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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
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151An important thing to remember is that functions that return data
152should translate newlines when appropriate. Often one line of code
153will suffice:
154
155 $data =~ s/\015?\012/\n/g;
156 return $data;
157
e41182b5 158
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159=head2 Numbers endianness and Width
160
161Different CPUs store integers and floating point numbers in different
162orders (called I<endianness>) and widths (32-bit and 64-bit being the
163most common). This affects your programs if they attempt to transfer
164numbers in binary format from a CPU architecture to another over some
165channel: either 'live' via network connections or storing the numbers
166to secondary storage such as a disk file.
167
168Conflicting storage orders make utter mess out of the numbers: if a
169little-endian host (Intel, Alpha) stores 0x12345678 (305419896 in
170decimal), a big-endian host (Motorola, MIPS, Sparc, PA) reads it as
1710x78563412 (2018915346 in decimal). To avoid this problem in network
172(socket) connections use the C<pack()> and C<unpack()> formats C<"n">
173and C<"N">, the "network" orders, they are guaranteed to be portable.
174
175Different widths can cause truncation even between platforms of equal
176endianness: the platform of shorter width loses the upper parts of the
177number. There is no good solution for this problem except to avoid
178transferring or storing raw binary numbers.
179
180One can circumnavigate both these problems in two ways: either
181transfer and store numbers always in text format, instead of raw
182binary, or consider using modules like C<Data::Dumper> (included in
183the standard distribution as of Perl 5.005) and C<Storable>.
184
433acd8a 185=head2 Files and Filesystems
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186
187Most platforms these days structure files in a hierarchical fashion.
188So, it is reasonably safe to assume that any platform supports the
189notion of a "path" to uniquely identify a file on the system. Just
190how that path is actually written, differs.
191
192While they are similar, file path specifications differ between Unix,
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193Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS> and probably others.
194Unix, for example, is one of the few OSes that has the idea of a single
195root directory.
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196
197VMS, Windows, and OS/2 can work similarly to Unix with C</> as path
198separator, or in their own idiosyncratic ways (such as having several
3c075c7d 199root directories and various "unrooted" device files such NIL: and
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200LPT:).
201
202S<Mac OS> uses C<:> as a path separator instead of C</>.
203
9b63e9ec 204The filesystem may support neither hard links (C<link()>) nor
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205symbolic links (C<symlink()>, C<readlink()>, C<lstat()>).
206
2ee0eb3c 207The filesystem may not support neither access timestamp nor change
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208timestamp (meaning that about the only portable timestamp is the
209modification timestamp), or one second granularity of any timestamps
210(e.g. the FAT filesystem limits the time granularity to two seconds).
211
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212VOS perl can emulate Unix filenames with C</> as path separator. The
213native pathname characters greater-than, less-than, number-sign, and
214percent-sign are always accepted.
215
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216C<RISC OS> perl can emulate Unix filenames with C</> as path
217separator, or go native and use C<.> for path separator and C<:> to
218signal filing systems and disc names.
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219
220As with the newline problem above, there are modules that can help. The
221C<File::Spec> modules provide methods to do the Right Thing on whatever
222platform happens to be running the program.
223
224 use File::Spec;
225 chdir(File::Spec->updir()); # go up one directory
226 $file = File::Spec->catfile(
227 File::Spec->curdir(), 'temp', 'file.txt'
228 );
229 # on Unix and Win32, './temp/file.txt'
230 # on Mac OS, ':temp:file.txt'
231
232File::Spec is available in the standard distribution, as of version
2335.004_05.
234
235In general, production code should not have file paths hardcoded; making
236them user supplied or from a configuration file is better, keeping in mind
237that file path syntax varies on different machines.
238
239This is especially noticeable in scripts like Makefiles and test suites,
240which often assume C</> as a path separator for subdirectories.
241
242Also of use is C<File::Basename>, from the standard distribution, which
243splits a pathname into pieces (base filename, full path to directory,
244and file suffix).
245
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246Even when on a single platform (if you can call UNIX a single platform),
247remember not to count on the existence or the contents of
248system-specific files or directories, like F</etc/passwd>,
249F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
250example, F</etc/passwd> may exist but it may not contain the encrypted
251passwords because the system is using some form of enhanced security --
252or it may not contain all the accounts because the system is using NIS.
253If code does need to rely on such a file, include a description of the
254file and its format in the code's documentation, and make it easy for
255the user to override the default location of the file.
256
257Don't assume a text file will end with a newline.
e41182b5 258
dd9f0070 259Do not have two files of the same name with different case, like
3c075c7d 260F<test.pl> and F<Test.pl>, as many platforms have case-insensitive
dd9f0070 261filenames. Also, try not to have non-word characters (except for C<.>)
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262in the names, and keep them to the 8.3 convention, for maximum
263portability.
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264
265Likewise, if using C<AutoSplit>, try to keep the split functions to
2668.3 naming and case-insensitive conventions; or, at the very least,
267make it so the resulting files have a unique (case-insensitively)
268first 8 characters.
269
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270There certainly can be whitespace in filenames. Many systems (DOS,
271VMS) cannot have more than one C<"."> in their filenames.
272
273Don't assume C<E<gt>> won't be the first character of a filename.
274Always use C<E<lt>> explicitly to open a file for reading.
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275
276 open(FILE, "<$existing_file") or die $!;
277
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278Actually, though, if filenames might use strange characters, it is
279safest to open it with C<sysopen> instead of C<open>, which is magic.
280
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281
282=head2 System Interaction
283
284Not all platforms provide for the notion of a command line, necessarily.
285These are usually platforms that rely on a Graphical User Interface (GUI)
286for user interaction. So a program requiring command lines might not work
287everywhere. But this is probably for the user of the program to deal
288with.
289
290Some platforms can't delete or rename files that are being held open by
291the system. Remember to C<close> files when you are done with them.
292Don't C<unlink> or C<rename> an open file. Don't C<tie> to or C<open> a
293file that is already tied to or opened; C<untie> or C<close> first.
294
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295Don't open the same file more than once at a time for writing, as some
296operating systems put mandatory locks on such files.
297
e41182b5 298Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 299Don't count on C<%ENV> entries being case-sensitive, or even
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300case-preserving.
301
0a47030a 302Don't count on signals.
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303
304Don't count on filename globbing. Use C<opendir>, C<readdir>, and
305C<closedir> instead.
306
b8099c3d 307Don't count on per-program environment variables, or per-program current
dd9f0070 308directories.
b8099c3d 309
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310Don't count on specific values of C<$!>.
311
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312
313=head2 Interprocess Communication (IPC)
314
315In general, don't directly access the system in code that is meant to be
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316portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>, C<``>,
317C<qx//>, C<open> with a C<|>, nor any of the other things that makes being
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318a Unix perl hacker worth being.
