This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Regenerate Changes
[perl5.git] / pod / perlport.pod
CommitLineData
e41182b5
GS
1=head1 NAME
2
3perlport - Writing portable Perl
4
e41182b5
GS
5=head1 DESCRIPTION
6
b7df3edc
GS
7Perl runs on numerous operating systems. While most of them share
8much in common, they also have their own unique features.
e41182b5
GS
9
10This document is meant to help you to find out what constitutes portable
b7df3edc 11Perl code. That way once you make a decision to write portably,
e41182b5
GS
12you know where the lines are drawn, and you can stay within them.
13
b7df3edc
GS
14There is a tradeoff between taking full advantage of one particular
15type of computer and taking advantage of a full range of them.
16Naturally, as you broaden your range and become more diverse, the
17common factors drop, and you are left with an increasingly smaller
18area of common ground in which you can operate to accomplish a
19particular task. Thus, when you begin attacking a problem, it is
20important to consider under which part of the tradeoff curve you
21want to operate. Specifically, you must decide whether it is
22important that the task that you are coding have the full generality
23of being portable, or whether to just get the job done right now.
24This is the hardest choice to be made. The rest is easy, because
25Perl provides many choices, whichever way you want to approach your
0a47030a
GS
26problem.
27
28Looking at it another way, writing portable code is usually about
b7df3edc
GS
29willfully limiting your available choices. Naturally, it takes
30discipline and sacrifice to do that. The product of portability
31and convenience may be a constant. You have been warned.
e41182b5
GS
32
33Be aware of two important points:
34
35=over 4
36
37=item Not all Perl programs have to be portable
38
b7df3edc 39There is no reason you should not use Perl as a language to glue Unix
e41182b5
GS
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
b7df3edc 44=item Nearly all of Perl already I<is> portable
e41182b5
GS
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
6ab3f9cb 50without modification. But there are some significant issues in
e41182b5
GS
51writing portable code, and this document is entirely about those issues.
52
53=back
54
b7df3edc
GS
55Here's the general rule: When you approach a task commonly done
56using a whole range of platforms, think about writing portable
e41182b5
GS
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
b7df3edc
GS
64When the code will run on only two or three operating systems, you
65may need to consider only the differences of those particular systems.
66The important thing is to decide where the code will run and to be
0a47030a
GS
67deliberate in your decision.
68
69The material below is separated into three main sections: main issues of
7ee27b7c 70portability (L<"ISSUES">), platform-specific issues (L<"PLATFORMS">), and
b7df3edc 71built-in perl functions that behave differently on various ports
7ee27b7c 72(L<"FUNCTION IMPLEMENTATIONS">).
e41182b5
GS
73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
b7df3edc 76all of which are in a state of constant evolution. Thus, this material
e41182b5 77should be considered a perpetual work in progress
cc07ed0b 78(C<< <IMG SRC="yellow_sign.gif" ALT="Under Construction"> >>).
e41182b5 79
e41182b5
GS
80=head1 ISSUES
81
82=head2 Newlines
83
638bc118 84In most operating systems, lines in files are terminated by newlines.
e41182b5 85Just what is used as a newline may vary from OS to OS. Unix
b7df3edc 86traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>,
e41182b5
GS
87and S<Mac OS> uses C<\015>.
88
b7df3edc
GS
89Perl uses C<\n> to represent the "logical" newline, where what is
90logical may depend on the platform in use. In MacPerl, C<\n> always
91means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
92when accessing a file in "text" mode, STDIO translates it to (or
56d7751a 93from) C<\015\012>, depending on whether you're reading or writing.
b7df3edc
GS
94Unix does the same thing on ttys in canonical mode. C<\015\012>
95is commonly referred to as CRLF.
96
31bb23b1
XN
97To trim trailing newlines from text lines use chomp(). With default
98settings that function looks for a trailing C<\n> character and thus
99trims in a portable way.
5b3eff12
MS
100
101When dealing with binary files (or text files in binary mode) be sure
102to explicitly set $/ to the appropriate value for your file format
103before using chomp().
104
b7df3edc
GS
105Because of the "text" mode translation, DOSish perls have limitations
106in using C<seek> and C<tell> on a file accessed in "text" mode.
107Stick to C<seek>-ing to locations you got from C<tell> (and no
108others), and you are usually free to use C<seek> and C<tell> even
109in "text" mode. Using C<seek> or C<tell> or other file operations
110may be non-portable. If you use C<binmode> on a file, however, you
111can usually C<seek> and C<tell> with arbitrary values in safety.
e41182b5
GS
112
113A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 114everywhere. When using protocols such as common Internet protocols,
e41182b5
GS
115C<\012> and C<\015> are called for specifically, and the values of
116the logical C<\n> and C<\r> (carriage return) are not reliable.
117
118 print SOCKET "Hi there, client!\r\n"; # WRONG
119 print SOCKET "Hi there, client!\015\012"; # RIGHT
120
0a47030a
GS
121However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
122and unsightly, as well as confusing to those maintaining the code. As
6ab3f9cb 123such, the Socket module supplies the Right Thing for those who want it.
e41182b5
GS
124
125 use Socket qw(:DEFAULT :crlf);
126 print SOCKET "Hi there, client!$CRLF" # RIGHT
127
6ab3f9cb 128When reading from a socket, remember that the default input record
b7df3edc
GS
129separator C<$/> is C<\n>, but robust socket code will recognize as
130either C<\012> or C<\015\012> as end of line:
e41182b5
GS
131
132 while (<SOCKET>) {
133 # ...
134 }
135
b7df3edc
GS
136Because both CRLF and LF end in LF, the input record separator can
137be set to LF and any CR stripped later. Better to write:
e41182b5
GS
138
139 use Socket qw(:DEFAULT :crlf);
140 local($/) = 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
b7df3edc
GS
147This example is preferred over the previous one--even for Unix
148platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
e41182b5
GS
149(and there was much rejoicing).
150
6ab3f9cb 151Similarly, functions that return text data--such as a function that
b7df3edc
GS
152fetches a web page--should sometimes translate newlines before
153returning the data, if they've not yet been translated to the local
154newline representation. A single line of code will often suffice:
2ee0eb3c 155
b7df3edc
GS
156 $data =~ s/\015?\012/\n/g;
157 return $data;
2ee0eb3c 158
6ab3f9cb
GS
159Some of this may be confusing. Here's a handy reference to the ASCII CR
160and LF characters. You can print it out and stick it in your wallet.
161
74555b7a
PP
162 LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
163 CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
6ab3f9cb
GS
164
165 | Unix | DOS | Mac |
166 ---------------------------
167 \n | LF | LF | CR |
168 \r | CR | CR | LF |
169 \n * | LF | CRLF | CR |
170 \r * | CR | CR | LF |
171 ---------------------------
172 * text-mode STDIO
173
b7df3edc
GS
174The Unix column assumes that you are not accessing a serial line
175(like a tty) in canonical mode. If you are, then CR on input becomes
176"\n", and "\n" on output becomes CRLF.
177
6ab3f9cb 178These are just the most common definitions of C<\n> and C<\r> in Perl.
522b859a
JH
179There may well be others. For example, on an EBCDIC implementation
180such as z/OS (OS/390) or OS/400 (using the ILE, the PASE is ASCII-based)
181the above material is similar to "Unix" but the code numbers change:
74555b7a 182
d770bc45
ST
183 LF eq \025 eq \x15 eq \cU eq chr(21) eq CP-1047 21
184 LF eq \045 eq \x25 eq chr(37) eq CP-0037 37
74555b7a
PP
185 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
186 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
187
188 | z/OS | OS/400 |
189 ----------------------
190 \n | LF | LF |
191 \r | CR | CR |
192 \n * | LF | LF |
193 \r * | CR | CR |
194 ----------------------
195 * text-mode STDIO
6ab3f9cb 196
322422de
GS
197=head2 Numbers endianness and Width
198
199Different CPUs store integers and floating point numbers in different
200orders (called I<endianness>) and widths (32-bit and 64-bit being the
b7df3edc
GS
201most common today). This affects your programs when they attempt to transfer
202numbers in binary format from one CPU architecture to another,
203usually either "live" via network connection, or by storing the
204numbers to secondary storage such as a disk file or tape.
322422de 205
b7df3edc 206Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 207little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
b84d4f81
JH
208decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2090x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
210Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
211them in big-endian mode. To avoid this problem in network (socket)
212connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
213"network" orders. These are guaranteed to be portable.
322422de 214
7a4d2905 215As of perl 5.9.2, you can also use the C<E<gt>> and C<E<lt>> modifiers
1109a392
MHM
216to force big- or little-endian byte-order. This is useful if you want
217to store signed integers or 64-bit integers, for example.
218
d1e3b762
GS
219You can explore the endianness of your platform by unpacking a
220data structure packed in native format such as:
221
222 print unpack("h*", pack("s2", 1, 2)), "\n";
223 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
224 # '00100020' on e.g. Motorola 68040
225
226If you need to distinguish between endian architectures you could use
227either of the variables set like so:
228
229 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 230 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 231
b7df3edc
GS
232Differing widths can cause truncation even between platforms of equal
233endianness. The platform of shorter width loses the upper parts of the
322422de
GS
234number. There is no good solution for this problem except to avoid
235transferring or storing raw binary numbers.
236
b7df3edc 237One can circumnavigate both these problems in two ways. Either
322422de 238transfer and store numbers always in text format, instead of raw
b7df3edc 239binary, or else consider using modules like Data::Dumper (included in
83df6a1d
JH
240the standard distribution as of Perl 5.005) and Storable (included as
241of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 242
979699d9
JH
243The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
244how far EBCDIC, or more precisely UTF-EBCDIC will go.
245
433acd8a 246=head2 Files and Filesystems
e41182b5
GS
247
248Most platforms these days structure files in a hierarchical fashion.
b7df3edc 249So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 250notion of a "path" to uniquely identify a file on the system. How
b7df3edc 251that path is really written, though, differs considerably.
e41182b5 252
4375e838 253Although similar, file path specifications differ between Unix,
b7df3edc
GS
254Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
255Unix, for example, is one of the few OSes that has the elegant idea
256of a single root directory.
322422de 257
6ab3f9cb
GS
258DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
259as path separator, or in their own idiosyncratic ways (such as having
260several root directories and various "unrooted" device files such NIL:
261and LPT:).
322422de
GS
262
263S<Mac OS> uses C<:> as a path separator instead of C</>.
264
6ab3f9cb
GS
265The filesystem may support neither hard links (C<link>) nor
266symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 267
6ab3f9cb 268The filesystem may support neither access timestamp nor change
433acd8a
JH
269timestamp (meaning that about the only portable timestamp is the
270modification timestamp), or one second granularity of any timestamps
271(e.g. the FAT filesystem limits the time granularity to two seconds).
272
74555b7a 273The "inode change timestamp" (the C<-C> filetest) may really be the
95a3fe12
MS
274"creation timestamp" (which it is not in UNIX).
