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 Because of the "text" mode translation, DOSish perls have limitations
98 in using C<seek> and C<tell> on a file accessed in "text" mode.
99 Stick to C<seek>-ing to locations you got from C<tell> (and no
100 others), and you are usually free to use C<seek> and C<tell> even
101 in "text" mode. Using C<seek> or C<tell> or other file operations
102 may be non-portable. If you use C<binmode> on a file, however, you
103 can usually C<seek> and C<tell> with arbitrary values in safety.
105 A common misconception in socket programming is that C<\n> eq C<\012>
106 everywhere. When using protocols such as common Internet protocols,
107 C<\012> and C<\015> are called for specifically, and the values of
108 the logical C<\n> and C<\r> (carriage return) are not reliable.
110 print SOCKET "Hi there, client!\r\n"; # WRONG
111 print SOCKET "Hi there, client!\015\012"; # RIGHT
113 However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
114 and unsightly, as well as confusing to those maintaining the code. As
115 such, the Socket module supplies the Right Thing for those who want it.
117 use Socket qw(:DEFAULT :crlf);
118 print SOCKET "Hi there, client!$CRLF" # RIGHT
120 When reading from a socket, remember that the default input record
121 separator C<$/> is C<\n>, but robust socket code will recognize as
122 either C<\012> or C<\015\012> as end of line:
128 Because both CRLF and LF end in LF, the input record separator can
129 be set to LF and any CR stripped later. Better to write:
131 use Socket qw(:DEFAULT :crlf);
132 local($/) = LF; # not needed if $/ is already \012
135 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
136 # s/\015?\012/\n/; # same thing
139 This example is preferred over the previous one--even for Unix
140 platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
141 (and there was much rejoicing).
143 Similarly, functions that return text data--such as a function that
144 fetches a web page--should sometimes translate newlines before
145 returning the data, if they've not yet been translated to the local
146 newline representation. A single line of code will often suffice:
148 $data =~ s/\015?\012/\n/g;
151 Some of this may be confusing. Here's a handy reference to the ASCII CR
152 and LF characters. You can print it out and stick it in your wallet.
154 LF == \012 == \x0A == \cJ == ASCII 10
155 CR == \015 == \x0D == \cM == ASCII 13
158 ---------------------------
161 \n * | LF | CRLF | CR |
162 \r * | CR | CR | LF |
163 ---------------------------
166 The Unix column assumes that you are not accessing a serial line
167 (like a tty) in canonical mode. If you are, then CR on input becomes
168 "\n", and "\n" on output becomes CRLF.
170 These are just the most common definitions of C<\n> and C<\r> in Perl.
171 There may well be others.
173 =head2 Numbers endianness and Width
175 Different CPUs store integers and floating point numbers in different
176 orders (called I<endianness>) and widths (32-bit and 64-bit being the
177 most common today). This affects your programs when they attempt to transfer
178 numbers in binary format from one CPU architecture to another,
179 usually either "live" via network connection, or by storing the
180 numbers to secondary storage such as a disk file or tape.
182 Conflicting storage orders make utter mess out of the numbers. If a
183 little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
184 decimal), a big-endian host (Motorola, Sparc, PA) reads it as
185 0x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
186 Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
187 them in big-endian mode. To avoid this problem in network (socket)
188 connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
189 "network" orders. These are guaranteed to be portable.
191 You can explore the endianness of your platform by unpacking a
192 data structure packed in native format such as:
194 print unpack("h*", pack("s2", 1, 2)), "\n";
195 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
196 # '00100020' on e.g. Motorola 68040
198 If you need to distinguish between endian architectures you could use
199 either of the variables set like so:
201 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
202 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
204 Differing widths can cause truncation even between platforms of equal
205 endianness. The platform of shorter width loses the upper parts of the
206 number. There is no good solution for this problem except to avoid
207 transferring or storing raw binary numbers.
209 One can circumnavigate both these problems in two ways. Either
210 transfer and store numbers always in text format, instead of raw
211 binary, or else consider using modules like Data::Dumper (included in
212 the standard distribution as of Perl 5.005) and Storable. Keeping
213 all data as text significantly simplifies matters.
215 =head2 Files and Filesystems
217 Most platforms these days structure files in a hierarchical fashion.
218 So, it is reasonably safe to assume that all platforms support the
219 notion of a "path" to uniquely identify a file on the system. How
220 that path is really written, though, differs considerably.
222 Although similar, file path specifications differ between Unix,
223 Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
224 Unix, for example, is one of the few OSes that has the elegant idea
225 of a single root directory.
227 DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
228 as path separator, or in their own idiosyncratic ways (such as having
229 several root directories and various "unrooted" device files such NIL:
232 S<Mac OS> uses C<:> as a path separator instead of C</>.
234 The filesystem may support neither hard links (C<link>) nor
235 symbolic links (C<symlink>, C<readlink>, C<lstat>).
237 The filesystem may support neither access timestamp nor change
238 timestamp (meaning that about the only portable timestamp is the
239 modification timestamp), or one second granularity of any timestamps
240 (e.g. the FAT filesystem limits the time granularity to two seconds).
242 VOS perl can emulate Unix filenames with C</> as path separator. The
243 native pathname characters greater-than, less-than, number-sign, and
244 percent-sign are always accepted.
246 S<RISC OS> perl can emulate Unix filenames with C</> as path
247 separator, or go native and use C<.> for path separator and C<:> to
248 signal filesystems and disk names.
250 If all this is intimidating, have no (well, maybe only a little)
251 fear. There are modules that can help. The File::Spec modules
252 provide methods to do the Right Thing on whatever platform happens
253 to be running the program.
255 use File::Spec::Functions;
256 chdir(updir()); # go up one directory
257 $file = catfile(curdir(), 'temp', 'file.txt');
258 # on Unix and Win32, './temp/file.txt'
259 # on Mac OS, ':temp:file.txt'
260 # on VMS, '[.temp]file.txt'
262 File::Spec is available in the standard distribution as of version
263 5.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
264 and some versions of perl come with version 0.6. If File::Spec
265 is not updated to 0.7 or later, you must use the object-oriented
266 interface from File::Spec (or upgrade File::Spec).
268 In general, production code should not have file paths hardcoded.
269 Making them user-supplied or read from a configuration file is
270 better, keeping in mind that file path syntax varies on different
273 This is especially noticeable in scripts like Makefiles and test suites,
274 which often assume C</> as a path separator for subdirectories.
276 Also of use is File::Basename from the standard distribution, which
277 splits a pathname into pieces (base filename, full path to directory,
280 Even when on a single platform (if you can call Unix a single platform),
281 remember not to count on the existence or the contents of particular
282 system-specific files or directories, like F</etc/passwd>,
283 F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
284 example, F</etc/passwd> may exist but not contain the encrypted
285 passwords, because the system is using some form of enhanced security.