319
320Commands that launch external processes are generally supported on
321most platforms (though many of them do not support any type of forking),
322but the problem with using them arises from what you invoke with them.
323External tools are often named differently on different platforms, often
324not available in the same location, often accept different arguments,
325often behave differently, and often represent their results in a
326platform-dependent way. Thus you should seldom depend on them to produce
327consistent results.
328
329One especially common bit of Perl code is opening a pipe to sendmail:
330
331 open(MAIL, '|/usr/lib/sendmail -t') or die $!;
332
333This is fine for systems programming when sendmail is known to be
334available. But it is not fine for many non-Unix systems, and even
335some Unix systems that may not have sendmail installed. If a portable
336solution is needed, see the C<Mail::Send> and C<Mail::Mailer> modules
337in the C<MailTools> distribution. C<Mail::Mailer> provides several
338mailing methods, including mail, sendmail, and direct SMTP
339(via C<Net::SMTP>) if a mail transfer agent is not available.
340
341The rule of thumb for portable code is: Do it all in portable Perl, or
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342use a module (that may internally implement it with platform-specific
343code, but expose a common interface).
e41182b5 344
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345The UNIX System V IPC (C<msg*(), sem*(), shm*()>) is not available
346even in all UNIX platforms.
e41182b5 347
3c075c7d 348
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349=head2 External Subroutines (XS)
350
351XS code, in general, can be made to work with any platform; but dependent
352libraries, header files, etc., might not be readily available or
353portable, or the XS code itself might be platform-specific, just as Perl
354code might be. If the libraries and headers are portable, then it is
355normally reasonable to make sure the XS code is portable, too.
356
357There is a different kind of portability issue with writing XS
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358code: availability of a C compiler on the end-user's system. C brings
359with it its own portability issues, and writing XS code will expose you to
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360some of those. Writing purely in perl is a comparatively easier way to
361achieve portability.
362
363
364=head2 Standard Modules
365
366In general, the standard modules work across platforms. Notable
367exceptions are C<CPAN.pm> (which currently makes connections to external
368programs that may not be available), platform-specific modules (like
369C<ExtUtils::MM_VMS>), and DBM modules.
370
371There is no one DBM module that is available on all platforms.
372C<SDBM_File> and the others are generally available on all Unix and DOSish
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373ports, but not in MacPerl, where only C<NBDM_File> and C<DB_File> are
374available.
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375
376The good news is that at least some DBM module should be available, and
377C<AnyDBM_File> will use whichever module it can find. Of course, then
378the code needs to be fairly strict, dropping to the lowest common
379denominator (e.g., not exceeding 1K for each record).
380
381
382=head2 Time and Date
383
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384The system's notion of time of day and calendar date is controlled in
385widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
386and even if it is, don't assume that you can control the timezone through
387that variable.
e41182b5 388
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389Don't assume that the epoch starts at 00:00:00, January 1, 1970,
390because that is OS-specific. Better to store a date in an unambiguous
391representation. The ISO 8601 standard defines YYYY-MM-DD as the date
392format. A text representation (like C<1 Jan 1970>) can be easily
393converted into an OS-specific value using a module like
394C<Date::Parse>. An array of values, such as those returned by
395C<localtime>, can be converted to an OS-specific representation using
396C<Time::Local>.
397
398
399=head2 Character sets and character encoding
400
401Assume very little about character sets. Do not assume anything about
402the numerical values (C<ord()>, C<chr()>) of characters. Do not
403assume that the alphabetic characters are encoded contiguously (in
3c075c7d 404numerical sense). Do not assume anything about the ordering of the
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405characters. The lowercase letters may come before or after the
406uppercase letters, the lowercase and uppercase may be interlaced so
b1ff3570 407that both 'a' and 'A' come before the 'b', the accented and other
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408international characters may be interlaced so that E<auml> comes
409before the 'b'.
410
411
412=head2 Internationalisation
413
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414If you may assume POSIX (a rather large assumption, that in practice
415means UNIX), you may read more about the POSIX locale system from
322422de 416L<perllocale>. The locale system at least attempts to make things a
3c075c7d 417little bit more portable, or at least more convenient and
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418native-friendly for non-English users. The system affects character
419sets and encoding, and date and time formatting, among other things.
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420
421
422=head2 System Resources
423
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424If your code is destined for systems with severely constrained (or
425missing!) virtual memory systems then you want to be I<especially> mindful
426of avoiding wasteful constructs such as:
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427
428 # NOTE: this is no longer "bad" in perl5.005
429 for (0..10000000) {} # bad
430 for (my $x = 0; $x <= 10000000; ++$x) {} # good
431
432 @lines = <VERY_LARGE_FILE>; # bad
433
434 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 435 $file = join('', <FILE>); # better
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436
437The last two may appear unintuitive to most people. The first of those
438two constructs repeatedly grows a string, while the second allocates a
439large chunk of memory in one go. On some systems, the latter is more
440efficient that the former.
441
0a47030a 442
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443=head2 Security
444
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445Most multi-user platforms provide basic levels of security that is usually
446felt at the file-system level. Other platforms usually don't
447(unfortunately). Thus the notion of user id, or "home" directory, or even
448the state of being logged-in, may be unrecognizable on many platforms. If
449you write programs that are security conscious, it is usually best to know
450what type of system you will be operating under, and write code explicitly
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451for that platform (or class of platforms).
452
0a47030a 453
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454=head2 Style
455
456For those times when it is necessary to have platform-specific code,
457consider keeping the platform-specific code in one place, making porting
458to other platforms easier. Use the C<Config> module and the special
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459variable C<$^O> to differentiate platforms, as described in
460L<"PLATFORMS">.
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461
462
0a47030a 463=head1 CPAN Testers
e41182b5 464
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465Modules uploaded to CPAN are tested by a variety of volunteers on
466different platforms. These CPAN testers are notified by mail of each
e41182b5 467new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 468this platform), or UNKNOWN (unknown), along with any relevant notations.
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469
470The purpose of the testing is twofold: one, to help developers fix any
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471problems in their code that crop up because of lack of testing on other
472platforms; two, to provide users with information about whether or not
473a given module works on a given platform.
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474
475=over 4
476
477=item Mailing list: cpan-testers@perl.org
478
479=item Testing results: C<http://www.connect.net/gbarr/cpan-test/>
480
481=back
482
483
484=head1 PLATFORMS
485
486As of version 5.002, Perl is built with a C<$^O> variable that
487indicates the operating system it was built on. This was implemented
488to help speed up code that would otherwise have to C<use Config;> and
489use the value of C<$Config{'osname'}>. Of course, to get
490detailed information about the system, looking into C<%Config> is
491certainly recommended.
