<endianness>) and widths (32-bit and 64-bit being the
197 most common today). This affects your programs when they attempt to transfer
198 numbers in binary format from one CPU architecture to another,
199 usually either "live" via network connection, or by storing the
200 numbers to secondary storage such as a disk file or tape.
202 Conflicting storage orders make utter mess out of the numbers. If a
203 little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
204 decimal), a big-endian host (Motorola, Sparc, PA) reads it as
205 0x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
206 Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
207 them in big-endian mode. To avoid this problem in network (socket)
208 connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
209 "network" orders. These are guaranteed to be portable.
211 You can explore the endianness of your platform by unpacking a
212 data structure packed in native format such as:
214 print unpack("h*", pack("s2", 1, 2)), "\n";
215 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
216 # '00100020' on e.g. Motorola 68040
218 If you need to distinguish between endian architectures you could use
219 either of the variables set like so:
221 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
222 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
224 Differing widths can cause truncation even between platforms of equal
225 endianness. The platform of shorter width loses the upper parts of the
226 number. There is no good solution for this problem except to avoid
227 transferring or storing raw binary numbers.
229 One can circumnavigate both these problems in two ways. Either
230 transfer and store numbers always in text format, instead of raw
231 binary, or else consider using modules like Data::Dumper (included in
232 the standard distribution as of Perl 5.005) and Storable (included as
233 of perl 5.8). Keeping all data as text significantly simplifies matters.
235 =head2 Files and Filesystems
237 Most platforms these days structure files in a hierarchical fashion.
238 So, it is reasonably safe to assume that all platforms support the
239 notion of a "path" to uniquely identify a file on the system. How
240 that path is really written, though, differs considerably.
242 Although similar, file path specifications differ between Unix,
243 Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
244 Unix, for example, is one of the few OSes that has the elegant idea
245 of a single root directory.
247 DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
248 as path separator, or in their own idiosyncratic ways (such as having
249 several root directories and various "unrooted" device files such NIL:
252 S<Mac OS> uses C<:> as a path separator instead of C</>.
254 The filesystem may support neither hard links (C<link>) nor
255 symbolic links (C<symlink>, C<readlink>, C<lstat>).
257 The filesystem may support neither access timestamp nor change
258 timestamp (meaning that about the only portable timestamp is the
259 modification timestamp), or one second granularity of any timestamps
260 (e.g. the FAT filesystem limits the time granularity to two seconds).
262 VOS perl can emulate Unix filenames with C</> as path separator. The
263 native pathname characters greater-than, less-than, number-sign, and
264 percent-sign are always accepted.
266 S<RISC OS> perl can emulate Unix filenames with C</> as path
267 separator, or go native and use C<.> for path separator and C<:> to
268 signal filesystems and disk names.
270 Don't assume UNIX filesystem access semantics: that read, write,
271 and execute are all the permissions there are, and even if they exist,
272 that their semantics (for example what do r, w, and x mean on
273 a directory) are the UNIX ones. The various UNIX/POSIX compatibility
274 layers usually try to make interfaces like chmod() work, but sometimes
275 there simply is no good mapping.
277 If all this is intimidating, have no (well, maybe only a little)
278 fear. There are modules that can help. The File::Spec modules
279 provide methods to do the Right Thing on whatever platform happens
280 to be running the program.
282 use File::Spec::Functions;
283 chdir(updir()); # go up one directory
284 $file = catfile(curdir(), 'temp', 'file.txt');
285 # on Unix and Win32, './temp/file.txt'
286 # on Mac OS, ':temp:file.txt'
287 # on VMS, '[.temp]file.txt'
289 File::Spec is available in the standard distribution as of version
290 5.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
291 and some versions of perl come with version 0.6. If File::Spec
292 is not updated to 0.7 or later, you must use the object-oriented
293 interface from File::Spec (or upgrade File::Spec).
295 In general, production code should not have file paths hardcoded.
296 Making them user-supplied or read from a configuration file is
297 better, keeping in mind that file path syntax varies on different
300 This is especially noticeable in scripts like Makefiles and test suites,
301 which often assume C</> as a path separator for subdirectories.
303 Also of use is File::Basename from the standard distribution, which
304 splits a pathname into pieces (base filename, full path to directory,
307 Even when on a single platform (if you can call Unix a single platform),
308 remember not to count on the existence or the contents of particular
309 system-specific files or directories, like F</etc/passwd>,
310 F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
311 example, F</etc/passwd> may exist but not contain the encrypted
312 passwords, because the system is using some form of enhanced security.
313 Or it may not contain all the accounts, because the system is using NIS.
314 If code does need to rely on such a file, include a description of the
315 file and its format in the code's documentation, then make it easy for
316 the user to override the default location of the file.
318 Don't assume a text file will end with a newline. They should,
321 Do not have two files or directories of the same name with different
322 case, like F<test.pl> and F<Test.pl>, as many platforms have
323 case-insensitive (or at least case-forgiving) filenames. Also, try
324 not to have non-word characters (except for C<.>) in the names, and
325 keep them to the 8.3 convention, for maximum portability, onerous a
326 burden though this may appear.
328 Likewise, when using the AutoSplit module, try to keep your functions to
329 8.3 naming and case-insensitive conventions; or, at the least,
330 make it so the resulting files have a unique (case-insensitively)
333 Whitespace in filenames is tolerated on most systems, but not all,
334 and even on systems where it might be tolerated, some utilities
335 might becoem confused by such whitespace.
337 Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
339 Don't assume C<< > >> won't be the first character of a filename.
340 Always use C<< < >> explicitly to open a file for reading,
341 unless you want the user to be able to specify a pipe open.
343 open(FILE, "< $existing_file") or die $!;
345 If filenames might use strange characters, it is safest to open it
346 with C<sysopen> instead of C<open>. C<open> is magic and can
347 translate characters like C<< > >>, C<< < >>, and C<|>, which may
348 be the wrong thing to do. (Sometimes, though, it's the right thing.)
350 Don't use C<:> as a part of a filename since many systems use that for
351 their own semantics (MacOS Classic for separating pathname components,
352 many networking schemes and utilities for separating the nodename and
353 the pathname, and so on).
355 The I<portable filename characters> as defined by ANSI C are
357 a b c d e f g h i j k l m n o p q r t u v w x y z
358 A B C D E F G H I J K L M N O P Q R T U V W X Y Z
362 and the "-" shouldn't be the first character.
364 =head2 System Interaction
366 Not all platforms provide a command line. These are usually platforms
367 that rely primarily on a Graphical User Interface (GUI) for user
368 interaction. A program requiring a command line interface might
369 not work everywhere. This is probably for the user of the program
370 to deal with, so don't stay up late worrying about it.
372 Some platforms can't delete or rename files held open by the system.
373 Remember to C<close> files when you are done with them. Don't
374 C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
375 file already tied or opened; C<untie> or C<close> it first.
377 Don't open the same file more than once at a time for writing, as some
378 operating systems put mandatory locks on such files.