275
495c5fdc
GP
276VOS perl can emulate Unix filenames with C</> as path separator. The
277native pathname characters greater-than, less-than, number-sign, and
278percent-sign are always accepted.
279
6ab3f9cb 280S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 281separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 282signal filesystems and disk names.
e41182b5 283
a1667ba3
JH
284Don't assume UNIX filesystem access semantics: that read, write,
285and execute are all the permissions there are, and even if they exist,
286that their semantics (for example what do r, w, and x mean on
287a directory) are the UNIX ones. The various UNIX/POSIX compatibility
288layers usually try to make interfaces like chmod() work, but sometimes
289there simply is no good mapping.
290
b7df3edc
GS
291If all this is intimidating, have no (well, maybe only a little)
292fear. There are modules that can help. The File::Spec modules
293provide methods to do the Right Thing on whatever platform happens
294to be running the program.
e41182b5 295
6ab3f9cb
GS
296 use File::Spec::Functions;
297 chdir(updir()); # go up one directory
298 $file = catfile(curdir(), 'temp', 'file.txt');
e41182b5
GS
299 # on Unix and Win32, './temp/file.txt'
300 # on Mac OS, ':temp:file.txt'
d1e3b762 301 # on VMS, '[.temp]file.txt'
e41182b5 302
b7df3edc 303File::Spec is available in the standard distribution as of version
d1e3b762
GS
3045.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
305and some versions of perl come with version 0.6. If File::Spec
306is not updated to 0.7 or later, you must use the object-oriented
307interface from File::Spec (or upgrade File::Spec).
e41182b5 308
b7df3edc
GS
309In general, production code should not have file paths hardcoded.
310Making them user-supplied or read from a configuration file is
311better, keeping in mind that file path syntax varies on different
312machines.
e41182b5
GS
313
314This is especially noticeable in scripts like Makefiles and test suites,
315which often assume C</> as a path separator for subdirectories.
316
b7df3edc 317Also of use is File::Basename from the standard distribution, which
e41182b5
GS
318splits a pathname into pieces (base filename, full path to directory,
319and file suffix).
320
19799a22 321Even when on a single platform (if you can call Unix a single platform),
b7df3edc 322remember not to count on the existence or the contents of particular
3c075c7d 323system-specific files or directories, like F</etc/passwd>,
b7df3edc
GS
324F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
325example, F</etc/passwd> may exist but not contain the encrypted
326passwords, because the system is using some form of enhanced security.
327Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 328If code does need to rely on such a file, include a description of the
b7df3edc 329file and its format in the code's documentation, then make it easy for
3c075c7d
CN
330the user to override the default location of the file.
331
b7df3edc
GS
332Don't assume a text file will end with a newline. They should,
333but people forget.
e41182b5 334
ec481373
JH
335Do not have two files or directories of the same name with different
336case, like F<test.pl> and F<Test.pl>, as many platforms have
337case-insensitive (or at least case-forgiving) filenames. Also, try
338not to have non-word characters (except for C<.>) in the names, and
339keep them to the 8.3 convention, for maximum portability, onerous a
340burden though this may appear.
dd9f0070 341
b7df3edc
GS
342Likewise, when using the AutoSplit module, try to keep your functions to
3438.3 naming and case-insensitive conventions; or, at the least,
dd9f0070
CN
344make it so the resulting files have a unique (case-insensitively)
345first 8 characters.
346
ec481373
JH
347Whitespace in filenames is tolerated on most systems, but not all,
348and even on systems where it might be tolerated, some utilities
fe829689 349might become confused by such whitespace.
ec481373 350
016930a6
JM
351Many systems (DOS, VMS ODS-2) cannot have more than one C<.> in their
352filenames.
433acd8a 353
c47ff5f1 354Don't assume C<< > >> won't be the first character of a filename.
fe829689
PN
355Always use C<< < >> explicitly to open a file for reading, or even
356better, use the three-arg version of open, unless you want the user to
357be able to specify a pipe open.
0a47030a 358
fe829689 359 open(FILE, '<', $existing_file) or die $!;
0a47030a 360
6ab3f9cb
GS
361If filenames might use strange characters, it is safest to open it
362with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 363translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 364be the wrong thing to do. (Sometimes, though, it's the right thing.)
fe829689
PN
365Three-arg open can also help protect against this translation in cases
366where it is undesirable.
e41182b5 367
ec481373 368Don't use C<:> as a part of a filename since many systems use that for
8939ba94 369their own semantics (Mac OS Classic for separating pathname components,
ec481373 370many networking schemes and utilities for separating the nodename and
08fef530
JH
371the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
372C<|>.
ec481373 373
e1516da7
JH
374Don't assume that in pathnames you can collapse two leading slashes
375C<//> into one: some networking and clustering filesystems have special
376semantics for that. Let the operating system to sort it out.
377
ec481373
JH
378The I<portable filename characters> as defined by ANSI C are
379
380 a b c d e f g h i j k l m n o p q r t u v w x y z
381 A B C D E F G H I J K L M N O P Q R T U V W X Y Z
382 0 1 2 3 4 5 6 7 8 9
383 . _ -
384
08fef530 385and the "-" shouldn't be the first character. If you want to be
e1516da7
JH
386hypercorrect, stay case-insensitive and within the 8.3 naming
387convention (all the files and directories have to be unique within one
388directory if their names are lowercased and truncated to eight
389characters before the C<.>, if any, and to three characters after the
390C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 391
e41182b5
GS
392=head2 System Interaction
393
b7df3edc
GS
394Not all platforms provide a command line. These are usually platforms
395that rely primarily on a Graphical User Interface (GUI) for user
396interaction. A program requiring a command line interface might
397not work everywhere. This is probably for the user of the program
398to deal with, so don't stay up late worrying about it.
e41182b5 399
c87488a3
HS
400Some platforms can't delete or rename files held open by the system,
401this limitation may also apply to changing filesystem metainformation
402like file permissions or owners. Remember to C<close> files when you
403are done with them. Don't C<unlink> or C<rename> an open file. Don't
404C<tie> or C<open> a file already tied or opened; C<untie> or C<close>
405it first.
e41182b5 406
0a47030a
GS
407Don't open the same file more than once at a time for writing, as some
408operating systems put mandatory locks on such files.
409
73e9292c
JH
410Don't assume that write/modify permission on a directory gives the
411right to add or delete files/directories in that directory. That is
412filesystem specific: in some filesystems you need write/modify
413permission also (or even just) in the file/directory itself. In some
414filesystems (AFS, DFS) the permission to add/delete directory entries
415is a completely separate permission.
416
417Don't assume that a single C<unlink> completely gets rid of the file:
418some filesystems (most notably the ones in VMS) have versioned
419filesystems, and unlink() removes only the most recent one (it doesn't
420remove all the versions because by default the native tools on those
421platforms remove just the most recent version, too). The portable
422idiom to remove all the versions of a file is
423
94bb614c 424 1 while unlink "file";
73e9292c
JH
425
426This will terminate if the file is undeleteable for some reason
427(protected, not there, and so on).
428
e41182b5 429Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 430Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 431case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 432if you really have to, make it conditional on C<$^O ne 'VMS'> since in
4a0d0822
JH
433VMS the C<%ENV> table is much more than a per-process key-value string
434table.
e41182b5 435
d1e3b762 436Don't count on signals or C<%SIG> for anything.
e41182b5
GS
437
438Don't count on filename globbing. Use C<opendir>, C<readdir>, and
439C<closedir> instead.
440
b8099c3d 441Don't count on per-program environment variables, or per-program current
dd9f0070 442directories.
b8099c3d 443
c87488a3
HS
444Don't count on specific values of C<$!>, neither numeric nor
445especially the strings values-- users may switch their locales causing
446error messages to be translated into their languages. If you can
447trust a POSIXish environment, you can portably use the symbols defined
448by the Errno module, like ENOENT. And don't trust on the values of C<$!>
449at all except immediately after a failed system call.
3c075c7d 450
a10d74f3
PG
451=head2 Command names versus file pathnames
452
453Don't assume that the name used to invoke a command or program with
454C<system> or C<exec> can also be used to test for the existence of the
455file that holds the executable code for that command or program.
68fb0eb7
PG
456First, many systems have "internal" commands that are built-in to the
457shell or OS and while these commands can be invoked, there is no
458corresponding file. Second, some operating systems (e.g., Cygwin,
459DJGPP, OS/2, and VOS) have required suffixes for executable files;
460these suffixes are generally permitted on the command name but are not
a10d74f3
PG
461required. Thus, a command like "perl" might exist in a file named
462"perl", "perl.exe", or "perl.pm", depending on the operating system.
463The variable "_exe" in the Config module holds the executable suffix,
68fb0eb7
PG
464if any. Third, the VMS port carefully sets up $^X and
465$Config{perlpath} so that no further processing is required. This is
466just as well, because the matching regular expression used below would
467then have to deal with a possible trailing version number in the VMS
468file name.
a10d74f3
PG
469
470To convert $^X to a file pathname, taking account of the requirements
471of the various operating system possibilities, say:
7ee27b7c 472
a10d74f3 473 use Config;
a10d74f3 474 $thisperl = $^X;
68fb0eb7
PG
475 if ($^O ne 'VMS')
476 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3
PG
477
478To convert $Config{perlpath} to a file pathname, say:
7ee27b7c 479
a10d74f3 480 use Config;
68fb0eb7
PG
481 $thisperl = $Config{perlpath};
482 if ($^O ne 'VMS')
483 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3 484
7137b697
JH
485=head2 Networking
486
487Don't assume that you can reach the public Internet.
488
489Don't assume that there is only one way to get through firewalls
490to the public Internet.
491
932f293e
JH
492Don't assume that you can reach outside world through any other port
493than 80, or some web proxy. ftp is blocked by many firewalls.
494
dbc6a9ce
JH
495Don't assume that you can send email by connecting to the local SMTP port.
496
7137b697 497Don't assume that you can reach yourself or any node by the name
dbc6a9ce 498'localhost'. The same goes for '127.0.0.1'. You will have to try both.
932f293e 499
86feb2c5
JH
500Don't assume that the host has only one network card, or that it
501can't bind to many virtual IP addresses.
932f293e
JH
502
503Don't assume a particular network device name.
7137b697 504
dbc6a9ce 505Don't assume a particular set of ioctl()s will work.
7137b697
JH
506
507Don't assume that you can ping hosts and get replies.
508
dbc6a9ce
JH
509Don't assume that any particular port (service) will respond.
510
7ee27b7c 511Don't assume that Sys::Hostname (or any other API or command)
dbc6a9ce
JH
512returns either a fully qualified hostname or a non-qualified hostname:
513it all depends on how the system had been configured. Also remember
514things like DHCP and NAT-- the hostname you get back might not be very
515useful.
516
932f293e
JH
517All the above "don't":s may look daunting, and they are -- but the key
518is to degrade gracefully if one cannot reach the particular network
519service one wants. Croaking or hanging do not look very professional.
