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1=head1 NAME
2
3perlport - Writing portable Perl
4
5
6=head1 DESCRIPTION
7
8Perl runs on a variety of operating systems. While most of them share
9a lot in common, they also have their own very particular and unique
10features.
11
12This document is meant to help you to find out what constitutes portable
0a47030a 13Perl code, so that once you have made your decision to write portably,
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14you know where the lines are drawn, and you can stay within them.
15
16There is a tradeoff between taking full advantage of B<a> particular type
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17of computer, and taking advantage of a full B<range> of them. Naturally,
18as you make your range bigger (and thus more diverse), the common
19denominators drop, and you are left with fewer areas of common ground in
20which you can operate to accomplish a particular task. Thus, when you
21begin attacking a problem, it is important to consider which part of the
22tradeoff curve you want to operate under. Specifically, whether it is
23important to you that the task that you are coding needs the full
24generality of being portable, or if it is sufficient to just get the job
25done. This is the hardest choice to be made. The rest is easy, because
26Perl provides lots of choices, whichever way you want to approach your
27problem.
28
29Looking at it another way, writing portable code is usually about
30willfully limiting your available choices. Naturally, it takes discipline
31to do that.
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32
33Be aware of two important points:
34
35=over 4
36
37=item Not all Perl programs have to be portable
38
39There is no reason why you should not use Perl as a language to glue Unix
40tools together, or to prototype a Macintosh application, or to manage the
41Windows registry. If it makes no sense to aim for portability for one
42reason or another in a given program, then don't bother.
43
44=item The vast majority of Perl B<is> portable
45
46Don't be fooled into thinking that it is hard to create portable Perl
47code. It isn't. Perl tries its level-best to bridge the gaps between
48what's available on different platforms, and all the means available to
49use those features. Thus almost all Perl code runs on any machine
50without modification. But there I<are> some significant issues in
51writing portable code, and this document is entirely about those issues.
52
53=back
54
55Here's the general rule: When you approach a task that is commonly done
56using a whole range of platforms, think in terms of writing portable
57code. That way, you don't sacrifice much by way of the implementation
58choices you can avail yourself of, and at the same time you can give
59your users lots of platform choices. On the other hand, when you have to
60take advantage of some unique feature of a particular platform, as is
61often the case with systems programming (whether for Unix, Windows,
62S<Mac OS>, VMS, etc.), consider writing platform-specific code.
63
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64When the code will run on only two or three operating systems, then you
65may only need to consider the differences of those particular systems.
66The important thing is to decide where the code will run, and to be
67deliberate in your decision.
68
69The material below is separated into three main sections: main issues of
70portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and
71builtin perl functions that behave differently on various ports
72(L<"FUNCTION IMPLEMENTATIONS">.
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73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
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76all of which are in a state of constant evolution. Thus this material
77should be considered a perpetual work in progress
78(E<lt>IMG SRC="yellow_sign.gif" ALT="Under Construction"E<gt>).
79
80
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81
82
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83=head1 ISSUES
84
85=head2 Newlines
86
638bc118 87In most operating systems, lines in files are terminated by newlines.
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88Just what is used as a newline may vary from OS to OS. Unix
89traditionally uses C<\012>, one kind of Windows I/O uses C<\015\012>,
90and S<Mac OS> uses C<\015>.
91
92Perl uses C<\n> to represent the "logical" newline, where what
93is logical may depend on the platform in use. In MacPerl, C<\n>
94always means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
95when accessing a file in "text" mode, STDIO translates it to (or from)
96C<\015\012>.
97
98Due to the "text" mode translation, DOSish perls have limitations
99of using C<seek> and C<tell> when a file is being accessed in "text"
100mode. Specifically, if you stick to C<seek>-ing to locations you got
101from C<tell> (and no others), you are usually free to use C<seek> and
102C<tell> even in "text" mode. In general, using C<seek> or C<tell> or
103other file operations that count bytes instead of characters, without
104considering the length of C<\n>, may be non-portable. If you use
105C<binmode> on a file, however, you can usually use C<seek> and C<tell>
106with arbitrary values quite safely.
107
108A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 109everywhere. When using protocols such as common Internet protocols,
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110C<\012> and C<\015> are called for specifically, and the values of
111the logical C<\n> and C<\r> (carriage return) are not reliable.
112
113 print SOCKET "Hi there, client!\r\n"; # WRONG
114 print SOCKET "Hi there, client!\015\012"; # RIGHT
115
116[NOTE: this does not necessarily apply to communications that are
117filtered by another program or module before sending to the socket; the
118the most popular EBCDIC webserver, for instance, accepts C<\r\n>,
119which translates those characters, along with all other
120characters in text streams, from EBCDIC to ASCII.]
121
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122However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
123and unsightly, as well as confusing to those maintaining the code. As
124such, the C<Socket> module supplies the Right Thing for those who want it.
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125
126 use Socket qw(:DEFAULT :crlf);
127 print SOCKET "Hi there, client!$CRLF" # RIGHT
128
129When reading I<from> a socket, remember that the default input record
130separator (C<$/>) is C<\n>, but code like this should recognize C<$/> as
131C<\012> or C<\015\012>:
132
133 while (<SOCKET>) {
134 # ...
135 }
136
137Better:
138
139 use Socket qw(:DEFAULT :crlf);
140 local($/) = LF; # not needed if $/ is already \012
141
142 while (<SOCKET>) {
143 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
144 # s/\015?\012/\n/; # same thing
145 }
146
147And this example is actually better than the previous one even for Unix
148platforms, because now any C<\015>'s (C<\cM>'s) are stripped out
149(and there was much rejoicing).
150
151
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152=head2 Numbers endianness and Width
153
154Different CPUs store integers and floating point numbers in different
155orders (called I<endianness>) and widths (32-bit and 64-bit being the
156most common). This affects your programs if they attempt to transfer
157numbers in binary format from a CPU architecture to another over some
158channel: either 'live' via network connections or storing the numbers
159to secondary storage such as a disk file.
160
161Conflicting storage orders make utter mess out of the numbers: if a
162little-endian host (Intel, Alpha) stores 0x12345678 (305419896 in
163decimal), a big-endian host (Motorola, MIPS, Sparc, PA) reads it as
1640x78563412 (2018915346 in decimal). To avoid this problem in network
165(socket) connections use the C<pack()> and C<unpack()> formats C<"n">
166and C<"N">, the "network" orders, they are guaranteed to be portable.
167
168Different widths can cause truncation even between platforms of equal
169endianness: the platform of shorter width loses the upper parts of the
170number. There is no good solution for this problem except to avoid
171transferring or storing raw binary numbers.
