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1=head1 NAME
2
3perlport - Writing portable Perl
4
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5=head1 DESCRIPTION
6
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7Perl runs on numerous operating systems. While most of them share
8much in common, they also have their own unique features.
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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,
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12you know where the lines are drawn, and you can stay within them.
13
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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
2c044526 22important that the task that you are coding has the full generality
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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
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26problem.
27
28Looking at it another way, writing portable code is usually about
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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.
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32
33Be aware of two important points:
34
35=over 4
36
37=item Not all Perl programs have to be portable
38
b7df3edc 39There is no reason you should not use Perl as a language to glue Unix
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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
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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
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51writing portable code, and this document is entirely about those issues.
52
53=back
54
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55Here's the general rule: When you approach a task commonly done
56using a whole range of platforms, think about writing portable
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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,
204ad8d5 62VMS, etc.), consider writing platform-specific code.
e41182b5 63
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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
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67deliberate in your decision.
68
69The material below is separated into three main sections: main issues of
5a0de581 70portability (L</"ISSUES">), platform-specific issues (L</"PLATFORMS">), and
2c044526 71built-in Perl functions that behave differently on various ports
5a0de581 72(L</"FUNCTION IMPLEMENTATIONS">).
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73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
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
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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>,
2c044526 87S<Mac OS> uses C<\015>, and z/OS uses C<\025>.
e41182b5 88
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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
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91means C<\015>. On EBCDIC platforms, C<\n> could be C<\025> or C<\045>.
92In DOSish perls, C<\n> usually means C<\012>, but when
51d9476f 93accessing a file in "text" mode, perl uses the C<:crlf> layer that
94translates it to (or from) C<\015\012>, depending on whether you're
95reading or writing. Unix does the same thing on ttys in canonical
96mode. C<\015\012> is commonly referred to as CRLF.
b7df3edc 97
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98To trim trailing newlines from text lines use
99L<C<chomp>|perlfunc/chomp VARIABLE>. With default settings that function
100looks for a trailing C<\n> character and thus trims in a portable way.
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101
102When dealing with binary files (or text files in binary mode) be sure
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103to explicitly set L<C<$E<sol>>|perlvar/$E<sol>> to the appropriate value for
104your file format before using L<C<chomp>|perlfunc/chomp VARIABLE>.
105
106Because of the "text" mode translation, DOSish perls have limitations in
107using L<C<seek>|perlfunc/seek FILEHANDLE,POSITION,WHENCE> and
108L<C<tell>|perlfunc/tell FILEHANDLE> on a file accessed in "text" mode.
109Stick to L<C<seek>|perlfunc/seek FILEHANDLE,POSITION,WHENCE>-ing to
110locations you got from L<C<tell>|perlfunc/tell FILEHANDLE> (and no
111others), and you are usually free to use
112L<C<seek>|perlfunc/seek FILEHANDLE,POSITION,WHENCE> and
113L<C<tell>|perlfunc/tell FILEHANDLE> even in "text" mode. Using
114L<C<seek>|perlfunc/seek FILEHANDLE,POSITION,WHENCE> or
115L<C<tell>|perlfunc/tell FILEHANDLE> or other file operations may be
116non-portable. If you use L<C<binmode>|perlfunc/binmode FILEHANDLE> on a
117file, however, you can usually
118L<C<seek>|perlfunc/seek FILEHANDLE,POSITION,WHENCE> and
119L<C<tell>|perlfunc/tell FILEHANDLE> with arbitrary values safely.
e41182b5 120
2c044526 121A common misconception in socket programming is that S<C<\n eq \012>>
0a47030a 122everywhere. When using protocols such as common Internet protocols,
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123C<\012> and C<\015> are called for specifically, and the values of
124the logical C<\n> and C<\r> (carriage return) are not reliable.
125
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126 print $socket "Hi there, client!\r\n"; # WRONG
127 print $socket "Hi there, client!\015\012"; # RIGHT
e41182b5 128
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129However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
130and unsightly, as well as confusing to those maintaining the code. As
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131such, the L<C<Socket>|Socket> module supplies the Right Thing for those
132who want it.
