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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, VOS, S<RISC OS> and probably others.
187Unix, for example, is one of the few OSes that has the idea of a single
188root directory.
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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
495c5fdc 192root directories and various "unrooted" device files such NIL: and
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193LPT:).
194
195S<Mac OS> uses C<:> as a path separator instead of C</>.
196
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197VOS perl can emulate Unix filenames with C</> as path separator. The
198native pathname characters greater-than, less-than, number-sign, and
199percent-sign are always accepted.
200
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201C<RISC OS> perl can emulate Unix filenames with C</> as path
202separator, or go native and use C<.> for path separator and C<:> to
203signal filing systems and disc names.
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204
205As with the newline problem above, there are modules that can help. The
206C<File::Spec> modules provide methods to do the Right Thing on whatever
207platform happens to be running the program.
208
209 use File::Spec;
210 chdir(File::Spec->updir()); # go up one directory
211 $file = File::Spec->catfile(
212 File::Spec->curdir(), 'temp', 'file.txt'
213 );
214 # on Unix and Win32, './temp/file.txt'
215 # on Mac OS, ':temp:file.txt'
216
217File::Spec is available in the standard distribution, as of version
2185.004_05.
219
220In general, production code should not have file paths hardcoded; making
221them user supplied or from a configuration file is better, keeping in mind
222that file path syntax varies on different machines.
223
224This is especially noticeable in scripts like Makefiles and test suites,
225which often assume C</> as a path separator for subdirectories.
226
227Also of use is C<File::Basename>, from the standard distribution, which
228splits a pathname into pieces (base filename, full path to directory,
229and file suffix).
230
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231Even when on a single platform (if you can call UNIX a single
232platform), remember not to count on the existence or the contents of
233system-specific files, like F</etc/passwd>, F</etc/sendmail.conf>, or
234F</etc/resolv.conf>. For example the F</etc/passwd> may exist but it
235may not contain the encrypted passwords because the system is using
236some form of enhanced security-- or it may not contain all the
237accounts because the system is using NIS. If code does need to rely
238on such a file, include a description of the file and its format in
239the code's documentation, and make it easy for the user to override
240the default location of the file.
e41182b5 241
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242Do not have two files of the same name with different case, like
243F<test.pl> and <Test.pl>, as many platforms have case-insensitive
244filenames. Also, try not to have non-word characters (except for C<.>)
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245in the names, and keep them to the 8.3 convention, for maximum
246portability.
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247
248Likewise, if using C<AutoSplit>, try to keep the split functions to
2498.3 naming and case-insensitive conventions; or, at the very least,
250make it so the resulting files have a unique (case-insensitively)
251first 8 characters.
252
0a47030a 253Don't assume C<E<lt>> won't be the first character of a filename. Always
ae6c4aac 254use C<E<lt>> explicitly to open a file for reading:
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255
256 open(FILE, "<$existing_file") or die $!;
257
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258
259=head2 System Interaction
260
261Not all platforms provide for the notion of a command line, necessarily.
262These are usually platforms that rely on a Graphical User Interface (GUI)
263for user interaction. So a program requiring command lines might not work
264everywhere. But this is probably for the user of the program to deal
265with.
266
267Some platforms can't delete or rename files that are being held open by
268the system. Remember to C<close> files when you are done with them.
269Don't C<unlink> or C<rename> an open file. Don't C<tie> to or C<open> a
270file that is already tied to or opened; C<untie> or C<close> first.
271
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272Don't open the same file more than once at a time for writing, as some
273operating systems put mandatory locks on such files.
274
e41182b5 275Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 276Don't count on C<%ENV> entries being case-sensitive, or even
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277case-preserving.
278
0a47030a 279Don't count on signals.
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280
281Don't count on filename globbing. Use C<opendir>, C<readdir>, and
282C<closedir> instead.
283
b8099c3d 284Don't count on per-program environment variables, or per-program current
dd9f0070 285directories.
b8099c3d 286
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287
288=head2 Interprocess Communication (IPC)
289
290In general, don't directly access the system in code that is meant to be
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291portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>, C<``>,
292C<qx//>, C<open> with a C<|>, nor any of the other things that makes being
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293a Unix perl hacker worth being.
294
295Commands that launch external processes are generally supported on
296most platforms (though many of them do not support any type of forking),
297but the problem with using them arises from what you invoke with them.
298External tools are often named differently on different platforms, often
299not available in the same location, often accept different arguments,
300often behave differently, and often represent their results in a
301platform-dependent way. Thus you should seldom depend on them to produce
302consistent results.
303
304One especially common bit of Perl code is opening a pipe to sendmail:
305
306 open(MAIL, '|/usr/lib/sendmail -t') or die $!;
307
308This is fine for systems programming when sendmail is known to be
309available. But it is not fine for many non-Unix systems, and even
310some Unix systems that may not have sendmail installed. If a portable
311solution is needed, see the C<Mail::Send> and C<Mail::Mailer> modules
312in the C<MailTools> distribution. C<Mail::Mailer> provides several
313mailing methods, including mail, sendmail, and direct SMTP
314(via C<Net::SMTP>) if a mail transfer agent is not available.
315
316The rule of thumb for portable code is: Do it all in portable Perl, or
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317use a module (that may internally implement it with platform-specific
318code, but expose a common interface).
e41182b5 319
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320The UNIX System V IPC (C<msg*(), sem*(), shm*()>) is not available
321even in all UNIX platforms.
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322
323=head2 External Subroutines (XS)
324
325XS code, in general, can be made to work with any platform; but dependent
326libraries, header files, etc., might not be readily available or
327portable, or the XS code itself might be platform-specific, just as Perl
328code might be. If the libraries and headers are portable, then it is
329normally reasonable to make sure the XS code is portable, too.
330
331There is a different kind of portability issue with writing XS
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332code: availability of a C compiler on the end-user's system. C brings
333with it its own portability issues, and writing XS code will expose you to
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334some of those. Writing purely in perl is a comparatively easier way to
335achieve portability.