172
173One can circumnavigate both these problems in two ways: either
174transfer and store numbers always in text format, instead of raw
175binary, or consider using modules like C<Data::Dumper> (included in
176the standard distribution as of Perl 5.005) and C<Storable>.
177
dd9f0070 178=head2 Files
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179
180Most platforms these days structure files in a hierarchical fashion.
181So, it is reasonably safe to assume that any platform supports the
182notion of a "path" to uniquely identify a file on the system. Just
183how that path is actually written, differs.
184
185While they are similar, file path specifications differ between Unix,
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186Windows, S<Mac OS>, OS/2, VMS, S<RISC OS> and probably others. Unix,
187for example, is one of the few OSes that has the idea of a single root
188directory.
189
190VMS, Windows, and OS/2 can work similarly to Unix with C</> as path
191separator, or in their own idiosyncratic ways (such as having several
192root directories and various "unrooted" device files such NIL: and
193LPT:).
194
195S<Mac OS> uses C<:> as a path separator instead of C</>.
196
197C<RISC OS> perl can emulate Unix filenames with C</> as path
198separator, or go native and use C<.> for path separator and C<:> to
199signal filing systems and disc names.
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200
201As with the newline problem above, there are modules that can help. The
202C<File::Spec> modules provide methods to do the Right Thing on whatever
203platform happens to be running the program.
204
205 use File::Spec;
206 chdir(File::Spec->updir()); # go up one directory
207 $file = File::Spec->catfile(
208 File::Spec->curdir(), 'temp', 'file.txt'
209 );
210 # on Unix and Win32, './temp/file.txt'
211 # on Mac OS, ':temp:file.txt'
212
213File::Spec is available in the standard distribution, as of version
2145.004_05.
215
216In general, production code should not have file paths hardcoded; making
217them user supplied or from a configuration file is better, keeping in mind
218that file path syntax varies on different machines.
219
220This is especially noticeable in scripts like Makefiles and test suites,
221which often assume C</> as a path separator for subdirectories.
222
223Also of use is C<File::Basename>, from the standard distribution, which
224splits a pathname into pieces (base filename, full path to directory,
225and file suffix).
226
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227Even when on a single platform (if you can call UNIX a single
228platform), remember not to count on the existence or the contents of
229system-specific files, like F</etc/passwd>, F</etc/sendmail.conf>, or
230F</etc/resolv.conf>. For example the F</etc/passwd> may exist but it
231may not contain the encrypted passwords because the system is using
232some form of enhanced security-- or it may not contain all the
233accounts because the system is using NIS. If code does need to rely
234on such a file, include a description of the file and its format in
235the code's documentation, and make it easy for the user to override
236the default location of the file.
e41182b5 237
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238Do not have two files of the same name with different case, like
239F<test.pl> and <Test.pl>, as many platforms have case-insensitive
240filenames. Also, try not to have non-word characters (except for C<.>)
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241in the names, and keep them to the 8.3 convention, for maximum
242portability.
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243
244Likewise, if using C<AutoSplit>, try to keep the split functions to
2458.3 naming and case-insensitive conventions; or, at the very least,
246make it so the resulting files have a unique (case-insensitively)
247first 8 characters.
248
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249Don't assume C<E<lt>> won't be the first character of a filename. Always
250use C<E<gt>> explicitly to open a file for reading:
251
252 open(FILE, "<$existing_file") or die $!;
253
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254
255=head2 System Interaction
256
257Not all platforms provide for the notion of a command line, necessarily.
258These are usually platforms that rely on a Graphical User Interface (GUI)
259for user interaction. So a program requiring command lines might not work
260everywhere. But this is probably for the user of the program to deal
261with.
262
263Some platforms can't delete or rename files that are being held open by
264the system. Remember to C<close> files when you are done with them.
265Don't C<unlink> or C<rename> an open file. Don't C<tie> to or C<open> a
266file that is already tied to or opened; C<untie> or C<close> first.
267
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268Don't open the same file more than once at a time for writing, as some
269operating systems put mandatory locks on such files.
270
e41182b5 271Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 272Don't count on C<%ENV> entries being case-sensitive, or even
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273case-preserving.
274
0a47030a 275Don't count on signals.
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276
277Don't count on filename globbing. Use C<opendir>, C<readdir>, and
278C<closedir> instead.
279
b8099c3d 280Don't count on per-program environment variables, or per-program current
dd9f0070 281directories.
b8099c3d 282
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283
284=head2 Interprocess Communication (IPC)
285
286In general, don't directly access the system in code that is meant to be
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287portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>, C<``>,
288C<qx//>, C<open> with a C<|>, nor any of the other things that makes being
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289a Unix perl hacker worth being.
290
291Commands that launch external processes are generally supported on
292most platforms (though many of them do not support any type of forking),
293but the problem with using them arises from what you invoke with them.
294External tools are often named differently on different platforms, often
295not available in the same location, often accept different arguments,
296often behave differently, and often represent their results in a
297platform-dependent way. Thus you should seldom depend on them to produce
298consistent results.
299
300One especially common bit of Perl code is opening a pipe to sendmail:
301
302 open(MAIL, '|/usr/lib/sendmail -t') or die $!;
303
304This is fine for systems programming when sendmail is known to be
305available. But it is not fine for many non-Unix systems, and even
306some Unix systems that may not have sendmail installed. If a portable
307solution is needed, see the C<Mail::Send> and C<Mail::Mailer> modules
308in the C<MailTools> distribution. C<Mail::Mailer> provides several
309mailing methods, including mail, sendmail, and direct SMTP
310(via C<Net::SMTP>) if a mail transfer agent is not available.
311
312The rule of thumb for portable code is: Do it all in portable Perl, or
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313use a module (that may internally implement it with platform-specific
314code, but expose a common interface).
e41182b5 315
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316The UNIX System V IPC (C<msg*(), sem*(), shm*()>) is not available
317even in all UNIX platforms.
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318
319=head2 External Subroutines (XS)
320
321XS code, in general, can be made to work with any platform; but dependent
322libraries, header files, etc., might not be readily available or
323portable, or the XS code itself might be platform-specific, just as Perl
324code might be. If the libraries and headers are portable, then it is
325normally reasonable to make sure the XS code is portable, too.
326
327There is a different kind of portability issue with writing XS
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328code: availability of a C compiler on the end-user's system. C brings
329with it its own portability issues, and writing XS code will expose you to
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330some of those. Writing purely in perl is a comparatively easier way to
331achieve portability.