492
493=head2 Unix
494
495Perl works on a bewildering variety of Unix and Unix-like platforms (see
496e.g. most of the files in the F<hints/> directory in the source code kit).
497On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
498too) is determined by lowercasing and stripping punctuation from the first
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499field of the string returned by typing C<uname -a> (or a similar command)
500at the shell prompt. Here, for example, are a few of the more popular
501Unix flavors:
e41182b5 502
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503 uname $^O $Config{'archname'}
504 -------------------------------------------
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505 AIX aix aix
506 FreeBSD freebsd freebsd-i386
507 Linux linux i386-linux
508 HP-UX hpux PA-RISC1.1
3c075c7d 509 IRIX irix irix
322422de 510 OSF1 dec_osf alpha-dec_osf
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511 SunOS solaris sun4-solaris
512 SunOS solaris i86pc-solaris
322422de 513 SunOS4 sunos sun4-sunos
e41182b5 514
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515Note that because the C<$Config{'archname'}> may depend on the hardware
516architecture it may vary quite a lot, much more than the C<$^O>.
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517
518=head2 DOS and Derivatives
519
520Perl has long been ported to PC style microcomputers running under
521systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
522bring yourself to mention (except for Windows CE, if you count that).
523Users familiar with I<COMMAND.COM> and/or I<CMD.EXE> style shells should
524be aware that each of these file specifications may have subtle
525differences:
526
527 $filespec0 = "c:/foo/bar/file.txt";
528 $filespec1 = "c:\\foo\\bar\\file.txt";
529 $filespec2 = 'c:\foo\bar\file.txt';
530 $filespec3 = 'c:\\foo\\bar\\file.txt';
531
532System calls accept either C</> or C<\> as the path separator. However,
533many command-line utilities of DOS vintage treat C</> as the option
534prefix, so they may get confused by filenames containing C</>. Aside
535from calling any external programs, C</> will work just fine, and
536probably better, as it is more consistent with popular usage, and avoids
537the problem of remembering what to backwhack and what not to.
538
0a47030a 539The DOS FAT filesystem can only accommodate "8.3" style filenames. Under
e41182b5 540the "case insensitive, but case preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 541filesystems you may have to be careful about case returned with functions
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542like C<readdir> or used with functions like C<open> or C<opendir>.
543
544DOS also treats several filenames as special, such as AUX, PRN, NUL, CON,
545COM1, LPT1, LPT2 etc. Unfortunately these filenames won't even work
546if you include an explicit directory prefix, in some cases. It is best
547to avoid such filenames, if you want your code to be portable to DOS
548and its derivatives.
549
550Users of these operating systems may also wish to make use of
551scripts such as I<pl2bat.bat> or I<pl2cmd> as appropriate to
552put wrappers around your scripts.
553
554Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
555and writing to files. C<binmode(FILEHANDLE)> will keep C<\n> translated
556as C<\012> for that filehandle. Since it is a noop on other systems,
557C<binmode> should be used for cross-platform code that deals with binary
558data.
559
560The C<$^O> variable and the C<$Config{'archname'}> values for various
561DOSish perls are as follows:
562
563 OS $^O $Config{'archname'}
564 --------------------------------------------
565 MS-DOS dos
566 PC-DOS dos
567 OS/2 os2
568 Windows 95 MSWin32 MSWin32-x86
569 Windows NT MSWin32 MSWin32-x86
570 Windows NT MSWin32 MSWin32-alpha
571 Windows NT MSWin32 MSWin32-ppc
572
573Also see:
574
575=over 4
576
577=item The djgpp environment for DOS, C<http://www.delorie.com/djgpp/>
578
579=item The EMX environment for DOS, OS/2, etc. C<emx@iaehv.nl>,
2ee0eb3c
CN
580C<http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html> or
581C<ftp://hobbes.nmsu.edu/pub/os2/dev/emx>
e41182b5
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582
583=item Build instructions for Win32, L<perlwin32>.
584
585=item The ActiveState Pages, C<http://www.activestate.com/>
586
587=back
588
589
dd9f0070 590=head2 S<Mac OS>
e41182b5
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591
592Any module requiring XS compilation is right out for most people, because
593MacPerl is built using non-free (and non-cheap!) compilers. Some XS
594modules that can work with MacPerl are built and distributed in binary
0a47030a
GS
595form on CPAN. See I<MacPerl: Power and Ease> and L<"CPAN Testers">
596for more details.
e41182b5
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597
598Directories are specified as:
599
600 volume:folder:file for absolute pathnames
601 volume:folder: for absolute pathnames
602 :folder:file for relative pathnames
603 :folder: for relative pathnames
604 :file for relative pathnames
605 file for relative pathnames
606
607Files in a directory are stored in alphabetical order. Filenames are
608limited to 31 characters, and may include any character except C<:>,
609which is reserved as a path separator.
610
0a47030a 611Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
3c075c7d 612C<Mac::Files> module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
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613
614In the MacPerl application, you can't run a program from the command line;
615programs that expect C<@ARGV> to be populated can be edited with something
616like the following, which brings up a dialog box asking for the command
617line arguments.
618
619 if (!@ARGV) {
620 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
621 }
622
623A MacPerl script saved as a droplet will populate C<@ARGV> with the full
624pathnames of the files dropped onto the script.
625
626Mac users can use programs on a kind of command line under MPW (Macintosh
627Programmer's Workshop, a free development environment from Apple).
628MacPerl was first introduced as an MPW tool, and MPW can be used like a
629shell:
630
631 perl myscript.plx some arguments
632
633ToolServer is another app from Apple that provides access to MPW tools
0a47030a 634from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
635C<system>, backticks, and piped C<open>.
636
637"S<Mac OS>" is the proper name for the operating system, but the value
638in C<$^O> is "MacOS". To determine architecture, version, or whether
639the application or MPW tool version is running, check:
640
641 $is_app = $MacPerl::Version =~ /App/;
642 $is_tool = $MacPerl::Version =~ /MPW/;
643 ($version) = $MacPerl::Version =~ /^(\S+)/;
644 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
645 $is_68k = $MacPerl::Architecture eq 'Mac68K';
646
3c075c7d
CN
647S<Mac OS X>, to be based on NeXT's OpenStep OS, will (in theory) be able
648to run MacPerl natively, but Unix perl will also run natively under the
649built-in Unix environment.
e41182b5
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650
651Also see:
652
653=over 4
654
655=item The MacPerl Pages, C<http://www.ptf.com/macperl/>.
656
657=item The MacPerl mailing list, C<mac-perl-request@iis.ee.ethz.ch>.
658
659=back
660
661
662=head2 VMS
663
664Perl on VMS is discussed in F<vms/perlvms.pod> in the perl distribution.