380 Don't assume that write/modify permission on a directory gives the
381 right to add or delete files/directories in that directory. That is
382 filesystem specific: in some filesystems you need write/modify
383 permission also (or even just) in the file/directory itself. In some
384 filesystems (AFS, DFS) the permission to add/delete directory entries
385 is a completely separate permission.
387 Don't assume that a single C<unlink> completely gets rid of the file:
388 some filesystems (most notably the ones in VMS) have versioned
389 filesystems, and unlink() removes only the most recent one (it doesn't
390 remove all the versions because by default the native tools on those
391 platforms remove just the most recent version, too). The portable
392 idiom to remove all the versions of a file is
394 1 while unlink "file";
396 This will terminate if the file is undeleteable for some reason
397 (protected, not there, and so on).
399 Don't count on a specific environment variable existing in C<%ENV>.
400 Don't count on C<%ENV> entries being case-sensitive, or even
401 case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
402 if you really have to, make it conditional on C<$^O ne 'VMS'> since in
403 VMS the C<%ENV> table is much more than a per-process key-value string
406 Don't count on signals or C<%SIG> for anything.
408 Don't count on filename globbing. Use C<opendir>, C<readdir>, and
411 Don't count on per-program environment variables, or per-program current
414 Don't count on specific values of C<$!>.
416 =head2 Interprocess Communication (IPC)
418 In general, don't directly access the system in code meant to be
419 portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
420 C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
421 that makes being a perl hacker worth being.
423 Commands that launch external processes are generally supported on
424 most platforms (though many of them do not support any type of
425 forking). The problem with using them arises from what you invoke
426 them on. External tools are often named differently on different
427 platforms, may not be available in the same location, might accept
428 different arguments, can behave differently, and often present their
429 results in a platform-dependent way. Thus, you should seldom depend
430 on them to produce consistent results. (Then again, if you're calling
431 I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
433 One especially common bit of Perl code is opening a pipe to B<sendmail>:
435 open(MAIL, '|/usr/lib/sendmail -t')
436 or die "cannot fork sendmail: $!";
438 This is fine for systems programming when sendmail is known to be
439 available. But it is not fine for many non-Unix systems, and even
440 some Unix systems that may not have sendmail installed. If a portable
441 solution is needed, see the various distributions on CPAN that deal
442 with it. Mail::Mailer and Mail::Send in the MailTools distribution are
443 commonly used, and provide several mailing methods, including mail,
444 sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
445 not available. Mail::Sendmail is a standalone module that provides
446 simple, platform-independent mailing.
448 The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
449 even on all Unix platforms.
451 Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
452 bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
453 both forms just pack the four bytes into network order. That this
454 would be equal to the C language C<in_addr> struct (which is what the
455 socket code internally uses) is not guaranteed. To be portable use
456 the routines of the Socket extension, such as C<inet_aton()>,
457 C<inet_ntoa()>, and C<sockaddr_in()>.
459 The rule of thumb for portable code is: Do it all in portable Perl, or
460 use a module (that may internally implement it with platform-specific
461 code, but expose a common interface).
463 =head2 External Subroutines (XS)
465 XS code can usually be made to work with any platform, but dependent
466 libraries, header files, etc., might not be readily available or
467 portable, or the XS code itself might be platform-specific, just as Perl
468 code might be. If the libraries and headers are portable, then it is
469 normally reasonable to make sure the XS code is portable, too.
471 A different type of portability issue arises when writing XS code:
472 availability of a C compiler on the end-user's system. C brings
473 with it its own portability issues, and writing XS code will expose
474 you to some of those. Writing purely in Perl is an easier way to
477 =head2 Standard Modules
479 In general, the standard modules work across platforms. Notable
480 exceptions are the CPAN module (which currently makes connections to external
481 programs that may not be available), platform-specific modules (like
482 ExtUtils::MM_VMS), and DBM modules.
484 There is no one DBM module available on all platforms.
485 SDBM_File and the others are generally available on all Unix and DOSish
486 ports, but not in MacPerl, where only NBDM_File and DB_File are
489 The good news is that at least some DBM module should be available, and
490 AnyDBM_File will use whichever module it can find. Of course, then
491 the code needs to be fairly strict, dropping to the greatest common
492 factor (e.g., not exceeding 1K for each record), so that it will
493 work with any DBM module. See L<AnyDBM_File> for more details.
497 The system's notion of time of day and calendar date is controlled in
498 widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
499 and even if it is, don't assume that you can control the timezone through
502 Don't assume that the epoch starts at 00:00:00, January 1, 1970,
503 because that is OS- and implementation-specific. It is better to store a date
504 in an unambiguous representation. The ISO-8601 standard defines
505 "YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
506 can be easily converted into an OS-specific value using a module like
507 Date::Parse. An array of values, such as those returned by
508 C<localtime>, can be converted to an OS-specific representation using
511 When calculating specific times, such as for tests in time or date modules,
512 it may be appropriate to calculate an offset for the epoch.
515 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
517 The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
518 some large number. C<$offset> can then be added to a Unix time value
519 to get what should be the proper value on any system.
521 =head2 Character sets and character encoding
523 Assume very little about character sets.
525 Assume nothing about numerical values (C<ord>, C<chr>) of characters.
526 Do not use explicit code point ranges (like \xHH-\xHH); use for
527 example symbolic character classes like C<[:print:]>.
529 Do not assume that the alphabetic characters are encoded contiguously
530 (in the numeric sense). There may be gaps.
532 Do not assume anything about the ordering of the characters.
533 The lowercase letters may come before or after the uppercase letters;
534 the lowercase and uppercase may be interlaced so that both `a' and `A'
535 come before `b'; the accented and other international characters may
536 be interlaced so that E<auml> comes before `b'.
538 =head2 Internationalisation
540 If you may assume POSIX (a rather large assumption), you may read
541 more about the POSIX locale system from L<perllocale>. The locale
542 system at least attempts to make things a little bit more portable,
543 or at least more convenient and native-friendly for non-English
544 users. The system affects character sets and encoding, and date
545 and time formatting--amongst other things.
547 =head2 System Resources
549 If your code is destined for systems with severely constrained (or
550 missing!) virtual memory systems then you want to be I<especially> mindful
551 of avoiding wasteful constructs such as:
553 # NOTE: this is no longer "bad" in perl5.005
554 for (0..10000000) {} # bad
555 for (my $x = 0; $x <= 10000000; ++$x) {} # good
557 @lines = <VERY_LARGE_FILE>; # bad
559 while (<FILE>) {$file .= $_} # sometimes bad
560 $file = join('', <FILE>); # better
562 The last two constructs may appear unintuitive to most people. The
563 first repeatedly grows a string, whereas the second allocates a
564 large chunk of memory in one go. On some systems, the second is
565 more efficient that the first.
569 Most multi-user platforms provide basic levels of security, usually
570 implemented at the filesystem level. Some, however, do
571 not-- unfortunately. Thus the notion of user id, or "home" directory,
572 or even the state of being logged-in, may be unrecognizable on many
573 platforms. If you write programs that are security-conscious, it
574 is usually best to know what type of system you will be running
575 under so that you can write code explicitly for that platform (or
578 Don't assume the UNIX filesystem access semantics: the operating
579 system or the filesystem may be using some ACL systems, which are
580 richer languages than the usual rwx. Even if the rwx exist,
581 their semantics might be different.