332
333
334=head2 Standard Modules
335
336In general, the standard modules work across platforms. Notable
337exceptions are C<CPAN.pm> (which currently makes connections to external
338programs that may not be available), platform-specific modules (like
339C<ExtUtils::MM_VMS>), and DBM modules.
340
341There is no one DBM module that is available on all platforms.
342C<SDBM_File> and the others are generally available on all Unix and DOSish
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343ports, but not in MacPerl, where only C<NBDM_File> and C<DB_File> are
344available.
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345
346The good news is that at least some DBM module should be available, and
347C<AnyDBM_File> will use whichever module it can find. Of course, then
348the code needs to be fairly strict, dropping to the lowest common
349denominator (e.g., not exceeding 1K for each record).
350
351
352=head2 Time and Date
353
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354The system's notion of time of day and calendar date is controlled in
355widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
356and even if it is, don't assume that you can control the timezone through
357that variable.
e41182b5 358
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359Don't assume that the epoch starts at 00:00:00, January 1, 1970,
360because that is OS-specific. Better to store a date in an unambiguous
361representation. The ISO 8601 standard defines YYYY-MM-DD as the date
362format. A text representation (like C<1 Jan 1970>) can be easily
363converted into an OS-specific value using a module like
364C<Date::Parse>. An array of values, such as those returned by
365C<localtime>, can be converted to an OS-specific representation using
366C<Time::Local>.
367
368
369=head2 Character sets and character encoding
370
371Assume very little about character sets. Do not assume anything about
372the numerical values (C<ord()>, C<chr()>) of characters. Do not
373assume that the alphabetic characters are encoded contiguously (in
374numerical sense). Do no assume anything about the ordering of the
375characters. The lowercase letters may come before or after the
376uppercase letters, the lowercase and uppercase may be interlaced so
b1ff3570 377that both 'a' and 'A' come before the 'b', the accented and other
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378international characters may be interlaced so that E<auml> comes
379before the 'b'.
380
381
382=head2 Internationalisation
383
384If you may assume POSIX (a rather large assumption, that: in practise
385that means UNIX) you may read more about the POSIX locale system from
386L<perllocale>. The locale system at least attempts to make things a
387little bit more portable or at least more convenient and
388native-friendly for non-English users. The system affects character
389sets and encoding, and date and time formatting, among other things.
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390
391
392=head2 System Resources
393
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394If your code is destined for systems with severely constrained (or
395missing!) virtual memory systems then you want to be I<especially> mindful
396of avoiding wasteful constructs such as:
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397
398 # NOTE: this is no longer "bad" in perl5.005
399 for (0..10000000) {} # bad
400 for (my $x = 0; $x <= 10000000; ++$x) {} # good
401
402 @lines = <VERY_LARGE_FILE>; # bad
403
404 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 405 $file = join('', <FILE>); # better
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406
407The last two may appear unintuitive to most people. The first of those
408two constructs repeatedly grows a string, while the second allocates a
409large chunk of memory in one go. On some systems, the latter is more
410efficient that the former.
411
0a47030a 412
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413=head2 Security
414
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415Most multi-user platforms provide basic levels of security that is usually
416felt at the file-system level. Other platforms usually don't
417(unfortunately). Thus the notion of user id, or "home" directory, or even
418the state of being logged-in, may be unrecognizable on many platforms. If
419you write programs that are security conscious, it is usually best to know
420what type of system you will be operating under, and write code explicitly
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421for that platform (or class of platforms).
422
0a47030a 423
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424=head2 Style
425
426For those times when it is necessary to have platform-specific code,
427consider keeping the platform-specific code in one place, making porting
428to other platforms easier. Use the C<Config> module and the special
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429variable C<$^O> to differentiate platforms, as described in
430L<"PLATFORMS">.
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431
432
0a47030a 433=head1 CPAN Testers
e41182b5 434
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435Modules uploaded to CPAN are tested by a variety of volunteers on
436different platforms. These CPAN testers are notified by mail of each
e41182b5 437new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 438this platform), or UNKNOWN (unknown), along with any relevant notations.
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439
440The purpose of the testing is twofold: one, to help developers fix any
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441problems in their code that crop up because of lack of testing on other
442platforms; two, to provide users with information about whether or not
443a given module works on a given platform.
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444
445=over 4
446
447=item Mailing list: cpan-testers@perl.org
448
449=item Testing results: C<http://www.connect.net/gbarr/cpan-test/>
450
451=back
452
453
454=head1 PLATFORMS
455
456As of version 5.002, Perl is built with a C<$^O> variable that
457indicates the operating system it was built on. This was implemented
458to help speed up code that would otherwise have to C<use Config;> and
459use the value of C<$Config{'osname'}>. Of course, to get
460detailed information about the system, looking into C<%Config> is
461certainly recommended.
462
463=head2 Unix
464
465Perl works on a bewildering variety of Unix and Unix-like platforms (see
466e.g. most of the files in the F<hints/> directory in the source code kit).
467On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
468too) is determined by lowercasing and stripping punctuation from the first
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469field of the string returned by typing C<uname -a> (or a similar command)
470at the shell prompt. Here, for example, are a few of the more popular
471Unix flavors:
e41182b5 472
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473 uname $^O $Config{'archname'}
474 -------------------------------------------
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475 AIX aix aix
476 FreeBSD freebsd freebsd-i386
477 Linux linux i386-linux
478 HP-UX hpux PA-RISC1.1
479 IRIX irix irix
480 OSF1 dec_osf alpha-dec_osf
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481 SunOS solaris sun4-solaris
482 SunOS solaris i86pc-solaris
322422de 483 SunOS4 sunos sun4-sunos
e41182b5 484
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485Note that because the C<$Config{'archname'}> may depend on the hardware
486architecture it may vary quite a lot, much more than the C<$^O>.
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487
488=head2 DOS and Derivatives
489
490Perl has long been ported to PC style microcomputers running under
491systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
492bring yourself to mention (except for Windows CE, if you count that).
493Users familiar with I<COMMAND.COM> and/or I<CMD.EXE> style shells should
494be aware that each of these file specifications may have subtle
495differences:
496
497 $filespec0 = "c:/foo/bar/file.txt";
498 $filespec1 = "c:\\foo\\bar\\file.txt";
499 $filespec2 = 'c:\foo\bar\file.txt';
500 $filespec3 = 'c:\\foo\\bar\\file.txt';
501
502System calls accept either C</> or C<\> as the path separator. However,
503many command-line utilities of DOS vintage treat C</> as the option
504prefix, so they may get confused by filenames containing C</>. Aside
505from calling any external programs, C</> will work just fine, and
506probably better, as it is more consistent with popular usage, and avoids
507the problem of remembering what to backwhack and what not to.