0a47030a 665Note that perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
666specifications as in either of the following:
667
668 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
669 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
670
671but not a mixture of both as in:
672
673 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
674 Can't open sys$login:/login.com: file specification syntax error
675
676Interacting with Perl from the Digital Command Language (DCL) shell
677often requires a different set of quotation marks than Unix shells do.
678For example:
679
680 $ perl -e "print ""Hello, world.\n"""
681 Hello, world.
682
683There are a number of ways to wrap your perl scripts in DCL .COM files if
684you are so inclined. For example:
685
686 $ write sys$output "Hello from DCL!"
687 $ if p1 .eqs. ""
688 $ then perl -x 'f$environment("PROCEDURE")
689 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
690 $ deck/dollars="__END__"
691 #!/usr/bin/perl
692
693 print "Hello from Perl!\n";
694
695 __END__
696 $ endif
697
698Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
699perl-in-DCL script expects to do things like C<$read = E<lt>STDINE<gt>;>.
700
701Filenames are in the format "name.extension;version". The maximum
702length for filenames is 39 characters, and the maximum length for
703extensions is also 39 characters. Version is a number from 1 to
70432767. Valid characters are C</[A-Z0-9$_-]/>.
705
706VMS' RMS filesystem is case insensitive and does not preserve case.
707C<readdir> returns lowercased filenames, but specifying a file for
b8099c3d 708opening remains case insensitive. Files without extensions have a
e41182b5 709trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
710will return F<a.> (though that file could be opened with
711C<open(FH, 'A')>).
e41182b5 712
f34d0673 713RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
CN
714(allowing 16 levels overall) prior to VMS 7.2. Hence
715C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
716C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
717have to take this into account, but at least they can refer to the former
f34d0673 718as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 719
0a47030a
GS
720The C<VMS::Filespec> module, which gets installed as part of the build
721process on VMS, is a pure Perl module that can easily be installed on
722non-VMS platforms and can be helpful for conversions to and from RMS
723native formats.
e41182b5
GS
724
725What C<\n> represents depends on the type of file that is open. It could
726be C<\015>, C<\012>, C<\015\012>, or nothing. Reading from a file
727translates newlines to C<\012>, unless C<binmode> was executed on that
728handle, just like DOSish perls.
729
730TCP/IP stacks are optional on VMS, so socket routines might not be
731implemented. UDP sockets may not be supported.
732
733The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
734that you are running on without resorting to loading all of C<%Config>
735you can examine the content of the C<@INC> array like so:
736
737 if (grep(/VMS_AXP/, @INC)) {
738 print "I'm on Alpha!\n";
739 } elsif (grep(/VMS_VAX/, @INC)) {
740 print "I'm on VAX!\n";
741 } else {
742 print "I'm not so sure about where $^O is...\n";
743 }
744
745Also see:
746
747=over 4
748
749=item L<perlvms.pod>
750
751=item vmsperl list, C<vmsperl-request@newman.upenn.edu>
752
753Put words C<SUBSCRIBE VMSPERL> in message body.
754
755=item vmsperl on the web, C<http://www.sidhe.org/vmsperl/index.html>
756
757=back
758
759
495c5fdc
GP
760=head2 VOS
761
762Perl on VOS is discussed in F<README.vos> in the perl distribution.
763Note that perl on VOS can accept either VOS- or Unix-style file
764specifications as in either of the following:
765
766 $ perl -ne "print if /perl_setup/i" >system>notices
767 $ perl -ne "print if /perl_setup/i" /system/notices
768
769or even a mixture of both as in:
770
771 $ perl -ne "print if /perl_setup/i" >system/notices
772
773Note that even though VOS allows the slash character to appear in object
774names, because the VOS port of Perl interprets it as a pathname
775delimiting character, VOS files, directories, or links whose names
776contain a slash character cannot be processed. Such files must be
777renamed before they can be processed by Perl.
778
2ee0eb3c 779The following C functions are unimplemented on VOS, and any attempt by
495c5fdc 780Perl to use them will result in a fatal error message and an immediate
2ee0eb3c
CN
781exit from Perl: dup, do_aspawn, do_spawn, fork, waitpid. Once these
782functions become available in the VOS POSIX.1 implementation, you can
783either recompile and rebind Perl, or you can download a newer port from
784ftp.stratus.com.
495c5fdc
GP
785
786The value of C<$^O> on VOS is "VOS". To determine the architecture that
787you are running on without resorting to loading all of C<%Config> you
788can examine the content of the C<@INC> array like so:
789
790 if (grep(/VOS/, @INC)) {
791 print "I'm on a Stratus box!\n";
792 } else {
793 print "I'm not on a Stratus box!\n";
794 die;
795 }
796
797 if (grep(/860/, @INC)) {
798 print "This box is a Stratus XA/R!\n";
799 } elsif (grep(/7100/, @INC)) {
800 print "This box is a Stratus HP 7100 or 8000!\n";
801 } elsif (grep(/8000/, @INC)) {
802 print "This box is a Stratus HP 8000!\n";
803 } else {
804 print "This box is a Stratus 68K...\n";
805 }
806
807Also see:
808
809=over 4
810
811=item L<README.vos>
812
813=item VOS mailing list
814
815There is no specific mailing list for Perl on VOS. You can post
816comments to the comp.sys.stratus newsgroup, or subscribe to the general
817Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
818the message body to majordomo@list.stratagy.com.
819
820=item VOS Perl on the web at C<http://ftp.stratus.com/pub/vos/vos.html>
821
822=back
823
824
e41182b5
GS
825=head2 EBCDIC Platforms
826
827Recent versions of Perl have been ported to platforms such as OS/400 on
7c5ffed3
JH
828AS/400 minicomputers as well as OS/390 & VM/ESA for IBM Mainframes. Such
829computers use EBCDIC character sets internally (usually Character Code
830Set ID 00819 for OS/400 and IBM-1047 for OS/390 & VM/ESA). Note that on
831the mainframe perl currently works under the "Unix system services
832for OS/390" (formerly known as OpenEdition) and VM/ESA OpenEdition.
e41182b5 833
7c5ffed3
JH
834As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
835sub-systems do not support the C<#!> shebang trick for script invocation.
836Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
837similar to the following simple script:
e41182b5
GS
838
839 : # use perl
840 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
841 if 0;
842 #!/usr/local/bin/perl # just a comment really
843
844 print "Hello from perl!\n";
845
846On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
847an effect on what happens with some perl functions (such as C<chr>,
848C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
849well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
850and C<|>, not to mention dealing with socket interfaces to ASCII computers
9b63e9ec 851(see L<Newlines>).
e41182b5
GS
852
853Fortunately, most web servers for the mainframe will correctly translate
854the C<\n> in the following statement to its ASCII equivalent (note that
7c5ffed3 855C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
856
857 print "Content-type: text/html\r\n\r\n";
858
859The value of C<$^O> on OS/390 is "os390".