583 (From security viewpoint testing for permissions before attempting to
584 do something is silly anyway: if one tries this, there is potential
585 for race conditions-- someone or something might change the
586 permissions between the permissions check and the actual operation.
587 Just try the operation.)
589 Don't assume the UNIX user and group semantics: especially, don't
590 expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
591 for switching identities (or memberships).
593 Don't assume set-uid and set-gid semantics. (And even if you do,
594 think twice: set-uid and set-gid are a known can of security worms.)
598 For those times when it is necessary to have platform-specific code,
599 consider keeping the platform-specific code in one place, making porting
600 to other platforms easier. Use the Config module and the special
601 variable C<$^O> to differentiate platforms, as described in
604 Be careful in the tests you supply with your module or programs.
605 Module code may be fully portable, but its tests might not be. This
606 often happens when tests spawn off other processes or call external
607 programs to aid in the testing, or when (as noted above) the tests
608 assume certain things about the filesystem and paths. Be careful
609 not to depend on a specific output style for errors, such as when
610 checking C<$!> after a system call. Some platforms expect a certain
611 output format, and perl on those platforms may have been adjusted
612 accordingly. Most specifically, don't anchor a regex when testing
617 Modules uploaded to CPAN are tested by a variety of volunteers on
618 different platforms. These CPAN testers are notified by mail of each
619 new upload, and reply to the list with PASS, FAIL, NA (not applicable to
620 this platform), or UNKNOWN (unknown), along with any relevant notations.
622 The purpose of the testing is twofold: one, to help developers fix any
623 problems in their code that crop up because of lack of testing on other
624 platforms; two, to provide users with information about whether
625 a given module works on a given platform.
629 =item Mailing list: cpan-testers@perl.org
631 =item Testing results: http://testers.cpan.org/
637 As of version 5.002, Perl is built with a C<$^O> variable that
638 indicates the operating system it was built on. This was implemented
639 to help speed up code that would otherwise have to C<use Config>
640 and use the value of C<$Config{osname}>. Of course, to get more
641 detailed information about the system, looking into C<%Config> is
642 certainly recommended.
644 C<%Config> cannot always be trusted, however, because it was built
645 at compile time. If perl was built in one place, then transferred
646 elsewhere, some values may be wrong. The values may even have been
647 edited after the fact.
651 Perl works on a bewildering variety of Unix and Unix-like platforms (see
652 e.g. most of the files in the F<hints/> directory in the source code kit).
653 On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
654 too) is determined either by lowercasing and stripping punctuation from the
655 first field of the string returned by typing C<uname -a> (or a similar command)
656 at the shell prompt or by testing the file system for the presence of
657 uniquely named files such as a kernel or header file. Here, for example,
658 are a few of the more popular Unix flavors:
660 uname $^O $Config{'archname'}
661 --------------------------------------------
663 BSD/OS bsdos i386-bsdos
664 dgux dgux AViiON-dgux
665 DYNIX/ptx dynixptx i386-dynixptx
666 FreeBSD freebsd freebsd-i386
667 Linux linux arm-linux
668 Linux linux i386-linux
669 Linux linux i586-linux
670 Linux linux ppc-linux
671 HP-UX hpux PA-RISC1.1
673 Mac OS X darwin darwin
674 MachTen PPC machten powerpc-machten
676 NeXT 4 next OPENSTEP-Mach
677 openbsd openbsd i386-openbsd
678 OSF1 dec_osf alpha-dec_osf
679 reliantunix-n svr4 RM400-svr4
680 SCO_SV sco_sv i386-sco_sv
681 SINIX-N svr4 RM400-svr4
682 sn4609 unicos CRAY_C90-unicos
683 sn6521 unicosmk t3e-unicosmk
684 sn9617 unicos CRAY_J90-unicos
685 SunOS solaris sun4-solaris
686 SunOS solaris i86pc-solaris
687 SunOS4 sunos sun4-sunos
689 Because the value of C<$Config{archname}> may depend on the
690 hardware architecture, it can vary more than the value of C<$^O>.
692 =head2 DOS and Derivatives
694 Perl has long been ported to Intel-style microcomputers running under
695 systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
696 bring yourself to mention (except for Windows CE, if you count that).
697 Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
698 be aware that each of these file specifications may have subtle
701 $filespec0 = "c:/foo/bar/file.txt";
702 $filespec1 = "c:\\foo\\bar\\file.txt";
703 $filespec2 = 'c:\foo\bar\file.txt';
704 $filespec3 = 'c:\\foo\\bar\\file.txt';
706 System calls accept either C</> or C<\> as the path separator.
707 However, many command-line utilities of DOS vintage treat C</> as
708 the option prefix, so may get confused by filenames containing C</>.
709 Aside from calling any external programs, C</> will work just fine,
710 and probably better, as it is more consistent with popular usage,
711 and avoids the problem of remembering what to backwhack and what
714 The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
715 the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
716 filesystems you may have to be careful about case returned with functions
717 like C<readdir> or used with functions like C<open> or C<opendir>.
719 DOS also treats several filenames as special, such as AUX, PRN,
720 NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
721 filenames won't even work if you include an explicit directory
722 prefix. It is best to avoid such filenames, if you want your code
723 to be portable to DOS and its derivatives. It's hard to know what
724 these all are, unfortunately.
726 Users of these operating systems may also wish to make use of
727 scripts such as I<pl2bat.bat> or I<pl2cmd> to
728 put wrappers around your scripts.
730 Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
731 and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
732 will keep C<\n> translated as C<\012> for that filehandle. Since it is a
733 no-op on other systems, C<binmode> should be used for cross-platform code
734 that deals with binary data. That's assuming you realize in advance
735 that your data is in binary. General-purpose programs should
736 often assume nothing about their data.
738 The C<$^O> variable and the C<$Config{archname}> values for various
739 DOSish perls are as follows:
741 OS $^O $Config{archname} ID Version
742 --------------------------------------------------------
746 Windows 3.1 ? ? 0 3 01
747 Windows 95 MSWin32 MSWin32-x86 1 4 00
748 Windows 98 MSWin32 MSWin32-x86 1 4 10
749 Windows ME MSWin32 MSWin32-x86 1 ?
750 Windows NT MSWin32 MSWin32-x86 2 4 xx
751 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
752 Windows NT MSWin32 MSWin32-ppc 2 4 xx
753 Windows 2000 MSWin32 MSWin32-x86 2 5 xx
754 Windows XP MSWin32 MSWin32-x86 2 ?
755 Windows CE MSWin32 ? 3
758 The various MSWin32 Perl's can distinguish the OS they are running on
759 via the value of the fifth element of the list returned from
760 Win32::GetOSVersion(). For example:
762 if ($^O eq 'MSWin32') {
763 my @os_version_info = Win32::GetOSVersion();
764 print +('3.1','95','NT')[$os_version_info[4]],"\n";
773 The djgpp environment for DOS, http://www.delorie.com/djgpp/
778 The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
779 http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
780 ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
784 Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
789 The C<Win32::*> modules in L<Win32>.
793 The ActiveState Pages, http://www.activestate.com/
797 The Cygwin environment for Win32; F<README.cygwin> (installed
798 as L<perlcygwin>), http://www.cygwin.com/
802 The U/WIN environment for Win32,
803 http://www.research.att.com/sw/tools/uwin/
807 Build instructions for OS/2, L<perlos2>
813 Any module requiring XS compilation is right out for most people, because
814 MacPerl is built using non-free (and non-cheap!) compilers. Some XS
815 modules that can work with MacPerl are built and distributed in binary
818 Directories are specified as:
820 volume:folder:file for absolute pathnames
821 volume:folder: for absolute pathnames
822 :folder:file for relative pathnames
823 :folder: for relative pathnames
824 :file for relative pathnames
825 file for relative pathnames
827 Files are stored in the directory in alphabetical order. Filenames are
828 limited to 31 characters, and may include any character except for
829 null and C<:>, which is reserved as the path separator.