286 Or it may not contain all the accounts, because the system is using NIS.
287 If code does need to rely on such a file, include a description of the
288 file and its format in the code's documentation, then make it easy for
289 the user to override the default location of the file.
291 Don't assume a text file will end with a newline. They should,
294 Do not have two files of the same name with different case, like
295 F<test.pl> and F<Test.pl>, as many platforms have case-insensitive
296 filenames. Also, try not to have non-word characters (except for C<.>)
297 in the names, and keep them to the 8.3 convention, for maximum
298 portability, onerous a burden though this may appear.
300 Likewise, when using the AutoSplit module, try to keep your functions to
301 8.3 naming and case-insensitive conventions; or, at the least,
302 make it so the resulting files have a unique (case-insensitively)
305 Whitespace in filenames is tolerated on most systems, but not all.
306 Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
308 Don't assume C<< > >> won't be the first character of a filename.
309 Always use C<< < >> explicitly to open a file for reading,
310 unless you want the user to be able to specify a pipe open.
312 open(FILE, "< $existing_file") or die $!;
314 If filenames might use strange characters, it is safest to open it
315 with C<sysopen> instead of C<open>. C<open> is magic and can
316 translate characters like C<< > >>, C<< < >>, and C<|>, which may
317 be the wrong thing to do. (Sometimes, though, it's the right thing.)
319 =head2 System Interaction
321 Not all platforms provide a command line. These are usually platforms
322 that rely primarily on a Graphical User Interface (GUI) for user
323 interaction. A program requiring a command line interface might
324 not work everywhere. This is probably for the user of the program
325 to deal with, so don't stay up late worrying about it.
327 Some platforms can't delete or rename files held open by the system.
328 Remember to C<close> files when you are done with them. Don't
329 C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
330 file already tied or opened; C<untie> or C<close> it first.
332 Don't open the same file more than once at a time for writing, as some
333 operating systems put mandatory locks on such files.
335 Don't count on a specific environment variable existing in C<%ENV>.
336 Don't count on C<%ENV> entries being case-sensitive, or even
337 case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
338 if you really have to, make it conditional on C<$^O ne 'VMS'> since in
339 VMS the C<%ENV> table is much more than a per-process key-value string
342 Don't count on signals or C<%SIG> for anything.
344 Don't count on filename globbing. Use C<opendir>, C<readdir>, and
347 Don't count on per-program environment variables, or per-program current
350 Don't count on specific values of C<$!>.
352 =head2 Interprocess Communication (IPC)
354 In general, don't directly access the system in code meant to be
355 portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
356 C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
357 that makes being a perl hacker worth being.
359 Commands that launch external processes are generally supported on
360 most platforms (though many of them do not support any type of
361 forking). The problem with using them arises from what you invoke
362 them on. External tools are often named differently on different
363 platforms, may not be available in the same location, might accept
364 different arguments, can behave differently, and often present their
365 results in a platform-dependent way. Thus, you should seldom depend
366 on them to produce consistent results. (Then again, if you're calling
367 I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
369 One especially common bit of Perl code is opening a pipe to B<sendmail>:
371 open(MAIL, '|/usr/lib/sendmail -t')
372 or die "cannot fork sendmail: $!";
374 This is fine for systems programming when sendmail is known to be
375 available. But it is not fine for many non-Unix systems, and even
376 some Unix systems that may not have sendmail installed. If a portable
377 solution is needed, see the various distributions on CPAN that deal
378 with it. Mail::Mailer and Mail::Send in the MailTools distribution are
379 commonly used, and provide several mailing methods, including mail,
380 sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
381 not available. Mail::Sendmail is a standalone module that provides
382 simple, platform-independent mailing.
384 The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
385 even on all Unix platforms.
387 The rule of thumb for portable code is: Do it all in portable Perl, or
388 use a module (that may internally implement it with platform-specific
389 code, but expose a common interface).
391 =head2 External Subroutines (XS)
393 XS code can usually be made to work with any platform, but dependent
394 libraries, header files, etc., might not be readily available or
395 portable, or the XS code itself might be platform-specific, just as Perl
396 code might be. If the libraries and headers are portable, then it is
397 normally reasonable to make sure the XS code is portable, too.
399 A different type of portability issue arises when writing XS code:
400 availability of a C compiler on the end-user's system. C brings
401 with it its own portability issues, and writing XS code will expose
402 you to some of those. Writing purely in Perl is an easier way to
405 =head2 Standard Modules
407 In general, the standard modules work across platforms. Notable
408 exceptions are the CPAN module (which currently makes connections to external
409 programs that may not be available), platform-specific modules (like
410 ExtUtils::MM_VMS), and DBM modules.
412 There is no one DBM module available on all platforms.
413 SDBM_File and the others are generally available on all Unix and DOSish
414 ports, but not in MacPerl, where only NBDM_File and DB_File are
417 The good news is that at least some DBM module should be available, and
418 AnyDBM_File will use whichever module it can find. Of course, then
419 the code needs to be fairly strict, dropping to the greatest common
420 factor (e.g., not exceeding 1K for each record), so that it will
421 work with any DBM module. See L<AnyDBM_File> for more details.
425 The system's notion of time of day and calendar date is controlled in
426 widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
427 and even if it is, don't assume that you can control the timezone through
430 Don't assume that the epoch starts at 00:00:00, January 1, 1970,
431 because that is OS- and implementation-specific. It is better to store a date
432 in an unambiguous representation. The ISO-8601 standard defines
433 "YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
434 can be easily converted into an OS-specific value using a module like
435 Date::Parse. An array of values, such as those returned by
436 C<localtime>, can be converted to an OS-specific representation using
439 When calculating specific times, such as for tests in time or date modules,
440 it may be appropriate to calculate an offset for the epoch.
443 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
445 The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
446 some large number. C<$offset> can then be added to a Unix time value
447 to get what should be the proper value on any system.
449 =head2 Character sets and character encoding
451 Assume little about character sets. Assume nothing about
452 numerical values (C<ord>, C<chr>) of characters. Do not
453 assume that the alphabetic characters are encoded contiguously (in
454 the numeric sense). Do not assume anything about the ordering of the
455 characters. The lowercase letters may come before or after the
456 uppercase letters; the lowercase and uppercase may be interlaced so
457 that both `a' and `A' come before `b'; the accented and other
458 international characters may be interlaced so that E<auml> comes
461 =head2 Internationalisation
463 If you may assume POSIX (a rather large assumption), you may read
464 more about the POSIX locale system from L<perllocale>. The locale
465 system at least attempts to make things a little bit more portable,
466 or at least more convenient and native-friendly for non-English
467 users. The system affects character sets and encoding, and date
468 and time formatting--amongst other things.