860
7c5ffed3 861The value of C<$^O> on VM/ESA is "vmesa".
3c075c7d 862
e41182b5
GS
863Some simple tricks for determining if you are running on an EBCDIC
864platform could include any of the following (perhaps all):
865
866 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
867
868 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
869
870 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
871
872Note that one thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
873of punctuation characters since these may differ from code page to code
874page (and once your module or script is rumoured to work with EBCDIC,
875folks will want it to work with all EBCDIC character sets).
e41182b5
GS
876
877Also see:
878
879=over 4
880
881=item perl-mvs list
882
883The perl-mvs@perl.org list is for discussion of porting issues as well as
884general usage issues for all EBCDIC Perls. Send a message body of
885"subscribe perl-mvs" to majordomo@perl.org.
886
0a47030a 887=item AS/400 Perl information at C<http://as400.rochester.ibm.com/>
e41182b5
GS
888
889=back
890
b8099c3d
CN
891
892=head2 Acorn RISC OS
893
0a47030a
GS
894As Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
895Unix and Unix filename emulation is turned on by default, it is quite
896likely that most simple scripts will work "out of the box". The native
897filing system is modular, and individual filing systems are free to be
898case-sensitive or insensitive, and are usually case-preserving. Some
899native filing systems have name length limits which file and directory
900names are silently truncated to fit - scripts should be aware that the
901standard disc filing system currently has a name length limit of B<10>
902characters, with up to 77 items in a directory, but other filing systems
903may not impose such limitations.
b8099c3d
CN
904
905Native filenames are of the form
906
907 Filesystem#Special_Field::DiscName.$.Directory.Directory.File
dd9f0070 908
b8099c3d
CN
909where
910
911 Special_Field is not usually present, but may contain . and $ .
912 Filesystem =~ m|[A-Za-z0-9_]|
913 DsicName =~ m|[A-Za-z0-9_/]|
914 $ represents the root directory
915 . is the path separator
916 @ is the current directory (per filesystem but machine global)
917 ^ is the parent directory
918 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
919
920The default filename translation is roughly C<tr|/.|./|;>
921
922Note that C<"ADFS::HardDisc.$.File" ne 'ADFS::HardDisc.$.File'> and that
0a47030a
GS
923the second stage of C<$> interpolation in regular expressions will fall
924foul of the C<$.> if scripts are not careful.
925
926Logical paths specified by system variables containing comma-separated
927search lists are also allowed, hence C<System:Modules> is a valid
928filename, and the filesystem will prefix C<Modules> with each section of
929C<System$Path> until a name is made that points to an object on disc.
930Writing to a new file C<System:Modules> would only be allowed if
931C<System$Path> contains a single item list. The filesystem will also
932expand system variables in filenames if enclosed in angle brackets, so
933C<E<lt>System$DirE<gt>.Modules> would look for the file
934S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
3c075c7d 935that B<fully qualified filenames can start with C<E<lt>E<gt>>> and should
0a47030a 936be protected when C<open> is used for input.
b8099c3d
CN
937
938Because C<.> was in use as a directory separator and filenames could not
939be assumed to be unique after 10 characters, Acorn implemented the C
940compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
941filenames specified in source code and store the respective files in
942subdirectories named after the suffix. Hence files are translated:
943
944 foo.h h.foo
945 C:foo.h C:h.foo (logical path variable)
946 sys/os.h sys.h.os (C compiler groks Unix-speak)
947 10charname.c c.10charname
948 10charname.o o.10charname
949 11charname_.c c.11charname (assuming filesystem truncates at 10)
950
951The Unix emulation library's translation of filenames to native assumes
0a47030a
GS
952that this sort of translation is required, and allows a user defined list
953of known suffixes which it will transpose in this fashion. This may
954appear transparent, but consider that with these rules C<foo/bar/baz.h>
955and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
956C<glob> cannot and do not attempt to emulate the reverse mapping. Other
957C<.>s in filenames are translated to C</>.
958
959As implied above the environment accessed through C<%ENV> is global, and
960the convention is that program specific environment variables are of the
961form C<Program$Name>. Each filing system maintains a current directory,
962and the current filing system's current directory is the B<global> current
963directory. Consequently, sociable scripts don't change the current
964directory but rely on full pathnames, and scripts (and Makefiles) cannot
965assume that they can spawn a child process which can change the current
966directory without affecting its parent (and everyone else for that
967matter).
968
969As native operating system filehandles are global and currently are
970allocated down from 255, with 0 being a reserved value the Unix emulation
971library emulates Unix filehandles. Consequently, you can't rely on
972passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
973
974The desire of users to express filenames of the form
975C<E<lt>Foo$DirE<gt>.Bar> on the command line unquoted causes problems,
976too: C<``> command output capture has to perform a guessing game. It
977assumes that a string C<E<lt>[^E<lt>E<gt>]+\$[^E<lt>E<gt>]E<gt>> is a
978reference to an environment variable, whereas anything else involving
979C<E<lt>> or C<E<gt>> is redirection, and generally manages to be 99%
980right. Of course, the problem remains that scripts cannot rely on any
981Unix tools being available, or that any tools found have Unix-like command
982line arguments.
983
984Extensions and XS are, in theory, buildable by anyone using free tools.
985In practice, many don't, as users of the Acorn platform are used to binary
986distribution. MakeMaker does run, but no available make currently copes
987with MakeMaker's makefiles; even if/when this is fixed, the lack of a
988Unix-like shell can cause problems with makefile rules, especially lines
989of the form C<cd sdbm && make all>, and anything using quoting.
b8099c3d
CN
990
991"S<RISC OS>" is the proper name for the operating system, but the value
992in C<$^O> is "riscos" (because we don't like shouting).
993
994Also see:
995
996=over 4
997
998=item perl list
999
1000=back
1001
1002
e41182b5
GS
1003=head2 Other perls
1004
b8099c3d
CN
1005Perl has been ported to a variety of platforms that do not fit into any of
1006the above categories. Some, such as AmigaOS, BeOS, QNX, and Plan 9, have
0a47030a 1007been well-integrated into the standard Perl source code kit. You may need
b8099c3d 1008to see the F<ports/> directory on CPAN for information, and possibly
0a47030a
GS
1009binaries, for the likes of: aos, atari, lynxos, riscos, Tandem Guardian,
1010vos, I<etc.> (yes we know that some of these OSes may fall under the Unix
1011category, but we are not a standards body.)
e41182b5
GS
1012
1013See also:
1014
1015=over 4
1016
1017=item Atari, Guido Flohr's page C<http://stud.uni-sb.de/~gufl0000/>
1018
1019=item HP 300 MPE/iX C<http://www.cccd.edu/~markb/perlix.html>
1020
1021=item Novell Netware
1022
0a47030a 1023A free perl5-based PERL.NLM for Novell Netware is available from
e41182b5
GS
1024C<http://www.novell.com/>
1025
1026=back
1027
1028
1029=head1 FUNCTION IMPLEMENTATIONS
1030
1031Listed below are functions unimplemented or implemented differently on
1032various platforms. Following each description will be, in parentheses, a
1033list of platforms that the description applies to.