508
0a47030a 509The DOS FAT filesystem can only accommodate "8.3" style filenames. Under
e41182b5 510the "case insensitive, but case preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 511filesystems you may have to be careful about case returned with functions
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512like C<readdir> or used with functions like C<open> or C<opendir>.
513
514DOS also treats several filenames as special, such as AUX, PRN, NUL, CON,
515COM1, LPT1, LPT2 etc. Unfortunately these filenames won't even work
516if you include an explicit directory prefix, in some cases. It is best
517to avoid such filenames, if you want your code to be portable to DOS
518and its derivatives.
519
520Users of these operating systems may also wish to make use of
521scripts such as I<pl2bat.bat> or I<pl2cmd> as appropriate to
522put wrappers around your scripts.
523
524Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
525and writing to files. C<binmode(FILEHANDLE)> will keep C<\n> translated
526as C<\012> for that filehandle. Since it is a noop on other systems,
527C<binmode> should be used for cross-platform code that deals with binary
528data.
529
530The C<$^O> variable and the C<$Config{'archname'}> values for various
531DOSish perls are as follows:
532
533 OS $^O $Config{'archname'}
534 --------------------------------------------
535 MS-DOS dos
536 PC-DOS dos
537 OS/2 os2
538 Windows 95 MSWin32 MSWin32-x86
539 Windows NT MSWin32 MSWin32-x86
540 Windows NT MSWin32 MSWin32-alpha
541 Windows NT MSWin32 MSWin32-ppc
542
543Also see:
544
545=over 4
546
547=item The djgpp environment for DOS, C<http://www.delorie.com/djgpp/>
548
549=item The EMX environment for DOS, OS/2, etc. C<emx@iaehv.nl>,
550C<http://www.juge.com/bbs/Hobb.19.html>
551
552=item Build instructions for Win32, L<perlwin32>.
553
554=item The ActiveState Pages, C<http://www.activestate.com/>
555
556=back
557
558
dd9f0070 559=head2 S<Mac OS>
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560
561Any module requiring XS compilation is right out for most people, because
562MacPerl is built using non-free (and non-cheap!) compilers. Some XS
563modules that can work with MacPerl are built and distributed in binary
0a47030a
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564form on CPAN. See I<MacPerl: Power and Ease> and L<"CPAN Testers">
565for more details.
e41182b5
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566
567Directories are specified as:
568
569 volume:folder:file for absolute pathnames
570 volume:folder: for absolute pathnames
571 :folder:file for relative pathnames
572 :folder: for relative pathnames
573 :file for relative pathnames
574 file for relative pathnames
575
576Files in a directory are stored in alphabetical order. Filenames are
577limited to 31 characters, and may include any character except C<:>,
578which is reserved as a path separator.
579
0a47030a
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580Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
581C<Mac::Files> module.
e41182b5
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582
583In the MacPerl application, you can't run a program from the command line;
584programs that expect C<@ARGV> to be populated can be edited with something
585like the following, which brings up a dialog box asking for the command
586line arguments.
587
588 if (!@ARGV) {
589 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
590 }
591
592A MacPerl script saved as a droplet will populate C<@ARGV> with the full
593pathnames of the files dropped onto the script.
594
595Mac users can use programs on a kind of command line under MPW (Macintosh
596Programmer's Workshop, a free development environment from Apple).
597MacPerl was first introduced as an MPW tool, and MPW can be used like a
598shell:
599
600 perl myscript.plx some arguments
601
602ToolServer is another app from Apple that provides access to MPW tools
0a47030a 603from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
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604C<system>, backticks, and piped C<open>.
605
606"S<Mac OS>" is the proper name for the operating system, but the value
607in C<$^O> is "MacOS". To determine architecture, version, or whether
608the application or MPW tool version is running, check:
609
610 $is_app = $MacPerl::Version =~ /App/;
611 $is_tool = $MacPerl::Version =~ /MPW/;
612 ($version) = $MacPerl::Version =~ /^(\S+)/;
613 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
614 $is_68k = $MacPerl::Architecture eq 'Mac68K';
615
0a47030a
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616S<Mac OS X>, to be based on NeXT's OpenStep OS, will be able to run
617MacPerl natively (in the Blue Box, and even in the Yellow Box, once some
618changes to the toolbox calls are made), but Unix perl will also run
619natively.
e41182b5
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620
621Also see:
622
623=over 4
624
625=item The MacPerl Pages, C<http://www.ptf.com/macperl/>.
626
627=item The MacPerl mailing list, C<mac-perl-request@iis.ee.ethz.ch>.
628
629=back
630
631
632=head2 VMS
633
634Perl on VMS is discussed in F<vms/perlvms.pod> in the perl distribution.
0a47030a 635Note that perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
636specifications as in either of the following:
637
638 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
639 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
640
641but not a mixture of both as in:
642
643 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
644 Can't open sys$login:/login.com: file specification syntax error
645
646Interacting with Perl from the Digital Command Language (DCL) shell
647often requires a different set of quotation marks than Unix shells do.
648For example:
649
650 $ perl -e "print ""Hello, world.\n"""
651 Hello, world.
652
653There are a number of ways to wrap your perl scripts in DCL .COM files if
654you are so inclined. For example:
655
656 $ write sys$output "Hello from DCL!"
657 $ if p1 .eqs. ""
658 $ then perl -x 'f$environment("PROCEDURE")
659 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
660 $ deck/dollars="__END__"
661 #!/usr/bin/perl
662
663 print "Hello from Perl!\n";
664
665 __END__
666 $ endif
667
668Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
669perl-in-DCL script expects to do things like C<$read = E<lt>STDINE<gt>;>.
670
671Filenames are in the format "name.extension;version". The maximum
672length for filenames is 39 characters, and the maximum length for
673extensions is also 39 characters. Version is a number from 1 to
67432767. Valid characters are C</[A-Z0-9$_-]/>.
675
676VMS' RMS filesystem is case insensitive and does not preserve case.
677C<readdir> returns lowercased filenames, but specifying a file for
b8099c3d 678opening remains case insensitive. Files without extensions have a
e41182b5 679trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
680will return F<a.> (though that file could be opened with
681C<open(FH, 'A')>).
e41182b5 682
f34d0673 683RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
CN
684(allowing 16 levels overall) prior to VMS 7.2. Hence
685C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
686C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
687have to take this into account, but at least they can refer to the former
f34d0673 688as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 689
0a47030a
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690The C<VMS::Filespec> module, which gets installed as part of the build
691process on VMS, is a pure Perl module that can easily be installed on
692non-VMS platforms and can be helpful for conversions to and from RMS
693native formats.
e41182b5
GS
694
695What C<\n> represents depends on the type of file that is open. It could
696be C<\015>, C<\012>, C<\015\012>, or nothing. Reading from a file
697translates newlines to C<\012>, unless C<binmode> was executed on that
698handle, just like DOSish perls.