470 =head2 System Resources
472 If your code is destined for systems with severely constrained (or
473 missing!) virtual memory systems then you want to be I<especially> mindful
474 of avoiding wasteful constructs such as:
476 # NOTE: this is no longer "bad" in perl5.005
477 for (0..10000000) {} # bad
478 for (my $x = 0; $x <= 10000000; ++$x) {} # good
480 @lines = <VERY_LARGE_FILE>; # bad
482 while (<FILE>) {$file .= $_} # sometimes bad
483 $file = join('', <FILE>); # better
485 The last two constructs may appear unintuitive to most people. The
486 first repeatedly grows a string, whereas the second allocates a
487 large chunk of memory in one go. On some systems, the second is
488 more efficient that the first.
492 Most multi-user platforms provide basic levels of security, usually
493 implemented at the filesystem level. Some, however, do
494 not--unfortunately. Thus the notion of user id, or "home" directory,
495 or even the state of being logged-in, may be unrecognizable on many
496 platforms. If you write programs that are security-conscious, it
497 is usually best to know what type of system you will be running
498 under so that you can write code explicitly for that platform (or
503 For those times when it is necessary to have platform-specific code,
504 consider keeping the platform-specific code in one place, making porting
505 to other platforms easier. Use the Config module and the special
506 variable C<$^O> to differentiate platforms, as described in
509 Be careful in the tests you supply with your module or programs.
510 Module code may be fully portable, but its tests might not be. This
511 often happens when tests spawn off other processes or call external
512 programs to aid in the testing, or when (as noted above) the tests
513 assume certain things about the filesystem and paths. Be careful
514 not to depend on a specific output style for errors, such as when
515 checking C<$!> after an system call. Some platforms expect a certain
516 output format, and perl on those platforms may have been adjusted
517 accordingly. Most specifically, don't anchor a regex when testing
522 Modules uploaded to CPAN are tested by a variety of volunteers on
523 different platforms. These CPAN testers are notified by mail of each
524 new upload, and reply to the list with PASS, FAIL, NA (not applicable to
525 this platform), or UNKNOWN (unknown), along with any relevant notations.
527 The purpose of the testing is twofold: one, to help developers fix any
528 problems in their code that crop up because of lack of testing on other
529 platforms; two, to provide users with information about whether
530 a given module works on a given platform.
534 =item Mailing list: cpan-testers@perl.org
536 =item Testing results: http://testers.cpan.org/
542 As of version 5.002, Perl is built with a C<$^O> variable that
543 indicates the operating system it was built on. This was implemented
544 to help speed up code that would otherwise have to C<use Config>
545 and use the value of C<$Config{osname}>. Of course, to get more
546 detailed information about the system, looking into C<%Config> is
547 certainly recommended.
549 C<%Config> cannot always be trusted, however, because it was built
550 at compile time. If perl was built in one place, then transferred
551 elsewhere, some values may be wrong. The values may even have been
552 edited after the fact.
556 Perl works on a bewildering variety of Unix and Unix-like platforms (see
557 e.g. most of the files in the F<hints/> directory in the source code kit).
558 On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
559 too) is determined either by lowercasing and stripping punctuation from the
560 first field of the string returned by typing C<uname -a> (or a similar command)
561 at the shell prompt or by testing the file system for the presence of
562 uniquely named files such as a kernel or header file. Here, for example,
563 are a few of the more popular Unix flavors:
565 uname $^O $Config{'archname'}
566 --------------------------------------------
568 BSD/OS bsdos i386-bsdos
569 dgux dgux AViiON-dgux
570 DYNIX/ptx dynixptx i386-dynixptx
571 FreeBSD freebsd freebsd-i386
572 Linux linux arm-linux
573 Linux linux i386-linux
574 Linux linux i586-linux
575 Linux linux ppc-linux
576 HP-UX hpux PA-RISC1.1
578 Mac OS X rhapsody rhapsody
579 MachTen PPC machten powerpc-machten
581 NeXT 4 next OPENSTEP-Mach
582 openbsd openbsd i386-openbsd
583 OSF1 dec_osf alpha-dec_osf
584 reliantunix-n svr4 RM400-svr4
585 SCO_SV sco_sv i386-sco_sv
586 SINIX-N svr4 RM400-svr4
587 sn4609 unicos CRAY_C90-unicos
588 sn6521 unicosmk t3e-unicosmk
589 sn9617 unicos CRAY_J90-unicos
590 SunOS solaris sun4-solaris
591 SunOS solaris i86pc-solaris
592 SunOS4 sunos sun4-sunos
594 Because the value of C<$Config{archname}> may depend on the
595 hardware architecture, it can vary more than the value of C<$^O>.
597 =head2 DOS and Derivatives
599 Perl has long been ported to Intel-style microcomputers running under
600 systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
601 bring yourself to mention (except for Windows CE, if you count that).
602 Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
603 be aware that each of these file specifications may have subtle
606 $filespec0 = "c:/foo/bar/file.txt";
607 $filespec1 = "c:\\foo\\bar\\file.txt";
608 $filespec2 = 'c:\foo\bar\file.txt';
609 $filespec3 = 'c:\\foo\\bar\\file.txt';
611 System calls accept either C</> or C<\> as the path separator.
612 However, many command-line utilities of DOS vintage treat C</> as
613 the option prefix, so may get confused by filenames containing C</>.
614 Aside from calling any external programs, C</> will work just fine,
615 and probably better, as it is more consistent with popular usage,
616 and avoids the problem of remembering what to backwhack and what
619 The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
620 the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
621 filesystems you may have to be careful about case returned with functions
622 like C<readdir> or used with functions like C<open> or C<opendir>.
624 DOS also treats several filenames as special, such as AUX, PRN,
625 NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
626 filenames won't even work if you include an explicit directory
627 prefix. It is best to avoid such filenames, if you want your code
628 to be portable to DOS and its derivatives. It's hard to know what
629 these all are, unfortunately.
631 Users of these operating systems may also wish to make use of
632 scripts such as I<pl2bat.bat> or I<pl2cmd> to
633 put wrappers around your scripts.
635 Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
636 and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
637 will keep C<\n> translated as C<\012> for that filehandle. Since it is a
638 no-op on other systems, C<binmode> should be used for cross-platform code
639 that deals with binary data. That's assuming you realize in advance
640 that your data is in binary. General-purpose programs should
641 often assume nothing about their data.