1034
1035The list may very well be incomplete, or wrong in some places. When in
1036doubt, consult the platform-specific README files in the Perl source
1037distribution, and other documentation resources for a given port.
1038
0a47030a 1039Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5
GS
1040
1041For many functions, you can also query C<%Config>, exported by default
1042from C<Config.pm>. For example, to check if the platform has the C<lstat>
0a47030a
GS
1043call, check C<$Config{'d_lstat'}>. See L<Config.pm> for a full
1044description of available variables.
e41182b5
GS
1045
1046
1047=head2 Alphabetical Listing of Perl Functions
1048
1049=over 8
1050
1051=item -X FILEHANDLE
1052
1053=item -X EXPR
1054
1055=item -X
1056
1057C<-r>, C<-w>, and C<-x> have only a very limited meaning; directories
1058and applications are executable, and there are no uid/gid
1059considerations. C<-o> is not supported. (S<Mac OS>)
1060
1061C<-r>, C<-w>, C<-x>, and C<-o> tell whether or not file is accessible,
1062which may not reflect UIC-based file protections. (VMS)
1063
b8099c3d
CN
1064C<-s> returns the size of the data fork, not the total size of data fork
1065plus resource fork. (S<Mac OS>).
1066
1067C<-s> by name on an open file will return the space reserved on disk,
1068rather than the current extent. C<-s> on an open filehandle returns the
1069current size. (S<RISC OS>)
1070
e41182b5 1071C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1072C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1073
1074C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1075(S<Mac OS>)
1076
1077C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1078(Win32, VMS, S<RISC OS>)
e41182b5
GS
1079
1080C<-d> is true if passed a device spec without an explicit directory.
1081(VMS)
1082
1083C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a
GS
1084with foreign characters; this is the case will all platforms, but may
1085affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1086
1087C<-x> (or C<-X>) determine if a file ends in one of the executable
1088suffixes. C<-S> is meaningless. (Win32)
1089
b8099c3d
CN
1090C<-x> (or C<-X>) determine if a file has an executable file type.
1091(S<RISC OS>)
1092
e41182b5
GS
1093=item binmode FILEHANDLE
1094
b8099c3d 1095Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1096
1097Reopens file and restores pointer; if function fails, underlying
1098filehandle may be closed, or pointer may be in a different position.
1099(VMS)
1100
1101The value returned by C<tell> may be affected after the call, and
1102the filehandle may be flushed. (Win32)
1103
1104=item chmod LIST
1105
1106Only limited meaning. Disabling/enabling write permission is mapped to
1107locking/unlocking the file. (S<Mac OS>)
1108
1109Only good for changing "owner" read-write access, "group", and "other"
1110bits are meaningless. (Win32)
1111
b8099c3d
CN
1112Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1113
495c5fdc
GP
1114Access permissions are mapped onto VOS access-control list changes. (VOS)
1115
e41182b5
GS
1116=item chown LIST
1117
495c5fdc 1118Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1119
1120Does nothing, but won't fail. (Win32)
1121
1122=item chroot FILENAME
1123
1124=item chroot
1125
7c5ffed3 1126Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1127
1128=item crypt PLAINTEXT,SALT
1129
1130May not be available if library or source was not provided when building
b8099c3d 1131perl. (Win32)
e41182b5 1132
495c5fdc
GP
1133Not implemented. (VOS)
1134
e41182b5
GS
1135=item dbmclose HASH
1136
495c5fdc 1137Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1138
1139=item dbmopen HASH,DBNAME,MODE
1140
495c5fdc 1141Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1142
1143=item dump LABEL
1144
b8099c3d 1145Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1146
1147Not implemented. (Win32)
1148
b8099c3d 1149Invokes VMS debugger. (VMS)
e41182b5
GS
1150
1151=item exec LIST
1152
1153Not implemented. (S<Mac OS>)
1154
7c5ffed3 1155Implemented via Spawn. (VM/ESA)
3c075c7d 1156
e41182b5
GS
1157=item fcntl FILEHANDLE,FUNCTION,SCALAR
1158
1159Not implemented. (Win32, VMS)
1160
1161=item flock FILEHANDLE,OPERATION
1162
495c5fdc 1163Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1164
1165Available only on Windows NT (not on Windows 95). (Win32)
1166
1167=item fork
1168
7c5ffed3 1169Not implemented. (S<Mac OS>, Win32, AmigaOS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1170
1171=item getlogin
1172
b8099c3d 1173Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1174
1175=item getpgrp PID
1176
495c5fdc 1177Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1178
1179=item getppid
1180
b8099c3d 1181Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1182
1183=item getpriority WHICH,WHO
1184
7c5ffed3 1185Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1186
1187=item getpwnam NAME
1188
1189Not implemented. (S<Mac OS>, Win32)
1190
b8099c3d
CN
1191Not useful. (S<RISC OS>)
1192
e41182b5
GS
1193=item getgrnam NAME
1194
b8099c3d 1195Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1196
1197=item getnetbyname NAME
1198
1199Not implemented. (S<Mac OS>, Win32, Plan9)
1200
1201=item getpwuid UID
1202
1203Not implemented. (S<Mac OS>, Win32)
1204
b8099c3d
CN
1205Not useful. (S<RISC OS>)
1206
e41182b5
GS
1207=item getgrgid GID
1208
b8099c3d 1209Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1210
1211=item getnetbyaddr ADDR,ADDRTYPE
1212
1213Not implemented. (S<Mac OS>, Win32, Plan9)
1214
1215=item getprotobynumber NUMBER
1216
1217Not implemented. (S<Mac OS>)
1218
1219=item getservbyport PORT,PROTO
1220
1221Not implemented. (S<Mac OS>)
1222
1223=item getpwent
1224
7c5ffed3 1225Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1226
1227=item getgrent
1228
7c5ffed3 1229Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5
GS
1230
1231=item gethostent
1232
1233Not implemented. (S<Mac OS>, Win32)
1234
1235=item getnetent
1236
1237Not implemented. (S<Mac OS>, Win32, Plan9)
1238
1239=item getprotoent
1240
1241Not implemented. (S<Mac OS>, Win32, Plan9)
1242
1243=item getservent
1244
1245Not implemented. (Win32, Plan9)
1246
1247=item setpwent
1248
b8099c3d 1249Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1250
1251=item setgrent
1252
b8099c3d 1253Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1254
1255=item sethostent STAYOPEN
1256
b8099c3d 1257Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1258
1259=item setnetent STAYOPEN
1260
b8099c3d 1261Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1262
1263=item setprotoent STAYOPEN
1264
b8099c3d 1265Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1266
1267=item setservent STAYOPEN
1268
b8099c3d 1269Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1270
1271=item endpwent
1272
7c5ffed3 1273Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1274
1275=item endgrent
1276
7c5ffed3 1277Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VM/ESA)
e41182b5
GS
1278
1279=item endhostent
1280
1281Not implemented. (S<Mac OS>, Win32)
1282
1283=item endnetent
1284
1285Not implemented. (S<Mac OS>, Win32, Plan9)
1286
1287=item endprotoent
1288
1289Not implemented. (S<Mac OS>, Win32, Plan9)
1290
1291=item endservent
1292
1293Not implemented. (Plan9, Win32)
1294
1295=item getsockopt SOCKET,LEVEL,OPTNAME
1296
1297Not implemented. (S<Mac OS>, Plan9)
1298
1299=item glob EXPR
1300
1301=item glob
1302
1303Globbing built-in, but only C<*> and C<?> metacharacters are supported.
