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. Keeping
233 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 If all this is intimidating, have no (well, maybe only a little)
271 fear. There are modules that can help. The File::Spec modules
272 provide methods to do the Right Thing on whatever platform happens
273 to be running the program.
275 use File::Spec::Functions;
276 chdir(updir()); # go up one directory
277 $file = catfile(curdir(), 'temp', 'file.txt');
278 # on Unix and Win32, './temp/file.txt'
279 # on Mac OS, ':temp:file.txt'
280 # on VMS, '[.temp]file.txt'
282 File::Spec is available in the standard distribution as of version
283 5.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
284 and some versions of perl come with version 0.6. If File::Spec
285 is not updated to 0.7 or later, you must use the object-oriented
286 interface from File::Spec (or upgrade File::Spec).
288 In general, production code should not have file paths hardcoded.
289 Making them user-supplied or read from a configuration file is
290 better, keeping in mind that file path syntax varies on different
293 This is especially noticeable in scripts like Makefiles and test suites,
294 which often assume C</> as a path separator for subdirectories.
296 Also of use is File::Basename from the standard distribution, which
297 splits a pathname into pieces (base filename, full path to directory,
300 Even when on a single platform (if you can call Unix a single platform),
301 remember not to count on the existence or the contents of particular
302 system-specific files or directories, like F</etc/passwd>,
303 F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
304 example, F</etc/passwd> may exist but not contain the encrypted
305 passwords, because the system is using some form of enhanced security.
306 Or it may not contain all the accounts, because the system is using NIS.
307 If code does need to rely on such a file, include a description of the
308 file and its format in the code's documentation, then make it easy for
309 the user to override the default location of the file.
311 Don't assume a text file will end with a newline. They should,
314 Do not have two files of the same name with different case, like
315 F<test.pl> and F<Test.pl>, as many platforms have case-insensitive
316 filenames. Also, try not to have non-word characters (except for C<.>)
317 in the names, and keep them to the 8.3 convention, for maximum
318 portability, onerous a burden though this may appear.
320 Likewise, when using the AutoSplit module, try to keep your functions to
321 8.3 naming and case-insensitive conventions; or, at the least,
322 make it so the resulting files have a unique (case-insensitively)
325 Whitespace in filenames is tolerated on most systems, but not all.
326 Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
328 Don't assume C<< > >> won't be the first character of a filename.
329 Always use C<< < >> explicitly to open a file for reading,
330 unless you want the user to be able to specify a pipe open.
332 open(FILE, "< $existing_file") or die $!;
334 If filenames might use strange characters, it is safest to open it
335 with C<sysopen> instead of C<open>. C<open> is magic and can
336 translate characters like C<< > >>, C<< < >>, and C<|>, which may
337 be the wrong thing to do. (Sometimes, though, it's the right thing.)
339 =head2 System Interaction
341 Not all platforms provide a command line. These are usually platforms
342 that rely primarily on a Graphical User Interface (GUI) for user
343 interaction. A program requiring a command line interface might
344 not work everywhere. This is probably for the user of the program
345 to deal with, so don't stay up late worrying about it.
347 Some platforms can't delete or rename files held open by the system.
348 Remember to C<close> files when you are done with them. Don't
349 C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
350 file already tied or opened; C<untie> or C<close> it first.
352 Don't open the same file more than once at a time for writing, as some
353 operating systems put mandatory locks on such files.
355 Don't count on a specific environment variable existing in C<%ENV>.
356 Don't count on C<%ENV> entries being case-sensitive, or even
357 case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
358 if you really have to, make it conditional on C<$^O ne 'VMS'> since in
359 VMS the C<%ENV> table is much more than a per-process key-value string
362 Don't count on signals or C<%SIG> for anything.
364 Don't count on filename globbing. Use C<opendir>, C<readdir>, and
367 Don't count on per-program environment variables, or per-program current
370 Don't count on specific values of C<$!>.
372 =head2 Interprocess Communication (IPC)
374 In general, don't directly access the system in code meant to be
375 portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
376 C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
377 that makes being a perl hacker worth being.
379 Commands that launch external processes are generally supported on
380 most platforms (though many of them do not support any type of
381 forking). The problem with using them arises from what you invoke
382 them on. External tools are often named differently on different
383 platforms, may not be available in the same location, might accept
384 different arguments, can behave differently, and often present their
385 results in a platform-dependent way. Thus, you should seldom depend
386 on them to produce consistent results. (Then again, if you're calling
387 I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
389 One especially common bit of Perl code is opening a pipe to B<sendmail>:
391 open(MAIL, '|/usr/lib/sendmail -t')
392 or die "cannot fork sendmail: $!";
394 This is fine for systems programming when sendmail is known to be
395 available. But it is not fine for many non-Unix systems, and even
396 some Unix systems that may not have sendmail installed. If a portable
397 solution is needed, see the various distributions on CPAN that deal
398 with it. Mail::Mailer and Mail::Send in the MailTools distribution are
399 commonly used, and provide several mailing methods, including mail,
400 sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
401 not available. Mail::Sendmail is a standalone module that provides
402 simple, platform-independent mailing.
404 The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
405 even on all Unix platforms.
407 The rule of thumb for portable code is: Do it all in portable Perl, or
408 use a module (that may internally implement it with platform-specific
409 code, but expose a common interface).
411 =head2 External Subroutines (XS)
413 XS code can usually be made to work with any platform, but dependent
414 libraries, header files, etc., might not be readily available or
415 portable, or the XS code itself might be platform-specific, just as Perl
416 code might be. If the libraries and headers are portable, then it is
417 normally reasonable to make sure the XS code is portable, too.
419 A different type of portability issue arises when writing XS code:
420 availability of a C compiler on the end-user's system. C brings
421 with it its own portability issues, and writing XS code will expose
422 you to some of those. Writing purely in Perl is an easier way to
425 =head2 Standard Modules
427 In general, the standard modules work across platforms. Notable
428 exceptions are the CPAN module (which currently makes connections to external
429 programs that may not be available), platform-specific modules (like
430 ExtUtils::MM_VMS), and DBM modules.
432 There is no one DBM module available on all platforms.
433 SDBM_File and the others are generally available on all Unix and DOSish
434 ports, but not in MacPerl, where only NBDM_File and DB_File are
437 The good news is that at least some DBM module should be available, and
438 AnyDBM_File will use whichever module it can find. Of course, then
439 the code needs to be fairly strict, dropping to the greatest common
440 factor (e.g., not exceeding 1K for each record), so that it will
441 work with any DBM module. See L<AnyDBM_File> for more details.