699
700TCP/IP stacks are optional on VMS, so socket routines might not be
701implemented. UDP sockets may not be supported.
702
703The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
704that you are running on without resorting to loading all of C<%Config>
705you can examine the content of the C<@INC> array like so:
706
707 if (grep(/VMS_AXP/, @INC)) {
708 print "I'm on Alpha!\n";
709 } elsif (grep(/VMS_VAX/, @INC)) {
710 print "I'm on VAX!\n";
711 } else {
712 print "I'm not so sure about where $^O is...\n";
713 }
714
715Also see:
716
717=over 4
718
719=item L<perlvms.pod>
720
721=item vmsperl list, C<vmsperl-request@newman.upenn.edu>
722
723Put words C<SUBSCRIBE VMSPERL> in message body.
724
725=item vmsperl on the web, C<http://www.sidhe.org/vmsperl/index.html>
726
727=back
728
729
730=head2 EBCDIC Platforms
731
732Recent versions of Perl have been ported to platforms such as OS/400 on
733AS/400 minicomputers as well as OS/390 for IBM Mainframes. Such computers
734use EBCDIC character sets internally (usually Character Code Set ID 00819
735for OS/400 and IBM-1047 for OS/390). Note that on the mainframe perl
736currently works under the "Unix system services for OS/390" (formerly
737known as OpenEdition).
738
739As of R2.5 of USS for OS/390 that Unix sub-system did not support the
740C<#!> shebang trick for script invocation. Hence, on OS/390 perl scripts
741can executed with a header similar to the following simple script:
742
743 : # use perl
744 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
745 if 0;
746 #!/usr/local/bin/perl # just a comment really
747
748 print "Hello from perl!\n";
749
750On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
751an effect on what happens with some perl functions (such as C<chr>,
752C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
753well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
754and C<|>, not to mention dealing with socket interfaces to ASCII computers
e41182b5
GS
755(see L<"NEWLINES">).
756
757Fortunately, most web servers for the mainframe will correctly translate
758the C<\n> in the following statement to its ASCII equivalent (note that
0a47030a 759C<\r> is the same under both Unix and OS/390):
e41182b5
GS
760
761 print "Content-type: text/html\r\n\r\n";
762
763The value of C<$^O> on OS/390 is "os390".
764
765Some simple tricks for determining if you are running on an EBCDIC
766platform could include any of the following (perhaps all):
767
768 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
769
770 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
771
772 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
773
774Note that one thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
775of punctuation characters since these may differ from code page to code
776page (and once your module or script is rumoured to work with EBCDIC,
777folks will want it to work with all EBCDIC character sets).
e41182b5
GS
778
779Also see:
780
781=over 4
782
783=item perl-mvs list
784
785The perl-mvs@perl.org list is for discussion of porting issues as well as
786general usage issues for all EBCDIC Perls. Send a message body of
787"subscribe perl-mvs" to majordomo@perl.org.
788
0a47030a 789=item AS/400 Perl information at C<http://as400.rochester.ibm.com/>
e41182b5
GS
790
791=back
792
b8099c3d
CN
793
794=head2 Acorn RISC OS
795
0a47030a
GS
796As Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
797Unix and Unix filename emulation is turned on by default, it is quite
798likely that most simple scripts will work "out of the box". The native
799filing system is modular, and individual filing systems are free to be
800case-sensitive or insensitive, and are usually case-preserving. Some
801native filing systems have name length limits which file and directory
802names are silently truncated to fit - scripts should be aware that the
803standard disc filing system currently has a name length limit of B<10>
804characters, with up to 77 items in a directory, but other filing systems
805may not impose such limitations.
b8099c3d
CN
806
807Native filenames are of the form
808
809 Filesystem#Special_Field::DiscName.$.Directory.Directory.File
dd9f0070 810
b8099c3d
CN
811where
812
813 Special_Field is not usually present, but may contain . and $ .
814 Filesystem =~ m|[A-Za-z0-9_]|
815 DsicName =~ m|[A-Za-z0-9_/]|
816 $ represents the root directory
817 . is the path separator
818 @ is the current directory (per filesystem but machine global)
819 ^ is the parent directory
820 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
821
822The default filename translation is roughly C<tr|/.|./|;>
823
824Note that C<"ADFS::HardDisc.$.File" ne 'ADFS::HardDisc.$.File'> and that
0a47030a
GS
825the second stage of C<$> interpolation in regular expressions will fall
826foul of the C<$.> if scripts are not careful.
827
828Logical paths specified by system variables containing comma-separated
829search lists are also allowed, hence C<System:Modules> is a valid
830filename, and the filesystem will prefix C<Modules> with each section of
831C<System$Path> until a name is made that points to an object on disc.
832Writing to a new file C<System:Modules> would only be allowed if
833C<System$Path> contains a single item list. The filesystem will also
834expand system variables in filenames if enclosed in angle brackets, so
835C<E<lt>System$DirE<gt>.Modules> would look for the file
836S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
837that B<fully qualified filenames can start with C<E<lt>E<gt>> and should
838be protected when C<open> is used for input.
b8099c3d
CN
839
840Because C<.> was in use as a directory separator and filenames could not
841be assumed to be unique after 10 characters, Acorn implemented the C
842compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
843filenames specified in source code and store the respective files in
844subdirectories named after the suffix. Hence files are translated:
845
846 foo.h h.foo
847 C:foo.h C:h.foo (logical path variable)
848 sys/os.h sys.h.os (C compiler groks Unix-speak)
849 10charname.c c.10charname
850 10charname.o o.10charname
851 11charname_.c c.11charname (assuming filesystem truncates at 10)
852
853The Unix emulation library's translation of filenames to native assumes
0a47030a
GS
854that this sort of translation is required, and allows a user defined list
855of known suffixes which it will transpose in this fashion. This may
856appear transparent, but consider that with these rules C<foo/bar/baz.h>
857and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
858C<glob> cannot and do not attempt to emulate the reverse mapping. Other
859C<.>s in filenames are translated to C</>.