520
e41182b5
GS
521=head2 Interprocess Communication (IPC)
522
b7df3edc
GS
523In general, don't directly access the system in code meant to be
524portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
525C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
526that makes being a perl hacker worth being.
e41182b5
GS
527
528Commands that launch external processes are generally supported on
b7df3edc
GS
529most platforms (though many of them do not support any type of
530forking). The problem with using them arises from what you invoke
531them on. External tools are often named differently on different
4375e838 532platforms, may not be available in the same location, might accept
b7df3edc
GS
533different arguments, can behave differently, and often present their
534results in a platform-dependent way. Thus, you should seldom depend
535on them to produce consistent results. (Then again, if you're calling
536I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 537
b7df3edc 538One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 539
b7df3edc
GS
540 open(MAIL, '|/usr/lib/sendmail -t')
541 or die "cannot fork sendmail: $!";
e41182b5
GS
542
543This is fine for systems programming when sendmail is known to be
544available. But it is not fine for many non-Unix systems, and even
545some Unix systems that may not have sendmail installed. If a portable
b7df3edc
GS
546solution is needed, see the various distributions on CPAN that deal
547with it. Mail::Mailer and Mail::Send in the MailTools distribution are
548commonly used, and provide several mailing methods, including mail,
549sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
550not available. Mail::Sendmail is a standalone module that provides
551simple, platform-independent mailing.
552
553The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
554even on all Unix platforms.
e41182b5 555
a81e5e2e
A
556Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
557bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
558both forms just pack the four bytes into network order. That this
559would be equal to the C language C<in_addr> struct (which is what the
560socket code internally uses) is not guaranteed. To be portable use
561the routines of the Socket extension, such as C<inet_aton()>,
562C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 563
e41182b5 564The rule of thumb for portable code is: Do it all in portable Perl, or
0a47030a
GS
565use a module (that may internally implement it with platform-specific
566code, but expose a common interface).
e41182b5 567
e41182b5
GS
568=head2 External Subroutines (XS)
569
b7df3edc 570XS code can usually be made to work with any platform, but dependent
e41182b5
GS
571libraries, header files, etc., might not be readily available or
572portable, or the XS code itself might be platform-specific, just as Perl
573code might be. If the libraries and headers are portable, then it is
574normally reasonable to make sure the XS code is portable, too.
575
b7df3edc
GS
576A different type of portability issue arises when writing XS code:
577availability of a C compiler on the end-user's system. C brings
578with it its own portability issues, and writing XS code will expose
579you to some of those. Writing purely in Perl is an easier way to
e41182b5
GS
580achieve portability.
581
e41182b5
GS
582=head2 Standard Modules
583
584In general, the standard modules work across platforms. Notable
6ab3f9cb 585exceptions are the CPAN module (which currently makes connections to external
e41182b5 586programs that may not be available), platform-specific modules (like
6ab3f9cb 587ExtUtils::MM_VMS), and DBM modules.
e41182b5 588
b7df3edc 589There is no one DBM module available on all platforms.
6ab3f9cb
GS
590SDBM_File and the others are generally available on all Unix and DOSish
591ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 592available.
e41182b5
GS
593
594The good news is that at least some DBM module should be available, and
6ab3f9cb 595AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
GS
596the code needs to be fairly strict, dropping to the greatest common
597factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 598work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 599
e41182b5
GS
600=head2 Time and Date
601
0a47030a 602The system's notion of time of day and calendar date is controlled in
b7df3edc 603widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a 604and even if it is, don't assume that you can control the timezone through
c87488a3
HS
605that variable. Don't assume anything about the three-letter timezone
606abbreviations (for example that MST would be the Mountain Standard Time,
607it's been known to stand for Moscow Standard Time). If you need to
608use timezones, express them in some unambiguous format like the
609exact number of minutes offset from UTC, or the POSIX timezone
610format.
e41182b5 611
322422de 612Don't assume that the epoch starts at 00:00:00, January 1, 1970,
c87488a3
HS
613because that is OS- and implementation-specific. It is better to
614store a date in an unambiguous representation. The ISO 8601 standard
615defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH-MM-SS
616(that's a literal "T" separating the date from the time).
617Please do use the ISO 8601 instead of making us to guess what
618date 02/03/04 might be. ISO 8601 even sorts nicely as-is.
619A text representation (like "1987-12-18") can be easily converted
620into an OS-specific value using a module like Date::Parse.
621An array of values, such as those returned by C<localtime>, can be
622converted to an OS-specific representation using Time::Local.
322422de 623
19799a22
GS
624When calculating specific times, such as for tests in time or date modules,
625it may be appropriate to calculate an offset for the epoch.
b7df3edc 626
19799a22
GS
627 require Time::Local;
628 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 629
19799a22
GS
630The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
631some large number. C<$offset> can then be added to a Unix time value
632to get what should be the proper value on any system.
322422de 633
bbac04ed
RGS
634On Windows (at least), you shouldn't pass a negative value to C<gmtime> or
635C<localtime>.
636
322422de
GS
637=head2 Character sets and character encoding
638
ec481373
JH
639Assume very little about character sets.
640
641Assume nothing about numerical values (C<ord>, C<chr>) of characters.
642Do not use explicit code point ranges (like \xHH-\xHH); use for
643example symbolic character classes like C<[:print:]>.
644
645Do not assume that the alphabetic characters are encoded contiguously
646(in the numeric sense). There may be gaps.
647
648Do not assume anything about the ordering of the characters.
649The lowercase letters may come before or after the uppercase letters;
b432a672
AL
650the lowercase and uppercase may be interlaced so that both "a" and "A"
651come before "b"; the accented and other international characters may
652be interlaced so that E<auml> comes before "b".
322422de
GS
653
654=head2 Internationalisation
655
b7df3edc
GS
656If you may assume POSIX (a rather large assumption), you may read
657more about the POSIX locale system from L<perllocale>. The locale
658system at least attempts to make things a little bit more portable,
659or at least more convenient and native-friendly for non-English
660users. The system affects character sets and encoding, and date
661and time formatting--amongst other things.
e41182b5 662
c87488a3
HS
663If you really want to be international, you should consider Unicode.
664See L<perluniintro> and L<perlunicode> for more information.
665
11264fdb
JH
666If you want to use non-ASCII bytes (outside the bytes 0x00..0x7f) in
667the "source code" of your code, to be portable you have to be explicit
668about what bytes they are. Someone might for example be using your
669code under a UTF-8 locale, in which case random native bytes might be
670illegal ("Malformed UTF-8 ...") This means that for example embedding
671ISO 8859-1 bytes beyond 0x7f into your strings might cause trouble
672later. If the bytes are native 8-bit bytes, you can use the C<bytes>
673pragma. If the bytes are in a string (regular expression being a
674curious string), you can often also use the C<\xHH> notation instead
2575c402
JW
675of embedding the bytes as-is. (If you want to write your code in UTF-8,
676you can use the C<utf8>.) The C<bytes> and C<utf8> pragmata are
677available since Perl 5.6.0.
11264fdb 678
e41182b5
GS
679=head2 System Resources
680
0a47030a
GS
681If your code is destined for systems with severely constrained (or
682missing!) virtual memory systems then you want to be I<especially> mindful
683of avoiding wasteful constructs such as:
e41182b5
GS
684
685 # NOTE: this is no longer "bad" in perl5.005
686 for (0..10000000) {} # bad
687 for (my $x = 0; $x <= 10000000; ++$x) {} # good
688
689 @lines = <VERY_LARGE_FILE>; # bad
690
691 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 692 $file = join('', <FILE>); # better
e41182b5 693
b7df3edc
GS
694The last two constructs may appear unintuitive to most people. The
695first repeatedly grows a string, whereas the second allocates a
696large chunk of memory in one go. On some systems, the second is
697more efficient that the first.
0a47030a 698
e41182b5
GS
699=head2 Security
700
b7df3edc
GS
701Most multi-user platforms provide basic levels of security, usually
702implemented at the filesystem level. Some, however, do
a1667ba3 703not-- unfortunately. Thus the notion of user id, or "home" directory,
b7df3edc
GS
704or even the state of being logged-in, may be unrecognizable on many
705platforms. If you write programs that are security-conscious, it
706is usually best to know what type of system you will be running
707under so that you can write code explicitly for that platform (or
708class of platforms).
0a47030a 709
a1667ba3
JH
710Don't assume the UNIX filesystem access semantics: the operating
711system or the filesystem may be using some ACL systems, which are
712richer languages than the usual rwx. Even if the rwx exist,
713their semantics might be different.
714
715(From security viewpoint testing for permissions before attempting to
716do something is silly anyway: if one tries this, there is potential
717for race conditions-- someone or something might change the
718permissions between the permissions check and the actual operation.
719Just try the operation.)
720
721Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 722expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
JH
723for switching identities (or memberships).
724
725Don't assume set-uid and set-gid semantics. (And even if you do,
726think twice: set-uid and set-gid are a known can of security worms.)
727
e41182b5
GS
728=head2 Style
729
730For those times when it is necessary to have platform-specific code,
731consider keeping the platform-specific code in one place, making porting
6ab3f9cb 732to other platforms easier. Use the Config module and the special
0a47030a
GS
733variable C<$^O> to differentiate platforms, as described in
734L<"PLATFORMS">.
e41182b5 735
b7df3edc
GS
736Be careful in the tests you supply with your module or programs.
737Module code may be fully portable, but its tests might not be. This
738often happens when tests spawn off other processes or call external
739programs to aid in the testing, or when (as noted above) the tests
c87488a3
HS
740assume certain things about the filesystem and paths. Be careful not
741to depend on a specific output style for errors, such as when checking
742C<$!> after a failed system call. Using C<$!> for anything else than
743displaying it as output is doubtful (though see the Errno module for
744testing reasonably portably for error value). Some platforms expect
745a certain output format, and Perl on those platforms may have been
746adjusted accordingly. Most specifically, don't anchor a regex when
747testing an error value.
e41182b5 748
0a47030a 749=head1 CPAN Testers
e41182b5 750
0a47030a
GS
751Modules uploaded to CPAN are tested by a variety of volunteers on
752different platforms. These CPAN testers are notified by mail of each
e41182b5 753new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 754this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
GS
755
756The purpose of the testing is twofold: one, to help developers fix any
0a47030a 757problems in their code that crop up because of lack of testing on other
b7df3edc 758platforms; two, to provide users with information about whether
0a47030a 759a given module works on a given platform.
e41182b5 760
7ee27b7c
AT
761Also see:
762
e41182b5
GS
763=over 4
764
7ee27b7c
AT
765=item *
766
767Mailing list: cpan-testers@perl.org
768
769=item *
e41182b5 770
7ee27b7c 771Testing results: http://testers.cpan.org/
e41182b5
GS
772
773=back
774
e41182b5
GS
775=head1 PLATFORMS
776
777As of version 5.002, Perl is built with a C<$^O> variable that
778indicates the operating system it was built on. This was implemented
b7df3edc
GS
779to help speed up code that would otherwise have to C<use Config>
780and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
GS
781detailed information about the system, looking into C<%Config> is
782certainly recommended.