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133
134 use Socket qw(:DEFAULT :crlf);
83a46a63 135 print $socket "Hi there, client!$CRLF" # RIGHT
e41182b5 136
6ab3f9cb 137When reading from a socket, remember that the default input record
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138separator L<C<$E<sol>>|perlvar/$E<sol>> is C<\n>, but robust socket code
139will recognize as either C<\012> or C<\015\012> as end of line:
e41182b5 140
83a46a63 141 while (<$socket>) { # NOT ADVISABLE!
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142 # ...
143 }
144
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145Because both CRLF and LF end in LF, the input record separator can
146be set to LF and any CR stripped later. Better to write:
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147
148 use Socket qw(:DEFAULT :crlf);
149 local($/) = LF; # not needed if $/ is already \012
150
83a46a63 151 while (<$socket>) {
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152 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
153 # s/\015?\012/\n/; # same thing
154 }
155
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156This example is preferred over the previous one--even for Unix
157platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
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158(and there was much rejoicing).
159
6ab3f9cb 160Similarly, functions that return text data--such as a function that
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161fetches a web page--should sometimes translate newlines before
162returning the data, if they've not yet been translated to the local
163newline representation. A single line of code will often suffice:
2ee0eb3c 164
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165 $data =~ s/\015?\012/\n/g;
166 return $data;
2ee0eb3c 167
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168Some of this may be confusing. Here's a handy reference to the ASCII CR
169and LF characters. You can print it out and stick it in your wallet.
170
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171 LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
172 CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
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173
174 | Unix | DOS | Mac |
175 ---------------------------
176 \n | LF | LF | CR |
177 \r | CR | CR | LF |
178 \n * | LF | CRLF | CR |
179 \r * | CR | CR | LF |
180 ---------------------------
181 * text-mode STDIO
182
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183The Unix column assumes that you are not accessing a serial line
184(like a tty) in canonical mode. If you are, then CR on input becomes
185"\n", and "\n" on output becomes CRLF.
186
6ab3f9cb 187These are just the most common definitions of C<\n> and C<\r> in Perl.
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188There may well be others. For example, on an EBCDIC implementation
189such as z/OS (OS/390) or OS/400 (using the ILE, the PASE is ASCII-based)
190the above material is similar to "Unix" but the code numbers change:
74555b7a 191
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192 LF eq \025 eq \x15 eq \cU eq chr(21) eq CP-1047 21
193 LF eq \045 eq \x25 eq chr(37) eq CP-0037 37
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194 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
195 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
196
197 | z/OS | OS/400 |
198 ----------------------
199 \n | LF | LF |
200 \r | CR | CR |
201 \n * | LF | LF |
202 \r * | CR | CR |
203 ----------------------
204 * text-mode STDIO
6ab3f9cb 205
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206=head2 Numbers endianness and Width
207
208Different CPUs store integers and floating point numbers in different
209orders (called I<endianness>) and widths (32-bit and 64-bit being the
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210most common today). This affects your programs when they attempt to transfer
211numbers in binary format from one CPU architecture to another,
212usually either "live" via network connection, or by storing the
213numbers to secondary storage such as a disk file or tape.
322422de 214
2c044526 215Conflicting storage orders make an utter mess out of the numbers. If a
d1e3b762 216little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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217decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2180x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
219Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
220them in big-endian mode. To avoid this problem in network (socket)
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221connections use the L<C<pack>|perlfunc/pack TEMPLATE,LIST> and
222L<C<unpack>|perlfunc/unpack TEMPLATE,EXPR> formats C<n> and C<N>, the
b84d4f81 223"network" orders. These are guaranteed to be portable.
322422de 224
2c044526 225As of Perl 5.10.0, you can also use the C<E<gt>> and C<E<lt>> modifiers
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226to force big- or little-endian byte-order. This is useful if you want
227to store signed integers or 64-bit integers, for example.