336
337
338=head2 Standard Modules
339
340In general, the standard modules work across platforms. Notable
341exceptions are C<CPAN.pm> (which currently makes connections to external
342programs that may not be available), platform-specific modules (like
343C<ExtUtils::MM_VMS>), and DBM modules.
344
345There is no one DBM module that is available on all platforms.
346C<SDBM_File> and the others are generally available on all Unix and DOSish
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347ports, but not in MacPerl, where only C<NBDM_File> and C<DB_File> are
348available.
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349
350The good news is that at least some DBM module should be available, and
351C<AnyDBM_File> will use whichever module it can find. Of course, then
352the code needs to be fairly strict, dropping to the lowest common
353denominator (e.g., not exceeding 1K for each record).
354
355
356=head2 Time and Date
357
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358The system's notion of time of day and calendar date is controlled in
359widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
360and even if it is, don't assume that you can control the timezone through
361that variable.
e41182b5 362
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363Don't assume that the epoch starts at 00:00:00, January 1, 1970,
364because that is OS-specific. Better to store a date in an unambiguous
365representation. The ISO 8601 standard defines YYYY-MM-DD as the date
366format. A text representation (like C<1 Jan 1970>) can be easily
367converted into an OS-specific value using a module like
368C<Date::Parse>. An array of values, such as those returned by
369C<localtime>, can be converted to an OS-specific representation using
370C<Time::Local>.
371
372
373=head2 Character sets and character encoding
374
375Assume very little about character sets. Do not assume anything about
376the numerical values (C<ord()>, C<chr()>) of characters. Do not
377assume that the alphabetic characters are encoded contiguously (in
378numerical sense). Do no assume anything about the ordering of the
379characters. The lowercase letters may come before or after the
380uppercase letters, the lowercase and uppercase may be interlaced so
b1ff3570 381that both 'a' and 'A' come before the 'b', the accented and other
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382international characters may be interlaced so that E<auml> comes
383before the 'b'.
384
385
386=head2 Internationalisation
387
388If you may assume POSIX (a rather large assumption, that: in practise
389that means UNIX) you may read more about the POSIX locale system from
390L<perllocale>. The locale system at least attempts to make things a
391little bit more portable or at least more convenient and
392native-friendly for non-English users. The system affects character
393sets and encoding, and date and time formatting, among other things.
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394
395
396=head2 System Resources
397
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398If your code is destined for systems with severely constrained (or
399missing!) virtual memory systems then you want to be I<especially> mindful
400of avoiding wasteful constructs such as:
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401
402 # NOTE: this is no longer "bad" in perl5.005
403 for (0..10000000) {} # bad
404 for (my $x = 0; $x <= 10000000; ++$x) {} # good
405
406 @lines = <VERY_LARGE_FILE>; # bad
407
408 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 409 $file = join('', <FILE>); # better
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410
411The last two may appear unintuitive to most people. The first of those
412two constructs repeatedly grows a string, while the second allocates a
413large chunk of memory in one go. On some systems, the latter is more
414efficient that the former.
415
0a47030a 416
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417=head2 Security
418
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419Most multi-user platforms provide basic levels of security that is usually
420felt at the file-system level. Other platforms usually don't
421(unfortunately). Thus the notion of user id, or "home" directory, or even
422the state of being logged-in, may be unrecognizable on many platforms. If
423you write programs that are security conscious, it is usually best to know
424what type of system you will be operating under, and write code explicitly
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425for that platform (or class of platforms).
426
0a47030a 427
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428=head2 Style
429
430For those times when it is necessary to have platform-specific code,
431consider keeping the platform-specific code in one place, making porting
432to other platforms easier. Use the C<Config> module and the special
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433variable C<$^O> to differentiate platforms, as described in
434L<"PLATFORMS">.
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435
436
0a47030a 437=head1 CPAN Testers
e41182b5 438
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439Modules uploaded to CPAN are tested by a variety of volunteers on
440different platforms. These CPAN testers are notified by mail of each
e41182b5 441new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 442this platform), or UNKNOWN (unknown), along with any relevant notations.
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443
444The purpose of the testing is twofold: one, to help developers fix any
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445problems in their code that crop up because of lack of testing on other
446platforms; two, to provide users with information about whether or not
447a given module works on a given platform.
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448
449=over 4
450
451=item Mailing list: cpan-testers@perl.org
452
453=item Testing results: C<http://www.connect.net/gbarr/cpan-test/>
454
455=back
456
457
458=head1 PLATFORMS
459
460As of version 5.002, Perl is built with a C<$^O> variable that
461indicates the operating system it was built on. This was implemented
462to help speed up code that would otherwise have to C<use Config;> and
463use the value of C<$Config{'osname'}>. Of course, to get
464detailed information about the system, looking into C<%Config> is
465certainly recommended.
466
467=head2 Unix
468
469Perl works on a bewildering variety of Unix and Unix-like platforms (see
470e.g. most of the files in the F<hints/> directory in the source code kit).
471On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
472too) is determined by lowercasing and stripping punctuation from the first
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473field of the string returned by typing C<uname -a> (or a similar command)
474at the shell prompt. Here, for example, are a few of the more popular
475Unix flavors:
e41182b5 476
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477 uname $^O $Config{'archname'}
478 -------------------------------------------
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479 AIX aix aix
480 FreeBSD freebsd freebsd-i386
481 Linux linux i386-linux
482 HP-UX hpux PA-RISC1.1
483 IRIX irix irix
484 OSF1 dec_osf alpha-dec_osf
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485 SunOS solaris sun4-solaris
486 SunOS solaris i86pc-solaris
322422de 487 SunOS4 sunos sun4-sunos
e41182b5 488
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489Note that because the C<$Config{'archname'}> may depend on the hardware
490architecture it may vary quite a lot, much more than the C<$^O>.
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491
492=head2 DOS and Derivatives
493
494Perl has long been ported to PC style microcomputers running under
495systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
496bring yourself to mention (except for Windows CE, if you count that).
