3 perlport - Writing portable Perl
7 Perl runs on numerous operating systems. While most of them share
8 much in common, they also have their own unique features.
10 This document is meant to help you to find out what constitutes portable
11 Perl code. That way once you make a decision to write portably,
12 you know where the lines are drawn, and you can stay within them.
14 There is a tradeoff between taking full advantage of one particular
15 type of computer and taking advantage of a full range of them.
16 Naturally, as you broaden your range and become more diverse, the
17 common factors drop, and you are left with an increasingly smaller
18 area of common ground in which you can operate to accomplish a
19 particular task. Thus, when you begin attacking a problem, it is
20 important to consider under which part of the tradeoff curve you
21 want to operate. Specifically, you must decide whether it is
22 important that the task that you are coding have the full generality
23 of being portable, or whether to just get the job done right now.
24 This is the hardest choice to be made. The rest is easy, because
25 Perl provides many choices, whichever way you want to approach your
28 Looking at it another way, writing portable code is usually about
29 willfully limiting your available choices. Naturally, it takes
30 discipline and sacrifice to do that. The product of portability
31 and convenience may be a constant. You have been warned.
33 Be aware of two important points:
37 =item Not all Perl programs have to be portable
39 There is no reason you should not use Perl as a language to glue Unix
40 tools together, or to prototype a Macintosh application, or to manage the
41 Windows registry. If it makes no sense to aim for portability for one
42 reason or another in a given program, then don't bother.
44 =item Nearly all of Perl already I<is> portable
46 Don't be fooled into thinking that it is hard to create portable Perl
47 code. It isn't. Perl tries its level-best to bridge the gaps between
48 what's available on different platforms, and all the means available to
49 use those features. Thus almost all Perl code runs on any machine
50 without modification. But there are some significant issues in
51 writing portable code, and this document is entirely about those issues.
55 Here's the general rule: When you approach a task commonly done
56 using a whole range of platforms, think about writing portable
57 code. That way, you don't sacrifice much by way of the implementation
58 choices you can avail yourself of, and at the same time you can give
59 your users lots of platform choices. On the other hand, when you have to
60 take advantage of some unique feature of a particular platform, as is
61 often the case with systems programming (whether for Unix, Windows,
62 S<Mac OS>, VMS, etc.), consider writing platform-specific code.
64 When the code will run on only two or three operating systems, you
65 may need to consider only the differences of those particular systems.
66 The important thing is to decide where the code will run and to be
67 deliberate in your decision.
69 The material below is separated into three main sections: main issues of
70 portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and
71 built-in perl functions that behave differently on various ports
72 (L<"FUNCTION IMPLEMENTATIONS">.
74 This information should not be considered complete; it includes possibly
75 transient information about idiosyncrasies of some of the ports, almost
76 all of which are in a state of constant evolution. Thus, this material
77 should be considered a perpetual work in progress
78 (<IMG SRC="yellow_sign.gif" ALT="Under Construction">).
84 In most operating systems, lines in files are terminated by newlines.
85 Just what is used as a newline may vary from OS to OS. Unix
86 traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>,
87 and S<Mac OS> uses C<\015>.
89 Perl uses C<\n> to represent the "logical" newline, where what is
90 logical may depend on the platform in use. In MacPerl, C<\n> always
91 means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
92 when accessing a file in "text" mode, STDIO translates it to (or
93 from) C<\015\012>, depending on whether you're reading or writing.
94 Unix does the same thing on ttys in canonical mode. C<\015\012>
95 is commonly referred to as CRLF.
97 A common cause of unportable programs is the misuse of chop() to trim
107 You can get away with this on Unix and MacOS (they have a single
108 character end-of-line), but the same program will break under DOSish
109 perls because you're only chop()ing half the end-of-line. Instead,
110 chomp() should be used to trim newlines. The Dunce::Files module can
111 help audit your code for misuses of chop().
113 When dealing with binary files (or text files in binary mode) be sure
114 to explicitly set $/ to the appropriate value for your file format
115 before using chomp().
117 Because of the "text" mode translation, DOSish perls have limitations
118 in using C<seek> and C<tell> on a file accessed in "text" mode.
119 Stick to C<seek>-ing to locations you got from C<tell> (and no
120 others), and you are usually free to use C<seek> and C<tell> even
121 in "text" mode. Using C<seek> or C<tell> or other file operations
122 may be non-portable. If you use C<binmode> on a file, however, you
123 can usually C<seek> and C<tell> with arbitrary values in safety.
125 A common misconception in socket programming is that C<\n> eq C<\012>
126 everywhere. When using protocols such as common Internet protocols,
127 C<\012> and C<\015> are called for specifically, and the values of
128 the logical C<\n> and C<\r> (carriage return) are not reliable.
130 print SOCKET "Hi there, client!\r\n"; # WRONG
131 print SOCKET "Hi there, client!\015\012"; # RIGHT
133 However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
134 and unsightly, as well as confusing to those maintaining the code. As
135 such, the Socket module supplies the Right Thing for those who want it.
137 use Socket qw(:DEFAULT :crlf);
138 print SOCKET "Hi there, client!$CRLF" # RIGHT
140 When reading from a socket, remember that the default input record
141 separator C<$/> is C<\n>, but robust socket code will recognize as
142 either C<\012> or C<\015\012> as end of line:
148 Because both CRLF and LF end in LF, the input record separator can
149 be set to LF and any CR stripped later. Better to write:
151 use Socket qw(:DEFAULT :crlf);
152 local($/) = LF; # not needed if $/ is already \012
155 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
156 # s/\015?\012/\n/; # same thing
159 This example is preferred over the previous one--even for Unix
160 platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
161 (and there was much rejoicing).
163 Similarly, functions that return text data--such as a function that
164 fetches a web page--should sometimes translate newlines before
165 returning the data, if they've not yet been translated to the local
166 newline representation. A single line of code will often suffice:
168 $data =~ s/\015?\012/\n/g;
171 Some of this may be confusing. Here's a handy reference to the ASCII CR
172 and LF characters. You can print it out and stick it in your wallet.
174 LF == \012 == \x0A == \cJ == ASCII 10
175 CR == \015 == \x0D == \cM == ASCII 13
178 ---------------------------
181 \n * | LF | CRLF | CR |
182 \r * | CR | CR | LF |
183 ---------------------------
186 The Unix column assumes that you are not accessing a serial line
187 (like a tty) in canonical mode. If you are, then CR on input becomes
188 "\n", and "\n" on output becomes CRLF.
190 These are just the most common definitions of C<\n> and C<\r> in Perl.
191 There may well be others.
193 =head2 Numbers endianness and Width
195 Different CPUs store integers and floating point numbers in different
196 orders (called I<endianness>) and widths (32-bit and 64-bit being the
197 most common today). This affects your programs when they attempt to transfer
198 numbers in binary format from one CPU architecture to another,
199 usually either "live" via network connection, or by storing the
200 numbers to secondary storage such as a disk file or tape.
202 Conflicting storage orders make utter mess out of the numbers. If a
203 little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
204 decimal), a big-endian host (Motorola, Sparc, PA) reads it as
205 0x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
206 Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
207 them in big-endian mode. To avoid this problem in network (socket)
208 connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
209 "network" orders. These are guaranteed to be portable.