228
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229You can explore the endianness of your platform by unpacking a
230data structure packed in native format such as:
231
232 print unpack("h*", pack("s2", 1, 2)), "\n";
233 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
234 # '00100020' on e.g. Motorola 68040
235
236If you need to distinguish between endian architectures you could use
237either of the variables set like so:
238
239 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 240 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 241
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242Differing widths can cause truncation even between platforms of equal
243endianness. The platform of shorter width loses the upper parts of the
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244number. There is no good solution for this problem except to avoid
245transferring or storing raw binary numbers.
246
b7df3edc 247One can circumnavigate both these problems in two ways. Either
322422de 248transfer and store numbers always in text format, instead of raw
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249binary, or else consider using modules like
250L<C<Data::Dumper>|Data::Dumper> and L<C<Storable>|Storable> (included as
251of Perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 252
433acd8a 253=head2 Files and Filesystems
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254
255Most platforms these days structure files in a hierarchical fashion.
b7df3edc 256So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 257notion of a "path" to uniquely identify a file on the system. How
b7df3edc 258that path is really written, though, differs considerably.
e41182b5 259
4375e838 260Although similar, file path specifications differ between Unix,
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261Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
262Unix, for example, is one of the few OSes that has the elegant idea
263of a single root directory.
322422de 264
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265DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
266as path separator, or in their own idiosyncratic ways (such as having
267several root directories and various "unrooted" device files such NIL:
268and LPT:).
322422de 269
204ad8d5 270S<Mac OS> 9 and earlier used C<:> as a path separator instead of C</>.
322422de 271
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272The filesystem may support neither hard links
273(L<C<link>|perlfunc/link OLDFILE,NEWFILE>) nor symbolic links
274(L<C<symlink>|perlfunc/symlink OLDFILE,NEWFILE>,
275L<C<readlink>|perlfunc/readlink EXPR>,
276L<C<lstat>|perlfunc/lstat FILEHANDLE>).
433acd8a 277
6ab3f9cb 278The filesystem may support neither access timestamp nor change
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279timestamp (meaning that about the only portable timestamp is the
280modification timestamp), or one second granularity of any timestamps
281(e.g. the FAT filesystem limits the time granularity to two seconds).
282
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283The "inode change timestamp" (the L<C<-C>|perlfunc/-X FILEHANDLE>
284filetest) may really be the "creation timestamp" (which it is not in
285Unix).
95a3fe12 286
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287VOS perl can emulate Unix filenames with C</> as path separator. The
288native pathname characters greater-than, less-than, number-sign, and
289percent-sign are always accepted.
290
6ab3f9cb 291S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 292separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 293signal filesystems and disk names.
e41182b5 294
e1020413 295Don't assume Unix filesystem access semantics: that read, write,
a1667ba3 296and execute are all the permissions there are, and even if they exist,
83a46a63 297that their semantics (for example what do C<r>, C<w>, and C<x> mean on
e1020413 298a directory) are the Unix ones. The various Unix/POSIX compatibility
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299layers usually try to make interfaces like L<C<chmod>|perlfunc/chmod LIST>
300work, but sometimes there simply is no good mapping.
a1667ba3 301
83a46a63 302The L<C<File::Spec>|File::Spec> modules provide methods to manipulate path
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303specifications and return the results in native format for each
304platform. This is often unnecessary as Unix-style paths are
305understood by Perl on every supported platform, but if you need to
306produce native paths for a native utility that does not understand
307Unix syntax, or if you are operating on paths or path components
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308in unknown (and thus possibly native) syntax, L<C<File::Spec>|File::Spec>
309is your friend. Here are two brief examples:
e41182b5 310
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311 use File::Spec::Functions;
312 chdir(updir()); # go up one directory
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313
314 # Concatenate a path from its components
315 my $file = catfile(updir(), 'temp', 'file.txt');
316 # on Unix: '../temp/file.txt'
317 # on Win32: '..\temp\file.txt'
318 # on VMS: '[-.temp]file.txt'
e41182b5 319
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320In general, production code should not have file paths hardcoded.
321Making them user-supplied or read from a configuration file is
322better, keeping in mind that file path syntax varies on different
323machines.