860
861As implied above the environment accessed through C<%ENV> is global, and
862the convention is that program specific environment variables are of the
863form C<Program$Name>. Each filing system maintains a current directory,
864and the current filing system's current directory is the B<global> current
865directory. Consequently, sociable scripts don't change the current
866directory but rely on full pathnames, and scripts (and Makefiles) cannot
867assume that they can spawn a child process which can change the current
868directory without affecting its parent (and everyone else for that
869matter).
870
871As native operating system filehandles are global and currently are
872allocated down from 255, with 0 being a reserved value the Unix emulation
873library emulates Unix filehandles. Consequently, you can't rely on
874passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
875
876The desire of users to express filenames of the form
877C<E<lt>Foo$DirE<gt>.Bar> on the command line unquoted causes problems,
878too: C<``> command output capture has to perform a guessing game. It
879assumes that a string C<E<lt>[^E<lt>E<gt>]+\$[^E<lt>E<gt>]E<gt>> is a
880reference to an environment variable, whereas anything else involving
881C<E<lt>> or C<E<gt>> is redirection, and generally manages to be 99%
882right. Of course, the problem remains that scripts cannot rely on any
883Unix tools being available, or that any tools found have Unix-like command
884line arguments.
885
886Extensions and XS are, in theory, buildable by anyone using free tools.
887In practice, many don't, as users of the Acorn platform are used to binary
888distribution. MakeMaker does run, but no available make currently copes
889with MakeMaker's makefiles; even if/when this is fixed, the lack of a
890Unix-like shell can cause problems with makefile rules, especially lines
891of the form C<cd sdbm && make all>, and anything using quoting.
b8099c3d
CN
892
893"S<RISC OS>" is the proper name for the operating system, but the value
894in C<$^O> is "riscos" (because we don't like shouting).
895
896Also see:
897
898=over 4
899
900=item perl list
901
902=back
903
904
e41182b5
GS
905=head2 Other perls
906
b8099c3d
CN
907Perl has been ported to a variety of platforms that do not fit into any of
908the above categories. Some, such as AmigaOS, BeOS, QNX, and Plan 9, have
0a47030a 909been well-integrated into the standard Perl source code kit. You may need
b8099c3d 910to see the F<ports/> directory on CPAN for information, and possibly
0a47030a
GS
911binaries, for the likes of: aos, atari, lynxos, riscos, Tandem Guardian,
912vos, I<etc.> (yes we know that some of these OSes may fall under the Unix
913category, but we are not a standards body.)
e41182b5
GS
914
915See also:
916
917=over 4
918
919=item Atari, Guido Flohr's page C<http://stud.uni-sb.de/~gufl0000/>
920
921=item HP 300 MPE/iX C<http://www.cccd.edu/~markb/perlix.html>
922
923=item Novell Netware
924
0a47030a 925A free perl5-based PERL.NLM for Novell Netware is available from
e41182b5
GS
926C<http://www.novell.com/>
927
928=back
929
930
931=head1 FUNCTION IMPLEMENTATIONS
932
933Listed below are functions unimplemented or implemented differently on
934various platforms. Following each description will be, in parentheses, a
935list of platforms that the description applies to.
936
937The list may very well be incomplete, or wrong in some places. When in
938doubt, consult the platform-specific README files in the Perl source
939distribution, and other documentation resources for a given port.
940
0a47030a 941Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5
GS
942
943For many functions, you can also query C<%Config>, exported by default
944from C<Config.pm>. For example, to check if the platform has the C<lstat>
0a47030a
GS
945call, check C<$Config{'d_lstat'}>. See L<Config.pm> for a full
946description of available variables.
e41182b5
GS
947
948
949=head2 Alphabetical Listing of Perl Functions
950
951=over 8
952
953=item -X FILEHANDLE
954
955=item -X EXPR
956
957=item -X
958
959C<-r>, C<-w>, and C<-x> have only a very limited meaning; directories
960and applications are executable, and there are no uid/gid
961considerations. C<-o> is not supported. (S<Mac OS>)
962
963C<-r>, C<-w>, C<-x>, and C<-o> tell whether or not file is accessible,
964which may not reflect UIC-based file protections. (VMS)
965
b8099c3d
CN
966C<-s> returns the size of the data fork, not the total size of data fork
967plus resource fork. (S<Mac OS>).
968
969C<-s> by name on an open file will return the space reserved on disk,
970rather than the current extent. C<-s> on an open filehandle returns the
971current size. (S<RISC OS>)
972
e41182b5 973C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 974C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
975
976C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
977(S<Mac OS>)
978
979C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 980(Win32, VMS, S<RISC OS>)
e41182b5
GS
981
982C<-d> is true if passed a device spec without an explicit directory.
983(VMS)
984
985C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a
GS
986with foreign characters; this is the case will all platforms, but may
987affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
988
989C<-x> (or C<-X>) determine if a file ends in one of the executable
990suffixes. C<-S> is meaningless. (Win32)
991
b8099c3d
CN
992C<-x> (or C<-X>) determine if a file has an executable file type.
993(S<RISC OS>)
994
e41182b5
GS
995=item binmode FILEHANDLE
996
b8099c3d 997Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
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998
999Reopens file and restores pointer; if function fails, underlying
1000filehandle may be closed, or pointer may be in a different position.
1001(VMS)
1002
1003The value returned by C<tell> may be affected after the call, and
1004the filehandle may be flushed. (Win32)
1005
1006=item chmod LIST
1007
1008Only limited meaning. Disabling/enabling write permission is mapped to
1009locking/unlocking the file. (S<Mac OS>)
1010
1011Only good for changing "owner" read-write access, "group", and "other"
1012bits are meaningless. (Win32)
1013
b8099c3d
CN
1014Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1015
e41182b5
GS
1016=item chown LIST
1017
b8099c3d 1018Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1019
1020Does nothing, but won't fail. (Win32)
1021
1022=item chroot FILENAME
1023
1024=item chroot
1025
b8099c3d 1026Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>)
e41182b5
GS
1027
1028=item crypt PLAINTEXT,SALT
1029
1030May not be available if library or source was not provided when building
b8099c3d 1031perl. (Win32)
e41182b5
GS
1032
1033=item dbmclose HASH
1034
1035Not implemented. (VMS, Plan9)
1036
1037=item dbmopen HASH,DBNAME,MODE
1038
1039Not implemented. (VMS, Plan9)
1040
1041=item dump LABEL
1042
b8099c3d 1043Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1044
1045Not implemented. (Win32)
1046
b8099c3d 1047Invokes VMS debugger. (VMS)
e41182b5
GS
1048
1049=item exec LIST
1050
1051Not implemented. (S<Mac OS>)
1052
1053=item fcntl FILEHANDLE,FUNCTION,SCALAR
1054
1055Not implemented. (Win32, VMS)
1056
1057=item flock FILEHANDLE,OPERATION
1058
b8099c3d 1059Not implemented (S<Mac OS>, VMS, S<RISC OS>).