643 The C<$^O> variable and the C<$Config{archname}> values for various
644 DOSish perls are as follows:
646 OS $^O $Config{'archname'}
647 --------------------------------------------
651 Windows 95 MSWin32 MSWin32-x86
652 Windows 98 MSWin32 MSWin32-x86
653 Windows NT MSWin32 MSWin32-x86
654 Windows NT MSWin32 MSWin32-ALPHA
655 Windows NT MSWin32 MSWin32-ppc
664 The djgpp environment for DOS, http://www.delorie.com/djgpp/
669 The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
670 http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
671 ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
675 Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
680 The C<Win32::*> modules in L<Win32>.
684 The ActiveState Pages, http://www.activestate.com/
688 The Cygwin environment for Win32; F<README.cygwin> (installed
689 as L<perlcygwin>), http://www.cygwin.com/
693 The U/WIN environment for Win32,
694 <http://www.research.att.com/sw/tools/uwin/
696 =item Build instructions for OS/2, L<perlos2>
703 Any module requiring XS compilation is right out for most people, because
704 MacPerl is built using non-free (and non-cheap!) compilers. Some XS
705 modules that can work with MacPerl are built and distributed in binary
708 Directories are specified as:
710 volume:folder:file for absolute pathnames
711 volume:folder: for absolute pathnames
712 :folder:file for relative pathnames
713 :folder: for relative pathnames
714 :file for relative pathnames
715 file for relative pathnames
717 Files are stored in the directory in alphabetical order. Filenames are
718 limited to 31 characters, and may include any character except for
719 null and C<:>, which is reserved as the path separator.
721 Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
722 Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
724 In the MacPerl application, you can't run a program from the command line;
725 programs that expect C<@ARGV> to be populated can be edited with something
726 like the following, which brings up a dialog box asking for the command
730 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
733 A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
734 pathnames of the files dropped onto the script.
736 Mac users can run programs under a type of command line interface
737 under MPW (Macintosh Programmer's Workshop, a free development
738 environment from Apple). MacPerl was first introduced as an MPW
739 tool, and MPW can be used like a shell:
741 perl myscript.plx some arguments
743 ToolServer is another app from Apple that provides access to MPW tools
744 from MPW and the MacPerl app, which allows MacPerl programs to use
745 C<system>, backticks, and piped C<open>.
747 "S<Mac OS>" is the proper name for the operating system, but the value
748 in C<$^O> is "MacOS". To determine architecture, version, or whether
749 the application or MPW tool version is running, check:
751 $is_app = $MacPerl::Version =~ /App/;
752 $is_tool = $MacPerl::Version =~ /MPW/;
753 ($version) = $MacPerl::Version =~ /^(\S+)/;
754 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
755 $is_68k = $MacPerl::Architecture eq 'Mac68K';
757 S<Mac OS X> and S<Mac OS X Server>, based on NeXT's OpenStep OS, will
758 (in theory) be able to run MacPerl natively, under the "Classic"
759 environment. The new "Cocoa" environment (formerly called the "Yellow Box")
760 may run a slightly modified version of MacPerl, using the Carbon interfaces.
762 S<Mac OS X Server> and its Open Source version, Darwin, both run Unix
763 perl natively (with a few patches). Full support for these
764 is slated for perl 5.6.
772 The MacPerl Pages, http://www.macperl.com/ .
776 The MacPerl mailing lists, http://www.macperl.org/ .
780 MacPerl Module Porters, http://pudge.net/mmp/ .
786 Perl on VMS is discussed in L<perlvms> in the perl distribution.
787 Perl on VMS can accept either VMS- or Unix-style file
788 specifications as in either of the following:
790 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
791 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
793 but not a mixture of both as in:
795 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
796 Can't open sys$login:/login.com: file specification syntax error
798 Interacting with Perl from the Digital Command Language (DCL) shell
799 often requires a different set of quotation marks than Unix shells do.
802 $ perl -e "print ""Hello, world.\n"""
805 There are several ways to wrap your perl scripts in DCL F<.COM> files, if
806 you are so inclined. For example:
808 $ write sys$output "Hello from DCL!"
810 $ then perl -x 'f$environment("PROCEDURE")
811 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
812 $ deck/dollars="__END__"
815 print "Hello from Perl!\n";
820 Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
821 perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
823 Filenames are in the format "name.extension;version". The maximum
824 length for filenames is 39 characters, and the maximum length for
825 extensions is also 39 characters. Version is a number from 1 to
826 32767. Valid characters are C</[A-Z0-9$_-]/>.
828 VMS's RMS filesystem is case-insensitive and does not preserve case.
829 C<readdir> returns lowercased filenames, but specifying a file for
830 opening remains case-insensitive. Files without extensions have a
831 trailing period on them, so doing a C<readdir> with a file named F<A.;5>
832 will return F<a.> (though that file could be opened with
835 RMS had an eight level limit on directory depths from any rooted logical
836 (allowing 16 levels overall) prior to VMS 7.2. Hence
837 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
838 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
839 have to take this into account, but at least they can refer to the former
840 as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
842 The VMS::Filespec module, which gets installed as part of the build
843 process on VMS, is a pure Perl module that can easily be installed on
844 non-VMS platforms and can be helpful for conversions to and from RMS
847 What C<\n> represents depends on the type of file opened. It could
848 be C<\015>, C<\012>, C<\015\012>, or nothing. The VMS::Stdio module
849 provides access to the special fopen() requirements of files with unusual
852 TCP/IP stacks are optional on VMS, so socket routines might not be
853 implemented. UDP sockets may not be supported.
855 The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
856 that you are running on without resorting to loading all of C<%Config>
857 you can examine the content of the C<@INC> array like so:
859 if (grep(/VMS_AXP/, @INC)) {
860 print "I'm on Alpha!\n";
862 } elsif (grep(/VMS_VAX/, @INC)) {
863 print "I'm on VAX!\n";
866 print "I'm not so sure about where $^O is...\n";
869 On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
870 logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
871 calls to C<localtime> are adjusted to count offsets from
872 01-JAN-1970 00:00:00.00, just like Unix.
880 F<README.vms> (installed as L<README_vms>), L<perlvms>
884 vmsperl list, majordomo@perl.org
886 (Put the words C<subscribe vmsperl> in message body.)
890 vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
896 Perl on VOS is discussed in F<README.vos> in the perl distribution
897 (installed as L<perlvos>). Perl on VOS can accept either VOS- or
898 Unix-style file specifications as in either of the following:
900 $ perl -ne "print if /perl_setup/i" >system>notices
901 $ perl -ne "print if /perl_setup/i" /system/notices
903 or even a mixture of both as in:
905 $ perl -ne "print if /perl_setup/i" >system/notices
907 Even though VOS allows the slash character to appear in object
908 names, because the VOS port of Perl interprets it as a pathname
909 delimiting character, VOS files, directories, or links whose names
910 contain a slash character cannot be processed. Such files must be
911 renamed before they can be processed by Perl. Note that VOS limits
912 file names to 32 or fewer characters.
914 See F<README.vos> for restrictions that apply when Perl is built
915 with the alpha version of VOS POSIX.1 support.
917 Perl on VOS is built without any extensions and does not support
920 The value of C<$^O> on VOS is "VOS". To determine the architecture that
921 you are running on without resorting to loading all of C<%Config> you
922 can examine the content of the @INC array like so:
925 print "I'm on a Stratus box!\n";
927 print "I'm not on a Stratus box!\n";
931 if (grep(/860/, @INC)) {
932 print "This box is a Stratus XA/R!\n";
934 } elsif (grep(/7100/, @INC)) {
935 print "This box is a Stratus HP 7100 or 8xxx!\n";
937 } elsif (grep(/8000/, @INC)) {
938 print "This box is a Stratus HP 8xxx!\n";
941 print "This box is a Stratus 68K!\n";
954 The VOS mailing list.
956 There is no specific mailing list for Perl on VOS. You can post
957 comments to the comp.sys.stratus newsgroup, or subscribe to the general
958 Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
959 the message body to majordomo@list.stratagy.com.