831 Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
832 Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
834 In the MacPerl application, you can't run a program from the command line;
835 programs that expect C<@ARGV> to be populated can be edited with something
836 like the following, which brings up a dialog box asking for the command
840 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
843 A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
844 pathnames of the files dropped onto the script.
846 Mac users can run programs under a type of command line interface
847 under MPW (Macintosh Programmer's Workshop, a free development
848 environment from Apple). MacPerl was first introduced as an MPW
849 tool, and MPW can be used like a shell:
851 perl myscript.plx some arguments
853 ToolServer is another app from Apple that provides access to MPW tools
854 from MPW and the MacPerl app, which allows MacPerl programs to use
855 C<system>, backticks, and piped C<open>.
857 "S<Mac OS>" is the proper name for the operating system, but the value
858 in C<$^O> is "MacOS". To determine architecture, version, or whether
859 the application or MPW tool version is running, check:
861 $is_app = $MacPerl::Version =~ /App/;
862 $is_tool = $MacPerl::Version =~ /MPW/;
863 ($version) = $MacPerl::Version =~ /^(\S+)/;
864 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
865 $is_68k = $MacPerl::Architecture eq 'Mac68K';
867 S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
868 "Classic" environment. There is no "Carbon" version of MacPerl to run
869 under the primary Mac OS X environment. S<Mac OS X> and its Open Source
870 version, Darwin, both run Unix perl natively.
878 MacPerl Development, http://dev.macperl.org/ .
882 The MacPerl Pages, http://www.macperl.com/ .
886 The MacPerl mailing lists, http://lists.perl.org/ .
892 Perl on VMS is discussed in L<perlvms> in the perl distribution.
893 Perl on VMS can accept either VMS- or Unix-style file
894 specifications as in either of the following:
896 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
897 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
899 but not a mixture of both as in:
901 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
902 Can't open sys$login:/login.com: file specification syntax error
904 Interacting with Perl from the Digital Command Language (DCL) shell
905 often requires a different set of quotation marks than Unix shells do.
908 $ perl -e "print ""Hello, world.\n"""
911 There are several ways to wrap your perl scripts in DCL F<.COM> files, if
912 you are so inclined. For example:
914 $ write sys$output "Hello from DCL!"
916 $ then perl -x 'f$environment("PROCEDURE")
917 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
918 $ deck/dollars="__END__"
921 print "Hello from Perl!\n";
926 Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
927 perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
929 Filenames are in the format "name.extension;version". The maximum
930 length for filenames is 39 characters, and the maximum length for
931 extensions is also 39 characters. Version is a number from 1 to
932 32767. Valid characters are C</[A-Z0-9$_-]/>.
934 VMS's RMS filesystem is case-insensitive and does not preserve case.
935 C<readdir> returns lowercased filenames, but specifying a file for
936 opening remains case-insensitive. Files without extensions have a
937 trailing period on them, so doing a C<readdir> with a file named F<A.;5>
938 will return F<a.> (though that file could be opened with
941 RMS had an eight level limit on directory depths from any rooted logical
942 (allowing 16 levels overall) prior to VMS 7.2. Hence
943 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
944 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
945 have to take this into account, but at least they can refer to the former
946 as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
948 The VMS::Filespec module, which gets installed as part of the build
949 process on VMS, is a pure Perl module that can easily be installed on
950 non-VMS platforms and can be helpful for conversions to and from RMS
953 What C<\n> represents depends on the type of file opened. It usually
954 represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
955 C<\000>, C<\040>, or nothing depending on the file organiztion and
956 record format. The VMS::Stdio module provides access to the
957 special fopen() requirements of files with unusual attributes on VMS.
959 TCP/IP stacks are optional on VMS, so socket routines might not be
960 implemented. UDP sockets may not be supported.
962 The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
963 that you are running on without resorting to loading all of C<%Config>
964 you can examine the content of the C<@INC> array like so:
966 if (grep(/VMS_AXP/, @INC)) {
967 print "I'm on Alpha!\n";
969 } elsif (grep(/VMS_VAX/, @INC)) {
970 print "I'm on VAX!\n";
973 print "I'm not so sure about where $^O is...\n";
976 On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
977 logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
978 calls to C<localtime> are adjusted to count offsets from
979 01-JAN-1970 00:00:00.00, just like Unix.
987 F<README.vms> (installed as L<README_vms>), L<perlvms>
991 vmsperl list, majordomo@perl.org
993 (Put the words C<subscribe vmsperl> in message body.)
997 vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
1003 Perl on VOS is discussed in F<README.vos> in the perl distribution
1004 (installed as L<perlvos>). Perl on VOS can accept either VOS- or
1005 Unix-style file specifications as in either of the following:
1007 $ perl -ne "print if /perl_setup/i" >system>notices
1008 $ perl -ne "print if /perl_setup/i" /system/notices
1010 or even a mixture of both as in:
1012 $ perl -ne "print if /perl_setup/i" >system/notices
1014 Even though VOS allows the slash character to appear in object
1015 names, because the VOS port of Perl interprets it as a pathname
1016 delimiting character, VOS files, directories, or links whose names
1017 contain a slash character cannot be processed. Such files must be
1018 renamed before they can be processed by Perl. Note that VOS limits
1019 file names to 32 or fewer characters.
1021 See F<README.vos> for restrictions that apply when Perl is built
1022 with the alpha version of VOS POSIX.1 support.
1024 Perl on VOS is built without any extensions and does not support
1027 The value of C<$^O> on VOS is "VOS". To determine the architecture that
1028 you are running on without resorting to loading all of C<%Config> you
1029 can examine the content of the @INC array like so:
1032 print "I'm on a Stratus box!\n";
1034 print "I'm not on a Stratus box!\n";
1038 if (grep(/860/, @INC)) {
1039 print "This box is a Stratus XA/R!\n";
1041 } elsif (grep(/7100/, @INC)) {
1042 print "This box is a Stratus HP 7100 or 8xxx!\n";
1044 } elsif (grep(/8000/, @INC)) {
1045 print "This box is a Stratus HP 8xxx!\n";
1048 print "This box is a Stratus 68K!\n";
1061 The VOS mailing list.
1063 There is no specific mailing list for Perl on VOS. You can post
1064 comments to the comp.sys.stratus newsgroup, or subscribe to the general
1065 Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
1066 the message body to majordomo@list.stratagy.com.