497Users familiar with I<COMMAND.COM> and/or I<CMD.EXE> style shells should
498be aware that each of these file specifications may have subtle
499differences:
500
501 $filespec0 = "c:/foo/bar/file.txt";
502 $filespec1 = "c:\\foo\\bar\\file.txt";
503 $filespec2 = 'c:\foo\bar\file.txt';
504 $filespec3 = 'c:\\foo\\bar\\file.txt';
505
506System calls accept either C</> or C<\> as the path separator. However,
507many command-line utilities of DOS vintage treat C</> as the option
508prefix, so they may get confused by filenames containing C</>. Aside
509from calling any external programs, C</> will work just fine, and
510probably better, as it is more consistent with popular usage, and avoids
511the problem of remembering what to backwhack and what not to.
512
0a47030a 513The DOS FAT filesystem can only accommodate "8.3" style filenames. Under
e41182b5 514the "case insensitive, but case preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 515filesystems you may have to be careful about case returned with functions
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516like C<readdir> or used with functions like C<open> or C<opendir>.
517
518DOS also treats several filenames as special, such as AUX, PRN, NUL, CON,
519COM1, LPT1, LPT2 etc. Unfortunately these filenames won't even work
520if you include an explicit directory prefix, in some cases. It is best
521to avoid such filenames, if you want your code to be portable to DOS
522and its derivatives.
523
524Users of these operating systems may also wish to make use of
525scripts such as I<pl2bat.bat> or I<pl2cmd> as appropriate to
526put wrappers around your scripts.
527
528Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
529and writing to files. C<binmode(FILEHANDLE)> will keep C<\n> translated
530as C<\012> for that filehandle. Since it is a noop on other systems,
531C<binmode> should be used for cross-platform code that deals with binary
532data.
533
534The C<$^O> variable and the C<$Config{'archname'}> values for various
535DOSish perls are as follows:
536
537 OS $^O $Config{'archname'}
538 --------------------------------------------
539 MS-DOS dos
540 PC-DOS dos
541 OS/2 os2
542 Windows 95 MSWin32 MSWin32-x86
543 Windows NT MSWin32 MSWin32-x86
544 Windows NT MSWin32 MSWin32-alpha
545 Windows NT MSWin32 MSWin32-ppc
546
547Also see:
548
549=over 4
550
551=item The djgpp environment for DOS, C<http://www.delorie.com/djgpp/>
552
553=item The EMX environment for DOS, OS/2, etc. C<emx@iaehv.nl>,
554C<http://www.juge.com/bbs/Hobb.19.html>
555
556=item Build instructions for Win32, L<perlwin32>.
557
558=item The ActiveState Pages, C<http://www.activestate.com/>
559
560=back
561
562
dd9f0070 563=head2 S<Mac OS>
e41182b5
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564
565Any module requiring XS compilation is right out for most people, because
566MacPerl is built using non-free (and non-cheap!) compilers. Some XS
567modules that can work with MacPerl are built and distributed in binary
0a47030a
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568form on CPAN. See I<MacPerl: Power and Ease> and L<"CPAN Testers">
569for more details.
e41182b5
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570
571Directories are specified as:
572
573 volume:folder:file for absolute pathnames
574 volume:folder: for absolute pathnames
575 :folder:file for relative pathnames
576 :folder: for relative pathnames
577 :file for relative pathnames
578 file for relative pathnames
579
580Files in a directory are stored in alphabetical order. Filenames are
581limited to 31 characters, and may include any character except C<:>,
582which is reserved as a path separator.
583
0a47030a
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584Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
585C<Mac::Files> module.
e41182b5
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586
587In the MacPerl application, you can't run a program from the command line;
588programs that expect C<@ARGV> to be populated can be edited with something
589like the following, which brings up a dialog box asking for the command
590line arguments.
591
592 if (!@ARGV) {
593 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
594 }
595
596A MacPerl script saved as a droplet will populate C<@ARGV> with the full
597pathnames of the files dropped onto the script.
598
599Mac users can use programs on a kind of command line under MPW (Macintosh
600Programmer's Workshop, a free development environment from Apple).
601MacPerl was first introduced as an MPW tool, and MPW can be used like a
602shell:
603
604 perl myscript.plx some arguments
605
606ToolServer is another app from Apple that provides access to MPW tools
0a47030a 607from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
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608C<system>, backticks, and piped C<open>.
609
610"S<Mac OS>" is the proper name for the operating system, but the value
611in C<$^O> is "MacOS". To determine architecture, version, or whether
612the application or MPW tool version is running, check:
613
614 $is_app = $MacPerl::Version =~ /App/;
615 $is_tool = $MacPerl::Version =~ /MPW/;
616 ($version) = $MacPerl::Version =~ /^(\S+)/;
617 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
618 $is_68k = $MacPerl::Architecture eq 'Mac68K';
619
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620S<Mac OS X>, to be based on NeXT's OpenStep OS, will be able to run
621MacPerl natively (in the Blue Box, and even in the Yellow Box, once some
622changes to the toolbox calls are made), but Unix perl will also run
623natively.
e41182b5
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624
625Also see:
626
627=over 4
628
629=item The MacPerl Pages, C<http://www.ptf.com/macperl/>.
630
631=item The MacPerl mailing list, C<mac-perl-request@iis.ee.ethz.ch>.
632
633=back
634
635
636=head2 VMS
637
638Perl on VMS is discussed in F<vms/perlvms.pod> in the perl distribution.
0a47030a 639Note that perl on VMS can accept either VMS- or Unix-style file
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640specifications as in either of the following:
641
642 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
643 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
644
645but not a mixture of both as in:
646
647 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
648 Can't open sys$login:/login.com: file specification syntax error
649
650Interacting with Perl from the Digital Command Language (DCL) shell
651often requires a different set of quotation marks than Unix shells do.
652For example:
653
654 $ perl -e "print ""Hello, world.\n"""
655 Hello, world.
656
657There are a number of ways to wrap your perl scripts in DCL .COM files if
658you are so inclined. For example:
659
660 $ write sys$output "Hello from DCL!"
661 $ if p1 .eqs. ""
662 $ then perl -x 'f$environment("PROCEDURE")
663 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
664 $ deck/dollars="__END__"
665 #!/usr/bin/perl
666
667 print "Hello from Perl!\n";
668
669 __END__
670 $ endif
671
672Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
673perl-in-DCL script expects to do things like C<$read = E<lt>STDINE<gt>;>.