211 You can explore the endianness of your platform by unpacking a
212 data structure packed in native format such as:
214 print unpack("h*", pack("s2", 1, 2)), "\n";
215 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
216 # '00100020' on e.g. Motorola 68040
218 If you need to distinguish between endian architectures you could use
219 either of the variables set like so:
221 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
222 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
224 Differing widths can cause truncation even between platforms of equal
225 endianness. The platform of shorter width loses the upper parts of the
226 number. There is no good solution for this problem except to avoid
227 transferring or storing raw binary numbers.
229 One can circumnavigate both these problems in two ways. Either
230 transfer and store numbers always in text format, instead of raw
231 binary, or else consider using modules like Data::Dumper (included in
232 the standard distribution as of Perl 5.005) and Storable (included as
233 of perl 5.8). Keeping all data as text significantly simplifies matters.
235 =head2 Files and Filesystems
237 Most platforms these days structure files in a hierarchical fashion.
238 So, it is reasonably safe to assume that all platforms support the
239 notion of a "path" to uniquely identify a file on the system. How
240 that path is really written, though, differs considerably.
242 Although similar, file path specifications differ between Unix,
243 Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
244 Unix, for example, is one of the few OSes that has the elegant idea
245 of a single root directory.
247 DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
248 as path separator, or in their own idiosyncratic ways (such as having
249 several root directories and various "unrooted" device files such NIL:
252 S<Mac OS> uses C<:> as a path separator instead of C</>.
254 The filesystem may support neither hard links (C<link>) nor
255 symbolic links (C<symlink>, C<readlink>, C<lstat>).
257 The filesystem may support neither access timestamp nor change
258 timestamp (meaning that about the only portable timestamp is the
259 modification timestamp), or one second granularity of any timestamps
260 (e.g. the FAT filesystem limits the time granularity to two seconds).
262 VOS perl can emulate Unix filenames with C</> as path separator. The
263 native pathname characters greater-than, less-than, number-sign, and
264 percent-sign are always accepted.
266 S<RISC OS> perl can emulate Unix filenames with C</> as path
267 separator, or go native and use C<.> for path separator and C<:> to
268 signal filesystems and disk names.
270 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 assume that write/modify permission on a directory gives the
356 right to add or delete files/directories in that directory. That is
357 filesystem specific: in some filesystems you need write/modify
358 permission also (or even just) in the file/directory itself. In some
359 filesystems (AFS, DFS) the permission to add/delete directory entries
360 is a completely separate permission.
362 Don't assume that a single C<unlink> completely gets rid of the file:
363 some filesystems (most notably the ones in VMS) have versioned
364 filesystems, and unlink() removes only the most recent one (it doesn't
365 remove all the versions because by default the native tools on those
366 platforms remove just the most recent version, too). The portable
367 idiom to remove all the versions of a file is
369 1 while unlink "file";
371 This will terminate if the file is undeleteable for some reason
372 (protected, not there, and so on).
374 Don't count on a specific environment variable existing in C<%ENV>.
375 Don't count on C<%ENV> entries being case-sensitive, or even
376 case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
377 if you really have to, make it conditional on C<$^O ne 'VMS'> since in
378 VMS the C<%ENV> table is much more than a per-process key-value string
381 Don't count on signals or C<%SIG> for anything.
383 Don't count on filename globbing. Use C<opendir>, C<readdir>, and
386 Don't count on per-program environment variables, or per-program current
389 Don't count on specific values of C<$!>.
391 =head2 Interprocess Communication (IPC)
393 In general, don't directly access the system in code meant to be
394 portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
395 C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
396 that makes being a perl hacker worth being.
398 Commands that launch external processes are generally supported on
399 most platforms (though many of them do not support any type of
400 forking). The problem with using them arises from what you invoke
401 them on. External tools are often named differently on different
402 platforms, may not be available in the same location, might accept
403 different arguments, can behave differently, and often present their
404 results in a platform-dependent way. Thus, you should seldom depend
405 on them to produce consistent results. (Then again, if you're calling
406 I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
408 One especially common bit of Perl code is opening a pipe to B<sendmail>:
410 open(MAIL, '|/usr/lib/sendmail -t')
411 or die "cannot fork sendmail: $!";
413 This is fine for systems programming when sendmail is known to be
414 available. But it is not fine for many non-Unix systems, and even
415 some Unix systems that may not have sendmail installed. If a portable
416 solution is needed, see the various distributions on CPAN that deal
417 with it. Mail::Mailer and Mail::Send in the MailTools distribution are
418 commonly used, and provide several mailing methods, including mail,
419 sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
420 not available. Mail::Sendmail is a standalone module that provides
421 simple, platform-independent mailing.
423 The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
424 even on all Unix platforms.
426 Do not use either the bare result of C<pack("N", 10, 20, 30, 40)>
427 or bare v-strings (such as C<v10.20.30.40>) or to represent
428 IPv4 addresses: both forms just pack the four bytes into network order.
429 That this would be equal to the C language C<in_addr> struct (which is
430 what the socket code internally uses) is not guaranteed. To be
431 portable use the routines of the Socket extension, such as
432 C<inet_aton()>, C<inet_ntoa()>, and C<sockaddr_in()>.
434 The rule of thumb for portable code is: Do it all in portable Perl, or
435 use a module (that may internally implement it with platform-specific
436 code, but expose a common interface).
438 =head2 External Subroutines (XS)
440 XS code can usually be made to work with any platform, but dependent
441 libraries, header files, etc., might not be readily available or
442 portable, or the XS code itself might be platform-specific, just as Perl
443 code might be. If the libraries and headers are portable, then it is
444 normally reasonable to make sure the XS code is portable, too.
446 A different type of portability issue arises when writing XS code:
447 availability of a C compiler on the end-user's system. C brings
448 with it its own portability issues, and writing XS code will expose
449 you to some of those. Writing purely in Perl is an easier way to
452 =head2 Standard Modules
454 In general, the standard modules work across platforms. Notable
455 exceptions are the CPAN module (which currently makes connections to external
456 programs that may not be available), platform-specific modules (like
457 ExtUtils::MM_VMS), and DBM modules.
459 There is no one DBM module available on all platforms.
460 SDBM_File and the others are generally available on all Unix and DOSish
461 ports, but not in MacPerl, where only NBDM_File and DB_File are
464 The good news is that at least some DBM module should be available, and
465 AnyDBM_File will use whichever module it can find. Of course, then
466 the code needs to be fairly strict, dropping to the greatest common
467 factor (e.g., not exceeding 1K for each record), so that it will
468 work with any DBM module. See L<AnyDBM_File> for more details.
472 The system's notion of time of day and calendar date is controlled in
473 widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
474 and even if it is, don't assume that you can control the timezone through
477 Don't assume that the epoch starts at 00:00:00, January 1, 1970,
478 because that is OS- and implementation-specific. It is better to store a date
479 in an unambiguous representation. The ISO-8601 standard defines
480 "YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
481 can be easily converted into an OS-specific value using a module like
482 Date::Parse. An array of values, such as those returned by
483 C<localtime>, can be converted to an OS-specific representation using
486 When calculating specific times, such as for tests in time or date modules,
487 it may be appropriate to calculate an offset for the epoch.