e41182b5
GS
1060
1061Available only on Windows NT (not on Windows 95). (Win32)
1062
1063=item fork
1064
b8099c3d 1065Not implemented. (S<Mac OS>, Win32, AmigaOS, S<RISC OS>)
e41182b5
GS
1066
1067=item getlogin
1068
b8099c3d 1069Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1070
1071=item getpgrp PID
1072
b8099c3d 1073Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1074
1075=item getppid
1076
b8099c3d 1077Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1078
1079=item getpriority WHICH,WHO
1080
b8099c3d 1081Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1082
1083=item getpwnam NAME
1084
1085Not implemented. (S<Mac OS>, Win32)
1086
b8099c3d
CN
1087Not useful. (S<RISC OS>)
1088
e41182b5
GS
1089=item getgrnam NAME
1090
b8099c3d 1091Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1092
1093=item getnetbyname NAME
1094
1095Not implemented. (S<Mac OS>, Win32, Plan9)
1096
1097=item getpwuid UID
1098
1099Not implemented. (S<Mac OS>, Win32)
1100
b8099c3d
CN
1101Not useful. (S<RISC OS>)
1102
e41182b5
GS
1103=item getgrgid GID
1104
b8099c3d 1105Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1106
1107=item getnetbyaddr ADDR,ADDRTYPE
1108
1109Not implemented. (S<Mac OS>, Win32, Plan9)
1110
1111=item getprotobynumber NUMBER
1112
1113Not implemented. (S<Mac OS>)
1114
1115=item getservbyport PORT,PROTO
1116
1117Not implemented. (S<Mac OS>)
1118
1119=item getpwent
1120
1121Not implemented. (S<Mac OS>, Win32)
1122
1123=item getgrent
1124
1125Not implemented. (S<Mac OS>, Win32, VMS)
1126
1127=item gethostent
1128
1129Not implemented. (S<Mac OS>, Win32)
1130
1131=item getnetent
1132
1133Not implemented. (S<Mac OS>, Win32, Plan9)
1134
1135=item getprotoent
1136
1137Not implemented. (S<Mac OS>, Win32, Plan9)
1138
1139=item getservent
1140
1141Not implemented. (Win32, Plan9)
1142
1143=item setpwent
1144
b8099c3d 1145Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1146
1147=item setgrent
1148
b8099c3d 1149Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1150
1151=item sethostent STAYOPEN
1152
b8099c3d 1153Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1154
1155=item setnetent STAYOPEN
1156
b8099c3d 1157Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1158
1159=item setprotoent STAYOPEN
1160
b8099c3d 1161Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1162
1163=item setservent STAYOPEN
1164
b8099c3d 1165Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1166
1167=item endpwent
1168
1169Not implemented. (S<Mac OS>, Win32)
1170
1171=item endgrent
1172
b8099c3d 1173Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1174
1175=item endhostent
1176
1177Not implemented. (S<Mac OS>, Win32)
1178
1179=item endnetent
1180
1181Not implemented. (S<Mac OS>, Win32, Plan9)
1182
1183=item endprotoent
1184
1185Not implemented. (S<Mac OS>, Win32, Plan9)
1186
1187=item endservent
1188
1189Not implemented. (Plan9, Win32)
1190
1191=item getsockopt SOCKET,LEVEL,OPTNAME
1192
1193Not implemented. (S<Mac OS>, Plan9)
1194
1195=item glob EXPR
1196
1197=item glob
1198
1199Globbing built-in, but only C<*> and C<?> metacharacters are supported.
1200(S<Mac OS>)
1201
0a47030a
GS
1202Features depend on external perlglob.exe or perlglob.bat. May be
1203overridden with something like File::DosGlob, which is recommended.
1204(Win32)
e41182b5 1205
b8099c3d 1206Globbing built-in, but only C<*> and C<?> metacharacters are supported.
0a47030a
GS
1207Globbing relies on operating system calls, which may return filenames
1208in any order. As most filesystems are case-insensitive, even "sorted"
1209filenames will not be in case-sensitive order. (S<RISC OS>)
b8099c3d 1210
e41182b5
GS
1211=item ioctl FILEHANDLE,FUNCTION,SCALAR
1212
1213Not implemented. (VMS)
1214
1215Available only for socket handles, and it does what the ioctlsocket() call
1216in the Winsock API does. (Win32)
1217
b8099c3d
CN
1218Available only for socket handles. (S<RISC OS>)
1219
e41182b5
GS
1220=item kill LIST
1221
0a47030a
GS
1222Not implemented, hence not useful for taint checking. (S<Mac OS>,
1223S<RISC OS>)
e41182b5 1224
0a47030a
GS
1225Available only for process handles returned by the C<system(1, ...)>
1226method of spawning a process. (Win32)
e41182b5
GS
1227
1228=item link OLDFILE,NEWFILE
1229
b8099c3d 1230Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1231
1232=item lstat FILEHANDLE
1233
1234=item lstat EXPR
1235
1236=item lstat
1237
b8099c3d 1238Not implemented. (VMS, S<RISC OS>)
e41182b5 1239
b8099c3d 1240Return values may be bogus. (Win32)
e41182b5
GS
1241
1242=item msgctl ID,CMD,ARG
1243
1244=item msgget KEY,FLAGS
1245
1246=item msgsnd ID,MSG,FLAGS
1247
1248=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1249
b8099c3d 1250Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>)
e41182b5
GS
1251
1252=item open FILEHANDLE,EXPR
1253
1254=item open FILEHANDLE
1255
1256The C<|> variants are only supported if ToolServer is installed.