674
675Filenames are in the format "name.extension;version". The maximum
676length for filenames is 39 characters, and the maximum length for
677extensions is also 39 characters. Version is a number from 1 to
67832767. Valid characters are C</[A-Z0-9$_-]/>.
679
680VMS' RMS filesystem is case insensitive and does not preserve case.
681C<readdir> returns lowercased filenames, but specifying a file for
b8099c3d 682opening remains case insensitive. Files without extensions have a
e41182b5 683trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
684will return F<a.> (though that file could be opened with
685C<open(FH, 'A')>).
e41182b5 686
f34d0673 687RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
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688(allowing 16 levels overall) prior to VMS 7.2. Hence
689C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
690C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
691have to take this into account, but at least they can refer to the former
f34d0673 692as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 693
0a47030a
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694The C<VMS::Filespec> module, which gets installed as part of the build
695process on VMS, is a pure Perl module that can easily be installed on
696non-VMS platforms and can be helpful for conversions to and from RMS
697native formats.
e41182b5
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698
699What C<\n> represents depends on the type of file that is open. It could
700be C<\015>, C<\012>, C<\015\012>, or nothing. Reading from a file
701translates newlines to C<\012>, unless C<binmode> was executed on that
702handle, just like DOSish perls.
703
704TCP/IP stacks are optional on VMS, so socket routines might not be
705implemented. UDP sockets may not be supported.
706
707The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
708that you are running on without resorting to loading all of C<%Config>
709you can examine the content of the C<@INC> array like so:
710
711 if (grep(/VMS_AXP/, @INC)) {
712 print "I'm on Alpha!\n";
713 } elsif (grep(/VMS_VAX/, @INC)) {
714 print "I'm on VAX!\n";
715 } else {
716 print "I'm not so sure about where $^O is...\n";
717 }
718
719Also see:
720
721=over 4
722
723=item L<perlvms.pod>
724
725=item vmsperl list, C<vmsperl-request@newman.upenn.edu>
726
727Put words C<SUBSCRIBE VMSPERL> in message body.
728
729=item vmsperl on the web, C<http://www.sidhe.org/vmsperl/index.html>
730
731=back
732
733
495c5fdc
GP
734=head2 VOS
735
736Perl on VOS is discussed in F<README.vos> in the perl distribution.
737Note that perl on VOS can accept either VOS- or Unix-style file
738specifications as in either of the following:
739
740 $ perl -ne "print if /perl_setup/i" >system>notices
741 $ perl -ne "print if /perl_setup/i" /system/notices
742
743or even a mixture of both as in:
744
745 $ perl -ne "print if /perl_setup/i" >system/notices
746
747Note that even though VOS allows the slash character to appear in object
748names, because the VOS port of Perl interprets it as a pathname
749delimiting character, VOS files, directories, or links whose names
750contain a slash character cannot be processed. Such files must be
751renamed before they can be processed by Perl.
752
753The following C functions are unimplemented on VOS, any any attempt by
754Perl to use them will result in a fatal error message and an immediate
755exit from Perl: dup, do_aspawn, do_spawn, execlp, execl, execvp, fork,
756waitpid. Once these functions become available in the VOS POSIX.1
757implementation, you can either recompile and rebind Perl, or you can
758download a newer port from ftp.stratus.com.
759
760The value of C<$^O> on VOS is "VOS". To determine the architecture that
761you are running on without resorting to loading all of C<%Config> you
762can examine the content of the C<@INC> array like so:
763
764 if (grep(/VOS/, @INC)) {
765 print "I'm on a Stratus box!\n";
766 } else {
767 print "I'm not on a Stratus box!\n";
768 die;
769 }
770
771 if (grep(/860/, @INC)) {
772 print "This box is a Stratus XA/R!\n";
773 } elsif (grep(/7100/, @INC)) {
774 print "This box is a Stratus HP 7100 or 8000!\n";
775 } elsif (grep(/8000/, @INC)) {
776 print "This box is a Stratus HP 8000!\n";
777 } else {
778 print "This box is a Stratus 68K...\n";
779 }
780
781Also see:
782
783=over 4
784
785=item L<README.vos>
786
787=item VOS mailing list
788
789There is no specific mailing list for Perl on VOS. You can post
790comments to the comp.sys.stratus newsgroup, or subscribe to the general
791Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
792the message body to majordomo@list.stratagy.com.
793
794=item VOS Perl on the web at C<http://ftp.stratus.com/pub/vos/vos.html>
795
796=back
797
798
e41182b5
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799=head2 EBCDIC Platforms
800
801Recent versions of Perl have been ported to platforms such as OS/400 on
802AS/400 minicomputers as well as OS/390 for IBM Mainframes. Such computers
803use EBCDIC character sets internally (usually Character Code Set ID 00819
804for OS/400 and IBM-1047 for OS/390). Note that on the mainframe perl
805currently works under the "Unix system services for OS/390" (formerly
806known as OpenEdition).
807
808As of R2.5 of USS for OS/390 that Unix sub-system did not support the
809C<#!> shebang trick for script invocation. Hence, on OS/390 perl scripts
810can executed with a header similar to the following simple script:
811
812 : # use perl
813 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
814 if 0;
815 #!/usr/local/bin/perl # just a comment really
816
817 print "Hello from perl!\n";
818
819On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
820an effect on what happens with some perl functions (such as C<chr>,
821C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
822well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
823and C<|>, not to mention dealing with socket interfaces to ASCII computers
e41182b5
GS
824(see L<"NEWLINES">).
825
826Fortunately, most web servers for the mainframe will correctly translate
827the C<\n> in the following statement to its ASCII equivalent (note that
0a47030a 828C<\r> is the same under both Unix and OS/390):
e41182b5
GS
829
830 print "Content-type: text/html\r\n\r\n";
831
832The value of C<$^O> on OS/390 is "os390".