490 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
492 The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
493 some large number. C<$offset> can then be added to a Unix time value
494 to get what should be the proper value on any system.
496 =head2 Character sets and character encoding
498 Assume little about character sets. Assume nothing about
499 numerical values (C<ord>, C<chr>) of characters. Do not
500 assume that the alphabetic characters are encoded contiguously (in
501 the numeric sense). Do not assume anything about the ordering of the
502 characters. The lowercase letters may come before or after the
503 uppercase letters; the lowercase and uppercase may be interlaced so
504 that both `a' and `A' come before `b'; the accented and other
505 international characters may be interlaced so that E<auml> comes
508 =head2 Internationalisation
510 If you may assume POSIX (a rather large assumption), you may read
511 more about the POSIX locale system from L<perllocale>. The locale
512 system at least attempts to make things a little bit more portable,
513 or at least more convenient and native-friendly for non-English
514 users. The system affects character sets and encoding, and date
515 and time formatting--amongst other things.
517 =head2 System Resources
519 If your code is destined for systems with severely constrained (or
520 missing!) virtual memory systems then you want to be I<especially> mindful
521 of avoiding wasteful constructs such as:
523 # NOTE: this is no longer "bad" in perl5.005
524 for (0..10000000) {} # bad
525 for (my $x = 0; $x <= 10000000; ++$x) {} # good
527 @lines = <VERY_LARGE_FILE>; # bad
529 while (<FILE>) {$file .= $_} # sometimes bad
530 $file = join('', <FILE>); # better
532 The last two constructs may appear unintuitive to most people. The
533 first repeatedly grows a string, whereas the second allocates a
534 large chunk of memory in one go. On some systems, the second is
535 more efficient that the first.
539 Most multi-user platforms provide basic levels of security, usually
540 implemented at the filesystem level. Some, however, do
541 not--unfortunately. Thus the notion of user id, or "home" directory,
542 or even the state of being logged-in, may be unrecognizable on many
543 platforms. If you write programs that are security-conscious, it
544 is usually best to know what type of system you will be running
545 under so that you can write code explicitly for that platform (or
550 For those times when it is necessary to have platform-specific code,
551 consider keeping the platform-specific code in one place, making porting
552 to other platforms easier. Use the Config module and the special
553 variable C<$^O> to differentiate platforms, as described in
556 Be careful in the tests you supply with your module or programs.
557 Module code may be fully portable, but its tests might not be. This
558 often happens when tests spawn off other processes or call external
559 programs to aid in the testing, or when (as noted above) the tests
560 assume certain things about the filesystem and paths. Be careful
561 not to depend on a specific output style for errors, such as when
562 checking C<$!> after an system call. Some platforms expect a certain
563 output format, and perl on those platforms may have been adjusted
564 accordingly. Most specifically, don't anchor a regex when testing
569 Modules uploaded to CPAN are tested by a variety of volunteers on
570 different platforms. These CPAN testers are notified by mail of each
571 new upload, and reply to the list with PASS, FAIL, NA (not applicable to
572 this platform), or UNKNOWN (unknown), along with any relevant notations.
574 The purpose of the testing is twofold: one, to help developers fix any
575 problems in their code that crop up because of lack of testing on other
576 platforms; two, to provide users with information about whether
577 a given module works on a given platform.
581 =item Mailing list: cpan-testers@perl.org
583 =item Testing results: http://testers.cpan.org/
589 As of version 5.002, Perl is built with a C<$^O> variable that
590 indicates the operating system it was built on. This was implemented
591 to help speed up code that would otherwise have to C<use Config>
592 and use the value of C<$Config{osname}>. Of course, to get more
593 detailed information about the system, looking into C<%Config> is
594 certainly recommended.
596 C<%Config> cannot always be trusted, however, because it was built
597 at compile time. If perl was built in one place, then transferred
598 elsewhere, some values may be wrong. The values may even have been
599 edited after the fact.
603 Perl works on a bewildering variety of Unix and Unix-like platforms (see
604 e.g. most of the files in the F<hints/> directory in the source code kit).
605 On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
606 too) is determined either by lowercasing and stripping punctuation from the
607 first field of the string returned by typing C<uname -a> (or a similar command)
608 at the shell prompt or by testing the file system for the presence of
609 uniquely named files such as a kernel or header file. Here, for example,
610 are a few of the more popular Unix flavors:
612 uname $^O $Config{'archname'}
613 --------------------------------------------
615 BSD/OS bsdos i386-bsdos
616 dgux dgux AViiON-dgux
617 DYNIX/ptx dynixptx i386-dynixptx
618 FreeBSD freebsd freebsd-i386
619 Linux linux arm-linux
620 Linux linux i386-linux
621 Linux linux i586-linux
622 Linux linux ppc-linux
623 HP-UX hpux PA-RISC1.1
625 Mac OS X darwin darwin
626 MachTen PPC machten powerpc-machten
628 NeXT 4 next OPENSTEP-Mach
629 openbsd openbsd i386-openbsd
630 OSF1 dec_osf alpha-dec_osf
631 reliantunix-n svr4 RM400-svr4
632 SCO_SV sco_sv i386-sco_sv
633 SINIX-N svr4 RM400-svr4
634 sn4609 unicos CRAY_C90-unicos
635 sn6521 unicosmk t3e-unicosmk
636 sn9617 unicos CRAY_J90-unicos
637 SunOS solaris sun4-solaris
638 SunOS solaris i86pc-solaris
639 SunOS4 sunos sun4-sunos
641 Because the value of C<$Config{archname}> may depend on the
642 hardware architecture, it can vary more than the value of C<$^O>.
644 =head2 DOS and Derivatives
646 Perl has long been ported to Intel-style microcomputers running under
647 systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
648 bring yourself to mention (except for Windows CE, if you count that).
649 Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
650 be aware that each of these file specifications may have subtle
653 $filespec0 = "c:/foo/bar/file.txt";
654 $filespec1 = "c:\\foo\\bar\\file.txt";
655 $filespec2 = 'c:\foo\bar\file.txt';
656 $filespec3 = 'c:\\foo\\bar\\file.txt';
658 System calls accept either C</> or C<\> as the path separator.
659 However, many command-line utilities of DOS vintage treat C</> as
660 the option prefix, so may get confused by filenames containing C</>.
661 Aside from calling any external programs, C</> will work just fine,
662 and probably better, as it is more consistent with popular usage,
663 and avoids the problem of remembering what to backwhack and what
666 The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
667 the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
668 filesystems you may have to be careful about case returned with functions
669 like C<readdir> or used with functions like C<open> or C<opendir>.
671 DOS also treats several filenames as special, such as AUX, PRN,
672 NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
673 filenames won't even work if you include an explicit directory
674 prefix. It is best to avoid such filenames, if you want your code
675 to be portable to DOS and its derivatives. It's hard to know what
676 these all are, unfortunately.
678 Users of these operating systems may also wish to make use of
679 scripts such as I<pl2bat.bat> or I<pl2cmd> to
680 put wrappers around your scripts.
682 Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
683 and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
684 will keep C<\n> translated as C<\012> for that filehandle. Since it is a
685 no-op on other systems, C<binmode> should be used for cross-platform code
686 that deals with binary data. That's assuming you realize in advance
687 that your data is in binary. General-purpose programs should
688 often assume nothing about their data.