1257(S<Mac OS>)
1258
b8099c3d 1259open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1260
1261=item pipe READHANDLE,WRITEHANDLE
1262
1263Not implemented. (S<Mac OS>)
1264
1265=item readlink EXPR
1266
1267=item readlink
1268
b8099c3d 1269Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1270
1271=item select RBITS,WBITS,EBITS,TIMEOUT
1272
1273Only implemented on sockets. (Win32)
1274
b8099c3d
CN
1275Only reliable on sockets. (S<RISC OS>)
1276
e41182b5
GS
1277=item semctl ID,SEMNUM,CMD,ARG
1278
1279=item semget KEY,NSEMS,FLAGS
1280
1281=item semop KEY,OPSTRING
1282
b8099c3d 1283Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1284
1285=item setpgrp PID,PGRP
1286
b8099c3d 1287Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1288
1289=item setpriority WHICH,WHO,PRIORITY
1290
b8099c3d 1291Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1292
1293=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1294
1295Not implemented. (S<Mac OS>, Plan9)
1296
1297=item shmctl ID,CMD,ARG
1298
1299=item shmget KEY,SIZE,FLAGS
1300
1301=item shmread ID,VAR,POS,SIZE
1302
1303=item shmwrite ID,STRING,POS,SIZE
1304
b8099c3d 1305Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1306
1307=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1308
b8099c3d 1309Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1310
1311=item stat FILEHANDLE
1312
1313=item stat EXPR
1314
1315=item stat
1316
1317mtime and atime are the same thing, and ctime is creation time instead of
1318inode change time. (S<Mac OS>)
1319
1320device and inode are not meaningful. (Win32)
1321
1322device and inode are not necessarily reliable. (VMS)
1323
b8099c3d
CN
1324mtime, atime and ctime all return the last modification time. Device and
1325inode are not necessarily reliable. (S<RISC OS>)
1326
e41182b5
GS
1327=item symlink OLDFILE,NEWFILE
1328
b8099c3d 1329Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1330
1331=item syscall LIST
1332
b8099c3d 1333Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1334
f34d0673
GS
1335=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1336
dd9f0070 1337The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1338numeric values on some systems. The flags exported by C<Fcntl>
1339(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1340OS>, OS/390)
f34d0673 1341
e41182b5
GS
1342=item system LIST
1343
1344Only implemented if ToolServer is installed. (S<Mac OS>)
1345
1346As an optimization, may not call the command shell specified in
1347C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1348process and immediately returns its process designator, without
1349waiting for it to terminate. Return value may be used subsequently
1350in C<wait> or C<waitpid>. (Win32)
1351
b8099c3d
CN
1352There is no shell to process metacharacters, and the native standard is
1353to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1354program. Redirection such as C<E<gt> foo> is performed (if at all) by
1355the run time library of the spawned program. C<system> I<list> will call
1356the Unix emulation library's C<exec> emulation, which attempts to provide
1357emulation of the stdin, stdout, stderr in force in the parent, providing
1358the child program uses a compatible version of the emulation library.
1359I<scalar> will call the native command line direct and no such emulation
1360of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1361
e41182b5
GS
1362=item times
1363
1364Only the first entry returned is nonzero. (S<Mac OS>)
1365
1366"cumulative" times will be bogus. On anything other than Windows NT,
1367"system" time will be bogus, and "user" time is actually the time
1368returned by the clock() function in the C runtime library. (Win32)
1369
b8099c3d
CN
1370Not useful. (S<RISC OS>)
1371
e41182b5
GS
1372=item truncate FILEHANDLE,LENGTH
1373
1374=item truncate EXPR,LENGTH
1375
1376Not implemented. (VMS)
1377
1378=item umask EXPR
1379
1380=item umask
1381
1382Returns undef where unavailable, as of version 5.005.
1383
1384=item utime LIST
1385
b8099c3d 1386Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1387
322422de
GS
1388May not behave as expected. Behavior depends on the C runtime
1389library's implementation of utime(), and the filesystem being
1390used. The FAT filesystem typically does not support an "access
1391time" field, and it may limit timestamps to a granularity of
1392two seconds. (Win32)
e41182b5
GS
1393
1394=item wait
1395
1396=item waitpid PID,FLAGS
1397
1398Not implemented. (S<Mac OS>)
1399
1400Can only be applied to process handles returned for processes spawned
1401using C<system(1, ...)>. (Win32)
1402
b8099c3d
CN
1403Not useful. (S<RISC OS>)
1404
e41182b5
GS
1405=back
1406
b8099c3d
CN
1407=head1 CHANGES
1408
1409=over 4
1410
0a47030a
GS
1411=item 1.33, 06 August 1998
1412
1413Integrate more minor changes.
1414
dd9f0070
CN
1415=item 1.32, 05 August 1998
1416
1417Integrate more minor changes.
1418
b8099c3d
CN
1419=item 1.30, 03 August 1998
1420
1421Major update for RISC OS, other minor changes.
1422
1423=item 1.23, 10 July 1998
1424
1425First public release with perl5.005.
1426
1427=back
e41182b5
GS
1428
1429=head1 AUTHORS / CONTRIBUTORS
1430
dd9f0070 1431Abigail E<lt>abigail@fnx.comE<gt>,
bd3fa61c 1432Charles Bailey E<lt>bailey@newman.upenn.eduE<gt>,
dd9f0070 1433Graham Barr E<lt>gbarr@pobox.comE<gt>,
e41182b5 1434Tom Christiansen E<lt>tchrist@perl.comE<gt>,
dd9f0070
CN
1435Nicholas Clark E<lt>Nicholas.Clark@liverpool.ac.ukE<gt>,
1436Andy Dougherty E<lt>doughera@lafcol.lafayette.eduE<gt>,
1437Dominic Dunlop E<lt>domo@vo.luE<gt>,
1438M.J.T. Guy E<lt>mjtg@cus.cam.ac.ukE<gt>,
1439Luther Huffman E<lt>lutherh@stratcom.comE<gt>,
1440Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>,
322422de 1441Andreas J. KE<ouml>nig E<lt>koenig@kulturbox.deE<gt>,
dd9f0070 1442Andrew M. Langmead E<lt>aml@world.std.comE<gt>,
e41182b5 1443Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>,
dd9f0070 1444Chris Nandor E<lt>pudge@pobox.comE<gt>,
322422de 1445Matthias Neeracher E<lt>neeri@iis.ee.ethz.chE<gt>,
e41182b5 1446Gary Ng E<lt>71564.1743@CompuServe.COME<gt>,
e41182b5 1447Tom Phoenix E<lt>rootbeer@teleport.comE<gt>,
dd9f0070 1448Peter Prymmer E<lt>pvhp@forte.comE<gt>,
322422de 1449Hugo van der Sanden E<lt>hv@crypt0.demon.co.ukE<gt>,
dd9f0070
CN
1450Gurusamy Sarathy E<lt>gsar@umich.eduE<gt>,
1451Paul J. Schinder E<lt>schinder@pobox.comE<gt>,
e41182b5 1452Dan Sugalski E<lt>sugalskd@ous.eduE<gt>,
dd9f0070 1453Nathan Torkington E<lt>gnat@frii.comE<gt>.
e41182b5
GS
1454
1455This document is maintained by Chris Nandor.
1456
1457=head1 VERSION
1458
322422de 1459Version 1.34, last modified 07 August 1998.
0a47030a 1460
e41182b5 1461