963 VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
967 =head2 EBCDIC Platforms
969 Recent versions of Perl have been ported to platforms such as OS/400 on
970 AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
971 Mainframes. Such computers use EBCDIC character sets internally (usually
972 Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
973 systems). On the mainframe perl currently works under the "Unix system
974 services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
975 the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
976 See L<perlos390> for details.
978 As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
979 sub-systems do not support the C<#!> shebang trick for script invocation.
980 Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
981 similar to the following simple script:
984 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
986 #!/usr/local/bin/perl # just a comment really
988 print "Hello from perl!\n";
990 OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
991 Calls to C<system> and backticks can use POSIX shell syntax on all
994 On the AS/400, if PERL5 is in your library list, you may need
995 to wrap your perl scripts in a CL procedure to invoke them like so:
998 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1001 This will invoke the perl script F<hello.pl> in the root of the
1002 QOpenSys file system. On the AS/400 calls to C<system> or backticks
1005 On these platforms, bear in mind that the EBCDIC character set may have
1006 an effect on what happens with some perl functions (such as C<chr>,
1007 C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1008 well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1009 and C<|>, not to mention dealing with socket interfaces to ASCII computers
1010 (see L<"Newlines">).
1012 Fortunately, most web servers for the mainframe will correctly
1013 translate the C<\n> in the following statement to its ASCII equivalent
1014 (C<\r> is the same under both Unix and OS/390 & VM/ESA):
1016 print "Content-type: text/html\r\n\r\n";
1018 The values of C<$^O> on some of these platforms includes:
1020 uname $^O $Config{'archname'}
1021 --------------------------------------------
1024 POSIX-BC posix-bc BS2000-posix-bc
1027 Some simple tricks for determining if you are running on an EBCDIC
1028 platform could include any of the following (perhaps all):
1030 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1032 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1034 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1036 One thing you may not want to rely on is the EBCDIC encoding
1037 of punctuation characters since these may differ from code page to code
1038 page (and once your module or script is rumoured to work with EBCDIC,
1039 folks will want it to work with all EBCDIC character sets).
1049 L<perlos390>, F<README.os390>, F<perlposix-bc>, F<README.vmesa>,
1054 The perl-mvs@perl.org list is for discussion of porting issues as well as
1055 general usage issues for all EBCDIC Perls. Send a message body of
1056 "subscribe perl-mvs" to majordomo@perl.org.
1060 AS/400 Perl information at
1061 http://as400.rochester.ibm.com/
1062 as well as on CPAN in the F<ports/> directory.
1066 =head2 Acorn RISC OS
1068 Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1069 Unix, and because Unix filename emulation is turned on by default,
1070 most simple scripts will probably work "out of the box". The native
1071 filesystem is modular, and individual filesystems are free to be
1072 case-sensitive or insensitive, and are usually case-preserving. Some
1073 native filesystems have name length limits, which file and directory
1074 names are silently truncated to fit. Scripts should be aware that the
1075 standard filesystem currently has a name length limit of B<10>
1076 characters, with up to 77 items in a directory, but other filesystems
1077 may not impose such limitations.
1079 Native filenames are of the form
1081 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
1085 Special_Field is not usually present, but may contain . and $ .
1086 Filesystem =~ m|[A-Za-z0-9_]|
1087 DsicName =~ m|[A-Za-z0-9_/]|
1088 $ represents the root directory
1089 . is the path separator
1090 @ is the current directory (per filesystem but machine global)
1091 ^ is the parent directory
1092 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1094 The default filename translation is roughly C<tr|/.|./|;>
1096 Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
1097 the second stage of C<$> interpolation in regular expressions will fall
1098 foul of the C<$.> if scripts are not careful.
1100 Logical paths specified by system variables containing comma-separated
1101 search lists are also allowed; hence C<System:Modules> is a valid
1102 filename, and the filesystem will prefix C<Modules> with each section of
1103 C<System$Path> until a name is made that points to an object on disk.
1104 Writing to a new file C<System:Modules> would be allowed only if
1105 C<System$Path> contains a single item list. The filesystem will also
1106 expand system variables in filenames if enclosed in angle brackets, so
1107 C<< <System$Dir>.Modules >> would look for the file
1108 S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
1109 that B<fully qualified filenames can start with C<< <> >>> and should
1110 be protected when C<open> is used for input.
1112 Because C<.> was in use as a directory separator and filenames could not
1113 be assumed to be unique after 10 characters, Acorn implemented the C
1114 compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1115 filenames specified in source code and store the respective files in
1116 subdirectories named after the suffix. Hence files are translated:
1119 C:foo.h C:h.foo (logical path variable)
1120 sys/os.h sys.h.os (C compiler groks Unix-speak)
1121 10charname.c c.10charname
1122 10charname.o o.10charname
1123 11charname_.c c.11charname (assuming filesystem truncates at 10)
1125 The Unix emulation library's translation of filenames to native assumes
1126 that this sort of translation is required, and it allows a user-defined list
1127 of known suffixes that it will transpose in this fashion. This may
1128 seem transparent, but consider that with these rules C<foo/bar/baz.h>
1129 and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1130 C<glob> cannot and do not attempt to emulate the reverse mapping. Other
1131 C<.>'s in filenames are translated to C</>.
1133 As implied above, the environment accessed through C<%ENV> is global, and
1134 the convention is that program specific environment variables are of the
1135 form C<Program$Name>. Each filesystem maintains a current directory,
1136 and the current filesystem's current directory is the B<global> current
1137 directory. Consequently, sociable programs don't change the current
1138 directory but rely on full pathnames, and programs (and Makefiles) cannot
1139 assume that they can spawn a child process which can change the current
1140 directory without affecting its parent (and everyone else for that
1143 Because native operating system filehandles are global and are currently
1144 allocated down from 255, with 0 being a reserved value, the Unix emulation
1145 library emulates Unix filehandles. Consequently, you can't rely on
1146 passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1148 The desire of users to express filenames of the form
1149 C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
1150 too: C<``> command output capture has to perform a guessing game. It
1151 assumes that a string C<< <[^<>]+\$[^<>]> >> is a
1152 reference to an environment variable, whereas anything else involving
1153 C<< < >> or C<< > >> is redirection, and generally manages to be 99%
1154 right. Of course, the problem remains that scripts cannot rely on any
1155 Unix tools being available, or that any tools found have Unix-like command
1158 Extensions and XS are, in theory, buildable by anyone using free
1159 tools. In practice, many don't, as users of the Acorn platform are
1160 used to binary distributions. MakeMaker does run, but no available
1161 make currently copes with MakeMaker's makefiles; even if and when
1162 this should be fixed, the lack of a Unix-like shell will cause
1163 problems with makefile rules, especially lines of the form C<cd
1164 sdbm && make all>, and anything using quoting.