690 The C<$^O> variable and the C<$Config{archname}> values for various
691 DOSish perls are as follows:
693 OS $^O $Config{archname} ID Version
694 --------------------------------------------------------
698 Windows 3.1 ? ? 0 3 01
699 Windows 95 MSWin32 MSWin32-x86 1 4 00
700 Windows 98 MSWin32 MSWin32-x86 1 4 10
701 Windows ME MSWin32 MSWin32-x86 1 ?
702 Windows NT MSWin32 MSWin32-x86 2 4 xx
703 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
704 Windows NT MSWin32 MSWin32-ppc 2 4 xx
705 Windows 2000 MSWin32 MSWin32-x86 2 5 xx
706 Windows XP MSWin32 MSWin32-x86 2 ?
707 Windows CE MSWin32 ? 3
710 The various MSWin32 Perl's can distinguish the OS they are running on
711 via the value of the fifth element of the list returned from
712 Win32::GetOSVersion(). For example:
714 if ($^O eq 'MSWin32') {
715 my @os_version_info = Win32::GetOSVersion();
716 print +('3.1','95','NT')[$os_version_info[4]],"\n";
725 The djgpp environment for DOS, http://www.delorie.com/djgpp/
730 The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
731 http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
732 ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
736 Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
741 The C<Win32::*> modules in L<Win32>.
745 The ActiveState Pages, http://www.activestate.com/
749 The Cygwin environment for Win32; F<README.cygwin> (installed
750 as L<perlcygwin>), http://www.cygwin.com/
754 The U/WIN environment for Win32,
755 http://www.research.att.com/sw/tools/uwin/
759 Build instructions for OS/2, L<perlos2>
765 Any module requiring XS compilation is right out for most people, because
766 MacPerl is built using non-free (and non-cheap!) compilers. Some XS
767 modules that can work with MacPerl are built and distributed in binary
770 Directories are specified as:
772 volume:folder:file for absolute pathnames
773 volume:folder: for absolute pathnames
774 :folder:file for relative pathnames
775 :folder: for relative pathnames
776 :file for relative pathnames
777 file for relative pathnames
779 Files are stored in the directory in alphabetical order. Filenames are
780 limited to 31 characters, and may include any character except for
781 null and C<:>, which is reserved as the path separator.
783 Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
784 Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
786 In the MacPerl application, you can't run a program from the command line;
787 programs that expect C<@ARGV> to be populated can be edited with something
788 like the following, which brings up a dialog box asking for the command
792 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
795 A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
796 pathnames of the files dropped onto the script.
798 Mac users can run programs under a type of command line interface
799 under MPW (Macintosh Programmer's Workshop, a free development
800 environment from Apple). MacPerl was first introduced as an MPW
801 tool, and MPW can be used like a shell:
803 perl myscript.plx some arguments
805 ToolServer is another app from Apple that provides access to MPW tools
806 from MPW and the MacPerl app, which allows MacPerl programs to use
807 C<system>, backticks, and piped C<open>.
809 "S<Mac OS>" is the proper name for the operating system, but the value
810 in C<$^O> is "MacOS". To determine architecture, version, or whether
811 the application or MPW tool version is running, check:
813 $is_app = $MacPerl::Version =~ /App/;
814 $is_tool = $MacPerl::Version =~ /MPW/;
815 ($version) = $MacPerl::Version =~ /^(\S+)/;
816 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
817 $is_68k = $MacPerl::Architecture eq 'Mac68K';
819 S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
820 "Classic" environment. There is no "Carbon" version of MacPerl to run
821 under the primary Mac OS X environment. S<Mac OS X> and its Open Source
822 version, Darwin, both run Unix perl natively.
830 MacPerl Development, http://dev.macperl.org/ .
834 The MacPerl Pages, http://www.macperl.com/ .
838 The MacPerl mailing lists, http://lists.perl.org/ .
844 Perl on VMS is discussed in L<perlvms> in the perl distribution.
845 Perl on VMS can accept either VMS- or Unix-style file
846 specifications as in either of the following:
848 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
849 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
851 but not a mixture of both as in:
853 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
854 Can't open sys$login:/login.com: file specification syntax error
856 Interacting with Perl from the Digital Command Language (DCL) shell
857 often requires a different set of quotation marks than Unix shells do.
860 $ perl -e "print ""Hello, world.\n"""
863 There are several ways to wrap your perl scripts in DCL F<.COM> files, if
864 you are so inclined. For example:
866 $ write sys$output "Hello from DCL!"
868 $ then perl -x 'f$environment("PROCEDURE")
869 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
870 $ deck/dollars="__END__"
873 print "Hello from Perl!\n";
878 Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
879 perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
881 Filenames are in the format "name.extension;version". The maximum
882 length for filenames is 39 characters, and the maximum length for
883 extensions is also 39 characters. Version is a number from 1 to
884 32767. Valid characters are C</[A-Z0-9$_-]/>.
886 VMS's RMS filesystem is case-insensitive and does not preserve case.
887 C<readdir> returns lowercased filenames, but specifying a file for
888 opening remains case-insensitive. Files without extensions have a
889 trailing period on them, so doing a C<readdir> with a file named F<A.;5>
890 will return F<a.> (though that file could be opened with
893 RMS had an eight level limit on directory depths from any rooted logical
894 (allowing 16 levels overall) prior to VMS 7.2. Hence
895 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
896 C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
897 have to take this into account, but at least they can refer to the former
898 as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
900 The VMS::Filespec module, which gets installed as part of the build
901 process on VMS, is a pure Perl module that can easily be installed on
902 non-VMS platforms and can be helpful for conversions to and from RMS
905 What C<\n> represents depends on the type of file opened. It usually
906 represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
907 C<\000>, C<\040>, or nothing depending on the file organiztion and
908 record format. The VMS::Stdio module provides access to the
909 special fopen() requirements of files with unusual attributes on VMS.
911 TCP/IP stacks are optional on VMS, so socket routines might not be
912 implemented. UDP sockets may not be supported.
914 The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
915 that you are running on without resorting to loading all of C<%Config>
916 you can examine the content of the C<@INC> array like so:
918 if (grep(/VMS_AXP/, @INC)) {
919 print "I'm on Alpha!\n";
921 } elsif (grep(/VMS_VAX/, @INC)) {
922 print "I'm on VAX!\n";
925 print "I'm not so sure about where $^O is...\n";
928 On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
929 logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
930 calls to C<localtime> are adjusted to count offsets from
931 01-JAN-1970 00:00:00.00, just like Unix.
939 F<README.vms> (installed as L<README_vms>), L<perlvms>
943 vmsperl list, majordomo@perl.org
945 (Put the words C<subscribe vmsperl> in message body.)
949 vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
955 Perl on VOS is discussed in F<README.vos> in the perl distribution
956 (installed as L<perlvos>). Perl on VOS can accept either VOS- or
957 Unix-style file specifications as in either of the following:
959 $ perl -ne "print if /perl_setup/i" >system>notices
960 $ perl -ne "print if /perl_setup/i" /system/notices
962 or even a mixture of both as in:
964 $ perl -ne "print if /perl_setup/i" >system/notices
966 Even though VOS allows the slash character to appear in object
967 names, because the VOS port of Perl interprets it as a pathname
968 delimiting character, VOS files, directories, or links whose names
969 contain a slash character cannot be processed. Such files must be
970 renamed before they can be processed by Perl. Note that VOS limits
971 file names to 32 or fewer characters.