833
834Some simple tricks for determining if you are running on an EBCDIC
835platform could include any of the following (perhaps all):
836
837 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
838
839 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
840
841 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
842
843Note that one thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
844of punctuation characters since these may differ from code page to code
845page (and once your module or script is rumoured to work with EBCDIC,
846folks will want it to work with all EBCDIC character sets).
e41182b5
GS
847
848Also see:
849
850=over 4
851
852=item perl-mvs list
853
854The perl-mvs@perl.org list is for discussion of porting issues as well as
855general usage issues for all EBCDIC Perls. Send a message body of
856"subscribe perl-mvs" to majordomo@perl.org.
857
0a47030a 858=item AS/400 Perl information at C<http://as400.rochester.ibm.com/>
e41182b5
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859
860=back
861
b8099c3d
CN
862
863=head2 Acorn RISC OS
864
0a47030a
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865As Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
866Unix and Unix filename emulation is turned on by default, it is quite
867likely that most simple scripts will work "out of the box". The native
868filing system is modular, and individual filing systems are free to be
869case-sensitive or insensitive, and are usually case-preserving. Some
870native filing systems have name length limits which file and directory
871names are silently truncated to fit - scripts should be aware that the
872standard disc filing system currently has a name length limit of B<10>
873characters, with up to 77 items in a directory, but other filing systems
874may not impose such limitations.
b8099c3d
CN
875
876Native filenames are of the form
877
878 Filesystem#Special_Field::DiscName.$.Directory.Directory.File
dd9f0070 879
b8099c3d
CN
880where
881
882 Special_Field is not usually present, but may contain . and $ .
883 Filesystem =~ m|[A-Za-z0-9_]|
884 DsicName =~ m|[A-Za-z0-9_/]|
885 $ represents the root directory
886 . is the path separator
887 @ is the current directory (per filesystem but machine global)
888 ^ is the parent directory
889 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
890
891The default filename translation is roughly C<tr|/.|./|;>
892
893Note that C<"ADFS::HardDisc.$.File" ne 'ADFS::HardDisc.$.File'> and that
0a47030a
GS
894the second stage of C<$> interpolation in regular expressions will fall
895foul of the C<$.> if scripts are not careful.
896
897Logical paths specified by system variables containing comma-separated
898search lists are also allowed, hence C<System:Modules> is a valid
899filename, and the filesystem will prefix C<Modules> with each section of
900C<System$Path> until a name is made that points to an object on disc.
901Writing to a new file C<System:Modules> would only be allowed if
902C<System$Path> contains a single item list. The filesystem will also
903expand system variables in filenames if enclosed in angle brackets, so
904C<E<lt>System$DirE<gt>.Modules> would look for the file
905S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
906that B<fully qualified filenames can start with C<E<lt>E<gt>> and should
907be protected when C<open> is used for input.
b8099c3d
CN
908
909Because C<.> was in use as a directory separator and filenames could not
910be assumed to be unique after 10 characters, Acorn implemented the C
911compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
912filenames specified in source code and store the respective files in
913subdirectories named after the suffix. Hence files are translated:
914
915 foo.h h.foo
916 C:foo.h C:h.foo (logical path variable)
917 sys/os.h sys.h.os (C compiler groks Unix-speak)
918 10charname.c c.10charname
919 10charname.o o.10charname
920 11charname_.c c.11charname (assuming filesystem truncates at 10)
921
922The Unix emulation library's translation of filenames to native assumes
0a47030a
GS
923that this sort of translation is required, and allows a user defined list
924of known suffixes which it will transpose in this fashion. This may
925appear transparent, but consider that with these rules C<foo/bar/baz.h>
926and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
927C<glob> cannot and do not attempt to emulate the reverse mapping. Other
928C<.>s in filenames are translated to C</>.
929
930As implied above the environment accessed through C<%ENV> is global, and
931the convention is that program specific environment variables are of the
932form C<Program$Name>. Each filing system maintains a current directory,
933and the current filing system's current directory is the B<global> current
934directory. Consequently, sociable scripts don't change the current
935directory but rely on full pathnames, and scripts (and Makefiles) cannot
936assume that they can spawn a child process which can change the current
937directory without affecting its parent (and everyone else for that
938matter).
939
940As native operating system filehandles are global and currently are
941allocated down from 255, with 0 being a reserved value the Unix emulation
942library emulates Unix filehandles. Consequently, you can't rely on
943passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
944
945The desire of users to express filenames of the form
946C<E<lt>Foo$DirE<gt>.Bar> on the command line unquoted causes problems,
947too: C<``> command output capture has to perform a guessing game. It
948assumes that a string C<E<lt>[^E<lt>E<gt>]+\$[^E<lt>E<gt>]E<gt>> is a
949reference to an environment variable, whereas anything else involving
950C<E<lt>> or C<E<gt>> is redirection, and generally manages to be 99%
951right. Of course, the problem remains that scripts cannot rely on any
952Unix tools being available, or that any tools found have Unix-like command
953line arguments.
954
955Extensions and XS are, in theory, buildable by anyone using free tools.
956In practice, many don't, as users of the Acorn platform are used to binary
957distribution. MakeMaker does run, but no available make currently copes
958with MakeMaker's makefiles; even if/when this is fixed, the lack of a
959Unix-like shell can cause problems with makefile rules, especially lines
960of the form C<cd sdbm && make all>, and anything using quoting.
b8099c3d
CN
961
962"S<RISC OS>" is the proper name for the operating system, but the value
963in C<$^O> is "riscos" (because we don't like shouting).
964
965Also see:
966
967=over 4
968
969=item perl list
970
971=back
972
973
e41182b5
GS
974=head2 Other perls
975
b8099c3d
CN
976Perl has been ported to a variety of platforms that do not fit into any of
977the above categories. Some, such as AmigaOS, BeOS, QNX, and Plan 9, have
0a47030a 978been well-integrated into the standard Perl source code kit. You may need
b8099c3d 979to see the F<ports/> directory on CPAN for information, and possibly
0a47030a
GS
980binaries, for the likes of: aos, atari, lynxos, riscos, Tandem Guardian,
981vos, I<etc.> (yes we know that some of these OSes may fall under the Unix
982category, but we are not a standards body.)
e41182b5
GS
983
984See also:
985
986=over 4
987
988=item Atari, Guido Flohr's page C<http://stud.uni-sb.de/~gufl0000/>
989
990=item HP 300 MPE/iX C<http://www.cccd.edu/~markb/perlix.html>
991
992=item Novell Netware
993
0a47030a 994A free perl5-based PERL.NLM for Novell Netware is available from
e41182b5
GS
995C<http://www.novell.com/>
996
997=back
998
999
1000=head1 FUNCTION IMPLEMENTATIONS
1001
1002Listed below are functions unimplemented or implemented differently on
1003various platforms. Following each description will be, in parentheses, a
1004list of platforms that the description applies to.