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324
325This is especially noticeable in scripts like Makefiles and test suites,
326which often assume C</> as a path separator for subdirectories.
327
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328Also of use is L<C<File::Basename>|File::Basename> from the standard
329distribution, which splits a pathname into pieces (base filename, full
330path to directory, and file suffix).
e41182b5 331
19799a22 332Even when on a single platform (if you can call Unix a single platform),
b7df3edc 333remember not to count on the existence or the contents of particular
3c075c7d 334system-specific files or directories, like F</etc/passwd>,
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335F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
336example, F</etc/passwd> may exist but not contain the encrypted
337passwords, because the system is using some form of enhanced security.
2c044526 338Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 339If code does need to rely on such a file, include a description of the
b7df3edc 340file and its format in the code's documentation, then make it easy for
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341the user to override the default location of the file.
342
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343Don't assume a text file will end with a newline. They should,
344but people forget.
e41182b5 345
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346Do not have two files or directories of the same name with different
347case, like F<test.pl> and F<Test.pl>, as many platforms have
348case-insensitive (or at least case-forgiving) filenames. Also, try
349not to have non-word characters (except for C<.>) in the names, and
350keep them to the 8.3 convention, for maximum portability, onerous a
351burden though this may appear.
dd9f0070 352
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353Likewise, when using the L<C<AutoSplit>|AutoSplit> module, try to keep
354your functions to 8.3 naming and case-insensitive conventions; or, at the
355least, make it so the resulting files have a unique (case-insensitively)
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356first 8 characters.
357
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358Whitespace in filenames is tolerated on most systems, but not all,
359and even on systems where it might be tolerated, some utilities
fe829689 360might become confused by such whitespace.
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362Many systems (DOS, VMS ODS-2) cannot have more than one C<.> in their
363filenames.
433acd8a 364
c47ff5f1 365Don't assume C<< > >> won't be the first character of a filename.
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366Always use the three-arg version of
367L<C<open>|perlfunc/open FILEHANDLE,EXPR>:
0a47030a 368
ceaffd1d 369 open my $fh, '<', $existing_file) or die $!;
0a47030a 370
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371Two-arg L<C<open>|perlfunc/open FILEHANDLE,EXPR> is magic and can
372translate characters like C<< > >>, C<< < >>, and C<|> in filenames,
373which is usually the wrong thing to do.
374L<C<sysopen>|perlfunc/sysopen FILEHANDLE,FILENAME,MODE> and three-arg
375L<C<open>|perlfunc/open FILEHANDLE,EXPR> don't have this problem.
e41182b5 376
ec481373 377Don't use C<:> as a part of a filename since many systems use that for
8939ba94 378their own semantics (Mac OS Classic for separating pathname components,
ec481373 379many networking schemes and utilities for separating the nodename and
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380the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
381C<|>.
ec481373 382
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383Don't assume that in pathnames you can collapse two leading slashes
384C<//> into one: some networking and clustering filesystems have special
2c044526 385semantics for that. Let the operating system sort it out.
e1516da7 386
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387The I<portable filename characters> as defined by ANSI C are
388
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389 a b c d e f g h i j k l m n o p q r s t u v w x y z
390 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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391 0 1 2 3 4 5 6 7 8 9
392 . _ -
393
83a46a63 394and C<-> shouldn't be the first character. If you want to be
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395hypercorrect, stay case-insensitive and within the 8.3 naming
396convention (all the files and directories have to be unique within one
397directory if their names are lowercased and truncated to eight
398characters before the C<.>, if any, and to three characters after the
399C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 400
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401=head2 System Interaction
402
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403Not all platforms provide a command line. These are usually platforms
404that rely primarily on a Graphical User Interface (GUI) for user
405interaction. A program requiring a command line interface might
406not work everywhere. This is probably for the user of the program
407to deal with, so don't stay up late worrying about it.
e41182b5 408
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409Some platforms can't delete or rename files held open by the system,
410this limitation may also apply to changing filesystem metainformation
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411like file permissions or owners. Remember to
412L<C<close>|perlfunc/close FILEHANDLE> files when you are done with them.