783
b7df3edc
GS
784C<%Config> cannot always be trusted, however, because it was built
785at compile time. If perl was built in one place, then transferred
786elsewhere, some values may be wrong. The values may even have been
787edited after the fact.
6ab3f9cb 788
e41182b5
GS
789=head2 Unix
790
791Perl works on a bewildering variety of Unix and Unix-like platforms (see
792e.g. most of the files in the F<hints/> directory in the source code kit).
793On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
794too) is determined either by lowercasing and stripping punctuation from the
795first field of the string returned by typing C<uname -a> (or a similar command)
796at the shell prompt or by testing the file system for the presence of
797uniquely named files such as a kernel or header file. Here, for example,
798are a few of the more popular Unix flavors:
e41182b5 799
b7df3edc 800 uname $^O $Config{'archname'}
6ab3f9cb 801 --------------------------------------------
b7df3edc 802 AIX aix aix
6ab3f9cb 803 BSD/OS bsdos i386-bsdos
e1516da7 804 Darwin darwin darwin
6ab3f9cb
GS
805 dgux dgux AViiON-dgux
806 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 807 FreeBSD freebsd freebsd-i386
d1e3b762 808 Linux linux arm-linux
b7df3edc 809 Linux linux i386-linux
6ab3f9cb
GS
810 Linux linux i586-linux
811 Linux linux ppc-linux
b7df3edc
GS
812 HP-UX hpux PA-RISC1.1
813 IRIX irix irix
b787fad4 814 Mac OS X darwin darwin
d1e3b762
GS
815 MachTen PPC machten powerpc-machten
816 NeXT 3 next next-fat
817 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 818 openbsd openbsd i386-openbsd
b7df3edc 819 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
820 reliantunix-n svr4 RM400-svr4
821 SCO_SV sco_sv i386-sco_sv
822 SINIX-N svr4 RM400-svr4
823 sn4609 unicos CRAY_C90-unicos
824 sn6521 unicosmk t3e-unicosmk
825 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
826 SunOS solaris sun4-solaris
827 SunOS solaris i86pc-solaris
828 SunOS4 sunos sun4-sunos
e41182b5 829
b7df3edc
GS
830Because the value of C<$Config{archname}> may depend on the
831hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 832
e41182b5
GS
833=head2 DOS and Derivatives
834
b7df3edc 835Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
836systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
837bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 838Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
839be aware that each of these file specifications may have subtle
840differences:
841
842 $filespec0 = "c:/foo/bar/file.txt";
843 $filespec1 = "c:\\foo\\bar\\file.txt";
844 $filespec2 = 'c:\foo\bar\file.txt';
845 $filespec3 = 'c:\\foo\\bar\\file.txt';
846
b7df3edc
GS
847System calls accept either C</> or C<\> as the path separator.
848However, many command-line utilities of DOS vintage treat C</> as
849the option prefix, so may get confused by filenames containing C</>.
850Aside from calling any external programs, C</> will work just fine,
851and probably better, as it is more consistent with popular usage,
852and avoids the problem of remembering what to backwhack and what
853not to.
e41182b5 854
b7df3edc
GS
855The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
856the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 857filesystems you may have to be careful about case returned with functions
e41182b5
GS
858like C<readdir> or used with functions like C<open> or C<opendir>.
859
b7df3edc
GS
860DOS also treats several filenames as special, such as AUX, PRN,
861NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
862filenames won't even work if you include an explicit directory
863prefix. It is best to avoid such filenames, if you want your code
864to be portable to DOS and its derivatives. It's hard to know what
865these all are, unfortunately.
e41182b5
GS
866
867Users of these operating systems may also wish to make use of
b7df3edc 868scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
869put wrappers around your scripts.
870
871Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
872and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
873will keep C<\n> translated as C<\012> for that filehandle. Since it is a
874no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
875that deals with binary data. That's assuming you realize in advance
876that your data is in binary. General-purpose programs should
877often assume nothing about their data.
e41182b5 878
b7df3edc 879The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
880DOSish perls are as follows:
881
67ac489e
MS
882 OS $^O $Config{archname} ID Version
883 --------------------------------------------------------
884 MS-DOS dos ?
885 PC-DOS dos ?
886 OS/2 os2 ?
887 Windows 3.1 ? ? 0 3 01
888 Windows 95 MSWin32 MSWin32-x86 1 4 00
889 Windows 98 MSWin32 MSWin32-x86 1 4 10
890 Windows ME MSWin32 MSWin32-x86 1 ?
891 Windows NT MSWin32 MSWin32-x86 2 4 xx
892 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
893 Windows NT MSWin32 MSWin32-ppc 2 4 xx
7ee27b7c
AT
894 Windows 2000 MSWin32 MSWin32-x86 2 5 00
895 Windows XP MSWin32 MSWin32-x86 2 5 01
896 Windows 2003 MSWin32 MSWin32-x86 2 5 02
67ac489e 897 Windows CE MSWin32 ? 3
7ee27b7c 898 Cygwin cygwin cygwin
e41182b5 899
34aaaa84
PP
900The various MSWin32 Perl's can distinguish the OS they are running on
901via the value of the fifth element of the list returned from
902Win32::GetOSVersion(). For example:
903
904 if ($^O eq 'MSWin32') {
905 my @os_version_info = Win32::GetOSVersion();
906 print +('3.1','95','NT')[$os_version_info[4]],"\n";
907 }
908
7939d86b
JH
909There are also Win32::IsWinNT() and Win32::IsWin95(), try C<perldoc Win32>,
910and as of libwin32 0.19 (not part of the core Perl distribution)
911Win32::GetOSName(). The very portable POSIX::uname() will work too:
1d65be3a
JH
912
913 c:\> perl -MPOSIX -we "print join '|', uname"
914 Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86
d99f392e 915
e41182b5
GS
916Also see:
917
918=over 4
919
c997b287 920=item *
e41182b5 921
c997b287
GS
922The djgpp environment for DOS, http://www.delorie.com/djgpp/
923and L<perldos>.
e41182b5 924
c997b287 925=item *
e41182b5 926
c997b287
GS
927The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
928http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
f224927c 929ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
e41182b5 930
c997b287 931=item *
d1e3b762 932
c997b287
GS
933Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
934in L<perlcygwin>.
935
936=item *
937
938The C<Win32::*> modules in L<Win32>.
939
940=item *
941
942The ActiveState Pages, http://www.activestate.com/
943
944=item *
945
946The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 947as L<perlcygwin>), http://www.cygwin.com/
c997b287
GS
948
949=item *
950
951The U/WIN environment for Win32,
cea6626f 952http://www.research.att.com/sw/tools/uwin/
c997b287 953
cea6626f 954=item *
d1e3b762 955
cea6626f 956Build instructions for OS/2, L<perlos2>
d1e3b762 957
e41182b5
GS
958=back
959
dd9f0070 960=head2 S<Mac OS>
e41182b5
GS
961
962Any module requiring XS compilation is right out for most people, because
963MacPerl is built using non-free (and non-cheap!) compilers. Some XS
964modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 965form on CPAN.
e41182b5
GS
966
967Directories are specified as:
968
969 volume:folder:file for absolute pathnames
970 volume:folder: for absolute pathnames
971 :folder:file for relative pathnames
972 :folder: for relative pathnames
973 :file for relative pathnames
974 file for relative pathnames
975
b7df3edc 976Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 977limited to 31 characters, and may include any character except for
b7df3edc 978null and C<:>, which is reserved as the path separator.
e41182b5 979
0a47030a 980Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 981Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
982
983In the MacPerl application, you can't run a program from the command line;
984programs that expect C<@ARGV> to be populated can be edited with something
985like the following, which brings up a dialog box asking for the command
986line arguments.
987
988 if (!@ARGV) {
989 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
990 }
991
b7df3edc 992A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
993pathnames of the files dropped onto the script.
994
b7df3edc
GS
995Mac users can run programs under a type of command line interface
996under MPW (Macintosh Programmer's Workshop, a free development
997environment from Apple). MacPerl was first introduced as an MPW
998tool, and MPW can be used like a shell:
e41182b5
GS
999
1000 perl myscript.plx some arguments
1001
1002ToolServer is another app from Apple that provides access to MPW tools
0a47030a 1003from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
1004C<system>, backticks, and piped C<open>.
1005
1006"S<Mac OS>" is the proper name for the operating system, but the value
1007in C<$^O> is "MacOS". To determine architecture, version, or whether
1008the application or MPW tool version is running, check:
1009
1010 $is_app = $MacPerl::Version =~ /App/;
1011 $is_tool = $MacPerl::Version =~ /MPW/;
1012 ($version) = $MacPerl::Version =~ /^(\S+)/;
1013 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
1014 $is_68k = $MacPerl::Architecture eq 'Mac68K';
1015
b787fad4
JH
1016S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
1017"Classic" environment. There is no "Carbon" version of MacPerl to run
1018under the primary Mac OS X environment. S<Mac OS X> and its Open Source
1019version, Darwin, both run Unix perl natively.
6ab3f9cb 1020
e41182b5
GS
1021Also see:
1022
1023=over 4
1024
c997b287
GS
1025=item *
1026
862b5365 1027MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
1028
1029=item *
1030
862b5365 1031The MacPerl Pages, http://www.macperl.com/ .
e41182b5 1032
c997b287 1033=item *
6ab3f9cb 1034
862b5365 1035The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5 1036
7ee27b7c
AT
1037=item *
1038
1039MPW, ftp://ftp.apple.com/developer/Tool_Chest/Core_Mac_OS_Tools/
1040
e41182b5
GS
1041=back
1042
e41182b5
GS
1043=head2 VMS
1044
c997b287 1045Perl on VMS is discussed in L<perlvms> in the perl distribution.
016930a6
JM
1046
1047The official name of VMS as of this writing is OpenVMS.
1048
b7df3edc 1049Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
1050specifications as in either of the following:
1051
1052 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
1053 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
1054
1055but not a mixture of both as in:
1056
1057 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
1058 Can't open sys$login:/login.com: file specification syntax error
1059
1060Interacting with Perl from the Digital Command Language (DCL) shell
1061often requires a different set of quotation marks than Unix shells do.
1062For example:
1063
1064 $ perl -e "print ""Hello, world.\n"""
1065 Hello, world.
1066
b7df3edc 1067There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
1068you are so inclined. For example:
1069
1070 $ write sys$output "Hello from DCL!"
1071 $ if p1 .eqs. ""
1072 $ then perl -x 'f$environment("PROCEDURE")
1073 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
1074 $ deck/dollars="__END__"
1075 #!/usr/bin/perl
1076
1077 print "Hello from Perl!\n";
1078
1079 __END__
1080 $ endif
1081
1082Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 1083perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5 1084
016930a6
JM
1085The VMS operating system has two filesystems, known as ODS-2 and ODS-5.
1086
1087For ODS-2, filenames are in the format "name.extension;version". The
1088maximum length for filenames is 39 characters, and the maximum length for
e41182b5
GS
1089extensions is also 39 characters. Version is a number from 1 to
109032767. Valid characters are C</[A-Z0-9$_-]/>.
1091
016930a6
JM
1092The ODS-2 filesystem is case-insensitive and does not preserve case.