973 See F<README.vos> for restrictions that apply when Perl is built
974 with the alpha version of VOS POSIX.1 support.
976 Perl on VOS is built without any extensions and does not support
979 The value of C<$^O> on VOS is "VOS". To determine the architecture that
980 you are running on without resorting to loading all of C<%Config> you
981 can examine the content of the @INC array like so:
984 print "I'm on a Stratus box!\n";
986 print "I'm not on a Stratus box!\n";
990 if (grep(/860/, @INC)) {
991 print "This box is a Stratus XA/R!\n";
993 } elsif (grep(/7100/, @INC)) {
994 print "This box is a Stratus HP 7100 or 8xxx!\n";
996 } elsif (grep(/8000/, @INC)) {
997 print "This box is a Stratus HP 8xxx!\n";
1000 print "This box is a Stratus 68K!\n";
1013 The VOS mailing list.
1015 There is no specific mailing list for Perl on VOS. You can post
1016 comments to the comp.sys.stratus newsgroup, or subscribe to the general
1017 Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
1018 the message body to majordomo@list.stratagy.com.
1022 VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
1026 =head2 EBCDIC Platforms
1028 Recent versions of Perl have been ported to platforms such as OS/400 on
1029 AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1030 Mainframes. Such computers use EBCDIC character sets internally (usually
1031 Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1032 systems). On the mainframe perl currently works under the "Unix system
1033 services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1034 the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
1035 See L<perlos390> for details.
1037 As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1038 sub-systems do not support the C<#!> shebang trick for script invocation.
1039 Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1040 similar to the following simple script:
1043 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1045 #!/usr/local/bin/perl # just a comment really
1047 print "Hello from perl!\n";
1049 OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1050 Calls to C<system> and backticks can use POSIX shell syntax on all
1053 On the AS/400, if PERL5 is in your library list, you may need
1054 to wrap your perl scripts in a CL procedure to invoke them like so:
1057 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1060 This will invoke the perl script F<hello.pl> in the root of the
1061 QOpenSys file system. On the AS/400 calls to C<system> or backticks
1064 On these platforms, bear in mind that the EBCDIC character set may have
1065 an effect on what happens with some perl functions (such as C<chr>,
1066 C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1067 well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1068 and C<|>, not to mention dealing with socket interfaces to ASCII computers
1069 (see L<"Newlines">).
1071 Fortunately, most web servers for the mainframe will correctly
1072 translate the C<\n> in the following statement to its ASCII equivalent
1073 (C<\r> is the same under both Unix and OS/390 & VM/ESA):
1075 print "Content-type: text/html\r\n\r\n";
1077 The values of C<$^O> on some of these platforms includes:
1079 uname $^O $Config{'archname'}
1080 --------------------------------------------
1083 POSIX-BC posix-bc BS2000-posix-bc
1086 Some simple tricks for determining if you are running on an EBCDIC
1087 platform could include any of the following (perhaps all):
1089 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1091 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1093 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1095 One thing you may not want to rely on is the EBCDIC encoding
1096 of punctuation characters since these may differ from code page to code
1097 page (and once your module or script is rumoured to work with EBCDIC,
1098 folks will want it to work with all EBCDIC character sets).
1108 L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
1113 The perl-mvs@perl.org list is for discussion of porting issues as well as
1114 general usage issues for all EBCDIC Perls. Send a message body of
1115 "subscribe perl-mvs" to majordomo@perl.org.
1119 AS/400 Perl information at
1120 http://as400.rochester.ibm.com/
1121 as well as on CPAN in the F<ports/> directory.
1125 =head2 Acorn RISC OS
1127 Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1128 Unix, and because Unix filename emulation is turned on by default,
1129 most simple scripts will probably work "out of the box". The native
1130 filesystem is modular, and individual filesystems are free to be
1131 case-sensitive or insensitive, and are usually case-preserving. Some
1132 native filesystems have name length limits, which file and directory
1133 names are silently truncated to fit. Scripts should be aware that the
1134 standard filesystem currently has a name length limit of B<10>
1135 characters, with up to 77 items in a directory, but other filesystems
1136 may not impose such limitations.
1138 Native filenames are of the form
1140 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
1144 Special_Field is not usually present, but may contain . and $ .
1145 Filesystem =~ m|[A-Za-z0-9_]|
1146 DsicName =~ m|[A-Za-z0-9_/]|
1147 $ represents the root directory
1148 . is the path separator
1149 @ is the current directory (per filesystem but machine global)
1150 ^ is the parent directory
1151 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1153 The default filename translation is roughly C<tr|/.|./|;>
1155 Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
1156 the second stage of C<$> interpolation in regular expressions will fall
1157 foul of the C<$.> if scripts are not careful.
1159 Logical paths specified by system variables containing comma-separated
1160 search lists are also allowed; hence C<System:Modules> is a valid
1161 filename, and the filesystem will prefix C<Modules> with each section of
1162 C<System$Path> until a name is made that points to an object on disk.
1163 Writing to a new file C<System:Modules> would be allowed only if
1164 C<System$Path> contains a single item list. The filesystem will also
1165 expand system variables in filenames if enclosed in angle brackets, so
1166 C<< <System$Dir>.Modules >> would look for the file
1167 S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
1168 that B<fully qualified filenames can start with C<< <> >>> and should
1169 be protected when C<open> is used for input.
1171 Because C<.> was in use as a directory separator and filenames could not
1172 be assumed to be unique after 10 characters, Acorn implemented the C
1173 compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1174 filenames specified in source code and store the respective files in
1175 subdirectories named after the suffix. Hence files are translated:
1178 C:foo.h C:h.foo (logical path variable)
1179 sys/os.h sys.h.os (C compiler groks Unix-speak)
1180 10charname.c c.10charname
1181 10charname.o o.10charname
1182 11charname_.c c.11charname (assuming filesystem truncates at 10)
1184 The Unix emulation library's translation of filenames to native assumes
1185 that this sort of translation is required, and it allows a user-defined list
1186 of known suffixes that it will transpose in this fashion. This may
1187 seem transparent, but consider that with these rules C<foo/bar/baz.h>
1188 and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1189 C<glob> cannot and do not attempt to emulate the reverse mapping. Other
1190 C<.>'s in filenames are translated to C</>.
1192 As implied above, the environment accessed through C<%ENV> is global, and
1193 the convention is that program specific environment variables are of the
1194 form C<Program$Name>. Each filesystem maintains a current directory,
1195 and the current filesystem's current directory is the B<global> current
1196 directory. Consequently, sociable programs don't change the current
1197 directory but rely on full pathnames, and programs (and Makefiles) cannot
1198 assume that they can spawn a child process which can change the current
1199 directory without affecting its parent (and everyone else for that
1202 Because native operating system filehandles are global and are currently
1203 allocated down from 255, with 0 being a reserved value, the Unix emulation
1204 library emulates Unix filehandles. Consequently, you can't rely on
1205 passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1207 The desire of users to express filenames of the form
1208 C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
1209 too: C<``> command output capture has to perform a guessing game. It
1210 assumes that a string C<< <[^<>]+\$[^<>]> >> is a
1211 reference to an environment variable, whereas anything else involving
1212 C<< < >> or C<< > >> is redirection, and generally manages to be 99%
1213 right. Of course, the problem remains that scripts cannot rely on any
1214 Unix tools being available, or that any tools found have Unix-like command
1217 Extensions and XS are, in theory, buildable by anyone using free
1218 tools. In practice, many don't, as users of the Acorn platform are
1219 used to binary distributions. MakeMaker does run, but no available
1220 make currently copes with MakeMaker's makefiles; even if and when
1221 this should be fixed, the lack of a Unix-like shell will cause
1222 problems with makefile rules, especially lines of the form C<cd
1223 sdbm && make all>, and anything using quoting.