1070 VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
1074 =head2 EBCDIC Platforms
1076 Recent versions of Perl have been ported to platforms such as OS/400 on
1077 AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1078 Mainframes. Such computers use EBCDIC character sets internally (usually
1079 Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1080 systems). On the mainframe perl currently works under the "Unix system
1081 services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1082 the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
1083 See L<perlos390> for details.
1085 As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1086 sub-systems do not support the C<#!> shebang trick for script invocation.
1087 Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1088 similar to the following simple script:
1091 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1093 #!/usr/local/bin/perl # just a comment really
1095 print "Hello from perl!\n";
1097 OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1098 Calls to C<system> and backticks can use POSIX shell syntax on all
1101 On the AS/400, if PERL5 is in your library list, you may need
1102 to wrap your perl scripts in a CL procedure to invoke them like so:
1105 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1108 This will invoke the perl script F<hello.pl> in the root of the
1109 QOpenSys file system. On the AS/400 calls to C<system> or backticks
1112 On these platforms, bear in mind that the EBCDIC character set may have
1113 an effect on what happens with some perl functions (such as C<chr>,
1114 C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1115 well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1116 and C<|>, not to mention dealing with socket interfaces to ASCII computers
1117 (see L<"Newlines">).
1119 Fortunately, most web servers for the mainframe will correctly
1120 translate the C<\n> in the following statement to its ASCII equivalent
1121 (C<\r> is the same under both Unix and OS/390 & VM/ESA):
1123 print "Content-type: text/html\r\n\r\n";
1125 The values of C<$^O> on some of these platforms includes:
1127 uname $^O $Config{'archname'}
1128 --------------------------------------------
1131 POSIX-BC posix-bc BS2000-posix-bc
1134 Some simple tricks for determining if you are running on an EBCDIC
1135 platform could include any of the following (perhaps all):
1137 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1139 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1141 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1143 One thing you may not want to rely on is the EBCDIC encoding
1144 of punctuation characters since these may differ from code page to code
1145 page (and once your module or script is rumoured to work with EBCDIC,
1146 folks will want it to work with all EBCDIC character sets).
1156 L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
1161 The perl-mvs@perl.org list is for discussion of porting issues as well as
1162 general usage issues for all EBCDIC Perls. Send a message body of
1163 "subscribe perl-mvs" to majordomo@perl.org.
1167 AS/400 Perl information at
1168 http://as400.rochester.ibm.com/
1169 as well as on CPAN in the F<ports/> directory.
1173 =head2 Acorn RISC OS
1175 Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1176 Unix, and because Unix filename emulation is turned on by default,
1177 most simple scripts will probably work "out of the box". The native
1178 filesystem is modular, and individual filesystems are free to be
1179 case-sensitive or insensitive, and are usually case-preserving. Some
1180 native filesystems have name length limits, which file and directory
1181 names are silently truncated to fit. Scripts should be aware that the
1182 standard filesystem currently has a name length limit of B<10>
1183 characters, with up to 77 items in a directory, but other filesystems
1184 may not impose such limitations.
1186 Native filenames are of the form
1188 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
1192 Special_Field is not usually present, but may contain . and $ .
1193 Filesystem =~ m|[A-Za-z0-9_]|
1194 DsicName =~ m|[A-Za-z0-9_/]|
1195 $ represents the root directory
1196 . is the path separator
1197 @ is the current directory (per filesystem but machine global)
1198 ^ is the parent directory
1199 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1201 The default filename translation is roughly C<tr|/.|./|;>
1203 Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
1204 the second stage of C<$> interpolation in regular expressions will fall
1205 foul of the C<$.> if scripts are not careful.
1207 Logical paths specified by system variables containing comma-separated
1208 search lists are also allowed; hence C<System:Modules> is a valid
1209 filename, and the filesystem will prefix C<Modules> with each section of
1210 C<System$Path> until a name is made that points to an object on disk.
1211 Writing to a new file C<System:Modules> would be allowed only if
1212 C<System$Path> contains a single item list. The filesystem will also
1213 expand system variables in filenames if enclosed in angle brackets, so
1214 C<< <System$Dir>.Modules >> would look for the file
1215 S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
1216 that B<fully qualified filenames can start with C<< <> >>> and should
1217 be protected when C<open> is used for input.
1219 Because C<.> was in use as a directory separator and filenames could not
1220 be assumed to be unique after 10 characters, Acorn implemented the C
1221 compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1222 filenames specified in source code and store the respective files in
1223 subdirectories named after the suffix. Hence files are translated:
1226 C:foo.h C:h.foo (logical path variable)
1227 sys/os.h sys.h.os (C compiler groks Unix-speak)
1228 10charname.c c.10charname
1229 10charname.o o.10charname
1230 11charname_.c c.11charname (assuming filesystem truncates at 10)
1232 The Unix emulation library's translation of filenames to native assumes
1233 that this sort of translation is required, and it allows a user-defined list
1234 of known suffixes that it will transpose in this fashion. This may
1235 seem transparent, but consider that with these rules C<foo/bar/baz.h>
1236 and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1237 C<glob> cannot and do not attempt to emulate the reverse mapping. Other
1238 C<.>'s in filenames are translated to C</>.
1240 As implied above, the environment accessed through C<%ENV> is global, and
1241 the convention is that program specific environment variables are of the
1242 form C<Program$Name>. Each filesystem maintains a current directory,
1243 and the current filesystem's current directory is the B<global> current
1244 directory. Consequently, sociable programs don't change the current
1245 directory but rely on full pathnames, and programs (and Makefiles) cannot
1246 assume that they can spawn a child process which can change the current
1247 directory without affecting its parent (and everyone else for that
1250 Because native operating system filehandles are global and are currently
1251 allocated down from 255, with 0 being a reserved value, the Unix emulation
1252 library emulates Unix filehandles. Consequently, you can't rely on
1253 passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1255 The desire of users to express filenames of the form
1256 C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
1257 too: C<``> command output capture has to perform a guessing game. It
1258 assumes that a string C<< <[^<>]+\$[^<>]> >> is a
1259 reference to an environment variable, whereas anything else involving
1260 C<< < >> or C<< > >> is redirection, and generally manages to be 99%
1261 right. Of course, the problem remains that scripts cannot rely on any
1262 Unix tools being available, or that any tools found have Unix-like command
1265 Extensions and XS are, in theory, buildable by anyone using free
1266 tools. In practice, many don't, as users of the Acorn platform are
1267 used to binary distributions. MakeMaker does run, but no available
1268 make currently copes with MakeMaker's makefiles; even if and when
1269 this should be fixed, the lack of a Unix-like shell will cause
1270 problems with makefile rules, especially lines of the form C<cd
1271 sdbm && make all>, and anything using quoting.