1304(S<Mac OS>)
1305
0a47030a
GS
1306Features depend on external perlglob.exe or perlglob.bat. May be
1307overridden with something like File::DosGlob, which is recommended.
1308(Win32)
e41182b5 1309
b8099c3d 1310Globbing built-in, but only C<*> and C<?> metacharacters are supported.
0a47030a
GS
1311Globbing relies on operating system calls, which may return filenames
1312in any order. As most filesystems are case-insensitive, even "sorted"
1313filenames will not be in case-sensitive order. (S<RISC OS>)
b8099c3d 1314
e41182b5
GS
1315=item ioctl FILEHANDLE,FUNCTION,SCALAR
1316
1317Not implemented. (VMS)
1318
1319Available only for socket handles, and it does what the ioctlsocket() call
1320in the Winsock API does. (Win32)
1321
b8099c3d
CN
1322Available only for socket handles. (S<RISC OS>)
1323
e41182b5
GS
1324=item kill LIST
1325
0a47030a
GS
1326Not implemented, hence not useful for taint checking. (S<Mac OS>,
1327S<RISC OS>)
e41182b5 1328
0a47030a
GS
1329Available only for process handles returned by the C<system(1, ...)>
1330method of spawning a process. (Win32)
e41182b5
GS
1331
1332=item link OLDFILE,NEWFILE
1333
b8099c3d 1334Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1335
433acd8a
JH
1336Link count not updated because hard links are not quite that hard
1337(They are sort of half-way between hard and soft links). (AmigaOS)
1338
e41182b5
GS
1339=item lstat FILEHANDLE
1340
1341=item lstat EXPR
1342
1343=item lstat
1344
b8099c3d 1345Not implemented. (VMS, S<RISC OS>)
e41182b5 1346
b8099c3d 1347Return values may be bogus. (Win32)
e41182b5
GS
1348
1349=item msgctl ID,CMD,ARG
1350
1351=item msgget KEY,FLAGS
1352
1353=item msgsnd ID,MSG,FLAGS
1354
1355=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1356
495c5fdc 1357Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1358
1359=item open FILEHANDLE,EXPR
1360
1361=item open FILEHANDLE
1362
1363The C<|> variants are only supported if ToolServer is installed.
1364(S<Mac OS>)
1365
b8099c3d 1366open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1367
1368=item pipe READHANDLE,WRITEHANDLE
1369
1370Not implemented. (S<Mac OS>)
1371
433acd8a
JH
1372Very limited functionality. (MiNT)
1373
e41182b5
GS
1374=item readlink EXPR
1375
1376=item readlink
1377
b8099c3d 1378Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1379
1380=item select RBITS,WBITS,EBITS,TIMEOUT
1381
1382Only implemented on sockets. (Win32)
1383
b8099c3d
CN
1384Only reliable on sockets. (S<RISC OS>)
1385
e41182b5
GS
1386=item semctl ID,SEMNUM,CMD,ARG
1387
1388=item semget KEY,NSEMS,FLAGS
1389
1390=item semop KEY,OPSTRING
1391
495c5fdc 1392Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1393
1394=item setpgrp PID,PGRP
1395
495c5fdc 1396Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1397
1398=item setpriority WHICH,WHO,PRIORITY
1399
495c5fdc 1400Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1401
1402=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1403
1404Not implemented. (S<Mac OS>, Plan9)
1405
1406=item shmctl ID,CMD,ARG
1407
1408=item shmget KEY,SIZE,FLAGS
1409
1410=item shmread ID,VAR,POS,SIZE
1411
1412=item shmwrite ID,STRING,POS,SIZE
1413
495c5fdc 1414Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1415
1416=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1417
7c5ffed3 1418Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1419
1420=item stat FILEHANDLE
1421
1422=item stat EXPR
1423
1424=item stat
1425
1426mtime and atime are the same thing, and ctime is creation time instead of
1427inode change time. (S<Mac OS>)
1428
1429device and inode are not meaningful. (Win32)
1430
1431device and inode are not necessarily reliable. (VMS)
1432
b8099c3d
CN
1433mtime, atime and ctime all return the last modification time. Device and
1434inode are not necessarily reliable. (S<RISC OS>)
1435
e41182b5
GS
1436=item symlink OLDFILE,NEWFILE
1437
b8099c3d 1438Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1439
1440=item syscall LIST
1441
7c5ffed3 1442Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1443
f34d0673
GS
1444=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1445
dd9f0070 1446The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1447numeric values on some systems. The flags exported by C<Fcntl>
1448(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 1449OS>, OS/390, VM/ESA)
f34d0673 1450
e41182b5
GS
1451=item system LIST
1452
1453Only implemented if ToolServer is installed. (S<Mac OS>)
1454
1455As an optimization, may not call the command shell specified in
1456C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1457process and immediately returns its process designator, without
1458waiting for it to terminate. Return value may be used subsequently
1459in C<wait> or C<waitpid>. (Win32)
1460
b8099c3d
CN
1461There is no shell to process metacharacters, and the native standard is
1462to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1463program. Redirection such as C<E<gt> foo> is performed (if at all) by
1464the run time library of the spawned program. C<system> I<list> will call
1465the Unix emulation library's C<exec> emulation, which attempts to provide
1466emulation of the stdin, stdout, stderr in force in the parent, providing
1467the child program uses a compatible version of the emulation library.