1225 "S<RISC OS>" is the proper name for the operating system, but the value
1226 in C<$^O> is "riscos" (because we don't like shouting).
1230 Perl has been ported to many platforms that do not fit into any of
1231 the categories listed above. Some, such as AmigaOS, Atari MiNT,
1232 BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1233 into the standard Perl source code kit. You may need to see the
1234 F<ports/> directory on CPAN for information, and possibly binaries,
1235 for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1236 Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1237 fall under the Unix category, but we are not a standards body.)
1239 Some approximate operating system names and their C<$^O> values
1240 in the "OTHER" category include:
1242 OS $^O $Config{'archname'}
1243 ------------------------------------------
1244 Amiga DOS amigaos m68k-amigos
1245 MPE/iX mpeix PA-RISC1.1
1253 Amiga, F<README.amiga> (installed as L<perlamiga>).
1257 Atari, F<README.mint> and Guido Flohr's web page
1258 http://stud.uni-sb.de/~gufl0000/
1262 Be OS, F<README.beos>
1266 HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
1267 http://www.bixby.org/mark/perlix.html
1271 A free perl5-based PERL.NLM for Novell Netware is available in
1272 precompiled binary and source code form from http://www.novell.com/
1273 as well as from CPAN.
1277 Plan 9, F<README.plan9>
1281 =head1 FUNCTION IMPLEMENTATIONS
1283 Listed below are functions that are either completely unimplemented
1284 or else have been implemented differently on various platforms.
1285 Following each description will be, in parentheses, a list of
1286 platforms that the description applies to.
1288 The list may well be incomplete, or even wrong in some places. When
1289 in doubt, consult the platform-specific README files in the Perl
1290 source distribution, and any other documentation resources accompanying
1293 Be aware, moreover, that even among Unix-ish systems there are variations.
1295 For many functions, you can also query C<%Config>, exported by
1296 default from the Config module. For example, to check whether the
1297 platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1298 L<Config> for a full description of available variables.
1300 =head2 Alphabetical Listing of Perl Functions
1310 C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
1311 and applications are executable, and there are no uid/gid
1312 considerations. C<-o> is not supported. (S<Mac OS>)
1314 C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1315 which may not reflect UIC-based file protections. (VMS)
1317 C<-s> returns the size of the data fork, not the total size of data fork
1318 plus resource fork. (S<Mac OS>).
1320 C<-s> by name on an open file will return the space reserved on disk,
1321 rather than the current extent. C<-s> on an open filehandle returns the
1322 current size. (S<RISC OS>)
1324 C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
1325 C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1327 C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1330 C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
1331 (Win32, VMS, S<RISC OS>)
1333 C<-d> is true if passed a device spec without an explicit directory.
1336 C<-T> and C<-B> are implemented, but might misclassify Mac text files
1337 with foreign characters; this is the case will all platforms, but may
1338 affect S<Mac OS> often. (S<Mac OS>)
1340 C<-x> (or C<-X>) determine if a file ends in one of the executable
1341 suffixes. C<-S> is meaningless. (Win32)
1343 C<-x> (or C<-X>) determine if a file has an executable file type.
1350 Not implemented. (Win32)
1352 =item binmode FILEHANDLE
1354 Meaningless. (S<Mac OS>, S<RISC OS>)
1356 Reopens file and restores pointer; if function fails, underlying
1357 filehandle may be closed, or pointer may be in a different position.
1360 The value returned by C<tell> may be affected after the call, and
1361 the filehandle may be flushed. (Win32)
1365 Only limited meaning. Disabling/enabling write permission is mapped to
1366 locking/unlocking the file. (S<Mac OS>)
1368 Only good for changing "owner" read-write access, "group", and "other"
1369 bits are meaningless. (Win32)
1371 Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1373 Access permissions are mapped onto VOS access-control list changes. (VOS)
1377 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
1379 Does nothing, but won't fail. (Win32)
1381 =item chroot FILENAME
1385 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
1387 =item crypt PLAINTEXT,SALT
1389 May not be available if library or source was not provided when building
1392 Not implemented. (VOS)
1396 Not implemented. (VMS, Plan9, VOS)
1398 =item dbmopen HASH,DBNAME,MODE
1400 Not implemented. (VMS, Plan9, VOS)
1404 Not useful. (S<Mac OS>, S<RISC OS>)
1406 Not implemented. (Win32)
1408 Invokes VMS debugger. (VMS)
1412 Not implemented. (S<Mac OS>)
1414 Implemented via Spawn. (VM/ESA)
1416 Does not automatically flush output handles on some platforms.
1417 (SunOS, Solaris, HP-UX)
1419 =item fcntl FILEHANDLE,FUNCTION,SCALAR
1421 Not implemented. (Win32, VMS)
1423 =item flock FILEHANDLE,OPERATION
1425 Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
1427 Available only on Windows NT (not on Windows 95). (Win32)
1431 Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1433 Emulated using multiple interpreters. See L<perlfork>. (Win32)
1435 Does not automatically flush output handles on some platforms.
1436 (SunOS, Solaris, HP-UX)
1440 Not implemented. (S<Mac OS>, S<RISC OS>)
1444 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1448 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1450 =item getpriority WHICH,WHO
1452 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1456 Not implemented. (S<Mac OS>, Win32)
1458 Not useful. (S<RISC OS>)
1462 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1464 =item getnetbyname NAME
1466 Not implemented. (S<Mac OS>, Win32, Plan9)
1470 Not implemented. (S<Mac OS>, Win32)
1472 Not useful. (S<RISC OS>)
1476 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1478 =item getnetbyaddr ADDR,ADDRTYPE
1480 Not implemented. (S<Mac OS>, Win32, Plan9)
1482 =item getprotobynumber NUMBER
1484 Not implemented. (S<Mac OS>)
1486 =item getservbyport PORT,PROTO
1488 Not implemented. (S<Mac OS>)
1492 Not implemented. (S<Mac OS>, Win32, VM/ESA)
1496 Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
1500 Not implemented. (S<Mac OS>, Win32)
1504 Not implemented. (S<Mac OS>, Win32, Plan9)
1508 Not implemented. (S<Mac OS>, Win32, Plan9)
1512 Not implemented. (Win32, Plan9)
1516 Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
1520 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
1522 =item sethostent STAYOPEN
1524 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1526 =item setnetent STAYOPEN
1528 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1530 =item setprotoent STAYOPEN
1532 Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
1534 =item setservent STAYOPEN
1536 Not implemented. (Plan9, Win32, S<RISC OS>)
1540 Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
1544 Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
1548 Not implemented. (S<Mac OS>, Win32)
1552 Not implemented. (S<Mac OS>, Win32, Plan9)
1556 Not implemented. (S<Mac OS>, Win32, Plan9)
1560 Not implemented. (Plan9, Win32)
1566 Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1567 mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1568 with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1569 function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1570 (C<1>); this mapping cannot be overridden. Any other argument to exit()
1571 is used directly as Perl's exit status. (VMS)
1573 =item getsockopt SOCKET,LEVEL,OPTNAME
1575 Not implemented. (Plan9)
1581 This operator is implemented via the File::Glob extension on most
1582 platforms. See L<File::Glob> for portability information.