1273 "S<RISC OS>" is the proper name for the operating system, but the value
1274 in C<$^O> is "riscos" (because we don't like shouting).
1278 Perl has been ported to many platforms that do not fit into any of
1279 the categories listed above. Some, such as AmigaOS, Atari MiNT,
1280 BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1281 into the standard Perl source code kit. You may need to see the
1282 F<ports/> directory on CPAN for information, and possibly binaries,
1283 for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1284 Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1285 fall under the Unix category, but we are not a standards body.)
1287 Some approximate operating system names and their C<$^O> values
1288 in the "OTHER" category include:
1290 OS $^O $Config{'archname'}
1291 ------------------------------------------
1292 Amiga DOS amigaos m68k-amigos
1293 MPE/iX mpeix PA-RISC1.1
1301 Amiga, F<README.amiga> (installed as L<perlamiga>).
1305 Atari, F<README.mint> and Guido Flohr's web page
1306 http://stud.uni-sb.de/~gufl0000/
1310 Be OS, F<README.beos>
1314 HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
1315 http://www.bixby.org/mark/perlix.html
1319 A free perl5-based PERL.NLM for Novell Netware is available in
1320 precompiled binary and source code form from http://www.novell.com/
1321 as well as from CPAN.
1325 Plan 9, F<README.plan9>
1329 =head1 FUNCTION IMPLEMENTATIONS
1331 Listed below are functions that are either completely unimplemented
1332 or else have been implemented differently on various platforms.
1333 Following each description will be, in parentheses, a list of
1334 platforms that the description applies to.
1336 The list may well be incomplete, or even wrong in some places. When
1337 in doubt, consult the platform-specific README files in the Perl
1338 source distribution, and any other documentation resources accompanying
1341 Be aware, moreover, that even among Unix-ish systems there are variations.
1343 For many functions, you can also query C<%Config>, exported by
1344 default from the Config module. For example, to check whether the
1345 platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1346 L<Config> for a full description of available variables.
1348 =head2 Alphabetical Listing of Perl Functions
1358 C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
1359 and applications are executable, and there are no uid/gid
1360 considerations. C<-o> is not supported. (S<Mac OS>)
1362 C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1363 which may not reflect UIC-based file protections. (VMS)
1365 C<-s> returns the size of the data fork, not the total size of data fork
1366 plus resource fork. (S<Mac OS>).
1368 C<-s> by name on an open file will return the space reserved on disk,
1369 rather than the current extent. C<-s> on an open filehandle returns the
1370 current size. (S<RISC OS>)
1372 C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
1373 C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1375 C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1378 C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
1379 (Win32, VMS, S<RISC OS>)
1381 C<-d> is true if passed a device spec without an explicit directory.
1384 C<-T> and C<-B> are implemented, but might misclassify Mac text files
1385 with foreign characters; this is the case will all platforms, but may
1386 affect S<Mac OS> often. (S<Mac OS>)
1388 C<-x> (or C<-X>) determine if a file ends in one of the executable
1389 suffixes. C<-S> is meaningless. (Win32)
1391 C<-x> (or C<-X>) determine if a file has an executable file type.
1398 Not implemented. (Win32)
1400 =item binmode FILEHANDLE
1402 Meaningless. (S<Mac OS>, S<RISC OS>)
1404 Reopens file and restores pointer; if function fails, underlying
1405 filehandle may be closed, or pointer may be in a different position.
1408 The value returned by C<tell> may be affected after the call, and
1409 the filehandle may be flushed. (Win32)
1413 Only limited meaning. Disabling/enabling write permission is mapped to
1414 locking/unlocking the file. (S<Mac OS>)
1416 Only good for changing "owner" read-write access, "group", and "other"
1417 bits are meaningless. (Win32)
1419 Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1421 Access permissions are mapped onto VOS access-control list changes. (VOS)
1425 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
1427 Does nothing, but won't fail. (Win32)
1429 =item chroot FILENAME
1433 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
1435 =item crypt PLAINTEXT,SALT
1437 May not be available if library or source was not provided when building
1440 Not implemented. (VOS)
1444 Not implemented. (VMS, Plan9, VOS)
1446 =item dbmopen HASH,DBNAME,MODE
1448 Not implemented. (VMS, Plan9, VOS)
1452 Not useful. (S<Mac OS>, S<RISC OS>)
1454 Not implemented. (Win32)
1456 Invokes VMS debugger. (VMS)
1460 Not implemented. (S<Mac OS>)
1462 Implemented via Spawn. (VM/ESA)
1464 Does not automatically flush output handles on some platforms.
1465 (SunOS, Solaris, HP-UX)
1471 Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1472 mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1473 with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1474 function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1475 (C<1>); this mapping cannot be overridden. Any other argument to exit()
1476 is used directly as Perl's exit status. (VMS)
1478 =item fcntl FILEHANDLE,FUNCTION,SCALAR
1480 Not implemented. (Win32, VMS)
1482 =item flock FILEHANDLE,OPERATION
1484 Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
1486 Available only on Windows NT (not on Windows 95). (Win32)
1490 Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1492 Emulated using multiple interpreters. See L<perlfork>. (Win32)
1494 Does not automatically flush output handles on some platforms.
1495 (SunOS, Solaris, HP-UX)
1499 Not implemented. (S<Mac OS>, S<RISC OS>)
1503 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1507 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1509 =item getpriority WHICH,WHO
1511 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1515 Not implemented. (S<Mac OS>, Win32)
1517 Not useful. (S<RISC OS>)
1521 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1523 =item getnetbyname NAME
1525 Not implemented. (S<Mac OS>, Win32, Plan9)
1529 Not implemented. (S<Mac OS>, Win32)
1531 Not useful. (S<RISC OS>)
1535 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1537 =item getnetbyaddr ADDR,ADDRTYPE
1539 Not implemented. (S<Mac OS>, Win32, Plan9)
1541 =item getprotobynumber NUMBER
1543 Not implemented. (S<Mac OS>)
1545 =item getservbyport PORT,PROTO
1547 Not implemented. (S<Mac OS>)
1551 Not implemented. (S<Mac OS>, Win32, VM/ESA)
1555 Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
1559 Not implemented. (S<Mac OS>, Win32)
1563 Not implemented. (S<Mac OS>, Win32, Plan9)
1567 Not implemented. (S<Mac OS>, Win32, Plan9)
1571 Not implemented. (Win32, Plan9)
1575 Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
1579 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1581 =item sethostent STAYOPEN
1583 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1585 =item setnetent STAYOPEN
1587 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1589 =item setprotoent STAYOPEN
1591 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1593 =item setservent STAYOPEN
1595 Not implemented. (Plan9, Win32, S<RISC OS>)
1599 Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
1603 Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
1607 Not implemented. (S<Mac OS>, Win32)
1611 Not implemented. (S<Mac OS>, Win32, Plan9)
1615 Not implemented. (S<Mac OS>, Win32, Plan9)
1619 Not implemented. (Plan9, Win32)
1621 =item getsockopt SOCKET,LEVEL,OPTNAME
1623 Not implemented. (Plan9)
1629 This operator is implemented via the File::Glob extension on most
1630 platforms. See L<File::Glob> for portability information.