1093Perl simulates this by converting all filenames to lowercase internally.
1094
1095For ODS-5, filenames may have almost any character in them and can include
1096Unicode characters. Characters that could be misinterpreted by the DCL
1097shell or file parsing utilities need to be prefixed with the C<^>
1098character, or replaced with hexadecimal characters prefixed with the
1099C<^> character. Such prefixing is only needed with the pathnames are
1100in VMS format in applications. Programs that can accept the UNIX format
1101of pathnames do not need the escape characters. The maximum length for
1102filenames is 255 characters. The ODS-5 file system can handle both
1103a case preserved and a case sensitive mode.
1104
1105ODS-5 is only available on the OpenVMS for 64 bit platforms.
1106
1107Support for the extended file specifications is being done as optional
1108settings to preserve backward compatibility with Perl scripts that
1109assume the previous VMS limitations.
1110
1111In general routines on VMS that get a UNIX format file specification
1112should return it in a UNIX format, and when they get a VMS format
1113specification they should return a VMS format unless they are documented
1114to do a conversion.
1115
1116For routines that generate return a file specification, VMS allows setting
1117if the C library which Perl is built on if it will be returned in VMS
1118format or in UNIX format.
1119
1120With the ODS-2 file system, there is not much difference in syntax of
1121filenames without paths for VMS or UNIX. With the extended character
1122set available with ODS-5 there can be a significant difference.
1123
1124Because of this, existing Perl scripts written for VMS were sometimes
1125treating VMS and UNIX filenames interchangeably. Without the extended
1126character set enabled, this behavior will mostly be maintained for
1127backwards compatibility.
1128
1129When extended characters are enabled with ODS-5, the handling of
1130UNIX formatted file specifications is to that of a UNIX system.
1131
1132VMS file specifications without extensions have a trailing dot. An
1133equivalent UNIX file specification should not show the trailing dot.
1134
1135The result of all of this, is that for VMS, for portable scripts, you
1136can not depend on Perl to present the filenames in lowercase, to be
1137case sensitive, and that the filenames could be returned in either
1138UNIX or VMS format.
1139
1140And if a routine returns a file specification, unless it is intended to
1141convert it, it should return it in the same format as it found it.
1142
1143C<readdir> by default has traditionally returned lowercased filenames.
1144When the ODS-5 support is enabled, it will return the exact case of the
1145filename on the disk.
1146
1147Files without extensions have a trailing period on them, so doing a
1148C<readdir> in the default mode with a file named F<A.;5> will
1149return F<a.> when VMS is (though that file could be opened with
0a47030a 1150C<open(FH, 'A')>).
e41182b5 1151
016930a6
JM
1152With support for extended file specifications and if C<opendir> was
1153given a UNIX format directory, a file named F<A.;5> will return F<a>
1154and optionally in the exact case on the disk. When C<opendir> is given
1155a VMS format directory, then C<readdir> should return F<a.>, and
1156again with the optionally the exact case.
1157
f34d0673 1158RMS had an eight level limit on directory depths from any rooted logical
1089a9e3
CB
1159(allowing 16 levels overall) prior to VMS 7.2, and even with versions of
1160VMS on VAX up through 7.3. Hence C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a
1161valid directory specification but C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is
1162not. F<Makefile.PL> authors might have to take this into account, but at
1163least they can refer to the former as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
1164
1165Pumpkings and module integrators can easily see whether files with too many
1166directory levels have snuck into the core by running the following in the
1167top-level source directory:
1168
1169 $ perl -ne "$_=~s/\s+.*//; print if scalar(split /\//) > 8;" < MANIFEST
1170
e41182b5 1171
6ab3f9cb 1172The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
1173process on VMS, is a pure Perl module that can easily be installed on
1174non-VMS platforms and can be helpful for conversions to and from RMS
016930a6
JM
1175native formats. It is also now the only way that you should check to
1176see if VMS is in a case sensitive mode.
e41182b5 1177
5e12dbfa
PP
1178What C<\n> represents depends on the type of file opened. It usually
1179represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
fa11829f 1180C<\000>, C<\040>, or nothing depending on the file organization and
5e12dbfa
PP
1181record format. The VMS::Stdio module provides access to the
1182special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
1183
1184TCP/IP stacks are optional on VMS, so socket routines might not be
1185implemented. UDP sockets may not be supported.
1186
016930a6
JM
1187The TCP/IP library support for all current versions of VMS is dynamically
1188loaded if present, so even if the routines are configured, they may
1189return a status indicating that they are not implemented.
1190
e41182b5
GS
1191The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
1192that you are running on without resorting to loading all of C<%Config>
1193you can examine the content of the C<@INC> array like so:
1194
1195 if (grep(/VMS_AXP/, @INC)) {
1196 print "I'm on Alpha!\n";
6ab3f9cb 1197
e41182b5
GS
1198 } elsif (grep(/VMS_VAX/, @INC)) {
1199 print "I'm on VAX!\n";
6ab3f9cb 1200
016930a6
JM
1201 } elsif (grep(/VMS_IA64/, @INC)) {
1202 print "I'm on IA64!\n";
1203
e41182b5
GS
1204 } else {
1205 print "I'm not so sure about where $^O is...\n";
1206 }
1207
016930a6
JM
1208In general, the significant differences should only be if Perl is running
1209on VMS_VAX or one of the 64 bit OpenVMS platforms.
1210
b7df3edc
GS
1211On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
1212logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 1213calls to C<localtime> are adjusted to count offsets from
b7df3edc 121401-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1215
e41182b5
GS
1216Also see:
1217
1218=over 4
1219
c997b287
GS
1220=item *
1221
1222F<README.vms> (installed as L<README_vms>), L<perlvms>
1223
1224=item *
1225
1089a9e3 1226vmsperl list, vmsperl-subscribe@perl.org
e41182b5 1227
c997b287 1228=item *
e41182b5 1229
c997b287 1230vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1231
1232=back
1233
495c5fdc
GP
1234=head2 VOS
1235
9a997319
JH
1236Perl on VOS is discussed in F<README.vos> in the perl distribution
1237(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1238Unix-style file specifications as in either of the following:
495c5fdc 1239
cc07ed0b
PG
1240 C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
1241 C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
495c5fdc
GP
1242
1243or even a mixture of both as in:
1244
cc07ed0b 1245 C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
495c5fdc 1246
b7df3edc 1247Even though VOS allows the slash character to appear in object
495c5fdc
GP
1248names, because the VOS port of Perl interprets it as a pathname
1249delimiting character, VOS files, directories, or links whose names
1250contain a slash character cannot be processed. Such files must be
a3dfe201
GS
1251renamed before they can be processed by Perl. Note that VOS limits
1252file names to 32 or fewer characters.
495c5fdc 1253
495c5fdc
GP
1254The value of C<$^O> on VOS is "VOS". To determine the architecture that
1255you are running on without resorting to loading all of C<%Config> you
c997b287 1256can examine the content of the @INC array like so:
495c5fdc 1257
24e8e380 1258 if ($^O =~ /VOS/) {
495c5fdc
GP
1259 print "I'm on a Stratus box!\n";
1260 } else {
1261 print "I'm not on a Stratus box!\n";
1262 die;
1263 }
1264
495c5fdc
GP
1265Also see:
1266
1267=over 4
1268
c997b287 1269=item *
495c5fdc 1270
cc07ed0b 1271F<README.vos> (installed as L<perlvos>)
c997b287
GS
1272
1273=item *
1274
1275The VOS mailing list.
495c5fdc
GP
1276
1277There is no specific mailing list for Perl on VOS. You can post
1278comments to the comp.sys.stratus newsgroup, or subscribe to the general
cc07ed0b 1279Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
495c5fdc
GP
1280the message body to majordomo@list.stratagy.com.
1281
c997b287
GS
1282=item *
1283
cc07ed0b 1284VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
495c5fdc
GP
1285
1286=back
1287
e41182b5
GS
1288=head2 EBCDIC Platforms
1289
1290Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1291AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1292Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1293Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1294systems). On the mainframe perl currently works under the "Unix system
1295services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1296the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
522b859a
JH
1297See L<perlos390> for details. Note that for OS/400 there is also a port of
1298Perl 5.8.1/5.9.0 or later to the PASE which is ASCII-based (as opposed to
1299ILE which is EBCDIC-based), see L<perlos400>.
e41182b5 1300
7c5ffed3
JH
1301As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1302sub-systems do not support the C<#!> shebang trick for script invocation.
1303Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1304similar to the following simple script:
e41182b5
GS
1305
1306 : # use perl
1307 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1308 if 0;
1309 #!/usr/local/bin/perl # just a comment really
1310
1311 print "Hello from perl!\n";
1312
d1e3b762
GS
1313OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1314Calls to C<system> and backticks can use POSIX shell syntax on all
1315S/390 systems.
1316
b7df3edc 1317On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1318to wrap your perl scripts in a CL procedure to invoke them like so:
1319
1320 BEGIN
1321 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1322 ENDPGM
1323
1324This will invoke the perl script F<hello.pl> in the root of the
1325QOpenSys file system. On the AS/400 calls to C<system> or backticks
1326must use CL syntax.
1327
e41182b5 1328On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1329an effect on what happens with some perl functions (such as C<chr>,
1330C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1331well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1332and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1333(see L<"Newlines">).
e41182b5 1334
b7df3edc
GS
1335Fortunately, most web servers for the mainframe will correctly
1336translate the C<\n> in the following statement to its ASCII equivalent
1337(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1338
1339 print "Content-type: text/html\r\n\r\n";
1340
d1e3b762 1341The values of C<$^O> on some of these platforms includes:
e41182b5 1342
d1e3b762
GS
1343 uname $^O $Config{'archname'}
1344 --------------------------------------------
1345 OS/390 os390 os390
1346 OS400 os400 os400
1347 POSIX-BC posix-bc BS2000-posix-bc
1348 VM/ESA vmesa vmesa
3c075c7d 1349
e41182b5
GS
1350Some simple tricks for determining if you are running on an EBCDIC
1351platform could include any of the following (perhaps all):
1352
1353 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1354
1355 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1356
1357 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1358
b7df3edc 1359One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1360of punctuation characters since these may differ from code page to code
1361page (and once your module or script is rumoured to work with EBCDIC,
1362folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1363
1364Also see:
1365
1366=over 4
1367
c997b287
GS
1368=item *
1369
dc5c060f 1370L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1371L<perlebcdic>.
c997b287
GS
1372
1373=item *
e41182b5
GS
1374
1375The perl-mvs@perl.org list is for discussion of porting issues as well as
1376general usage issues for all EBCDIC Perls. Send a message body of
1377"subscribe perl-mvs" to majordomo@perl.org.