1166 "S<RISC OS>" is the proper name for the operating system, but the value
1167 in C<$^O> is "riscos" (because we don't like shouting).
1171 Perl has been ported to many platforms that do not fit into any of
1172 the categories listed above. Some, such as AmigaOS, Atari MiNT,
1173 BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1174 into the standard Perl source code kit. You may need to see the
1175 F<ports/> directory on CPAN for information, and possibly binaries,
1176 for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1177 Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1178 fall under the Unix category, but we are not a standards body.)
1180 Some approximate operating system names and their C<$^O> values
1181 in the "OTHER" category include:
1183 OS $^O $Config{'archname'}
1184 ------------------------------------------
1185 Amiga DOS amigaos m68k-amigos
1186 MPE/iX mpeix PA-RISC1.1
1194 Amiga, F<README.amiga> (installed as L<perlamiga>).
1198 Atari, F<README.mint> and Guido Flohr's web page
1199 http://stud.uni-sb.de/~gufl0000/
1203 Be OS, F<README.beos>
1207 HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
1208 http://www.cccd.edu/~markb/perlix.html
1212 A free perl5-based PERL.NLM for Novell Netware is available in
1213 precompiled binary and source code form from http://www.novell.com/
1214 as well as from CPAN.
1218 Plan 9, F<README.plan9>
1222 =head1 FUNCTION IMPLEMENTATIONS
1224 Listed below are functions that are either completely unimplemented
1225 or else have been implemented differently on various platforms.
1226 Following each description will be, in parentheses, a list of
1227 platforms that the description applies to.
1229 The list may well be incomplete, or even wrong in some places. When
1230 in doubt, consult the platform-specific README files in the Perl
1231 source distribution, and any other documentation resources accompanying
1234 Be aware, moreover, that even among Unix-ish systems there are variations.
1236 For many functions, you can also query C<%Config>, exported by
1237 default from the Config module. For example, to check whether the
1238 platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1239 L<Config> for a full description of available variables.
1241 =head2 Alphabetical Listing of Perl Functions
1251 C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
1252 and applications are executable, and there are no uid/gid
1253 considerations. C<-o> is not supported. (S<Mac OS>)
1255 C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1256 which may not reflect UIC-based file protections. (VMS)
1258 C<-s> returns the size of the data fork, not the total size of data fork
1259 plus resource fork. (S<Mac OS>).
1261 C<-s> by name on an open file will return the space reserved on disk,
1262 rather than the current extent. C<-s> on an open filehandle returns the
1263 current size. (S<RISC OS>)
1265 C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
1266 C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1268 C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1271 C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
1272 (Win32, VMS, S<RISC OS>)
1274 C<-d> is true if passed a device spec without an explicit directory.
1277 C<-T> and C<-B> are implemented, but might misclassify Mac text files
1278 with foreign characters; this is the case will all platforms, but may
1279 affect S<Mac OS> often. (S<Mac OS>)
1281 C<-x> (or C<-X>) determine if a file ends in one of the executable
1282 suffixes. C<-S> is meaningless. (Win32)
1284 C<-x> (or C<-X>) determine if a file has an executable file type.
1291 Not implemented. (Win32)
1293 =item binmode FILEHANDLE
1295 Meaningless. (S<Mac OS>, S<RISC OS>)
1297 Reopens file and restores pointer; if function fails, underlying
1298 filehandle may be closed, or pointer may be in a different position.
1301 The value returned by C<tell> may be affected after the call, and
1302 the filehandle may be flushed. (Win32)
1306 Only limited meaning. Disabling/enabling write permission is mapped to
1307 locking/unlocking the file. (S<Mac OS>)
1309 Only good for changing "owner" read-write access, "group", and "other"
1310 bits are meaningless. (Win32)
1312 Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1314 Access permissions are mapped onto VOS access-control list changes. (VOS)
1318 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
1320 Does nothing, but won't fail. (Win32)
1322 =item chroot FILENAME
1326 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
1328 =item crypt PLAINTEXT,SALT
1330 May not be available if library or source was not provided when building
1333 Not implemented. (VOS)
1337 Not implemented. (VMS, Plan9, VOS)
1339 =item dbmopen HASH,DBNAME,MODE
1341 Not implemented. (VMS, Plan9, VOS)
1345 Not useful. (S<Mac OS>, S<RISC OS>)
1347 Not implemented. (Win32)
1349 Invokes VMS debugger. (VMS)
1353 Not implemented. (S<Mac OS>)
1355 Implemented via Spawn. (VM/ESA)
1357 Does not automatically flush output handles on some platforms.
1358 (SunOS, Solaris, HP-UX)
1360 =item fcntl FILEHANDLE,FUNCTION,SCALAR
1362 Not implemented. (Win32, VMS)
1364 =item flock FILEHANDLE,OPERATION
1366 Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
1368 Available only on Windows NT (not on Windows 95). (Win32)
1372 Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1374 Emulated using multiple interpreters. See L<perlfork>. (Win32)
1376 Does not automatically flush output handles on some platforms.
1377 (SunOS, Solaris, HP-UX)
1381 Not implemented. (S<Mac OS>, S<RISC OS>)
1385 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1389 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1391 =item getpriority WHICH,WHO
1393 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1397 Not implemented. (S<Mac OS>, Win32)
1399 Not useful. (S<RISC OS>)
1403 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1405 =item getnetbyname NAME
1407 Not implemented. (S<Mac OS>, Win32, Plan9)
1411 Not implemented. (S<Mac OS>, Win32)
1413 Not useful. (S<RISC OS>)
1417 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1419 =item getnetbyaddr ADDR,ADDRTYPE
1421 Not implemented. (S<Mac OS>, Win32, Plan9)
1423 =item getprotobynumber NUMBER
1425 Not implemented. (S<Mac OS>)
1427 =item getservbyport PORT,PROTO
1429 Not implemented. (S<Mac OS>)
1433 Not implemented. (S<Mac OS>, Win32, VM/ESA)
1437 Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
1441 Not implemented. (S<Mac OS>, Win32)
1445 Not implemented. (S<Mac OS>, Win32, Plan9)
1449 Not implemented. (S<Mac OS>, Win32, Plan9)
1453 Not implemented. (Win32, Plan9)
1457 Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
1461 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1463 =item sethostent STAYOPEN
1465 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1467 =item setnetent STAYOPEN
1469 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1471 =item setprotoent STAYOPEN
1473 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1475 =item setservent STAYOPEN
1477 Not implemented. (Plan9, Win32, S<RISC OS>)
1481 Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
1485 Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
1489 Not implemented. (S<Mac OS>, Win32)
1493 Not implemented. (S<Mac OS>, Win32, Plan9)
1497 Not implemented. (S<Mac OS>, Win32, Plan9)
1501 Not implemented. (Plan9, Win32)
1503 =item getsockopt SOCKET,LEVEL,OPTNAME
1505 Not implemented. (S<Mac OS>, Plan9)
1511 Globbing built-in, but only C<*> and C<?> metacharacters are supported.
1514 This operator is implemented via the File::Glob extension on most
1515 platforms. See L<File::Glob> for portability information.