1632 =item ioctl FILEHANDLE,FUNCTION,SCALAR
1634 Not implemented. (VMS)
1636 Available only for socket handles, and it does what the ioctlsocket() call
1637 in the Winsock API does. (Win32)
1639 Available only for socket handles. (S<RISC OS>)
1641 =item kill SIGNAL, LIST
1643 C<kill(0, LIST)> is implemented for the sake of taint checking;
1644 use with other signals is unimplemented. (S<Mac OS>)
1646 Not implemented, hence not useful for taint checking. (S<RISC OS>)
1648 C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1649 a signal to the identified process like it does on Unix platforms.
1650 Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1651 and makes it exit immediately with exit status $sig. As in Unix, if
1652 $sig is 0 and the specified process exists, it returns true without
1653 actually terminating it. (Win32)
1655 =item link OLDFILE,NEWFILE
1657 Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
1659 Link count not updated because hard links are not quite that hard
1660 (They are sort of half-way between hard and soft links). (AmigaOS)
1662 Hard links are implemented on Win32 (Windows NT and Windows 2000)
1665 =item lstat FILEHANDLE
1671 Not implemented. (VMS, S<RISC OS>)
1673 Return values (especially for device and inode) may be bogus. (Win32)
1675 =item msgctl ID,CMD,ARG
1677 =item msgget KEY,FLAGS
1679 =item msgsnd ID,MSG,FLAGS
1681 =item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1683 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
1685 =item open FILEHANDLE,EXPR
1687 =item open FILEHANDLE
1689 The C<|> variants are supported only if ToolServer is installed.
1692 open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
1694 Opening a process does not automatically flush output handles on some
1695 platforms. (SunOS, Solaris, HP-UX)
1697 =item pipe READHANDLE,WRITEHANDLE
1699 Very limited functionality. (MiNT)
1705 Not implemented. (Win32, VMS, S<RISC OS>)
1707 =item select RBITS,WBITS,EBITS,TIMEOUT
1709 Only implemented on sockets. (Win32, VMS)
1711 Only reliable on sockets. (S<RISC OS>)
1713 Note that the C<select FILEHANDLE> form is generally portable.
1715 =item semctl ID,SEMNUM,CMD,ARG
1717 =item semget KEY,NSEMS,FLAGS
1719 =item semop KEY,OPSTRING
1721 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1725 Not implemented. (MPE/iX, Win32)
1727 =item setpgrp PID,PGRP
1729 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1731 =item setpriority WHICH,WHO,PRIORITY
1733 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1737 Not implemented. (MPE/iX, Win32)
1739 =item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1741 Not implemented. (Plan9)
1743 =item shmctl ID,CMD,ARG
1745 =item shmget KEY,SIZE,FLAGS
1747 =item shmread ID,VAR,POS,SIZE
1749 =item shmwrite ID,STRING,POS,SIZE
1751 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1753 =item sockatmark SOCKET
1755 A relatively recent addition to socket functions, may not
1756 be implemented even in UNIX platforms.
1758 =item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1760 Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1762 =item stat FILEHANDLE
1768 Platforms that do not have rdev, blksize, or blocks will return these
1769 as '', so numeric comparison or manipulation of these fields may cause
1770 'not numeric' warnings.
1772 mtime and atime are the same thing, and ctime is creation time instead of
1773 inode change time. (S<Mac OS>)
1775 device and inode are not meaningful. (Win32)
1777 device and inode are not necessarily reliable. (VMS)
1779 mtime, atime and ctime all return the last modification time. Device and
1780 inode are not necessarily reliable. (S<RISC OS>)
1782 dev, rdev, blksize, and blocks are not available. inode is not
1783 meaningful and will differ between stat calls on the same file. (os2)
1785 some versions of cygwin when doing a stat("foo") and if not finding it
1786 may then attempt to stat("foo.exe") (Cygwin)
1788 =item symlink OLDFILE,NEWFILE
1790 Not implemented. (Win32, VMS, S<RISC OS>)
1794 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1796 =item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1798 The traditional "0", "1", and "2" MODEs are implemented with different
1799 numeric values on some systems. The flags exported by C<Fcntl>
1800 (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1801 OS>, OS/390, VM/ESA)
1805 In general, do not assume the UNIX/POSIX semantics that you can shift
1806 C<$?> right by eight to get the exit value, or that C<$? & 127>
1807 would give you the number of the signal that terminated the program,
1808 or that C<$? & 128> would test true if the program was terminated by a
1809 coredump. Instead, use the POSIX W*() interfaces: for example, use
1810 WIFEXITED($?) an WEXITVALUE($?) to test for a normal exit and the exit
1811 value, and WIFSIGNALED($?) and WTERMSIG($?) for a signal exit and the
1812 signal. Core dumping is not a portable concept, so there's no portable
1813 way to test for that.
1815 Only implemented if ToolServer is installed. (S<Mac OS>)
1817 As an optimization, may not call the command shell specified in
1818 C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1819 process and immediately returns its process designator, without
1820 waiting for it to terminate. Return value may be used subsequently
1821 in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1822 by setting $? to "255 << 8". C<$?> is set in a way compatible with
1823 Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1824 as described in the documentation). (Win32)
1826 There is no shell to process metacharacters, and the native standard is
1827 to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1828 program. Redirection such as C<< > foo >> is performed (if at all) by
1829 the run time library of the spawned program. C<system> I<list> will call
1830 the Unix emulation library's C<exec> emulation, which attempts to provide
1831 emulation of the stdin, stdout, stderr in force in the parent, providing
1832 the child program uses a compatible version of the emulation library.
1833 I<scalar> will call the native command line direct and no such emulation
1834 of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1836 Far from being POSIX compliant. Because there may be no underlying
1837 /bin/sh tries to work around the problem by forking and execing the
1838 first token in its argument string. Handles basic redirection
1839 ("<" or ">") on its own behalf. (MiNT)
1841 Does not automatically flush output handles on some platforms.
1842 (SunOS, Solaris, HP-UX)
1844 The return value is POSIX-like (shifted up by 8 bits), which only allows
1845 room for a made-up value derived from the severity bits of the native
1846 32-bit condition code (unless overridden by C<use vmsish 'status'>).
1847 For more details see L<perlvms/$?>. (VMS)
1851 Only the first entry returned is nonzero. (S<Mac OS>)
1853 "cumulative" times will be bogus. On anything other than Windows NT
1854 or Windows 2000, "system" time will be bogus, and "user" time is
1855 actually the time returned by the clock() function in the C runtime
1858 Not useful. (S<RISC OS>)
1860 =item truncate FILEHANDLE,LENGTH
1862 =item truncate EXPR,LENGTH
1864 Not implemented. (Older versions of VMS)
1866 Truncation to zero-length only. (VOS)
1868 If a FILEHANDLE is supplied, it must be writable and opened in append
1869 mode (i.e., use C<<< open(FH, '>>filename') >>>
1870 or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1871 should not be held open elsewhere. (Win32)
1877 Returns undef where unavailable, as of version 5.005.
1879 C<umask> works but the correct permissions are set only when the file
1880 is finally closed. (AmigaOS)
1884 Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
1886 May not behave as expected. Behavior depends on the C runtime
1887 library's implementation of utime(), and the filesystem being
1888 used. The FAT filesystem typically does not support an "access
1889 time" field, and it may limit timestamps to a granularity of
1890 two seconds. (Win32)
1894 =item waitpid PID,FLAGS
1896 Not implemented. (S<Mac OS>, VOS)
1898 Can only be applied to process handles returned for processes spawned
1899 using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
1901 Not useful. (S<RISC OS>)
1909 =item v1.48, 02 February 2001
1911 Various updates from perl5-porters over the past year, supported
1912 platforms update from Jarkko Hietaniemi.