445 The system's notion of time of day and calendar date is controlled in
446 widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
447 and even if it is, don't assume that you can control the timezone through
450 Don't assume that the epoch starts at 00:00:00, January 1, 1970,
451 because that is OS- and implementation-specific. It is better to store a date
452 in an unambiguous representation. The ISO-8601 standard defines
453 "YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
454 can be easily converted into an OS-specific value using a module like
455 Date::Parse. An array of values, such as those returned by
456 C<localtime>, can be converted to an OS-specific representation using
459 When calculating specific times, such as for tests in time or date modules,
460 it may be appropriate to calculate an offset for the epoch.
463 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
465 The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
466 some large number. C<$offset> can then be added to a Unix time value
467 to get what should be the proper value on any system.
469 =head2 Character sets and character encoding
471 Assume little about character sets. Assume nothing about
472 numerical values (C<ord>, C<chr>) of characters. Do not
473 assume that the alphabetic characters are encoded contiguously (in
474 the numeric sense). Do not assume anything about the ordering of the
475 characters. The lowercase letters may come before or after the
476 uppercase letters; the lowercase and uppercase may be interlaced so
477 that both `a' and `A' come before `b'; the accented and other
478 international characters may be interlaced so that E<auml> comes
481 =head2 Internationalisation
483 If you may assume POSIX (a rather large assumption), you may read
484 more about the POSIX locale system from L<perllocale>. The locale
485 system at least attempts to make things a little bit more portable,
486 or at least more convenient and native-friendly for non-English
487 users. The system affects character sets and encoding, and date
488 and time formatting--amongst other things.
490 =head2 System Resources
492 If your code is destined for systems with severely constrained (or
493 missing!) virtual memory systems then you want to be I<especially> mindful
494 of avoiding wasteful constructs such as:
496 # NOTE: this is no longer "bad" in perl5.005
497 for (0..10000000) {} # bad
498 for (my $x = 0; $x <= 10000000; ++$x) {} # good
500 @lines = <VERY_LARGE_FILE>; # bad
502 while (<FILE>) {$file .= $_} # sometimes bad
503 $file = join('', <FILE>); # better
505 The last two constructs may appear unintuitive to most people. The
506 first repeatedly grows a string, whereas the second allocates a
507 large chunk of memory in one go. On some systems, the second is
508 more efficient that the first.
512 Most multi-user platforms provide basic levels of security, usually
513 implemented at the filesystem level. Some, however, do
514 not--unfortunately. Thus the notion of user id, or "home" directory,
515 or even the state of being logged-in, may be unrecognizable on many
516 platforms. If you write programs that are security-conscious, it
517 is usually best to know what type of system you will be running
518 under so that you can write code explicitly for that platform (or
523 For those times when it is necessary to have platform-specific code,
524 consider keeping the platform-specific code in one place, making porting
525 to other platforms easier. Use the Config module and the special
526 variable C<$^O> to differentiate platforms, as described in
529 Be careful in the tests you supply with your module or programs.
530 Module code may be fully portable, but its tests might not be. This
531 often happens when tests spawn off other processes or call external
532 programs to aid in the testing, or when (as noted above) the tests
533 assume certain things about the filesystem and paths. Be careful
534 not to depend on a specific output style for errors, such as when
535 checking C<$!> after an system call. Some platforms expect a certain
536 output format, and perl on those platforms may have been adjusted
537 accordingly. Most specifically, don't anchor a regex when testing
542 Modules uploaded to CPAN are tested by a variety of volunteers on
543 different platforms. These CPAN testers are notified by mail of each
544 new upload, and reply to the list with PASS, FAIL, NA (not applicable to
545 this platform), or UNKNOWN (unknown), along with any relevant notations.
547 The purpose of the testing is twofold: one, to help developers fix any
548 problems in their code that crop up because of lack of testing on other
549 platforms; two, to provide users with information about whether
550 a given module works on a given platform.
554 =item Mailing list: cpan-testers@perl.org
556 =item Testing results: http://testers.cpan.org/
562 As of version 5.002, Perl is built with a C<$^O> variable that
563 indicates the operating system it was built on. This was implemented
564 to help speed up code that would otherwise have to C<use Config>
565 and use the value of C<$Config{osname}>. Of course, to get more
566 detailed information about the system, looking into C<%Config> is
567 certainly recommended.
569 C<%Config> cannot always be trusted, however, because it was built
570 at compile time. If perl was built in one place, then transferred
571 elsewhere, some values may be wrong. The values may even have been
572 edited after the fact.
576 Perl works on a bewildering variety of Unix and Unix-like platforms (see
577 e.g. most of the files in the F<hints/> directory in the source code kit).
578 On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
579 too) is determined either by lowercasing and stripping punctuation from the
580 first field of the string returned by typing C<uname -a> (or a similar command)
581 at the shell prompt or by testing the file system for the presence of
582 uniquely named files such as a kernel or header file. Here, for example,
583 are a few of the more popular Unix flavors:
585 uname $^O $Config{'archname'}
586 --------------------------------------------
588 BSD/OS bsdos i386-bsdos
589 dgux dgux AViiON-dgux
590 DYNIX/ptx dynixptx i386-dynixptx
591 FreeBSD freebsd freebsd-i386
592 Linux linux arm-linux
593 Linux linux i386-linux
594 Linux linux i586-linux
595 Linux linux ppc-linux
596 HP-UX hpux PA-RISC1.1
598 Mac OS X rhapsody rhapsody
599 MachTen PPC machten powerpc-machten
601 NeXT 4 next OPENSTEP-Mach
602 openbsd openbsd i386-openbsd
603 OSF1 dec_osf alpha-dec_osf
604 reliantunix-n svr4 RM400-svr4
605 SCO_SV sco_sv i386-sco_sv
606 SINIX-N svr4 RM400-svr4
607 sn4609 unicos CRAY_C90-unicos
608 sn6521 unicosmk t3e-unicosmk
609 sn9617 unicos CRAY_J90-unicos
610 SunOS solaris sun4-solaris
611 SunOS solaris i86pc-solaris
612 SunOS4 sunos sun4-sunos
614 Because the value of C<$Config{archname}> may depend on the
615 hardware architecture, it can vary more than the value of C<$^O>.