1468I<scalar> will call the native command line direct and no such emulation
1469of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1470
433acd8a
JH
1471Far from being POSIX compliant. Because there may be no underlying
1472/bin/sh tries to work around the problem by forking and execing the
9b63e9ec
CN
1473first token in its argument string. Handles basic redirection
1474("E<lt>" or "E<gt>") on its own behalf. (MiNT)
433acd8a 1475
e41182b5
GS
1476=item times
1477
1478Only the first entry returned is nonzero. (S<Mac OS>)
1479
1480"cumulative" times will be bogus. On anything other than Windows NT,
1481"system" time will be bogus, and "user" time is actually the time
1482returned by the clock() function in the C runtime library. (Win32)
1483
b8099c3d
CN
1484Not useful. (S<RISC OS>)
1485
e41182b5
GS
1486=item truncate FILEHANDLE,LENGTH
1487
1488=item truncate EXPR,LENGTH
1489
1490Not implemented. (VMS)
1491
495c5fdc
GP
1492Truncation to zero-length only. (VOS)
1493
4cfdb94f
GS
1494If a FILEHANDLE is supplied, it must be writable and opened in append
1495mode (i.e., use C<open(FH, '>>filename')>
1496or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1497should not be held open elsewhere. (Win32)
1498
e41182b5
GS
1499=item umask EXPR
1500
1501=item umask
1502
1503Returns undef where unavailable, as of version 5.005.
1504
9b63e9ec
CN
1505C<umask()> works but the correct permissions are only set when the file
1506is finally close()d. (AmigaOS)
433acd8a 1507
e41182b5
GS
1508=item utime LIST
1509
b8099c3d 1510Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1511
322422de
GS
1512May not behave as expected. Behavior depends on the C runtime
1513library's implementation of utime(), and the filesystem being
1514used. The FAT filesystem typically does not support an "access
1515time" field, and it may limit timestamps to a granularity of
1516two seconds. (Win32)
e41182b5
GS
1517
1518=item wait
1519
1520=item waitpid PID,FLAGS
1521
495c5fdc 1522Not implemented. (S<Mac OS>, VOS)
e41182b5
GS
1523
1524Can only be applied to process handles returned for processes spawned
1525using C<system(1, ...)>. (Win32)
1526
b8099c3d
CN
1527Not useful. (S<RISC OS>)
1528
e41182b5
GS
1529=back
1530
b8099c3d
CN
1531=head1 CHANGES
1532
1533=over 4
1534
2ee0eb3c
CN
1535=item v1.39, 11 February, 1999
1536
1537Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1538note about newlines added.
1539
9b63e9ec
CN
1540=item v1.38, 31 December 1998
1541
1542More changes from Jarkko.
1543
3c075c7d
CN
1544=item v1.37, 19 December 1998
1545
1546More minor changes. Merge two separate version 1.35 documents.
1547
1548=item v1.36, 9 September 1998
1549
1550Updated for Stratus VOS. Also known as version 1.35.
1551
1552=item v1.35, 13 August 1998
495c5fdc 1553
3c075c7d
CN
1554Integrate more minor changes, plus addition of new sections under
1555L<"ISSUES">: L<"Numbers endianness and Width">,
1556L<"Character sets and character encoding">,
1557L<"Internationalisation">.
495c5fdc 1558
3c075c7d 1559=item v1.33, 06 August 1998
0a47030a
GS
1560
1561Integrate more minor changes.
1562
3c075c7d 1563=item v1.32, 05 August 1998
dd9f0070
CN
1564
1565Integrate more minor changes.
1566
3c075c7d 1567=item v1.30, 03 August 1998
b8099c3d
CN
1568
1569Major update for RISC OS, other minor changes.
1570
3c075c7d 1571=item v1.23, 10 July 1998
b8099c3d
CN
1572
1573First public release with perl5.005.
1574
1575=back
e41182b5
GS
1576
1577=head1 AUTHORS / CONTRIBUTORS
1578
dd9f0070 1579Abigail E<lt>abigail@fnx.comE<gt>,
bd3fa61c 1580Charles Bailey E<lt>bailey@newman.upenn.eduE<gt>,
dd9f0070 1581Graham Barr E<lt>gbarr@pobox.comE<gt>,
e41182b5 1582Tom Christiansen E<lt>tchrist@perl.comE<gt>,
dd9f0070
CN
1583Nicholas Clark E<lt>Nicholas.Clark@liverpool.ac.ukE<gt>,
1584Andy Dougherty E<lt>doughera@lafcol.lafayette.eduE<gt>,
1585Dominic Dunlop E<lt>domo@vo.luE<gt>,
7c5ffed3 1586Neale Ferguson E<lt>neale@mailbox.tabnsw.com.auE<gt>
495c5fdc 1587Paul Green E<lt>Paul_Green@stratus.comE<gt>,
dd9f0070 1588M.J.T. Guy E<lt>mjtg@cus.cam.ac.ukE<gt>,
7c5ffed3 1589Jarkko Hietaniemi E<lt>jhi@iki.fi<gt>,
dd9f0070
CN
1590Luther Huffman E<lt>lutherh@stratcom.comE<gt>,
1591Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>,
322422de 1592Andreas J. KE<ouml>nig E<lt>koenig@kulturbox.deE<gt>,
3c075c7d 1593Markus Laker E<lt>mlaker@contax.co.ukE<gt>,
dd9f0070 1594Andrew M. Langmead E<lt>aml@world.std.comE<gt>,
e41182b5 1595Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>,
dd9f0070 1596Chris Nandor E<lt>pudge@pobox.comE<gt>,
322422de 1597Matthias Neeracher E<lt>neeri@iis.ee.ethz.chE<gt>,
e41182b5 1598Gary Ng E<lt>71564.1743@CompuServe.COME<gt>,
e41182b5 1599Tom Phoenix E<lt>rootbeer@teleport.comE<gt>,
dd9f0070 1600Peter Prymmer E<lt>pvhp@forte.comE<gt>,
322422de 1601Hugo van der Sanden E<lt>hv@crypt0.demon.co.ukE<gt>,
dd9f0070
CN
1602Gurusamy Sarathy E<lt>gsar@umich.eduE<gt>,
1603Paul J. Schinder E<lt>schinder@pobox.comE<gt>,
2ee0eb3c 1604Michael G Schwern E<lt>schwern@pobox.comE<gt>,
e41182b5 1605Dan Sugalski E<lt>sugalskd@ous.eduE<gt>,
dd9f0070 1606Nathan Torkington E<lt>gnat@frii.comE<gt>.
e41182b5 1607
3c075c7d
CN
1608This document is maintained by Chris Nandor
1609E<lt>pudge@pobox.comE<gt>.
e41182b5
GS
1610
1611=head1 VERSION
1612
2ee0eb3c 1613Version 1.39, last modified 11 February 1999