1517 =item ioctl FILEHANDLE,FUNCTION,SCALAR
1519 Not implemented. (VMS)
1521 Available only for socket handles, and it does what the ioctlsocket() call
1522 in the Winsock API does. (Win32)
1524 Available only for socket handles. (S<RISC OS>)
1526 =item kill SIGNAL, LIST
1528 Not implemented, hence not useful for taint checking. (S<Mac OS>,
1531 C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1532 a signal to the identified process like it does on Unix platforms.
1533 Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1534 and makes it exit immediately with exit status $sig. As in Unix, if
1535 $sig is 0 and the specified process exists, it returns true without
1536 actually terminating it. (Win32)
1538 =item link OLDFILE,NEWFILE
1540 Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
1542 Link count not updated because hard links are not quite that hard
1543 (They are sort of half-way between hard and soft links). (AmigaOS)
1545 Hard links are implemented on Win32 (Windows NT and Windows 2000)
1548 =item lstat FILEHANDLE
1554 Not implemented. (VMS, S<RISC OS>)
1556 Return values (especially for device and inode) may be bogus. (Win32)
1558 =item msgctl ID,CMD,ARG
1560 =item msgget KEY,FLAGS
1562 =item msgsnd ID,MSG,FLAGS
1564 =item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1566 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
1568 =item open FILEHANDLE,EXPR
1570 =item open FILEHANDLE
1572 The C<|> variants are supported only if ToolServer is installed.
1575 open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
1577 Opening a process does not automatically flush output handles on some
1578 platforms. (SunOS, Solaris, HP-UX)
1580 =item pipe READHANDLE,WRITEHANDLE
1582 Not implemented. (S<Mac OS>)
1584 Very limited functionality. (MiNT)
1590 Not implemented. (Win32, VMS, S<RISC OS>)
1592 =item select RBITS,WBITS,EBITS,TIMEOUT
1594 Only implemented on sockets. (Win32)
1596 Only reliable on sockets. (S<RISC OS>)
1598 Note that the C<socket FILEHANDLE> form is generally portable.
1600 =item semctl ID,SEMNUM,CMD,ARG
1602 =item semget KEY,NSEMS,FLAGS
1604 =item semop KEY,OPSTRING
1606 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1610 Not implemented. (MPE/iX, Win32)
1612 =item setpgrp PID,PGRP
1614 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1616 =item setpriority WHICH,WHO,PRIORITY
1618 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1622 Not implemented. (MPE/iX, Win32)
1624 =item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1626 Not implemented. (S<Mac OS>, Plan9)
1628 =item shmctl ID,CMD,ARG
1630 =item shmget KEY,SIZE,FLAGS
1632 =item shmread ID,VAR,POS,SIZE
1634 =item shmwrite ID,STRING,POS,SIZE
1636 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1638 =item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1640 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1642 =item stat FILEHANDLE
1648 Platforms that do not have rdev, blksize, or blocks will return these
1649 as '', so numeric comparison or manipulation of these fields may cause
1650 'not numeric' warnings.
1652 mtime and atime are the same thing, and ctime is creation time instead of
1653 inode change time. (S<Mac OS>)
1655 device and inode are not meaningful. (Win32)
1657 device and inode are not necessarily reliable. (VMS)
1659 mtime, atime and ctime all return the last modification time. Device and
1660 inode are not necessarily reliable. (S<RISC OS>)
1662 dev, rdev, blksize, and blocks are not available. inode is not
1663 meaningful and will differ between stat calls on the same file. (os2)
1665 =item symlink OLDFILE,NEWFILE
1667 Not implemented. (Win32, VMS, S<RISC OS>)
1671 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1673 =item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1675 The traditional "0", "1", and "2" MODEs are implemented with different
1676 numeric values on some systems. The flags exported by C<Fcntl>
1677 (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1678 OS>, OS/390, VM/ESA)
1682 Only implemented if ToolServer is installed. (S<Mac OS>)
1684 As an optimization, may not call the command shell specified in
1685 C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1686 process and immediately returns its process designator, without
1687 waiting for it to terminate. Return value may be used subsequently
1688 in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1689 by setting $? to "255 << 8". C<$?> is set in a way compatible with
1690 Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1691 as described in the documentation). (Win32)
1693 There is no shell to process metacharacters, and the native standard is
1694 to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1695 program. Redirection such as C<< > foo >> is performed (if at all) by
1696 the run time library of the spawned program. C<system> I<list> will call
1697 the Unix emulation library's C<exec> emulation, which attempts to provide
1698 emulation of the stdin, stdout, stderr in force in the parent, providing
1699 the child program uses a compatible version of the emulation library.
1700 I<scalar> will call the native command line direct and no such emulation
1701 of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1703 Far from being POSIX compliant. Because there may be no underlying
1704 /bin/sh tries to work around the problem by forking and execing the
1705 first token in its argument string. Handles basic redirection
1706 ("<" or ">") on its own behalf. (MiNT)
1708 Does not automatically flush output handles on some platforms.
1709 (SunOS, Solaris, HP-UX)
1713 Only the first entry returned is nonzero. (S<Mac OS>)
1715 "cumulative" times will be bogus. On anything other than Windows NT
1716 or Windows 2000, "system" time will be bogus, and "user" time is
1717 actually the time returned by the clock() function in the C runtime
1720 Not useful. (S<RISC OS>)
1722 =item truncate FILEHANDLE,LENGTH
1724 =item truncate EXPR,LENGTH
1726 Not implemented. (VMS)
1728 Truncation to zero-length only. (VOS)
1730 If a FILEHANDLE is supplied, it must be writable and opened in append
1731 mode (i.e., use C<open(FH, '>>filename')>
1732 or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1733 should not be held open elsewhere. (Win32)
1739 Returns undef where unavailable, as of version 5.005.
1741 C<umask> works but the correct permissions are set only when the file
1742 is finally closed. (AmigaOS)
1746 Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
1748 May not behave as expected. Behavior depends on the C runtime
1749 library's implementation of utime(), and the filesystem being
1750 used. The FAT filesystem typically does not support an "access
1751 time" field, and it may limit timestamps to a granularity of
1752 two seconds. (Win32)
1756 =item waitpid PID,FLAGS
1758 Not implemented. (S<Mac OS>, VOS)
1760 Can only be applied to process handles returned for processes spawned
1761 using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
1763 Not useful. (S<RISC OS>)
1771 =item v1.47, 22 March 2000
1773 Various cleanups from Tom Christiansen, including migration of
1774 long platform listings from L<perl>.