413Don't L<C<unlink>|perlfunc/unlink LIST> or
414L<C<rename>|perlfunc/rename OLDNAME,NEWNAME> an open file. Don't
415L<C<tie>|perlfunc/tie VARIABLE,CLASSNAME,LIST> or
416L<C<open>|perlfunc/open FILEHANDLE,EXPR> a file already tied or opened;
417L<C<untie>|perlfunc/untie VARIABLE> or
418L<C<close>|perlfunc/close FILEHANDLE> it first.
e41182b5 419
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420Don't open the same file more than once at a time for writing, as some
421operating systems put mandatory locks on such files.
422
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423Don't assume that write/modify permission on a directory gives the
424right to add or delete files/directories in that directory. That is
425filesystem specific: in some filesystems you need write/modify
426permission also (or even just) in the file/directory itself. In some
427filesystems (AFS, DFS) the permission to add/delete directory entries
428is a completely separate permission.
429
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430Don't assume that a single L<C<unlink>|perlfunc/unlink LIST> completely
431gets rid of the file: some filesystems (most notably the ones in VMS) have
432versioned filesystems, and L<C<unlink>|perlfunc/unlink LIST> removes only
433the most recent one (it doesn't remove all the versions because by default
434the native tools on those platforms remove just the most recent version,
435too). The portable idiom to remove all the versions of a file is
73e9292c 436
94bb614c 437 1 while unlink "file";
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438
439This will terminate if the file is undeleteable for some reason
440(protected, not there, and so on).
441
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442Don't count on a specific environment variable existing in
443L<C<%ENV>|perlvar/%ENV>. Don't count on L<C<%ENV>|perlvar/%ENV> entries
444being case-sensitive, or even case-preserving. Don't try to clear
445L<C<%ENV>|perlvar/%ENV> by saying C<%ENV = ();>, or, if you really have
446to, make it conditional on C<$^O ne 'VMS'> since in VMS the
447L<C<%ENV>|perlvar/%ENV> table is much more than a per-process key-value
448string table.
449
450On VMS, some entries in the L<C<%ENV>|perlvar/%ENV> hash are dynamically
451created when their key is used on a read if they did not previously
452exist. The values for C<$ENV{HOME}>, C<$ENV{TERM}>, C<$ENV{PATH}>, and
453C<$ENV{USER}>, are known to be dynamically generated. The specific names
454that are dynamically generated may vary with the version of the C library
455on VMS, and more may exist than are documented.
456
457On VMS by default, changes to the L<C<%ENV>|perlvar/%ENV> hash persist
458after perl exits. Subsequent invocations of perl in the same process can
459inadvertently inherit environment settings that were meant to be
460temporary.
461
462Don't count on signals or L<C<%SIG>|perlvar/%SIG> for anything.
463
464Don't count on filename globbing. Use
465L<C<opendir>|perlfunc/opendir DIRHANDLE,EXPR>,
466L<C<readdir>|perlfunc/readdir DIRHANDLE>, and
467L<C<closedir>|perlfunc/closedir DIRHANDLE> instead.
e41182b5 468
b8099c3d 469Don't count on per-program environment variables, or per-program current
dd9f0070 470directories.
b8099c3d 471
83a46a63 472Don't count on specific values of L<C<$!>|perlvar/$!>, neither numeric nor
2c044526 473especially the string values. Users may switch their locales causing
c87488a3
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474error messages to be translated into their languages. If you can
475trust a POSIXish environment, you can portably use the symbols defined
83a46a63
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476by the L<C<Errno>|Errno> module, like C<ENOENT>. And don't trust on the
477values of L<C<$!>|perlvar/$!> at all except immediately after a failed
478system call.
3c075c7d 479
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480=head2 Command names versus file pathnames
481
482Don't assume that the name used to invoke a command or program with
83a46a63
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483L<C<system>|perlfunc/system LIST> or L<C<exec>|perlfunc/exec LIST> can
484also be used to test for the existence of the file that holds the
485executable code for that command or program.