1378
7ee27b7c 1379=item *
c997b287
GS
1380
1381AS/400 Perl information at
b1866b2d 1382http://as400.rochester.ibm.com/
d1e3b762 1383as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1384
1385=back
1386
b8099c3d
CN
1387=head2 Acorn RISC OS
1388
b7df3edc
GS
1389Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1390Unix, and because Unix filename emulation is turned on by default,
1391most simple scripts will probably work "out of the box". The native
6ab3f9cb 1392filesystem is modular, and individual filesystems are free to be
0a47030a 1393case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1394native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1395names are silently truncated to fit. Scripts should be aware that the
1396standard filesystem currently has a name length limit of B<10>
1397characters, with up to 77 items in a directory, but other filesystems
0a47030a 1398may not impose such limitations.
b8099c3d
CN
1399
1400Native filenames are of the form
1401
6ab3f9cb 1402 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1403
b8099c3d
CN
1404where
1405
1406 Special_Field is not usually present, but may contain . and $ .
1407 Filesystem =~ m|[A-Za-z0-9_]|
1408 DsicName =~ m|[A-Za-z0-9_/]|
1409 $ represents the root directory
1410 . is the path separator
1411 @ is the current directory (per filesystem but machine global)
1412 ^ is the parent directory
1413 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1414
1415The default filename translation is roughly C<tr|/.|./|;>
1416
6ab3f9cb 1417Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1418the second stage of C<$> interpolation in regular expressions will fall
1419foul of the C<$.> if scripts are not careful.
1420
1421Logical paths specified by system variables containing comma-separated
b7df3edc 1422search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1423filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1424C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1425Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1426C<System$Path> contains a single item list. The filesystem will also
1427expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1428C<< <System$Dir>.Modules >> would look for the file
0a47030a 1429S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1430that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1431be protected when C<open> is used for input.
b8099c3d
CN
1432
1433Because C<.> was in use as a directory separator and filenames could not
1434be assumed to be unique after 10 characters, Acorn implemented the C
1435compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1436filenames specified in source code and store the respective files in
b7df3edc 1437subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1438
1439 foo.h h.foo
1440 C:foo.h C:h.foo (logical path variable)
1441 sys/os.h sys.h.os (C compiler groks Unix-speak)
1442 10charname.c c.10charname
1443 10charname.o o.10charname
1444 11charname_.c c.11charname (assuming filesystem truncates at 10)
1445
1446The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1447that this sort of translation is required, and it allows a user-defined list
1448of known suffixes that it will transpose in this fashion. This may
1449seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1450and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1451C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1452C<.>'s in filenames are translated to C</>.
0a47030a 1453
b7df3edc 1454As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1455the convention is that program specific environment variables are of the
6ab3f9cb
GS
1456form C<Program$Name>. Each filesystem maintains a current directory,
1457and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1458directory. Consequently, sociable programs don't change the current
1459directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1460assume that they can spawn a child process which can change the current
1461directory without affecting its parent (and everyone else for that
1462matter).
1463
b7df3edc
GS
1464Because native operating system filehandles are global and are currently
1465allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1466library emulates Unix filehandles. Consequently, you can't rely on
1467passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1468
1469The desire of users to express filenames of the form
c47ff5f1 1470C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1471too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1472assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1473reference to an environment variable, whereas anything else involving
c47ff5f1 1474C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1475right. Of course, the problem remains that scripts cannot rely on any
1476Unix tools being available, or that any tools found have Unix-like command
1477line arguments.
1478
b7df3edc
GS
1479Extensions and XS are, in theory, buildable by anyone using free
1480tools. In practice, many don't, as users of the Acorn platform are
1481used to binary distributions. MakeMaker does run, but no available
1482make currently copes with MakeMaker's makefiles; even if and when
1483this should be fixed, the lack of a Unix-like shell will cause
1484problems with makefile rules, especially lines of the form C<cd
1485sdbm && make all>, and anything using quoting.
b8099c3d
CN
1486
1487"S<RISC OS>" is the proper name for the operating system, but the value
1488in C<$^O> is "riscos" (because we don't like shouting).
1489
e41182b5
GS
1490=head2 Other perls
1491
b7df3edc
GS
1492Perl has been ported to many platforms that do not fit into any of
1493the categories listed above. Some, such as AmigaOS, Atari MiNT,
1494BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1495into the standard Perl source code kit. You may need to see the
1496F<ports/> directory on CPAN for information, and possibly binaries,
1497for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1498Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1499fall under the Unix category, but we are not a standards body.)
e41182b5 1500
d1e3b762
GS
1501Some approximate operating system names and their C<$^O> values
1502in the "OTHER" category include:
1503
1504 OS $^O $Config{'archname'}
1505 ------------------------------------------
1506 Amiga DOS amigaos m68k-amigos
cec2c193 1507 BeOS beos
d1e3b762
GS
1508 MPE/iX mpeix PA-RISC1.1
1509
e41182b5
GS
1510See also:
1511
1512=over 4
1513
c997b287
GS
1514=item *
1515
1516Amiga, F<README.amiga> (installed as L<perlamiga>).
1517
1518=item *
d1e3b762 1519
c997b287
GS
1520Atari, F<README.mint> and Guido Flohr's web page
1521http://stud.uni-sb.de/~gufl0000/
e41182b5 1522
c997b287 1523=item *
d1e3b762 1524
c997b287 1525Be OS, F<README.beos>
e41182b5 1526
c997b287
GS
1527=item *
1528
1529HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1530http://www.bixby.org/mark/perlix.html
c997b287
GS
1531
1532=item *
e41182b5 1533
6ab3f9cb 1534A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1535precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1536as well as from CPAN.
e41182b5 1537
13a2d996 1538=item *
c997b287 1539
e6f03d26 1540S<Plan 9>, F<README.plan9>
d1e3b762 1541
e41182b5
GS
1542=back
1543
e41182b5
GS
1544=head1 FUNCTION IMPLEMENTATIONS
1545
b7df3edc
GS
1546Listed below are functions that are either completely unimplemented
1547or else have been implemented differently on various platforms.
1548Following each description will be, in parentheses, a list of
1549platforms that the description applies to.
e41182b5 1550
b7df3edc
GS
1551The list may well be incomplete, or even wrong in some places. When
1552in doubt, consult the platform-specific README files in the Perl
1553source distribution, and any other documentation resources accompanying
1554a given port.
e41182b5 1555
0a47030a 1556Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1557
b7df3edc
GS
1558For many functions, you can also query C<%Config>, exported by
1559default from the Config module. For example, to check whether the
1560platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1561L<Config> for a full description of available variables.
e41182b5
GS
1562
1563=head2 Alphabetical Listing of Perl Functions
1564
1565=over 8
1566
e41182b5
GS
1567=item -X
1568
b7df3edc 1569C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1570and applications are executable, and there are no uid/gid
b7df3edc 1571considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1572
b7df3edc
GS
1573C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1574which may not reflect UIC-based file protections. (VMS)
e41182b5 1575
b8099c3d
CN
1576C<-s> returns the size of the data fork, not the total size of data fork
1577plus resource fork. (S<Mac OS>).
1578
1579C<-s> by name on an open file will return the space reserved on disk,
1580rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1581current size. (S<RISC OS>)
b8099c3d 1582
e41182b5 1583C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1584C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1585
1586C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1587(S<Mac OS>)
1588
1589C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1590(Win32, VMS, S<RISC OS>)
e41182b5
GS
1591
1592C<-d> is true if passed a device spec without an explicit directory.
1593(VMS)
1594
1595C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1596with foreign characters; this is the case will all platforms, but may
b7df3edc 1597affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1598
1599C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1600suffixes. C<-S> is meaningless. (Win32)
e41182b5 1601
b8099c3d
CN
1602C<-x> (or C<-X>) determine if a file has an executable file type.
1603(S<RISC OS>)
1604
47cd99a4 1605=item atan2
519bc777
RGS
1606
1607Due to issues with various CPUs, math libraries, compilers, and standards,
1608results for C<atan2()> may vary depending on any combination of the above.
1609Perl attempts to conform to the Open Group/IEEE standards for the results
1610returned from C<atan2()>, but cannot force the issue if the system Perl is
1611run on does not allow it. (Tru64, HP-UX 10.20)
1612
1613The current version of the standards for C<atan2()> is available at
1614L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.
1615
47cd99a4 1616=item binmode
e41182b5 1617
b7df3edc 1618Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1619
1620Reopens file and restores pointer; if function fails, underlying
1621filehandle may be closed, or pointer may be in a different position.
1622(VMS)
1623
1624The value returned by C<tell> may be affected after the call, and
1625the filehandle may be flushed. (Win32)
1626
47cd99a4 1627=item chmod
e41182b5 1628
b7df3edc 1629Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1630locking/unlocking the file. (S<Mac OS>)
1631
1632Only good for changing "owner" read-write access, "group", and "other"
1633bits are meaningless. (Win32)
1634
b8099c3d
CN
1635Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1636
495c5fdc
GP
1637Access permissions are mapped onto VOS access-control list changes. (VOS)
1638
4e51f8e4 1639The actual permissions set depend on the value of the C<CYGWIN>
789f0d36 1640in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1641
47cd99a4 1642=item chown
e41182b5 1643
3fd80bd6 1644Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5
GS
1645
1646Does nothing, but won't fail. (Win32)
1647
3fd80bd6
PG
1648A little funky, because VOS's notion of ownership is a little funky (VOS).
1649
e41182b5
GS
1650=item chroot
1651
e6f03d26 1652Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS, VM/ESA)
e41182b5 1653
47cd99a4 1654=item crypt
e41182b5
GS
1655
1656May not be available if library or source was not provided when building
b8099c3d 1657perl. (Win32)
e41182b5 1658
47cd99a4 1659=item dbmclose
e41182b5 1660
e6f03d26 1661Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1662
47cd99a4 1663=item dbmopen
e41182b5 1664
e6f03d26 1665Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1666
47cd99a4 1667=item dump
e41182b5 1668
b8099c3d 1669Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5 1670
84d78eb7 1671Not supported. (Cygwin, Win32)
e41182b5 1672
b8099c3d 1673Invokes VMS debugger. (VMS)
e41182b5 1674
47cd99a4 1675=item exec
e41182b5
GS
1676
1677Not implemented. (S<Mac OS>)
1678
7c5ffed3 1679Implemented via Spawn. (VM/ESA)
3c075c7d 1680
0f897271
GS
1681Does not automatically flush output handles on some platforms.
1682(SunOS, Solaris, HP-UX)
1683
fe12c0e8
MS
1684=item exit
1685
1686Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1687mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1688with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1689function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1690(C<1>); this mapping cannot be overridden. Any other argument to exit()
016930a6
JM
1691is used directly as Perl's exit status. On VMS, unless the future
1692POSIX_EXIT mode is enabled, the exit code should always be a valid
1693VMS exit code and not a generic number. When the POSIX_EXIT mode is
1694enabled, a generic number will be encoded in a method compatible with
1695the C library _POSIX_EXIT macro so that it can be decoded by other
1696programs, particularly ones written in C, like the GNV package. (VMS)
fe12c0e8 1697
47cd99a4 1698=item fcntl
e41182b5 1699
016930a6
JM
1700Not implemented. (Win32)
1701Some functions available based on the version of VMS. (VMS)
e41182b5 1702
47cd99a4 1703=item flock
e41182b5 1704
495c5fdc 1705Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1706
1707Available only on Windows NT (not on Windows 95). (Win32)
1708
1709=item fork
1710
3fd80bd6 1711Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VM/ESA, VMS)
0f897271
GS
1712
1713Emulated using multiple interpreters. See L<perlfork>. (Win32)
1714
1715Does not automatically flush output handles on some platforms.