617 =head2 DOS and Derivatives
619 Perl has long been ported to Intel-style microcomputers running under
620 systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
621 bring yourself to mention (except for Windows CE, if you count that).
622 Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
623 be aware that each of these file specifications may have subtle
626 $filespec0 = "c:/foo/bar/file.txt";
627 $filespec1 = "c:\\foo\\bar\\file.txt";
628 $filespec2 = 'c:\foo\bar\file.txt';
629 $filespec3 = 'c:\\foo\\bar\\file.txt';
631 System calls accept either C</> or C<\> as the path separator.
632 However, many command-line utilities of DOS vintage treat C</> as
633 the option prefix, so may get confused by filenames containing C</>.
634 Aside from calling any external programs, C</> will work just fine,
635 and probably better, as it is more consistent with popular usage,
636 and avoids the problem of remembering what to backwhack and what
639 The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
640 the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
641 filesystems you may have to be careful about case returned with functions
642 like C<readdir> or used with functions like C<open> or C<opendir>.
644 DOS also treats several filenames as special, such as AUX, PRN,
645 NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
646 filenames won't even work if you include an explicit directory
647 prefix. It is best to avoid such filenames, if you want your code
648 to be portable to DOS and its derivatives. It's hard to know what
649 these all are, unfortunately.
651 Users of these operating systems may also wish to make use of
652 scripts such as I<pl2bat.bat> or I<pl2cmd> to
653 put wrappers around your scripts.
655 Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
656 and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
657 will keep C<\n> translated as C<\012> for that filehandle. Since it is a
658 no-op on other systems, C<binmode> should be used for cross-platform code
659 that deals with binary data. That's assuming you realize in advance
660 that your data is in binary. General-purpose programs should
661 often assume nothing about their data.
663 The C<$^O> variable and the C<$Config{archname}> values for various
664 DOSish perls are as follows:
666 OS $^O $Config{'archname'}
667 --------------------------------------------
671 Windows 95 MSWin32 MSWin32-x86
672 Windows 98 MSWin32 MSWin32-x86
673 Windows NT MSWin32 MSWin32-x86
674 Windows NT MSWin32 MSWin32-ALPHA
675 Windows NT MSWin32 MSWin32-ppc
684 The djgpp environment for DOS, http://www.delorie.com/djgpp/
689 The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
690 http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
691 ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
695 Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
700 The C<Win32::*> modules in L<Win32>.
704 The ActiveState Pages, http://www.activestate.com/
708 The Cygwin environment for Win32; F<README.cygwin> (installed
709 as L<perlcygwin>), http://www.cygwin.com/
713 The U/WIN environment for Win32,
714 <http://www.research.att.com/sw/tools/uwin/
716 =item Build instructions for OS/2, L<perlos2>
723 Any module requiring XS compilation is right out for most people, because
724 MacPerl is built using non-free (and non-cheap!) compilers. Some XS
725 modules that can work with MacPerl are built and distributed in binary
728 Directories are specified as:
730 volume:folder:file for absolute pathnames
731 volume:folder: for absolute pathnames
732 :folder:file for relative pathnames
733 :folder: for relative pathnames
734 :file for relative pathnames
735 file for relative pathnames
737 Files are stored in the directory in alphabetical order. Filenames are
738 limited to 31 characters, and may include any character except for
739 null and C<:>, which is reserved as the path separator.
741 Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
742 Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
744 In the MacPerl application, you can't run a program from the command line;
745 programs that expect C<@ARGV> to be populated can be edited with something
746 like the following, which brings up a dialog box asking for the command
750 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
753 A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
754 pathnames of the files dropped onto the script.
756 Mac users can run programs under a type of command line interface
757 under MPW (Macintosh Programmer's Workshop, a free development
758 environment from Apple). MacPerl was first introduced as an MPW
759 tool, and MPW can be used like a shell:
761 perl myscript.plx some arguments
763 ToolServer is another app from Apple that provides access to MPW tools
764 from MPW and the MacPerl app, which allows MacPerl programs to use
765 C<system>, backticks, and piped C<open>.
767 "S<Mac OS>" is the proper name for the operating system, but the value
768 in C<$^O> is "MacOS". To determine architecture, version, or whether
769 the application or MPW tool version is running, check:
771 $is_app = $MacPerl::Version =~ /App/;
772 $is_tool = $MacPerl::Version =~ /MPW/;
773 ($version) = $MacPerl::Version =~ /^(\S+)/;
774 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
775 $is_68k = $MacPerl::Architecture eq 'Mac68K';
777 S<Mac OS X> and S<Mac OS X Server>, based on NeXT's OpenStep OS, will
778 (in theory) be able to run MacPerl natively, under the "Classic"
779 environment. The new "Cocoa" environment (formerly called the "Yellow Box")
780 may run a slightly modified version of MacPerl, using the Carbon interfaces.
782 S<Mac OS X Server> and its Open Source version, Darwin, both run Unix
783 perl natively (with a few patches). Full support for these
784 is slated for perl 5.6.
792 The MacPerl Pages, http://www.macperl.com/ .
796 The MacPerl mailing lists, http://www.macperl.org/ .
800 MacPerl Module Porters, http://pudge.net/mmp/ .
806 Perl on VMS is discussed in L<perlvms> in the perl distribution.
807 Perl on VMS can accept either VMS- or Unix-style file
808 specifications as in either of the following:
810 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
811 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
813 but not a mixture of both as in:
815 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
816 Can't open sys$login:/login.com: file specification syntax error
818 Interacting with Perl from the Digital Command Language (DCL) shell
819 often requires a different set of quotation marks than Unix shells do.
822 $ perl -e "print ""Hello, world.\n"""
825 There are several ways to wrap your perl scripts in DCL F<.COM> files, if
826 you are so inclined. For example:
828 $ write sys$output "Hello from DCL!"