68fb0eb7
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486First, many systems have "internal" commands that are built-in to the
487shell or OS and while these commands can be invoked, there is no
488corresponding file. Second, some operating systems (e.g., Cygwin,
489DJGPP, OS/2, and VOS) have required suffixes for executable files;
490these suffixes are generally permitted on the command name but are not
83a46a63
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491required. Thus, a command like C<perl> might exist in a file named
492F<perl>, F<perl.exe>, or F<perl.pm>, depending on the operating system.
493The variable L<C<$Config{_exe}>|Config/C<_exe>> in the
494L<C<Config>|Config> module holds the executable suffix, if any. Third,
495the VMS port carefully sets up L<C<$^X>|perlvar/$^X> and
496L<C<$Config{perlpath}>|Config/C<perlpath>> so that no further processing
497is required. This is just as well, because the matching regular
498expression used below would then have to deal with a possible trailing
499version number in the VMS file name.
500
501To convert L<C<$^X>|perlvar/$^X> to a file pathname, taking account of
502the requirements of the various operating system possibilities, say:
7ee27b7c 503
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504 use Config;
505 my $thisperl = $^X;
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506 if ($^O ne 'VMS') {
507 $thisperl .= $Config{_exe}
508 unless $thisperl =~ m/\Q$Config{_exe}\E$/i;
509 }
a10d74f3 510
83a46a63 511To convert L<C<$Config{perlpath}>|Config/C<perlpath>> to a file pathname, say:
7ee27b7c 512
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513 use Config;
514 my $thisperl = $Config{perlpath};
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515 if ($^O ne 'VMS') {
516 $thisperl .= $Config{_exe}
517 unless $thisperl =~ m/\Q$Config{_exe}\E$/i;
518 }
a10d74f3 519
7137b697
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520=head2 Networking
521
522Don't assume that you can reach the public Internet.
523
524Don't assume that there is only one way to get through firewalls
525to the public Internet.
526
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527Don't assume that you can reach outside world through any other port
528than 80, or some web proxy. ftp is blocked by many firewalls.
529
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530Don't assume that you can send email by connecting to the local SMTP port.
531
7137b697 532Don't assume that you can reach yourself or any node by the name
dbc6a9ce 533'localhost'. The same goes for '127.0.0.1'. You will have to try both.
932f293e 534
86feb2c5
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535Don't assume that the host has only one network card, or that it
536can't bind to many virtual IP addresses.
932f293e
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537
538Don't assume a particular network device name.
7137b697 539
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540Don't assume a particular set of
541L<C<ioctl>|perlfunc/ioctl FILEHANDLE,FUNCTION,SCALAR>s will work.
7137b697
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542
543Don't assume that you can ping hosts and get replies.
544
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545Don't assume that any particular port (service) will respond.
546
83a46a63
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547Don't assume that L<C<Sys::Hostname>|Sys::Hostname> (or any other API or
548command) returns either a fully qualified hostname or a non-qualified
549hostname: it all depends on how the system had been configured. Also
550remember that for things such as DHCP and NAT, the hostname you get back
551might not be very useful.
dbc6a9ce 552
a746ef5c 553All the above I<don't>s may look daunting, and they are, but the key
932f293e
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554is to degrade gracefully if one cannot reach the particular network
555service one wants. Croaking or hanging do not look very professional.
556
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557=head2 Interprocess Communication (IPC)
558
b7df3edc 559In general, don't directly access the system in code meant to be
83a46a63
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560portable. That means, no L<C<system>|perlfunc/system LIST>,
561L<C<exec>|perlfunc/exec LIST>, L<C<fork>|perlfunc/fork>,
562L<C<pipe>|perlfunc/pipe READHANDLE,WRITEHANDLE>,
563L<C<``> or C<qxE<sol>E<sol>>|perlop/C<qxE<sol>I<STRING>E<sol>>>,
564L<C<open>|perlfunc/open FILEHANDLE,EXPR> with a C<|>, nor any of the other
565things that makes being a Perl hacker worth being.