1005
1006The list may very well be incomplete, or wrong in some places. When in
1007doubt, consult the platform-specific README files in the Perl source
1008distribution, and other documentation resources for a given port.
1009
0a47030a 1010Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5
GS
1011
1012For many functions, you can also query C<%Config>, exported by default
1013from C<Config.pm>. For example, to check if the platform has the C<lstat>
0a47030a
GS
1014call, check C<$Config{'d_lstat'}>. See L<Config.pm> for a full
1015description of available variables.
e41182b5
GS
1016
1017
1018=head2 Alphabetical Listing of Perl Functions
1019
1020=over 8
1021
1022=item -X FILEHANDLE
1023
1024=item -X EXPR
1025
1026=item -X
1027
1028C<-r>, C<-w>, and C<-x> have only a very limited meaning; directories
1029and applications are executable, and there are no uid/gid
1030considerations. C<-o> is not supported. (S<Mac OS>)
1031
1032C<-r>, C<-w>, C<-x>, and C<-o> tell whether or not file is accessible,
1033which may not reflect UIC-based file protections. (VMS)
1034
b8099c3d
CN
1035C<-s> returns the size of the data fork, not the total size of data fork
1036plus resource fork. (S<Mac OS>).
1037
1038C<-s> by name on an open file will return the space reserved on disk,
1039rather than the current extent. C<-s> on an open filehandle returns the
1040current size. (S<RISC OS>)
1041
e41182b5 1042C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1043C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1044
1045C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1046(S<Mac OS>)
1047
1048C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1049(Win32, VMS, S<RISC OS>)
e41182b5
GS
1050
1051C<-d> is true if passed a device spec without an explicit directory.
1052(VMS)
1053
1054C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a
GS
1055with foreign characters; this is the case will all platforms, but may
1056affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1057
1058C<-x> (or C<-X>) determine if a file ends in one of the executable
1059suffixes. C<-S> is meaningless. (Win32)
1060
b8099c3d
CN
1061C<-x> (or C<-X>) determine if a file has an executable file type.
1062(S<RISC OS>)
1063
e41182b5
GS
1064=item binmode FILEHANDLE
1065
b8099c3d 1066Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1067
1068Reopens file and restores pointer; if function fails, underlying
1069filehandle may be closed, or pointer may be in a different position.
1070(VMS)
1071
1072The value returned by C<tell> may be affected after the call, and
1073the filehandle may be flushed. (Win32)
1074
1075=item chmod LIST
1076
1077Only limited meaning. Disabling/enabling write permission is mapped to
1078locking/unlocking the file. (S<Mac OS>)
1079
1080Only good for changing "owner" read-write access, "group", and "other"
1081bits are meaningless. (Win32)
1082
b8099c3d
CN
1083Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1084
495c5fdc
GP
1085Access permissions are mapped onto VOS access-control list changes. (VOS)
1086
e41182b5
GS
1087=item chown LIST
1088
495c5fdc 1089Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1090
1091Does nothing, but won't fail. (Win32)
1092
1093=item chroot FILENAME
1094
1095=item chroot
1096
495c5fdc 1097Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1098
1099=item crypt PLAINTEXT,SALT
1100
1101May not be available if library or source was not provided when building
b8099c3d 1102perl. (Win32)
e41182b5 1103
495c5fdc
GP
1104Not implemented. (VOS)
1105
e41182b5
GS
1106=item dbmclose HASH
1107
495c5fdc 1108Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1109
1110=item dbmopen HASH,DBNAME,MODE
1111
495c5fdc 1112Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1113
1114=item dump LABEL
1115
b8099c3d 1116Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1117
1118Not implemented. (Win32)
1119
b8099c3d 1120Invokes VMS debugger. (VMS)
e41182b5
GS
1121
1122=item exec LIST
1123
1124Not implemented. (S<Mac OS>)
1125
1126=item fcntl FILEHANDLE,FUNCTION,SCALAR
1127
1128Not implemented. (Win32, VMS)
1129
1130=item flock FILEHANDLE,OPERATION
1131
495c5fdc 1132Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1133
1134Available only on Windows NT (not on Windows 95). (Win32)
1135
1136=item fork
1137
495c5fdc 1138Not implemented. (S<Mac OS>, Win32, AmigaOS, S<RISC OS>, VOS)
e41182b5
GS
1139
1140=item getlogin
1141
b8099c3d 1142Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1143
1144=item getpgrp PID
1145
495c5fdc 1146Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1147
1148=item getppid
1149
b8099c3d 1150Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1151
1152=item getpriority WHICH,WHO
1153
495c5fdc 1154Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1155
1156=item getpwnam NAME
1157
1158Not implemented. (S<Mac OS>, Win32)
1159
b8099c3d
CN
1160Not useful. (S<RISC OS>)
1161
e41182b5
GS
1162=item getgrnam NAME
1163
b8099c3d 1164Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1165
1166=item getnetbyname NAME
1167
1168Not implemented. (S<Mac OS>, Win32, Plan9)
1169
1170=item getpwuid UID
1171
1172Not implemented. (S<Mac OS>, Win32)
1173
b8099c3d
CN
1174Not useful. (S<RISC OS>)
1175
e41182b5
GS
1176=item getgrgid GID
1177
b8099c3d 1178Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1179
1180=item getnetbyaddr ADDR,ADDRTYPE
1181
1182Not implemented. (S<Mac OS>, Win32, Plan9)
1183
1184=item getprotobynumber NUMBER
1185
1186Not implemented. (S<Mac OS>)
1187
1188=item getservbyport PORT,PROTO
1189
1190Not implemented. (S<Mac OS>)
1191
1192=item getpwent
1193
1194Not implemented. (S<Mac OS>, Win32)
1195
1196=item getgrent
1197
1198Not implemented. (S<Mac OS>, Win32, VMS)
1199
1200=item gethostent
1201
1202Not implemented. (S<Mac OS>, Win32)
1203
1204=item getnetent
1205
1206Not implemented. (S<Mac OS>, Win32, Plan9)
1207
1208=item getprotoent
1209
1210Not implemented. (S<Mac OS>, Win32, Plan9)
1211
1212=item getservent
1213
1214Not implemented. (Win32, Plan9)
1215
1216=item setpwent
1217
b8099c3d 1218Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1219
1220=item setgrent
1221
b8099c3d 1222Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1223