830 $ then perl -x 'f$environment("PROCEDURE")
831 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
832 $ deck/dollars="__END__"
835 print "Hello from Perl!\n";
840 Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
841 perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
843 Filenames are in the format "name.extension;version". The maximum
844 length for filenames is 39 characters, and the maximum length for
845 extensions is also 39 characters. Version is a number from 1 to
846 32767. Valid characters are C</[A-Z0-9$_-]/>.
848 VMS's RMS filesystem is case-insensitive and does not preserve case.
849 C<readdir> returns lowercased filenames, but specifying a file for
850 opening remains case-insensitive. Files without extensions have a
851 trailing period on them, so doing a C<readdir> with a file named F<A.;5>
852 will return F<a.> (though that file could be opened with
855 RMS had an eight level limit on directory depths from any rooted logical
856 (allowing 16 levels overall) prior to VMS 7.2. Hence
857 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
858 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
859 have to take this into account, but at least they can refer to the former
860 as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
862 The VMS::Filespec module, which gets installed as part of the build
863 process on VMS, is a pure Perl module that can easily be installed on
864 non-VMS platforms and can be helpful for conversions to and from RMS
867 What C<\n> represents depends on the type of file opened. It could
868 be C<\015>, C<\012>, C<\015\012>, or nothing. The VMS::Stdio module
869 provides access to the special fopen() requirements of files with unusual
872 TCP/IP stacks are optional on VMS, so socket routines might not be
873 implemented. UDP sockets may not be supported.
875 The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
876 that you are running on without resorting to loading all of C<%Config>
877 you can examine the content of the C<@INC> array like so:
879 if (grep(/VMS_AXP/, @INC)) {
880 print "I'm on Alpha!\n";
882 } elsif (grep(/VMS_VAX/, @INC)) {
883 print "I'm on VAX!\n";
886 print "I'm not so sure about where $^O is...\n";
889 On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
890 logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
891 calls to C<localtime> are adjusted to count offsets from
892 01-JAN-1970 00:00:00.00, just like Unix.
900 F<README.vms> (installed as L<README_vms>), L<perlvms>
904 vmsperl list, majordomo@perl.org
906 (Put the words C<subscribe vmsperl> in message body.)
910 vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
916 Perl on VOS is discussed in F<README.vos> in the perl distribution
917 (installed as L<perlvos>). Perl on VOS can accept either VOS- or
918 Unix-style file specifications as in either of the following:
920 $ perl -ne "print if /perl_setup/i" >system>notices
921 $ perl -ne "print if /perl_setup/i" /system/notices
923 or even a mixture of both as in:
925 $ perl -ne "print if /perl_setup/i" >system/notices
927 Even though VOS allows the slash character to appear in object
928 names, because the VOS port of Perl interprets it as a pathname
929 delimiting character, VOS files, directories, or links whose names
930 contain a slash character cannot be processed. Such files must be
931 renamed before they can be processed by Perl. Note that VOS limits
932 file names to 32 or fewer characters.
934 See F<README.vos> for restrictions that apply when Perl is built
935 with the alpha version of VOS POSIX.1 support.
937 Perl on VOS is built without any extensions and does not support
940 The value of C<$^O> on VOS is "VOS". To determine the architecture that
941 you are running on without resorting to loading all of C<%Config> you
942 can examine the content of the @INC array like so:
945 print "I'm on a Stratus box!\n";
947 print "I'm not on a Stratus box!\n";
951 if (grep(/860/, @INC)) {
952 print "This box is a Stratus XA/R!\n";
954 } elsif (grep(/7100/, @INC)) {
955 print "This box is a Stratus HP 7100 or 8xxx!\n";
957 } elsif (grep(/8000/, @INC)) {
958 print "This box is a Stratus HP 8xxx!\n";
961 print "This box is a Stratus 68K!\n";
974 The VOS mailing list.
976 There is no specific mailing list for Perl on VOS. You can post
977 comments to the comp.sys.stratus newsgroup, or subscribe to the general
978 Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
979 the message body to majordomo@list.stratagy.com.
983 VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
987 =head2 EBCDIC Platforms
989 Recent versions of Perl have been ported to platforms such as OS/400 on
990 AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
991 Mainframes. Such computers use EBCDIC character sets internally (usually
992 Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
993 systems). On the mainframe perl currently works under the "Unix system
994 services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
995 the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
996 See L<perlos390> for details.
998 As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
999 sub-systems do not support the C<#!> shebang trick for script invocation.
1000 Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1001 similar to the following simple script:
1004 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1006 #!/usr/local/bin/perl # just a comment really
1008 print "Hello from perl!\n";
1010 OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1011 Calls to C<system> and backticks can use POSIX shell syntax on all
1014 On the AS/400, if PERL5 is in your library list, you may need
1015 to wrap your perl scripts in a CL procedure to invoke them like so:
1018 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1021 This will invoke the perl script F<hello.pl> in the root of the
1022 QOpenSys file system. On the AS/400 calls to C<system> or backticks
1025 On these platforms, bear in mind that the EBCDIC character set may have
1026 an effect on what happens with some perl functions (such as C<chr>,
1027 C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1028 well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1029 and C<|>, not to mention dealing with socket interfaces to ASCII computers
1030 (see L<"Newlines">).
1032 Fortunately, most web servers for the mainframe will correctly
1033 translate the C<\n> in the following statement to its ASCII equivalent
1034 (C<\r> is the same under both Unix and OS/390 & VM/ESA):
1036 print "Content-type: text/html\r\n\r\n";
1038 The values of C<$^O> on some of these platforms includes:
1040 uname $^O $Config{'archname'}
1041 --------------------------------------------
1044 POSIX-BC posix-bc BS2000-posix-bc
1047 Some simple tricks for determining if you are running on an EBCDIC
1048 platform could include any of the following (perhaps all):
1050 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1052 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1054 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1056 One thing you may not want to rely on is the EBCDIC encoding
1057 of punctuation characters since these may differ from code page to code
1058 page (and once your module or script is rumoured to work with EBCDIC,
1059 folks will want it to work with all EBCDIC character sets).
1069 L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
1074 The perl-mvs@perl.org list is for discussion of porting issues as well as
1075 general usage issues for all EBCDIC Perls. Send a message body of
1076 "subscribe perl-mvs" to majordomo@perl.org.