1776 =item v1.46, 12 February 2000
1778 Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1780 =item v1.45, 20 December 1999
1782 Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1784 =item v1.44, 19 July 1999
1786 A bunch of updates from Peter Prymmer for C<$^O> values,
1787 endianness, File::Spec, VMS, BS2000, OS/400.
1789 =item v1.43, 24 May 1999
1791 Added a lot of cleaning up from Tom Christiansen.
1793 =item v1.42, 22 May 1999
1795 Added notes about tests, sprintf/printf, and epoch offsets.
1797 =item v1.41, 19 May 1999
1799 Lots more little changes to formatting and content.
1801 Added a bunch of C<$^O> and related values
1802 for various platforms; fixed mail and web addresses, and added
1803 and changed miscellaneous notes. (Peter Prymmer)
1805 =item v1.40, 11 April 1999
1807 Miscellaneous changes.
1809 =item v1.39, 11 February 1999
1811 Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1812 note about newlines added.
1814 =item v1.38, 31 December 1998
1816 More changes from Jarkko.
1818 =item v1.37, 19 December 1998
1820 More minor changes. Merge two separate version 1.35 documents.
1822 =item v1.36, 9 September 1998
1824 Updated for Stratus VOS. Also known as version 1.35.
1826 =item v1.35, 13 August 1998
1828 Integrate more minor changes, plus addition of new sections under
1829 L<"ISSUES">: L<"Numbers endianness and Width">,
1830 L<"Character sets and character encoding">,
1831 L<"Internationalisation">.
1833 =item v1.33, 06 August 1998
1835 Integrate more minor changes.
1837 =item v1.32, 05 August 1998
1839 Integrate more minor changes.
1841 =item v1.30, 03 August 1998
1843 Major update for RISC OS, other minor changes.
1845 =item v1.23, 10 July 1998
1847 First public release with perl5.005.
1851 =head1 Supported Platforms
1853 As of early March 2000 (the Perl release 5.6.0), the following
1854 platforms are able to build Perl from the standard source code
1855 distribution available at http://www.perl.com/CPAN/src/index.html
1887 1) in DOS mode either the DOS or OS/2 ports can be used
1888 2) new in 5.6.0: the BSD/NeXT-based UNIX of Mac OS X
1889 3) formerly known as Digital UNIX and before that DEC OSF/1
1890 4) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
1892 The following platforms worked for the previous major release
1893 (5.005_03 being the latest maintenance release of that, as of early
1894 March 2000), but be did not manage to test these in time for the 5.6.0
1895 release of Perl. There is a very good chance that these will work
1896 just fine with 5.6.0.
1912 The following platform worked for the previous major release (5.005_03
1913 being the latest maintenance release of that, as of early March 2000).
1914 However, standardization on UTF-8 as the internal string representation
1915 in 5.6.0 has introduced incompatibilities in this EBCDIC platform.
1916 Support for this platform may be enabled in a future release:
1920 1) Previously known as MVS, or OpenEdition MVS.
1922 Strongly related to the OS390 platform by also being EBCDIC-based
1923 mainframe platforms are the following platforms:
1928 These are also not expected to work under 5.6.0 for the same reasons
1929 as OS390. Contact the mailing list perl-mvs@perl.org for more details.
1931 MacOS (Classic, pre-X) is almost 5.6.0-ready; building from the source
1932 does work with 5.6.0, but additional MacOS specific source code is needed
1933 for a complete port. Contact the mailing list macperl-porters@macperl.org
1934 for more information.
1936 The following platforms have been known to build Perl from source in
1937 the past, but we haven't been able to verify their status for the
1938 current release, either because the hardware/software platforms are
1939 rare or because we don't have an active champion on these
1971 Support for the following platform is planned for a future Perl release:
1975 The following platforms have their own source code distributions and
1976 binaries available via http://www.perl.com/CPAN/ports/index.html:
1982 Tandem Guardian 5.004
1984 The following platforms have only binaries available via
1985 http://www.perl.com/CPAN/ports/index.html :
1989 Acorn RISCOS 5.005_02
1993 Although we do suggest that you always build your own Perl from
1994 the source code, both for maximal configurability and for security,
1995 in case you are in a hurry you can check
1996 http://www.perl.com/CPAN/ports/index.html for binary distributions.
2000 L<perlaix>, L<perlamiga>, L<perlcygwin>, L<perldos>, L<perlepoc>,
2001 L<perlebcdic>, L<perlhpux>, L<perlos2>, L<perlos390>, L<perlposix-bc>,
2002 L<perlwin32>, L<perlvms>, L<perlvos>, and L<Win32>.
2004 =head1 AUTHORS / CONTRIBUTORS
2006 Abigail <abigail@fnx.com>,
2007 Charles Bailey <bailey@newman.upenn.edu>,
2008 Graham Barr <gbarr@pobox.com>,
2009 Tom Christiansen <tchrist@perl.com>,
2010 Nicholas Clark <Nicholas.Clark@liverpool.ac.uk>,
2011 Thomas Dorner <Thomas.Dorner@start.de>,
2012 Andy Dougherty <doughera@lafcol.lafayette.edu>,
2013 Dominic Dunlop <domo@vo.lu>,
2014 Neale Ferguson <neale@mailbox.tabnsw.com.au>,
2015 David J. Fiander <davidf@mks.com>,
2016 Paul Green <Paul_Green@stratus.com>,
2017 M.J.T. Guy <mjtg@cus.cam.ac.uk>,
2018 Jarkko Hietaniemi <jhi@iki.fi>,
2019 Luther Huffman <lutherh@stratcom.com>,
2020 Nick Ing-Simmons <nick@ni-s.u-net.com>,
2021 Andreas J. KE<ouml>nig <koenig@kulturbox.de>,
2022 Markus Laker <mlaker@contax.co.uk>,
2023 Andrew M. Langmead <aml@world.std.com>,
2024 Larry Moore <ljmoore@freespace.net>,
2025 Paul Moore <Paul.Moore@uk.origin-it.com>,
2026 Chris Nandor <pudge@pobox.com>,
2027 Matthias Neeracher <neeri@iis.ee.ethz.ch>,
2028 Gary Ng <71564.1743@CompuServe.COM>,
2029 Tom Phoenix <rootbeer@teleport.com>,
2030 AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2031 Peter Prymmer <pvhp@forte.com>,
2032 Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2033 Gurusamy Sarathy <gsar@activestate.com>,
2034 Paul J. Schinder <schinder@pobox.com>,
2035 Michael G Schwern <schwern@pobox.com>,
2036 Dan Sugalski <sugalskd@ous.edu>,
2037 Nathan Torkington <gnat@frii.com>.
2039 This document is maintained by Chris Nandor
2044 Version 1.47, last modified 22 March 2000