1584 =item ioctl FILEHANDLE,FUNCTION,SCALAR
1586 Not implemented. (VMS)
1588 Available only for socket handles, and it does what the ioctlsocket() call
1589 in the Winsock API does. (Win32)
1591 Available only for socket handles. (S<RISC OS>)
1593 =item kill SIGNAL, LIST
1595 C<kill(0, LIST)> is implemented for the sake of taint checking;
1596 use with other signals is unimplemented. (S<Mac OS>)
1598 Not implemented, hence not useful for taint checking. (S<RISC OS>)
1600 C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1601 a signal to the identified process like it does on Unix platforms.
1602 Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1603 and makes it exit immediately with exit status $sig. As in Unix, if
1604 $sig is 0 and the specified process exists, it returns true without
1605 actually terminating it. (Win32)
1607 =item link OLDFILE,NEWFILE
1609 Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
1611 Link count not updated because hard links are not quite that hard
1612 (They are sort of half-way between hard and soft links). (AmigaOS)
1614 Hard links are implemented on Win32 (Windows NT and Windows 2000)
1617 =item lstat FILEHANDLE
1623 Not implemented. (VMS, S<RISC OS>)
1625 Return values (especially for device and inode) may be bogus. (Win32)
1627 =item msgctl ID,CMD,ARG
1629 =item msgget KEY,FLAGS
1631 =item msgsnd ID,MSG,FLAGS
1633 =item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1635 Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
1637 =item open FILEHANDLE,EXPR
1639 =item open FILEHANDLE
1641 The C<|> variants are supported only if ToolServer is installed.
1644 open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
1646 Opening a process does not automatically flush output handles on some
1647 platforms. (SunOS, Solaris, HP-UX)
1649 =item pipe READHANDLE,WRITEHANDLE
1651 Very limited functionality. (MiNT)
1657 Not implemented. (Win32, VMS, S<RISC OS>)
1659 =item select RBITS,WBITS,EBITS,TIMEOUT
1661 Only implemented on sockets. (Win32)
1663 Only reliable on sockets. (S<RISC OS>)
1665 Note that the C<socket FILEHANDLE> form is generally portable.
1667 =item semctl ID,SEMNUM,CMD,ARG
1669 =item semget KEY,NSEMS,FLAGS
1671 =item semop KEY,OPSTRING
1673 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1677 Not implemented. (MPE/iX, Win32)
1679 =item setpgrp PID,PGRP
1681 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1683 =item setpriority WHICH,WHO,PRIORITY
1685 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1689 Not implemented. (MPE/iX, Win32)
1691 =item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1693 Not implemented. (Plan9)
1695 =item shmctl ID,CMD,ARG
1697 =item shmget KEY,SIZE,FLAGS
1699 =item shmread ID,VAR,POS,SIZE
1701 =item shmwrite ID,STRING,POS,SIZE
1703 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
1705 =item sockatmark SOCKET
1707 A relatively recent addition to socket functions, may not
1708 be implemented even in UNIX platforms.
1710 =item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1712 Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1714 =item stat FILEHANDLE
1720 Platforms that do not have rdev, blksize, or blocks will return these
1721 as '', so numeric comparison or manipulation of these fields may cause
1722 'not numeric' warnings.
1724 mtime and atime are the same thing, and ctime is creation time instead of
1725 inode change time. (S<Mac OS>)
1727 device and inode are not meaningful. (Win32)
1729 device and inode are not necessarily reliable. (VMS)
1731 mtime, atime and ctime all return the last modification time. Device and
1732 inode are not necessarily reliable. (S<RISC OS>)
1734 dev, rdev, blksize, and blocks are not available. inode is not
1735 meaningful and will differ between stat calls on the same file. (os2)
1737 some versions of cygwin when doing a stat("foo") and if not finding it
1738 may then attempt to stat("foo.exe") (Cygwin)
1740 =item symlink OLDFILE,NEWFILE
1742 Not implemented. (Win32, VMS, S<RISC OS>)
1746 Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
1748 =item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1750 The traditional "0", "1", and "2" MODEs are implemented with different
1751 numeric values on some systems. The flags exported by C<Fcntl>
1752 (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1753 OS>, OS/390, VM/ESA)
1757 Only implemented if ToolServer is installed. (S<Mac OS>)
1759 As an optimization, may not call the command shell specified in
1760 C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1761 process and immediately returns its process designator, without
1762 waiting for it to terminate. Return value may be used subsequently
1763 in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1764 by setting $? to "255 << 8". C<$?> is set in a way compatible with
1765 Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1766 as described in the documentation). (Win32)
1768 There is no shell to process metacharacters, and the native standard is
1769 to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1770 program. Redirection such as C<< > foo >> is performed (if at all) by
1771 the run time library of the spawned program. C<system> I<list> will call
1772 the Unix emulation library's C<exec> emulation, which attempts to provide
1773 emulation of the stdin, stdout, stderr in force in the parent, providing
1774 the child program uses a compatible version of the emulation library.
1775 I<scalar> will call the native command line direct and no such emulation
1776 of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1778 Far from being POSIX compliant. Because there may be no underlying
1779 /bin/sh tries to work around the problem by forking and execing the
1780 first token in its argument string. Handles basic redirection
1781 ("<" or ">") on its own behalf. (MiNT)
1783 Does not automatically flush output handles on some platforms.
1784 (SunOS, Solaris, HP-UX)
1786 The return value is POSIX-like (shifted up by 8 bits), which only allows
1787 room for a made-up value derived from the severity bits of the native
1788 32-bit condition code (unless overridden by C<use vmsish 'status'>).