1080 AS/400 Perl information at
1081 http://as400.rochester.ibm.com/
1082 as well as on CPAN in the F<ports/> directory.
1086 =head2 Acorn RISC OS
1088 Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1089 Unix, and because Unix filename emulation is turned on by default,
1090 most simple scripts will probably work "out of the box". The native
1091 filesystem is modular, and individual filesystems are free to be
1092 case-sensitive or insensitive, and are usually case-preserving. Some
1093 native filesystems have name length limits, which file and directory
1094 names are silently truncated to fit. Scripts should be aware that the
1095 standard filesystem currently has a name length limit of B<10>
1096 characters, with up to 77 items in a directory, but other filesystems
1097 may not impose such limitations.
1099 Native filenames are of the form
1101 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
1105 Special_Field is not usually present, but may contain . and $ .
1106 Filesystem =~ m|[A-Za-z0-9_]|
1107 DsicName =~ m|[A-Za-z0-9_/]|
1108 $ represents the root directory
1109 . is the path separator
1110 @ is the current directory (per filesystem but machine global)
1111 ^ is the parent directory
1112 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1114 The default filename translation is roughly C<tr|/.|./|;>
1116 Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
1117 the second stage of C<$> interpolation in regular expressions will fall
1118 foul of the C<$.> if scripts are not careful.
1120 Logical paths specified by system variables containing comma-separated
1121 search lists are also allowed; hence C<System:Modules> is a valid
1122 filename, and the filesystem will prefix C<Modules> with each section of
1123 C<System$Path> until a name is made that points to an object on disk.
1124 Writing to a new file C<System:Modules> would be allowed only if
1125 C<System$Path> contains a single item list. The filesystem will also
1126 expand system variables in filenames if enclosed in angle brackets, so
1127 C<< <System$Dir>.Modules >> would look for the file
1128 S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
1129 that B<fully qualified filenames can start with C<< <> >>> and should
1130 be protected when C<open> is used for input.
1132 Because C<.> was in use as a directory separator and filenames could not
1133 be assumed to be unique after 10 characters, Acorn implemented the C
1134 compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1135 filenames specified in source code and store the respective files in
1136 subdirectories named after the suffix. Hence files are translated:
1139 C:foo.h C:h.foo (logical path variable)
1140 sys/os.h sys.h.os (C compiler groks Unix-speak)
1141 10charname.c c.10charname
1142 10charname.o o.10charname
1143 11charname_.c c.11charname (assuming filesystem truncates at 10)
1145 The Unix emulation library's translation of filenames to native assumes
1146 that this sort of translation is required, and it allows a user-defined list
1147 of known suffixes that it will transpose in this fashion. This may
1148 seem transparent, but consider that with these rules C<foo/bar/baz.h>
1149 and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1150 C<glob> cannot and do not attempt to emulate the reverse mapping. Other
1151 C<.>'s in filenames are translated to C</>.
1153 As implied above, the environment accessed through C<%ENV> is global, and
1154 the convention is that program specific environment variables are of the
1155 form C<Program$Name>. Each filesystem maintains a current directory,
1156 and the current filesystem's current directory is the B<global> current
1157 directory. Consequently, sociable programs don't change the current
1158 directory but rely on full pathnames, and programs (and Makefiles) cannot
1159 assume that they can spawn a child process which can change the current
1160 directory without affecting its parent (and everyone else for that
1163 Because native operating system filehandles are global and are currently
1164 allocated down from 255, with 0 being a reserved value, the Unix emulation
1165 library emulates Unix filehandles. Consequently, you can't rely on
1166 passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1168 The desire of users to express filenames of the form
1169 C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
1170 too: C<``> command output capture has to perform a guessing game. It
1171 assumes that a string C<< <[^<>]+\$[^<>]> >> is a
1172 reference to an environment variable, whereas anything else involving
1173 C<< < >> or C<< > >> is redirection, and generally manages to be 99%
1174 right. Of course, the problem remains that scripts cannot rely on any
1175 Unix tools being available, or that any tools found have Unix-like command
1178 Extensions and XS are, in theory, buildable by anyone using free
1179 tools. In practice, many don't, as users of the Acorn platform are
1180 used to binary distributions. MakeMaker does run, but no available
1181 make currently copes with MakeMaker's makefiles; even if and when
1182 this should be fixed, the lack of a Unix-like shell will cause
1183 problems with makefile rules, especially lines of the form C<cd
1184 sdbm && make all>, and anything using quoting.
1186 "S<RISC OS>" is the proper name for the operating system, but the value
1187 in C<$^O> is "riscos" (because we don't like shouting).
1191 Perl has been ported to many platforms that do not fit into any of
1192 the categories listed above. Some, such as AmigaOS, Atari MiNT,
1193 BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1194 into the standard Perl source code kit. You may need to see the
1195 F<ports/> directory on CPAN for information, and possibly binaries,
1196 for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1197 Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1198 fall under the Unix category, but we are not a standards body.)
1200 Some approximate operating system names and their C<$^O> values
1201 in the "OTHER" category include:
1203 OS $^O $Config{'archname'}
1204 ------------------------------------------
1205 Amiga DOS amigaos m68k-amigos
1206 MPE/iX mpeix PA-RISC1.1
1214 Amiga, F<README.amiga> (installed as L<perlamiga>).
1218 Atari, F<README.mint> and Guido Flohr's web page
1219 http://stud.uni-sb.de/~gufl0000/
1223 Be OS, F<README.beos>
1227 HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
1228 http://www.cccd.edu/~markb/perlix.html
1232 A free perl5-based PERL.NLM for Novell Netware is available in
1233 precompiled binary and source code form from http://www.novell.com/
1234 as well as from CPAN.
1238 Plan 9, F<README.plan9>
1242 =head1 FUNCTION IMPLEMENTATIONS
1244 Listed below are functions that are either completely unimplemented
1245 or else have been implemented differently on various platforms.
1246 Following each description will be, in parentheses, a list of
1247 platforms that the description applies to.