1716(SunOS, Solaris, HP-UX)
e41182b5
GS
1717
1718=item getlogin
1719
b8099c3d 1720Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5 1721
47cd99a4 1722=item getpgrp
e41182b5 1723
3fd80bd6 1724Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1725
1726=item getppid
1727
41cbbefa 1728Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1729
47cd99a4 1730=item getpriority
e41182b5 1731
7c5ffed3 1732Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1733
47cd99a4 1734=item getpwnam
e41182b5
GS
1735
1736Not implemented. (S<Mac OS>, Win32)
1737
b8099c3d
CN
1738Not useful. (S<RISC OS>)
1739
47cd99a4 1740=item getgrnam
e41182b5 1741
b8099c3d 1742Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1743
47cd99a4 1744=item getnetbyname
e41182b5 1745
e6f03d26 1746Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1747
47cd99a4 1748=item getpwuid
e41182b5
GS
1749
1750Not implemented. (S<Mac OS>, Win32)
1751
b8099c3d
CN
1752Not useful. (S<RISC OS>)
1753
47cd99a4 1754=item getgrgid
e41182b5 1755
b8099c3d 1756Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1757
47cd99a4 1758=item getnetbyaddr
e41182b5 1759
e6f03d26 1760Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1761
47cd99a4 1762=item getprotobynumber
e41182b5
GS
1763
1764Not implemented. (S<Mac OS>)
1765
47cd99a4 1766=item getservbyport
e41182b5
GS
1767
1768Not implemented. (S<Mac OS>)
1769
1770=item getpwent
1771
7c5ffed3 1772Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1773
1774=item getgrent
1775
7c5ffed3 1776Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5 1777
ef5a6dd7
JH
1778=item gethostbyname
1779
1780C<gethostbyname('localhost')> does not work everywhere: you may have
1781to use C<gethostbyname('127.0.0.1')>. (S<Mac OS>, S<Irix 5>)
1782
e41182b5
GS
1783=item gethostent
1784
1785Not implemented. (S<Mac OS>, Win32)
1786
1787=item getnetent
1788
e6f03d26 1789Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1790
1791=item getprotoent
1792
e6f03d26 1793Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1794
1795=item getservent
1796
e6f03d26 1797Not implemented. (Win32, S<Plan 9>)
e41182b5 1798
47cd99a4 1799=item sethostent
e41182b5 1800
e6f03d26 1801Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1802
47cd99a4 1803=item setnetent
e41182b5 1804
e6f03d26 1805Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1806
47cd99a4 1807=item setprotoent
e41182b5 1808
e6f03d26 1809Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1810
47cd99a4 1811=item setservent
e41182b5 1812
e6f03d26 1813Not implemented. (S<Plan 9>, Win32, S<RISC OS>)
e41182b5
GS
1814
1815=item endpwent
1816
a3dfe201 1817Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1818
1819=item endgrent
1820
a3dfe201 1821Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1822
1823=item endhostent
1824
1825Not implemented. (S<Mac OS>, Win32)
1826
1827=item endnetent
1828
e6f03d26 1829Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1830
1831=item endprotoent
1832
e6f03d26 1833Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1834
1835=item endservent
1836
e6f03d26 1837Not implemented. (S<Plan 9>, Win32)
e41182b5
GS
1838
1839=item getsockopt SOCKET,LEVEL,OPTNAME
1840
e6f03d26 1841Not implemented. (S<Plan 9>)
e41182b5 1842
e41182b5
GS
1843=item glob
1844
63f87e49
GS
1845This operator is implemented via the File::Glob extension on most
1846platforms. See L<File::Glob> for portability information.
b8099c3d 1847
62aa5637
MS
1848=item gmtime
1849
1850Same portability caveats as L<localtime>.
1851
e41182b5
GS
1852=item ioctl FILEHANDLE,FUNCTION,SCALAR
1853
1854Not implemented. (VMS)
1855
1856Available only for socket handles, and it does what the ioctlsocket() call
1857in the Winsock API does. (Win32)
1858
b8099c3d
CN
1859Available only for socket handles. (S<RISC OS>)
1860
47cd99a4 1861=item kill
e41182b5 1862
862b5365
JH
1863C<kill(0, LIST)> is implemented for the sake of taint checking;
1864use with other signals is unimplemented. (S<Mac OS>)
1865
1866Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1867
63f87e49
GS
1868C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1869a signal to the identified process like it does on Unix platforms.
1870Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1871and makes it exit immediately with exit status $sig. As in Unix, if
1872$sig is 0 and the specified process exists, it returns true without
1873actually terminating it. (Win32)
e41182b5 1874
d0302514
JD
1875C<kill(-9, $pid)> will terminate the process specified by $pid and
1876recursively all child processes owned by it. This is different from
1877the Unix semantics, where the signal will be delivered to all
1878processes in the same process group as the process specified by
1879$pid. (Win32)
1880
016930a6
JM
1881Is not supported for process identification number of 0 or negative
1882numbers. (VMS)
1883
47cd99a4 1884=item link
e41182b5 1885
016930a6 1886Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>)
e41182b5 1887
433acd8a
JH
1888Link count not updated because hard links are not quite that hard
1889(They are sort of half-way between hard and soft links). (AmigaOS)
1890
63d6c08b
JD
1891Hard links are implemented on Win32 under NTFS only. They are
1892natively supported on Windows 2000 and later. On Windows NT they
1893are implemented using the Windows POSIX subsystem support and the
1894Perl process will need Administrator or Backup Operator privileges
1895to create hard links.
a3dfe201 1896
016930a6
JM
1897Available on 64 bit OpenVMS 8.2 and later. (VMS)
1898
62aa5637
MS
1899=item localtime
1900
1901Because Perl currently relies on the native standard C localtime()
1902function, it is only safe to use times between 0 and (2**31)-1. Times
1903outside this range may result in unexpected behavior depending on your
1904operating system's implementation of localtime().
1905
e41182b5
GS
1906=item lstat
1907
016930a6 1908Not implemented. (S<RISC OS>)
e41182b5 1909
63f87e49 1910Return values (especially for device and inode) may be bogus. (Win32)
e41182b5 1911
47cd99a4 1912=item msgctl
e41182b5 1913
47cd99a4 1914=item msgget
e41182b5 1915
47cd99a4 1916=item msgsnd
e41182b5 1917
47cd99a4 1918=item msgrcv
e41182b5 1919
e6f03d26 1920Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS)
e41182b5 1921
47cd99a4 1922=item open
e41182b5 1923
b7df3edc 1924The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1925(S<Mac OS>)
1926
c47ff5f1 1927open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1928
0f897271
GS
1929Opening a process does not automatically flush output handles on some
1930platforms. (SunOS, Solaris, HP-UX)
1931
47cd99a4 1932=item pipe
e41182b5 1933
433acd8a
JH
1934Very limited functionality. (MiNT)
1935
e41182b5
GS
1936=item readlink
1937
b8099c3d 1938Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1939
47cd99a4 1940=item rename
c9b2b9d4
SS
1941
1942Can't move directories between directories on different logical volumes. (Win32)
1943
47cd99a4 1944=item select
e41182b5 1945
689c5c24 1946Only implemented on sockets. (Win32, VMS)
e41182b5 1947
b8099c3d
CN
1948Only reliable on sockets. (S<RISC OS>)
1949
76e05f0b 1950Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1951
47cd99a4 1952=item semctl
e41182b5 1953
47cd99a4 1954=item semget
e41182b5 1955
47cd99a4 1956=item semop
e41182b5 1957
495c5fdc 1958Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1959
a3dfe201
GS
1960=item setgrent
1961
3fd80bd6 1962Not implemented. (S<Mac OS>, MPE/iX, VMS, Win32, S<RISC OS>, VOS)
a3dfe201 1963
47cd99a4 1964=item setpgrp
e41182b5 1965
495c5fdc 1966Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1967
47cd99a4 1968=item setpriority
e41182b5 1969
495c5fdc 1970Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1971
a3dfe201
GS
1972=item setpwent
1973
3fd80bd6 1974Not implemented. (S<Mac OS>, MPE/iX, Win32, S<RISC OS>, VOS)
a3dfe201 1975
47cd99a4 1976=item setsockopt
e41182b5 1977
e6f03d26 1978Not implemented. (S<Plan 9>)
e41182b5 1979
47cd99a4 1980=item shmctl
e41182b5 1981
47cd99a4 1982=item shmget
e41182b5 1983
47cd99a4 1984=item shmread
e41182b5 1985
47cd99a4 1986=item shmwrite
e41182b5 1987
495c5fdc 1988Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1989
47cd99a4 1990=item sockatmark
80cbd5ad
JH
1991
1992A relatively recent addition to socket functions, may not
1993be implemented even in UNIX platforms.
1994
47cd99a4 1995=item socketpair
e41182b5 1996
016930a6
JM
1997Not implemented. (Win32, S<RISC OS>, VOS, VM/ESA)
1998
1999Available on 64 bit OpenVMS 8.2 and later. (VMS)
e41182b5 2000
e41182b5
GS
2001=item stat
2002
d62e1b7f
JH
2003Platforms that do not have rdev, blksize, or blocks will return these
2004as '', so numeric comparison or manipulation of these fields may cause
2005'not numeric' warnings.
2006
e41182b5 2007mtime and atime are the same thing, and ctime is creation time instead of
3f1f789b
JH
2008inode change time. (S<Mac OS>).
2009
2010ctime not supported on UFS (S<Mac OS X>).
e41182b5 2011
95a3fe12
MS
2012ctime is creation time instead of inode change time (Win32).
2013
e41182b5
GS
2014device and inode are not meaningful. (Win32)
2015
2016device and inode are not necessarily reliable. (VMS)
2017
b8099c3d
CN
2018mtime, atime and ctime all return the last modification time. Device and
2019inode are not necessarily reliable. (S<RISC OS>)
2020
d62e1b7f
JH
2021dev, rdev, blksize, and blocks are not available. inode is not
2022meaningful and will differ between stat calls on the same file. (os2)
2023
73e9292c
JH
2024some versions of cygwin when doing a stat("foo") and if not finding it
2025may then attempt to stat("foo.exe") (Cygwin)
2026
1fafdf34
JD
2027On Win32 stat() needs to open the file to determine the link count
2028and update attributes that may have been changed through hard links.