1789 For more details see L<perlvms/$?>. (VMS)
1793 Only the first entry returned is nonzero. (S<Mac OS>)
1795 "cumulative" times will be bogus. On anything other than Windows NT
1796 or Windows 2000, "system" time will be bogus, and "user" time is
1797 actually the time returned by the clock() function in the C runtime
1800 Not useful. (S<RISC OS>)
1802 =item truncate FILEHANDLE,LENGTH
1804 =item truncate EXPR,LENGTH
1806 Not implemented. (Older versions of VMS)
1808 Truncation to zero-length only. (VOS)
1810 If a FILEHANDLE is supplied, it must be writable and opened in append
1811 mode (i.e., use C<<< open(FH, '>>filename') >>>
1812 or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1813 should not be held open elsewhere. (Win32)
1819 Returns undef where unavailable, as of version 5.005.
1821 C<umask> works but the correct permissions are set only when the file
1822 is finally closed. (AmigaOS)
1826 Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
1828 May not behave as expected. Behavior depends on the C runtime
1829 library's implementation of utime(), and the filesystem being
1830 used. The FAT filesystem typically does not support an "access
1831 time" field, and it may limit timestamps to a granularity of
1832 two seconds. (Win32)
1836 =item waitpid PID,FLAGS
1838 Not implemented. (S<Mac OS>, VOS)
1840 Can only be applied to process handles returned for processes spawned
1841 using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
1843 Not useful. (S<RISC OS>)
1851 =item v1.48, 02 February 2001
1853 Various updates from perl5-porters over the past year, supported
1854 platforms update from Jarkko Hietaniemi.
1856 =item v1.47, 22 March 2000
1858 Various cleanups from Tom Christiansen, including migration of
1859 long platform listings from L<perl>.
1861 =item v1.46, 12 February 2000
1863 Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1865 =item v1.45, 20 December 1999
1867 Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1869 =item v1.44, 19 July 1999
1871 A bunch of updates from Peter Prymmer for C<$^O> values,
1872 endianness, File::Spec, VMS, BS2000, OS/400.
1874 =item v1.43, 24 May 1999
1876 Added a lot of cleaning up from Tom Christiansen.
1878 =item v1.42, 22 May 1999
1880 Added notes about tests, sprintf/printf, and epoch offsets.
1882 =item v1.41, 19 May 1999
1884 Lots more little changes to formatting and content.
1886 Added a bunch of C<$^O> and related values
1887 for various platforms; fixed mail and web addresses, and added
1888 and changed miscellaneous notes. (Peter Prymmer)
1890 =item v1.40, 11 April 1999
1892 Miscellaneous changes.
1894 =item v1.39, 11 February 1999
1896 Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1897 note about newlines added.
1899 =item v1.38, 31 December 1998
1901 More changes from Jarkko.
1903 =item v1.37, 19 December 1998
1905 More minor changes. Merge two separate version 1.35 documents.
1907 =item v1.36, 9 September 1998
1909 Updated for Stratus VOS. Also known as version 1.35.
1911 =item v1.35, 13 August 1998
1913 Integrate more minor changes, plus addition of new sections under
1914 L<"ISSUES">: L<"Numbers endianness and Width">,
1915 L<"Character sets and character encoding">,
1916 L<"Internationalisation">.
1918 =item v1.33, 06 August 1998
1920 Integrate more minor changes.
1922 =item v1.32, 05 August 1998
1924 Integrate more minor changes.
1926 =item v1.30, 03 August 1998
1928 Major update for RISC OS, other minor changes.
1930 =item v1.23, 10 July 1998
1932 First public release with perl5.005.
1936 =head1 Supported Platforms
1938 As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
1939 platforms are able to build Perl from the standard source code
1940 distribution available at http://www.perl.com/CPAN/src/index.html
1963 Tru64 UNIX (DEC OSF/1, Digital UNIX)
1969 1) in DOS mode either the DOS or OS/2 ports can be used
1970 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
1971 the source does work with 5.6.1, but additional MacOS specific
1972 source code is needed for a complete build. See the web
1973 site http://dev.macperl.org/ for more information.
1974 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
1976 The following platforms worked for the previous releases (5.6.0 and 5.7.0),
1977 but we did not manage to test these in time for the 5.7.1 release.
1978 There is a very good chance that these will work fine with the 5.7.1.
1996 The following platform worked for the 5.005_03 major release but not
1997 for 5.6.0. Standardization on UTF-8 as the internal string
1998 representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
1999 EBCDIC platform. While Perl 5.7.1 will build on this platform some
2000 regression tests may fail and the C<use utf8;> pragma typically
2001 introduces text handling errors.
2005 1) previously known as MVS, about to become z/OS.
2007 Strongly related to the OS/390 platform by also being EBCDIC-based
2008 mainframe platforms are the following platforms:
2013 These are also expected to work, albeit with no UTF-8 support, under 5.6.1
2014 for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
2017 The following platforms have been known to build Perl from source in
2018 the past (5.005_03 and earlier), but we haven't been able to verify
2019 their status for the current release, either because the
2020 hardware/software platforms are rare or because we don't have an
2021 active champion on these platforms--or both. They used to work,
2022 though, so go ahead and try compiling them, and let perlbug@perl.org
2061 Support for the following platform is planned for a future Perl release:
2065 The following platforms have their own source code distributions and
2066 binaries available via http://www.perl.com/CPAN/ports/index.html:
2072 Tandem Guardian 5.004
2074 The following platforms have only binaries available via
2075 http://www.perl.com/CPAN/ports/index.html :
2079 Acorn RISCOS 5.005_02
2083 Although we do suggest that you always build your own Perl from
2084 the source code, both for maximal configurability and for security,
2085 in case you are in a hurry you can check
2086 http://www.perl.com/CPAN/ports/index.html for binary distributions.
2090 L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
2091 L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
2092 L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
2093 L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
2094 L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
2095 L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
2097 =head1 AUTHORS / CONTRIBUTORS
2099 Abigail <abigail@foad.org>,
2100 Charles Bailey <bailey@newman.upenn.edu>,
2101 Graham Barr <gbarr@pobox.com>,
2102 Tom Christiansen <tchrist@perl.com>,
2103 Nicholas Clark <nick@ccl4.org>,
2104 Thomas Dorner <Thomas.Dorner@start.de>,
2105 Andy Dougherty <doughera@lafayette.edu>,
2106 Dominic Dunlop <domo@computer.org>,
2107 Neale Ferguson <neale@vma.tabnsw.com.au>,
2108 David J. Fiander <davidf@mks.com>,
2109 Paul Green <Paul_Green@stratus.com>,
2110 M.J.T. Guy <mjtg@cam.ac.uk>,
2111 Jarkko Hietaniemi <jhi@iki.fi>,
2112 Luther Huffman <lutherh@stratcom.com>,
2113 Nick Ing-Simmons <nick@ing-simmons.net>,
2114 Andreas J. KE<ouml>nig <a.koenig@mind.de>,
2115 Markus Laker <mlaker@contax.co.uk>,
2116 Andrew M. Langmead <aml@world.std.com>,
2117 Larry Moore <ljmoore@freespace.net>,
2118 Paul Moore <Paul.Moore@uk.origin-it.com>,
2119 Chris Nandor <pudge@pobox.com>,
2120 Matthias Neeracher <neeri@iis.ee.ethz.ch>,
2121 Philip Newton <pne@cpan.org>,
2122 Gary Ng <71564.1743@CompuServe.COM>,
2123 Tom Phoenix <rootbeer@teleport.com>,
2124 AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2125 Peter Prymmer <pvhp@forte.com>,
2126 Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2127 Gurusamy Sarathy <gsar@activestate.com>,
2128 Paul J. Schinder <schinder@pobox.com>,
2129 Michael G Schwern <schwern@pobox.com>,
2130 Dan Sugalski <dan@sidhe.org>,
2131 Nathan Torkington <gnat@frii.com>.
2135 Version 1.50, last modified 10 Jul 2001