1249 The list may well be incomplete, or even wrong in some places. When
1250 in doubt, consult the platform-specific README files in the Perl
1251 source distribution, and any other documentation resources accompanying
1254 Be aware, moreover, that even among Unix-ish systems there are variations.
1256 For many functions, you can also query C<%Config>, exported by
1257 default from the Config module. For example, to check whether the
1258 platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1259 L<Config> for a full description of available variables.
1261 =head2 Alphabetical Listing of Perl Functions
1271 C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
1272 and applications are executable, and there are no uid/gid
1273 considerations. C<-o> is not supported. (S<Mac OS>)
1275 C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1276 which may not reflect UIC-based file protections. (VMS)
1278 C<-s> returns the size of the data fork, not the total size of data fork
1279 plus resource fork. (S<Mac OS>).
1281 C<-s> by name on an open file will return the space reserved on disk,
1282 rather than the current extent. C<-s> on an open filehandle returns the
1283 current size. (S<RISC OS>)
1285 C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
1286 C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1288 C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1291 C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
1292 (Win32, VMS, S<RISC OS>)
1294 C<-d> is true if passed a device spec without an explicit directory.
1297 C<-T> and C<-B> are implemented, but might misclassify Mac text files
1298 with foreign characters; this is the case will all platforms, but may
1299 affect S<Mac OS> often. (S<Mac OS>)
1301 C<-x> (or C<-X>) determine if a file ends in one of the executable
1302 suffixes. C<-S> is meaningless. (Win32)
1304 C<-x> (or C<-X>) determine if a file has an executable file type.
1311 Not implemented. (Win32)
1313 =item binmode FILEHANDLE
1315 Meaningless. (S<Mac OS>, S<RISC OS>)
1317 Reopens file and restores pointer; if function fails, underlying
1318 filehandle may be closed, or pointer may be in a different position.
1321 The value returned by C<tell> may be affected after the call, and
1322 the filehandle may be flushed. (Win32)
1326 Only limited meaning. Disabling/enabling write permission is mapped to
1327 locking/unlocking the file. (S<Mac OS>)
1329 Only good for changing "owner" read-write access, "group", and "other"
1330 bits are meaningless. (Win32)
1332 Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1334 Access permissions are mapped onto VOS access-control list changes. (VOS)
1338 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
1340 Does nothing, but won't fail. (Win32)
1342 =item chroot FILENAME
1346 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
1348 =item crypt PLAINTEXT,SALT
1350 May not be available if library or source was not provided when building
1353 Not implemented. (VOS)
1357 Not implemented. (VMS, Plan9, VOS)
1359 =item dbmopen HASH,DBNAME,MODE
1361 Not implemented. (VMS, Plan9, VOS)
1365 Not useful. (S<Mac OS>, S<RISC OS>)
1367 Not implemented. (Win32)
1369 Invokes VMS debugger. (VMS)
1373 Not implemented. (S<Mac OS>)
1375 Implemented via Spawn. (VM/ESA)
1377 Does not automatically flush output handles on some platforms.
1378 (SunOS, Solaris, HP-UX)
1380 =item fcntl FILEHANDLE,FUNCTION,SCALAR
1382 Not implemented. (Win32, VMS)
1384 =item flock FILEHANDLE,OPERATION
1386 Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
1388 Available only on Windows NT (not on Windows 95). (Win32)
1392 Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1394 Emulated using multiple interpreters. See L<perlfork>. (Win32)
1396 Does not automatically flush output handles on some platforms.
1397 (SunOS, Solaris, HP-UX)
1401 Not implemented. (S<Mac OS>, S<RISC OS>)
1405 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1409 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1411 =item getpriority WHICH,WHO
1413 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1417 Not implemented. (S<Mac OS>, Win32)
1419 Not useful. (S<RISC OS>)
1423 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1425 =item getnetbyname NAME
1427 Not implemented. (S<Mac OS>, Win32, Plan9)
1431 Not implemented. (S<Mac OS>, Win32)
1433 Not useful. (S<RISC OS>)
1437 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1439 =item getnetbyaddr ADDR,ADDRTYPE
1441 Not implemented. (S<Mac OS>, Win32, Plan9)
1443 =item getprotobynumber NUMBER
1445 Not implemented. (S<Mac OS>)
1447 =item getservbyport PORT,PROTO
1449 Not implemented. (S<Mac OS>)
1453 Not implemented. (S<Mac OS>, Win32, VM/ESA)
1457 Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
1461 Not implemented. (S<Mac OS>, Win32)
1465 Not implemented. (S<Mac OS>, Win32, Plan9)
1469 Not implemented. (S<Mac OS>, Win32, Plan9)
1473 Not implemented. (Win32, Plan9)
1477 Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
1481 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1483 =item sethostent STAYOPEN
1485 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1487 =item setnetent STAYOPEN
1489 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1491 =item setprotoent STAYOPEN
1493 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1495 =item setservent STAYOPEN
1497 Not implemented. (Plan9, Win32, S<RISC OS>)
1501 Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
1505 Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
1509 Not implemented. (S<Mac OS>, Win32)
1513 Not implemented. (S<Mac OS>, Win32, Plan9)
1517 Not implemented. (S<Mac OS>, Win32, Plan9)
1521 Not implemented. (Plan9, Win32)
1523 =item getsockopt SOCKET,LEVEL,OPTNAME
1525 Not implemented. (S<Mac OS>, Plan9)
1531 Globbing built-in, but only C<*> and C<?> metacharacters are supported.
1534 This operator is implemented via the File::Glob extension on most
1535 platforms. See L<File::Glob> for portability information.
1537 =item ioctl FILEHANDLE,FUNCTION,SCALAR
1539 Not implemented. (VMS)
1541 Available only for socket handles, and it does what the ioctlsocket() call
1542 in the Winsock API does. (Win32)
1544 Available only for socket handles. (S<RISC OS>)
1546 =item kill SIGNAL, LIST
1548 Not implemented, hence not useful for taint checking. (S<Mac OS>,
1551 C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1552 a signal to the identified process like it does on Unix platforms.