1224=item sethostent STAYOPEN
1225
b8099c3d 1226Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1227
1228=item setnetent STAYOPEN
1229
b8099c3d 1230Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1231
1232=item setprotoent STAYOPEN
1233
b8099c3d 1234Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1235
1236=item setservent STAYOPEN
1237
b8099c3d 1238Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1239
1240=item endpwent
1241
1242Not implemented. (S<Mac OS>, Win32)
1243
1244=item endgrent
1245
b8099c3d 1246Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1247
1248=item endhostent
1249
1250Not implemented. (S<Mac OS>, Win32)
1251
1252=item endnetent
1253
1254Not implemented. (S<Mac OS>, Win32, Plan9)
1255
1256=item endprotoent
1257
1258Not implemented. (S<Mac OS>, Win32, Plan9)
1259
1260=item endservent
1261
1262Not implemented. (Plan9, Win32)
1263
1264=item getsockopt SOCKET,LEVEL,OPTNAME
1265
1266Not implemented. (S<Mac OS>, Plan9)
1267
1268=item glob EXPR
1269
1270=item glob
1271
1272Globbing built-in, but only C<*> and C<?> metacharacters are supported.
1273(S<Mac OS>)
1274
0a47030a
GS
1275Features depend on external perlglob.exe or perlglob.bat. May be
1276overridden with something like File::DosGlob, which is recommended.
1277(Win32)
e41182b5 1278
b8099c3d 1279Globbing built-in, but only C<*> and C<?> metacharacters are supported.
0a47030a
GS
1280Globbing relies on operating system calls, which may return filenames
1281in any order. As most filesystems are case-insensitive, even "sorted"
1282filenames will not be in case-sensitive order. (S<RISC OS>)
b8099c3d 1283
e41182b5
GS
1284=item ioctl FILEHANDLE,FUNCTION,SCALAR
1285
1286Not implemented. (VMS)
1287
1288Available only for socket handles, and it does what the ioctlsocket() call
1289in the Winsock API does. (Win32)
1290
b8099c3d
CN
1291Available only for socket handles. (S<RISC OS>)
1292
e41182b5
GS
1293=item kill LIST
1294
0a47030a
GS
1295Not implemented, hence not useful for taint checking. (S<Mac OS>,
1296S<RISC OS>)
e41182b5 1297
0a47030a
GS
1298Available only for process handles returned by the C<system(1, ...)>
1299method of spawning a process. (Win32)
e41182b5
GS
1300
1301=item link OLDFILE,NEWFILE
1302
b8099c3d 1303Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1304
1305=item lstat FILEHANDLE
1306
1307=item lstat EXPR
1308
1309=item lstat
1310
b8099c3d 1311Not implemented. (VMS, S<RISC OS>)
e41182b5 1312
b8099c3d 1313Return values may be bogus. (Win32)
e41182b5
GS
1314
1315=item msgctl ID,CMD,ARG
1316
1317=item msgget KEY,FLAGS
1318
1319=item msgsnd ID,MSG,FLAGS
1320
1321=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1322
495c5fdc 1323Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1324
1325=item open FILEHANDLE,EXPR
1326
1327=item open FILEHANDLE
1328
1329The C<|> variants are only supported if ToolServer is installed.
1330(S<Mac OS>)
1331
b8099c3d 1332open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1333
1334=item pipe READHANDLE,WRITEHANDLE
1335
1336Not implemented. (S<Mac OS>)
1337
1338=item readlink EXPR
1339
1340=item readlink
1341
b8099c3d 1342Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1343
1344=item select RBITS,WBITS,EBITS,TIMEOUT
1345
1346Only implemented on sockets. (Win32)
1347
b8099c3d
CN
1348Only reliable on sockets. (S<RISC OS>)
1349
e41182b5
GS
1350=item semctl ID,SEMNUM,CMD,ARG
1351
1352=item semget KEY,NSEMS,FLAGS
1353
1354=item semop KEY,OPSTRING
1355
495c5fdc 1356Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1357
1358=item setpgrp PID,PGRP
1359
495c5fdc 1360Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1361
1362=item setpriority WHICH,WHO,PRIORITY
1363
495c5fdc 1364Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1365
1366=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1367
1368Not implemented. (S<Mac OS>, Plan9)
1369
1370=item shmctl ID,CMD,ARG
1371
1372=item shmget KEY,SIZE,FLAGS
1373
1374=item shmread ID,VAR,POS,SIZE
1375
1376=item shmwrite ID,STRING,POS,SIZE
1377
495c5fdc 1378Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1379
1380=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1381
495c5fdc 1382Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1383
1384=item stat FILEHANDLE
1385
1386=item stat EXPR
1387
1388=item stat
1389
1390mtime and atime are the same thing, and ctime is creation time instead of
1391inode change time. (S<Mac OS>)
1392
1393device and inode are not meaningful. (Win32)
1394
1395device and inode are not necessarily reliable. (VMS)
1396
b8099c3d
CN
1397mtime, atime and ctime all return the last modification time. Device and
1398inode are not necessarily reliable. (S<RISC OS>)
1399
e41182b5
GS
1400=item symlink OLDFILE,NEWFILE
1401
b8099c3d 1402Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1403
1404=item syscall LIST
1405
495c5fdc 1406Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1407
f34d0673
GS
1408=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1409
dd9f0070 1410The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1411numeric values on some systems. The flags exported by C<Fcntl>
1412(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
1413OS>, OS/390)
f34d0673 1414
e41182b5
GS
1415=item system LIST
1416
1417Only implemented if ToolServer is installed. (S<Mac OS>)
1418
1419As an optimization, may not call the command shell specified in
1420C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
1421process and immediately returns its process designator, without
1422waiting for it to terminate. Return value may be used subsequently
1423in C<wait> or C<waitpid>. (Win32)
1424
b8099c3d
CN
1425There is no shell to process metacharacters, and the native standard is
1426to pass a command line terminated by "\n" "\r" or "\0" to the spawned
1427program. Redirection such as C<E<gt> foo> is performed (if at all) by
1428the run time library of the spawned program. C<system> I<list> will call
1429the Unix emulation library's C<exec> emulation, which attempts to provide
1430emulation of the stdin, stdout, stderr in force in the parent, providing
1431the child program uses a compatible version of the emulation library.