1914 =item v1.47, 22 March 2000
1916 Various cleanups from Tom Christiansen, including migration of
1917 long platform listings from L<perl>.
1919 =item v1.46, 12 February 2000
1921 Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1923 =item v1.45, 20 December 1999
1925 Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1927 =item v1.44, 19 July 1999
1929 A bunch of updates from Peter Prymmer for C<$^O> values,
1930 endianness, File::Spec, VMS, BS2000, OS/400.
1932 =item v1.43, 24 May 1999
1934 Added a lot of cleaning up from Tom Christiansen.
1936 =item v1.42, 22 May 1999
1938 Added notes about tests, sprintf/printf, and epoch offsets.
1940 =item v1.41, 19 May 1999
1942 Lots more little changes to formatting and content.
1944 Added a bunch of C<$^O> and related values
1945 for various platforms; fixed mail and web addresses, and added
1946 and changed miscellaneous notes. (Peter Prymmer)
1948 =item v1.40, 11 April 1999
1950 Miscellaneous changes.
1952 =item v1.39, 11 February 1999
1954 Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1955 note about newlines added.
1957 =item v1.38, 31 December 1998
1959 More changes from Jarkko.
1961 =item v1.37, 19 December 1998
1963 More minor changes. Merge two separate version 1.35 documents.
1965 =item v1.36, 9 September 1998
1967 Updated for Stratus VOS. Also known as version 1.35.
1969 =item v1.35, 13 August 1998
1971 Integrate more minor changes, plus addition of new sections under
1972 L<"ISSUES">: L<"Numbers endianness and Width">,
1973 L<"Character sets and character encoding">,
1974 L<"Internationalisation">.
1976 =item v1.33, 06 August 1998
1978 Integrate more minor changes.
1980 =item v1.32, 05 August 1998
1982 Integrate more minor changes.
1984 =item v1.30, 03 August 1998
1986 Major update for RISC OS, other minor changes.
1988 =item v1.23, 10 July 1998
1990 First public release with perl5.005.
1994 =head1 Supported Platforms
1996 As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
1997 platforms are able to build Perl from the standard source code
1998 distribution available at http://www.cpan.org/src/index.html
2021 Tru64 UNIX (DEC OSF/1, Digital UNIX)
2027 1) in DOS mode either the DOS or OS/2 ports can be used
2028 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
2029 the source does work with 5.6.1, but additional MacOS specific
2030 source code is needed for a complete build. See the web
2031 site http://dev.macperl.org/ for more information.
2032 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
2034 The following platforms worked for the previous releases (5.6.0 and 5.7.0),
2035 but we did not manage to test these in time for the 5.7.1 release.
2036 There is a very good chance that these will work fine with the 5.7.1.
2054 The following platform worked for the 5.005_03 major release but not
2055 for 5.6.0. Standardization on UTF-8 as the internal string
2056 representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
2057 EBCDIC platform. While Perl 5.7.1 will build on this platform some
2058 regression tests may fail and the C<use utf8;> pragma typically
2059 introduces text handling errors.
2063 1) previously known as MVS, about to become z/OS.
2065 Strongly related to the OS/390 platform by also being EBCDIC-based
2066 mainframe platforms are the following platforms:
2071 These are also expected to work, albeit with no UTF-8 support, under 5.6.1
2072 for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
2075 The following platforms have been known to build Perl from source in
2076 the past (5.005_03 and earlier), but we haven't been able to verify
2077 their status for the current release, either because the
2078 hardware/software platforms are rare or because we don't have an
2079 active champion on these platforms--or both. They used to work,
2080 though, so go ahead and try compiling them, and let perlbug@perl.org
2119 Support for the following platform is planned for a future Perl release:
2123 The following platforms have their own source code distributions and
2124 binaries available via http://www.cpan.org/ports/index.html:
2130 Tandem Guardian 5.004
2132 The following platforms have only binaries available via
2133 http://www.cpan.org/ports/index.html :
2137 Acorn RISCOS 5.005_02
2141 Although we do suggest that you always build your own Perl from
2142 the source code, both for maximal configurability and for security,
2143 in case you are in a hurry you can check
2144 http://www.cpan.org/ports/index.html for binary distributions.
2148 L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
2149 L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
2150 L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
2151 L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
2152 L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
2153 L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
2155 =head1 AUTHORS / CONTRIBUTORS
2157 Abigail <abigail@foad.org>,
2158 Charles Bailey <bailey@newman.upenn.edu>,
2159 Graham Barr <gbarr@pobox.com>,
2160 Tom Christiansen <tchrist@perl.com>,
2161 Nicholas Clark <nick@ccl4.org>,
2162 Thomas Dorner <Thomas.Dorner@start.de>,
2163 Andy Dougherty <doughera@lafayette.edu>,
2164 Dominic Dunlop <domo@computer.org>,
2165 Neale Ferguson <neale@vma.tabnsw.com.au>,
2166 David J. Fiander <davidf@mks.com>,
2167 Paul Green <Paul_Green@stratus.com>,
2168 M.J.T. Guy <mjtg@cam.ac.uk>,
2169 Jarkko Hietaniemi <jhi@iki.fi>,
2170 Luther Huffman <lutherh@stratcom.com>,
2171 Nick Ing-Simmons <nick@ing-simmons.net>,
2172 Andreas J. KE<ouml>nig <a.koenig@mind.de>,
2173 Markus Laker <mlaker@contax.co.uk>,
2174 Andrew M. Langmead <aml@world.std.com>,
2175 Larry Moore <ljmoore@freespace.net>,
2176 Paul Moore <Paul.Moore@uk.origin-it.com>,
2177 Chris Nandor <pudge@pobox.com>,
2178 Matthias Neeracher <neeri@iis.ee.ethz.ch>,
2179 Philip Newton <pne@cpan.org>,
2180 Gary Ng <71564.1743@CompuServe.COM>,
2181 Tom Phoenix <rootbeer@teleport.com>,
2182 AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2183 Peter Prymmer <pvhp@forte.com>,
2184 Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2185 Gurusamy Sarathy <gsar@activestate.com>,
2186 Paul J. Schinder <schinder@pobox.com>,
2187 Michael G Schwern <schwern@pobox.com>,
2188 Dan Sugalski <dan@sidhe.org>,
2189 Nathan Torkington <gnat@frii.com>.
2193 Version 1.50, last modified 10 Jul 2001