1553 Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1554 and makes it exit immediately with exit status $sig. As in Unix, if
1555 $sig is 0 and the specified process exists, it returns true without
1556 actually terminating it. (Win32)
1558 =item link OLDFILE,NEWFILE
1560 Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
1562 Link count not updated because hard links are not quite that hard
1563 (They are sort of half-way between hard and soft links). (AmigaOS)
1565 Hard links are implemented on Win32 (Windows NT and Windows 2000)
1568 =item lstat FILEHANDLE
1574 Not implemented. (VMS, S<RISC OS>)
1576 Return values (especially for device and inode) may be bogus. (Win32)
1578 =item msgctl ID,CMD,ARG
1580 =item msgget KEY,FLAGS
1582 =item msgsnd ID,MSG,FLAGS
1584 =item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1586 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
1588 =item open FILEHANDLE,EXPR
1590 =item open FILEHANDLE
1592 The C<|> variants are supported only if ToolServer is installed.
1595 open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
1597 Opening a process does not automatically flush output handles on some
1598 platforms. (SunOS, Solaris, HP-UX)
1600 =item pipe READHANDLE,WRITEHANDLE
1602 Not implemented. (S<Mac OS>)
1604 Very limited functionality. (MiNT)
1610 Not implemented. (Win32, VMS, S<RISC OS>)
1612 =item select RBITS,WBITS,EBITS,TIMEOUT
1614 Only implemented on sockets. (Win32)
1616 Only reliable on sockets. (S<RISC OS>)
1618 Note that the C<socket FILEHANDLE> form is generally portable.
1620 =item semctl ID,SEMNUM,CMD,ARG
1622 =item semget KEY,NSEMS,FLAGS
1624 =item semop KEY,OPSTRING
1626 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1630 Not implemented. (MPE/iX, Win32)
1632 =item setpgrp PID,PGRP
1634 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1636 =item setpriority WHICH,WHO,PRIORITY
1638 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1642 Not implemented. (MPE/iX, Win32)
1644 =item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1646 Not implemented. (S<Mac OS>, Plan9)
1648 =item shmctl ID,CMD,ARG
1650 =item shmget KEY,SIZE,FLAGS
1652 =item shmread ID,VAR,POS,SIZE
1654 =item shmwrite ID,STRING,POS,SIZE
1656 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1658 =item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1660 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1662 =item stat FILEHANDLE
1668 Platforms that do not have rdev, blksize, or blocks will return these
1669 as '', so numeric comparison or manipulation of these fields may cause
1670 'not numeric' warnings.
1672 mtime and atime are the same thing, and ctime is creation time instead of
1673 inode change time. (S<Mac OS>)
1675 device and inode are not meaningful. (Win32)
1677 device and inode are not necessarily reliable. (VMS)
1679 mtime, atime and ctime all return the last modification time. Device and
1680 inode are not necessarily reliable. (S<RISC OS>)
1682 dev, rdev, blksize, and blocks are not available. inode is not
1683 meaningful and will differ between stat calls on the same file. (os2)
1685 =item symlink OLDFILE,NEWFILE
1687 Not implemented. (Win32, VMS, S<RISC OS>)
1691 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1693 =item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1695 The traditional "0", "1", and "2" MODEs are implemented with different
1696 numeric values on some systems. The flags exported by C<Fcntl>
1697 (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1698 OS>, OS/390, VM/ESA)
1702 Only implemented if ToolServer is installed. (S<Mac OS>)
1704 As an optimization, may not call the command shell specified in
1705 C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1706 process and immediately returns its process designator, without
1707 waiting for it to terminate. Return value may be used subsequently
1708 in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1709 by setting $? to "255 << 8". C<$?> is set in a way compatible with
1710 Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1711 as described in the documentation). (Win32)
1713 There is no shell to process metacharacters, and the native standard is
1714 to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1715 program. Redirection such as C<< > foo >> is performed (if at all) by
1716 the run time library of the spawned program. C<system> I<list> will call
1717 the Unix emulation library's C<exec> emulation, which attempts to provide
1718 emulation of the stdin, stdout, stderr in force in the parent, providing
1719 the child program uses a compatible version of the emulation library.
1720 I<scalar> will call the native command line direct and no such emulation
1721 of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1723 Far from being POSIX compliant. Because there may be no underlying
1724 /bin/sh tries to work around the problem by forking and execing the
1725 first token in its argument string. Handles basic redirection
1726 ("<" or ">") on its own behalf. (MiNT)
1728 Does not automatically flush output handles on some platforms.
1729 (SunOS, Solaris, HP-UX)
1733 Only the first entry returned is nonzero. (S<Mac OS>)
1735 "cumulative" times will be bogus. On anything other than Windows NT
1736 or Windows 2000, "system" time will be bogus, and "user" time is
1737 actually the time returned by the clock() function in the C runtime
1740 Not useful. (S<RISC OS>)
1742 =item truncate FILEHANDLE,LENGTH
1744 =item truncate EXPR,LENGTH
1746 Not implemented. (VMS)
1748 Truncation to zero-length only. (VOS)
1750 If a FILEHANDLE is supplied, it must be writable and opened in append
1751 mode (i.e., use C<open(FH, '>>filename')>
1752 or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1753 should not be held open elsewhere. (Win32)
1759 Returns undef where unavailable, as of version 5.005.
1761 C<umask> works but the correct permissions are set only when the file
1762 is finally closed. (AmigaOS)
1766 Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
1768 May not behave as expected. Behavior depends on the C runtime
1769 library's implementation of utime(), and the filesystem being
1770 used. The FAT filesystem typically does not support an "access
1771 time" field, and it may limit timestamps to a granularity of
1772 two seconds. (Win32)
1776 =item waitpid PID,FLAGS
1778 Not implemented. (S<Mac OS>, VOS)
1780 Can only be applied to process handles returned for processes spawned
1781 using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
1783 Not useful. (S<RISC OS>)
1791 =item v1.47, 22 March 2000
1793 Various cleanups from Tom Christiansen, including migration of
1794 long platform listings from L<perl>.
1796 =item v1.46, 12 February 2000
1798 Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1800 =item v1.45, 20 December 1999
1802 Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1804 =item v1.44, 19 July 1999
1806 A bunch of updates from Peter Prymmer for C<$^O> values,
1807 endianness, File::Spec, VMS, BS2000, OS/400.