1432I<scalar> will call the native command line direct and no such emulation
1433of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1434
e41182b5
GS
1435=item times
1436
1437Only the first entry returned is nonzero. (S<Mac OS>)
1438
1439"cumulative" times will be bogus. On anything other than Windows NT,
1440"system" time will be bogus, and "user" time is actually the time
1441returned by the clock() function in the C runtime library. (Win32)
1442
b8099c3d
CN
1443Not useful. (S<RISC OS>)
1444
e41182b5
GS
1445=item truncate FILEHANDLE,LENGTH
1446
1447=item truncate EXPR,LENGTH
1448
1449Not implemented. (VMS)
1450
495c5fdc
GP
1451Truncation to zero-length only. (VOS)
1452
4cfdb94f
GS
1453If a FILEHANDLE is supplied, it must be writable and opened in append
1454mode (i.e., use C<open(FH, '>>filename')>
1455or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1456should not be held open elsewhere. (Win32)
1457
e41182b5
GS
1458=item umask EXPR
1459
1460=item umask
1461
1462Returns undef where unavailable, as of version 5.005.
1463
1464=item utime LIST
1465
b8099c3d 1466Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1467
322422de
GS
1468May not behave as expected. Behavior depends on the C runtime
1469library's implementation of utime(), and the filesystem being
1470used. The FAT filesystem typically does not support an "access
1471time" field, and it may limit timestamps to a granularity of
1472two seconds. (Win32)
e41182b5
GS
1473
1474=item wait
1475
1476=item waitpid PID,FLAGS
1477
495c5fdc 1478Not implemented. (S<Mac OS>, VOS)
e41182b5
GS
1479
1480Can only be applied to process handles returned for processes spawned
1481using C<system(1, ...)>. (Win32)
1482
b8099c3d
CN
1483Not useful. (S<RISC OS>)
1484
e41182b5
GS
1485=back
1486
b8099c3d
CN
1487=head1 CHANGES
1488
1489=over 4
1490
495c5fdc
GP
1491=item 1.35, 9 September 1998
1492
1493Updated for Stratus VOS.
1494
0a47030a
GS
1495=item 1.33, 06 August 1998
1496
1497Integrate more minor changes.
1498
dd9f0070
CN
1499=item 1.32, 05 August 1998
1500
1501Integrate more minor changes.
1502
b8099c3d
CN
1503=item 1.30, 03 August 1998
1504
1505Major update for RISC OS, other minor changes.
1506
1507=item 1.23, 10 July 1998
1508
1509First public release with perl5.005.
1510
1511=back
e41182b5
GS
1512
1513=head1 AUTHORS / CONTRIBUTORS
1514
dd9f0070 1515Abigail E<lt>abigail@fnx.comE<gt>,
bd3fa61c 1516Charles Bailey E<lt>bailey@newman.upenn.eduE<gt>,
dd9f0070 1517Graham Barr E<lt>gbarr@pobox.comE<gt>,
e41182b5 1518Tom Christiansen E<lt>tchrist@perl.comE<gt>,
dd9f0070
CN
1519Nicholas Clark E<lt>Nicholas.Clark@liverpool.ac.ukE<gt>,
1520Andy Dougherty E<lt>doughera@lafcol.lafayette.eduE<gt>,
1521Dominic Dunlop E<lt>domo@vo.luE<gt>,
495c5fdc 1522Paul Green E<lt>Paul_Green@stratus.comE<gt>,
dd9f0070
CN
1523M.J.T. Guy E<lt>mjtg@cus.cam.ac.ukE<gt>,
1524Luther Huffman E<lt>lutherh@stratcom.comE<gt>,
1525Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>,
322422de 1526Andreas J. KE<ouml>nig E<lt>koenig@kulturbox.deE<gt>,
dd9f0070 1527Andrew M. Langmead E<lt>aml@world.std.comE<gt>,
e41182b5 1528Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>,
dd9f0070 1529Chris Nandor E<lt>pudge@pobox.comE<gt>,
322422de 1530Matthias Neeracher E<lt>neeri@iis.ee.ethz.chE<gt>,
e41182b5 1531Gary Ng E<lt>71564.1743@CompuServe.COME<gt>,
e41182b5 1532Tom Phoenix E<lt>rootbeer@teleport.comE<gt>,
dd9f0070 1533Peter Prymmer E<lt>pvhp@forte.comE<gt>,
322422de 1534Hugo van der Sanden E<lt>hv@crypt0.demon.co.ukE<gt>,
dd9f0070
CN
1535Gurusamy Sarathy E<lt>gsar@umich.eduE<gt>,
1536Paul J. Schinder E<lt>schinder@pobox.comE<gt>,
e41182b5 1537Dan Sugalski E<lt>sugalskd@ous.eduE<gt>,
dd9f0070 1538Nathan Torkington E<lt>gnat@frii.comE<gt>.
e41182b5
GS
1539
1540This document is maintained by Chris Nandor.
1541
1542=head1 VERSION
1543
495c5fdc
GP
1544Version 1.35, last modified 09 September 1998.
1545
0a47030a 1546
e41182b5 1547