2029Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up stat() by
2030not performing this operation. (Win32)
2031
47cd99a4 2032=item symlink
e41182b5 2033
b8099c3d 2034Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 2035
47cd99a4 2036=item syscall
e41182b5 2037
7c5ffed3 2038Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 2039
47cd99a4 2040=item sysopen
f34d0673 2041
dd9f0070 2042The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
2043numeric values on some systems. The flags exported by C<Fcntl>
2044(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 2045OS>, OS/390, VM/ESA)
f34d0673 2046
47cd99a4 2047=item system
e41182b5
GS
2048
2049Only implemented if ToolServer is installed. (S<Mac OS>)
2050
2051As an optimization, may not call the command shell specified in
b7df3edc 2052C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
2053process and immediately returns its process designator, without
2054waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
2055in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
2056by setting $? to "255 << 8". C<$?> is set in a way compatible with
2057Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
2058as described in the documentation). (Win32)
e41182b5 2059
b8099c3d
CN
2060There is no shell to process metacharacters, and the native standard is
2061to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 2062program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
2063the run time library of the spawned program. C<system> I<list> will call
2064the Unix emulation library's C<exec> emulation, which attempts to provide
2065emulation of the stdin, stdout, stderr in force in the parent, providing
2066the child program uses a compatible version of the emulation library.
2067I<scalar> will call the native command line direct and no such emulation
2068of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
2069
433acd8a
JH
2070Far from being POSIX compliant. Because there may be no underlying
2071/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 2072first token in its argument string. Handles basic redirection
c47ff5f1 2073("<" or ">") on its own behalf. (MiNT)
433acd8a 2074
0f897271
GS
2075Does not automatically flush output handles on some platforms.
2076(SunOS, Solaris, HP-UX)
2077
9bc98430
CB
2078The return value is POSIX-like (shifted up by 8 bits), which only allows
2079room for a made-up value derived from the severity bits of the native
208032-bit condition code (unless overridden by C<use vmsish 'status'>).
016930a6
JM
2081If the native condition code is one that has a POSIX value encoded, the
2082POSIX value will be decoded to extract the expected exit value.
9bc98430
CB
2083For more details see L<perlvms/$?>. (VMS)
2084
e41182b5
GS
2085=item times
2086
2087Only the first entry returned is nonzero. (S<Mac OS>)
2088
63f87e49
GS
2089"cumulative" times will be bogus. On anything other than Windows NT
2090or Windows 2000, "system" time will be bogus, and "user" time is
2091actually the time returned by the clock() function in the C runtime
2092library. (Win32)
e41182b5 2093
b8099c3d
CN
2094Not useful. (S<RISC OS>)
2095
47cd99a4 2096=item truncate
e41182b5 2097
6d738113 2098Not implemented. (Older versions of VMS)
e41182b5 2099
3fd80bd6 2100Truncation to same-or-shorter lengths only. (VOS)
495c5fdc 2101
4cfdb94f 2102If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 2103mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
2104or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
2105should not be held open elsewhere. (Win32)
2106
e41182b5
GS
2107=item umask
2108
2109Returns undef where unavailable, as of version 5.005.
2110
b7df3edc
GS
2111C<umask> works but the correct permissions are set only when the file
2112is finally closed. (AmigaOS)
433acd8a 2113
47cd99a4 2114=item utime
e41182b5 2115
15c65113 2116Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 2117
322422de
GS
2118May not behave as expected. Behavior depends on the C runtime
2119library's implementation of utime(), and the filesystem being
2120used. The FAT filesystem typically does not support an "access
2121time" field, and it may limit timestamps to a granularity of
2122two seconds. (Win32)
e41182b5
GS
2123
2124=item wait
2125
47cd99a4 2126=item waitpid
e41182b5 2127
3fd80bd6 2128Not implemented. (S<Mac OS>)
e41182b5
GS
2129
2130Can only be applied to process handles returned for processes spawned
a6f858fb 2131using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 2132
b8099c3d
CN
2133Not useful. (S<RISC OS>)
2134
e41182b5
GS
2135=back
2136
2137
ba58ab26
JH
2138=head1 Supported Platforms
2139
522b859a 2140As of July 2002 (the Perl release 5.8.0), the following platforms are
cec2c193
JH
2141able to build Perl from the standard source code distribution
2142available at http://www.cpan.org/src/index.html
2143
2144 AIX
2145 BeOS
6f683aa2 2146 BSD/OS (BSDi)
cec2c193
JH
2147 Cygwin
2148 DG/UX
811b48f2 2149 DOS DJGPP 1)
cec2c193
JH
2150 DYNIX/ptx
2151 EPOC R5
2152 FreeBSD
6f683aa2 2153 HI-UXMPP (Hitachi) (5.8.0 worked but we didn't know it)
cec2c193
JH
2154 HP-UX
2155 IRIX
2156 Linux
8939ba94 2157 Mac OS Classic
6f683aa2 2158 Mac OS X (Darwin)
cec2c193
JH
2159 MPE/iX
2160 NetBSD
2161 NetWare
2162 NonStop-UX
6f683aa2 2163 ReliantUNIX (formerly SINIX)
cec2c193 2164 OpenBSD
6f683aa2 2165 OpenVMS (formerly VMS)
3ebac25b 2166 Open UNIX (Unixware) (since Perl 5.8.1/5.9.0)
cec2c193 2167 OS/2
522b859a 2168 OS/400 (using the PASE) (since Perl 5.8.1/5.9.0)
70de81db 2169 PowerUX
6f683aa2 2170 POSIX-BC (formerly BS2000)
cec2c193
JH
2171 QNX
2172 Solaris
70de81db 2173 SunOS 4
6f683aa2
JH
2174 SUPER-UX (NEC)
2175 Tru64 UNIX (formerly DEC OSF/1, Digital UNIX)
cec2c193
JH
2176 UNICOS
2177 UNICOS/mk
2178 UTS
2179 VOS
811b48f2 2180 Win95/98/ME/2K/XP 2)
c40b5d1d 2181 WinCE
6f683aa2 2182 z/OS (formerly OS/390)
cec2c193 2183 VM/ESA
ba58ab26 2184
811b48f2
JH
2185 1) in DOS mode either the DOS or OS/2 ports can be used
2186 2) compilers: Borland, MinGW (GCC), VC6
cec2c193 2187
c40b5d1d 2188The following platforms worked with the previous releases (5.6 and
cec2c193
JH
21895.7), but we did not manage either to fix or to test these in time
2190for the 5.8.0 release. There is a very good chance that many of these
70de81db 2191will work fine with the 5.8.0.
cec2c193 2192
8da2b1be 2193 BSD/OS
cec2c193
JH
2194 DomainOS
2195 Hurd
2196 LynxOS
2197 MachTen
2198 PowerMAX
2199 SCO SV
cec2c193
JH
2200 SVR4
2201 Unixware
2202 Windows 3.1
ba58ab26 2203
70de81db
JH
2204Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used):
2205
2206 AmigaOS
2207
ba58ab26 2208The following platforms have been known to build Perl from source in
fd46a41b
JH
2209the past (5.005_03 and earlier), but we haven't been able to verify
2210their status for the current release, either because the
2211hardware/software platforms are rare or because we don't have an
2212active champion on these platforms--or both. They used to work,
2213though, so go ahead and try compiling them, and let perlbug@perl.org
2214of any trouble.
ba58ab26 2215
cec2c193
JH
2216 3b1
2217 A/UX
cec2c193
JH
2218 ConvexOS
2219 CX/UX
2220 DC/OSx
2221 DDE SMES
2222 DOS EMX
2223 Dynix
2224 EP/IX
2225 ESIX
2226 FPS
2227 GENIX
2228 Greenhills
2229 ISC
2230 MachTen 68k
2231 MiNT
2232 MPC
2233 NEWS-OS
2234 NextSTEP
2235 OpenSTEP
2236 Opus
2237 Plan 9
cec2c193 2238 RISC/os
8da2b1be 2239 SCO ODT/OSR
cec2c193
JH
2240 Stellar
2241 SVR2
2242 TI1500
2243 TitanOS
2244 Ultrix
2245 Unisys Dynix
ba58ab26
JH
2246
2247The following platforms have their own source code distributions and
1577cd80 2248binaries available via http://www.cpan.org/ports/
ba58ab26 2249
cec2c193 2250 Perl release
ba58ab26 2251
522b859a 2252 OS/400 (ILE) 5.005_02
cec2c193 2253 Tandem Guardian 5.004
ba58ab26
JH
2254
2255The following platforms have only binaries available via
a93751fa 2256http://www.cpan.org/ports/index.html :
ba58ab26 2257
cec2c193 2258 Perl release
ba58ab26 2259
cec2c193
JH
2260 Acorn RISCOS 5.005_02
2261 AOS 5.002
2262 LynxOS 5.004_02
ba58ab26
JH
2263
2264Although we do suggest that you always build your own Perl from
2265the source code, both for maximal configurability and for security,
2266in case you are in a hurry you can check
a93751fa 2267http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2268
c997b287
GS
2269=head1 SEE ALSO
2270
cec2c193 2271L<perlaix>, L<perlamiga>, L<perlapollo>, L<perlbeos>, L<perlbs2000>,
18a271bd 2272L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>,
469e7be4 2273L<perlebcdic>, L<perlfreebsd>, L<perlhurd>, L<perlhpux>, L<perlirix>,
0d53b15f 2274L<perlmachten>, L<perlmacos>, L<perlmacosx>, L<perlmint>, L<perlmpeix>,
522b859a
JH
2275L<perlnetware>, L<perlos2>, L<perlos390>, L<perlos400>,
2276L<perlplan9>, L<perlqnx>, L<perlsolaris>, L<perltru64>,
2277L<perlunicode>, L<perlvmesa>, L<perlvms>, L<perlvos>,
2278L<perlwin32>, and L<Win32>.
c997b287 2279
e41182b5
GS
2280=head1 AUTHORS / CONTRIBUTORS
2281
06e9666b 2282Abigail <abigail@foad.org>,
c47ff5f1
GS
2283Charles Bailey <bailey@newman.upenn.edu>,
2284Graham Barr <gbarr@pobox.com>,
2285Tom Christiansen <tchrist@perl.com>,
06e9666b 2286Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2287Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2288Andy Dougherty <doughera@lafayette.edu>,
2289Dominic Dunlop <domo@computer.org>,
2290Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1 2291David J. Fiander <davidf@mks.com>,
3fd80bd6 2292Paul Green <Paul.Green@stratus.com>,
06e9666b 2293M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2294Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2295Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2296Nick Ing-Simmons <nick@ing-simmons.net>,
2297Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2298Markus Laker <mlaker@contax.co.uk>,
2299Andrew M. Langmead <aml@world.std.com>,
2300Larry Moore <ljmoore@freespace.net>,
2301Paul Moore <Paul.Moore@uk.origin-it.com>,
2302Chris Nandor <pudge@pobox.com>,
1afc07ec 2303Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2304Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2305Gary Ng <71564.1743@CompuServe.COM>,
2306Tom Phoenix <rootbeer@teleport.com>,
2307AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2308Peter Prymmer <pvhp@forte.com>,
2309Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2310Gurusamy Sarathy <gsar@activestate.com>,
2311Paul J. Schinder <schinder@pobox.com>,
2312Michael G Schwern <schwern@pobox.com>,
06e9666b 2313Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2314Nathan Torkington <gnat@frii.com>.
016930a6 2315John Malmberg <wb8tyw@qsl.net>