1809 =item v1.43, 24 May 1999
1811 Added a lot of cleaning up from Tom Christiansen.
1813 =item v1.42, 22 May 1999
1815 Added notes about tests, sprintf/printf, and epoch offsets.
1817 =item v1.41, 19 May 1999
1819 Lots more little changes to formatting and content.
1821 Added a bunch of C<$^O> and related values
1822 for various platforms; fixed mail and web addresses, and added
1823 and changed miscellaneous notes. (Peter Prymmer)
1825 =item v1.40, 11 April 1999
1827 Miscellaneous changes.
1829 =item v1.39, 11 February 1999
1831 Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1832 note about newlines added.
1834 =item v1.38, 31 December 1998
1836 More changes from Jarkko.
1838 =item v1.37, 19 December 1998
1840 More minor changes. Merge two separate version 1.35 documents.
1842 =item v1.36, 9 September 1998
1844 Updated for Stratus VOS. Also known as version 1.35.
1846 =item v1.35, 13 August 1998
1848 Integrate more minor changes, plus addition of new sections under
1849 L<"ISSUES">: L<"Numbers endianness and Width">,
1850 L<"Character sets and character encoding">,
1851 L<"Internationalisation">.
1853 =item v1.33, 06 August 1998
1855 Integrate more minor changes.
1857 =item v1.32, 05 August 1998
1859 Integrate more minor changes.
1861 =item v1.30, 03 August 1998
1863 Major update for RISC OS, other minor changes.
1865 =item v1.23, 10 July 1998
1867 First public release with perl5.005.
1871 =head1 Supported Platforms
1873 As of early March 2000 (the Perl release 5.6.0), the following
1874 platforms are able to build Perl from the standard source code
1875 distribution available at http://www.perl.com/CPAN/src/index.html
1907 1) in DOS mode either the DOS or OS/2 ports can be used
1908 2) new in 5.6.0: the BSD/NeXT-based UNIX of Mac OS X
1909 3) formerly known as Digital UNIX and before that DEC OSF/1
1910 4) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
1912 The following platforms worked for the previous major release
1913 (5.005_03 being the latest maintenance release of that, as of early
1914 March 2000), but be did not manage to test these in time for the 5.6.0
1915 release of Perl. There is a very good chance that these will work
1916 just fine with 5.6.0.
1932 The following platform worked for the previous major release (5.005_03
1933 being the latest maintenance release of that, as of early March 2000).
1934 However, standardization on UTF-8 as the internal string representation
1935 in 5.6.0 has introduced incompatibilities in this EBCDIC platform.
1936 Support for this platform may be enabled in a future release:
1940 1) Previously known as MVS, or OpenEdition MVS.
1942 Strongly related to the OS390 platform by also being EBCDIC-based
1943 mainframe platforms are the following platforms:
1948 These are also not expected to work under 5.6.0 for the same reasons
1949 as OS390. Contact the mailing list perl-mvs@perl.org for more details.
1951 MacOS (Classic, pre-X) is almost 5.6.0-ready; building from the source
1952 does work with 5.6.0, but additional MacOS specific source code is needed
1953 for a complete port. Contact the mailing list macperl-porters@macperl.org
1954 for more information.
1956 The following platforms have been known to build Perl from source in
1957 the past, but we haven't been able to verify their status for the
1958 current release, either because the hardware/software platforms are
1959 rare or because we don't have an active champion on these
1991 Support for the following platform is planned for a future Perl release:
1995 The following platforms have their own source code distributions and
1996 binaries available via http://www.perl.com/CPAN/ports/index.html:
2002 Tandem Guardian 5.004
2004 The following platforms have only binaries available via
2005 http://www.perl.com/CPAN/ports/index.html :
2009 Acorn RISCOS 5.005_02
2013 Although we do suggest that you always build your own Perl from
2014 the source code, both for maximal configurability and for security,
2015 in case you are in a hurry you can check
2016 http://www.perl.com/CPAN/ports/index.html for binary distributions.
2020 L<perlaix>, L<perlamiga>, L<perlcygwin>, L<perldos>, L<perlepoc>,
2021 L<perlebcdic>, L<perlhpux>, L<perlos2>, L<perlos390>, L<perlbs2000>,
2022 L<perlwin32>, L<perlvms>, L<perlvos>, and L<Win32>.
2024 =head1 AUTHORS / CONTRIBUTORS
2026 Abigail <abigail@fnx.com>,
2027 Charles Bailey <bailey@newman.upenn.edu>,
2028 Graham Barr <gbarr@pobox.com>,
2029 Tom Christiansen <tchrist@perl.com>,
2030 Nicholas Clark <Nicholas.Clark@liverpool.ac.uk>,
2031 Thomas Dorner <Thomas.Dorner@start.de>,
2032 Andy Dougherty <doughera@lafcol.lafayette.edu>,
2033 Dominic Dunlop <domo@vo.lu>,
2034 Neale Ferguson <neale@mailbox.tabnsw.com.au>,
2035 David J. Fiander <davidf@mks.com>,
2036 Paul Green <Paul_Green@stratus.com>,
2037 M.J.T. Guy <mjtg@cus.cam.ac.uk>,
2038 Jarkko Hietaniemi <jhi@iki.fi>,
2039 Luther Huffman <lutherh@stratcom.com>,
2040 Nick Ing-Simmons <nick@ni-s.u-net.com>,
2041 Andreas J. KE<ouml>nig <koenig@kulturbox.de>,
2042 Markus Laker <mlaker@contax.co.uk>,
2043 Andrew M. Langmead <aml@world.std.com>,
2044 Larry Moore <ljmoore@freespace.net>,
2045 Paul Moore <Paul.Moore@uk.origin-it.com>,
2046 Chris Nandor <pudge@pobox.com>,
2047 Matthias Neeracher <neeri@iis.ee.ethz.ch>,
2048 Gary Ng <71564.1743@CompuServe.COM>,
2049 Tom Phoenix <rootbeer@teleport.com>,
2050 AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2051 Peter Prymmer <pvhp@forte.com>,
2052 Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2053 Gurusamy Sarathy <gsar@activestate.com>,
2054 Paul J. Schinder <schinder@pobox.com>,
2055 Michael G Schwern <schwern@pobox.com>,
2056 Dan Sugalski <sugalskd@ous.edu>,
2057 Nathan Torkington <gnat@frii.com>.
2059 This document is maintained by Chris Nandor
2064 Version 1.47, last modified 22 March 2000