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566
567Commands that launch external processes are generally supported on
b7df3edc
GS
568most platforms (though many of them do not support any type of
569forking). The problem with using them arises from what you invoke
570them on. External tools are often named differently on different
4375e838 571platforms, may not be available in the same location, might accept
b7df3edc
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572different arguments, can behave differently, and often present their
573results in a platform-dependent way. Thus, you should seldom depend
83a46a63
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574on them to produce consistent results. (Then again, if you're calling
575C<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 576
b7df3edc 577One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 578
83a46a63 579 open(my $mail, '|-', '/usr/lib/sendmail -t')
b7df3edc 580 or die "cannot fork sendmail: $!";
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581
582This is fine for systems programming when sendmail is known to be
583available. But it is not fine for many non-Unix systems, and even
584some Unix systems that may not have sendmail installed. If a portable
b7df3edc 585solution is needed, see the various distributions on CPAN that deal
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586with it. L<C<Mail::Mailer>|Mail::Mailer> and L<C<Mail::Send>|Mail::Send>
587in the C<MailTools> distribution are commonly used, and provide several
588mailing methods, including C<mail>, C<sendmail>, and direct SMTP (via
589L<C<Net::SMTP>|Net::SMTP>) if a mail transfer agent is not available.
590L<C<Mail::Sendmail>|Mail::Sendmail> is a standalone module that provides
b7df3edc
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591simple, platform-independent mailing.
592
593The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
594even on all Unix platforms.
e41182b5 595
a81e5e2e
A
596Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
597bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
598both forms just pack the four bytes into network order. That this
599would be equal to the C language C<in_addr> struct (which is what the
600socket code internally uses) is not guaranteed. To be portable use
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601the routines of the L<C<Socket>|Socket> module, such as
602L<C<inet_aton>|Socket/$ip_address = inet_aton $string>,
603L<C<inet_ntoa>|Socket/$string = inet_ntoa $ip_address>, and
604L<C<sockaddr_in>|Socket/$sockaddr = sockaddr_in $port, $ip_address>.
6b2463a0 605
e41182b5 606The rule of thumb for portable code is: Do it all in portable Perl, or
0a47030a 607use a module (that may internally implement it with platform-specific
2c044526 608code, but exposes a common interface).
e41182b5 609
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610=head2 External Subroutines (XS)
611
b7df3edc 612XS code can usually be made to work with any platform, but dependent
e41182b5
GS
613libraries, header files, etc., might not be readily available or
614portable, or the XS code itself might be platform-specific, just as Perl
615code might be. If the libraries and headers are portable, then it is
616normally reasonable to make sure the XS code is portable, too.
617
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618A different type of portability issue arises when writing XS code:
619availability of a C compiler on the end-user's system. C brings
620with it its own portability issues, and writing XS code will expose
621you to some of those. Writing purely in Perl is an easier way to
e41182b5
GS
622achieve portability.
623
e41182b5
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624=head2 Standard Modules
625
626In general, the standard modules work across platforms. Notable
83a46a63
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627exceptions are the L<C<CPAN>|CPAN> module (which currently makes
628connections to external programs that may not be available),
629platform-specific modules (like L<C<ExtUtils::MM_VMS>|ExtUtils::MM_VMS>),
630and DBM modules.
e41182b5 631
b7df3edc 632There is no one DBM module available on all platforms.
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633L<C<SDBM_File>|SDBM_File> and the others are generally available on all
634Unix and DOSish ports, but not in MacPerl, where only
635L<C<NDBM_File>|NDBM_File> and L<C<DB_File>|DB_File> are available.
e41182b5
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636
637The good news is that at least some DBM module should be available, and
83a46a63
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638L<C<AnyDBM_File>|AnyDBM_File> will use whichever module it can find. Of
639course, then the code needs to be fairly strict, dropping to the greatest
640common factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 641work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 642
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643=head2 Time and Date
644
0a47030a 645The system's notion of time of day and calendar date is controlled in
b7df3edc 646widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a 647and even if it is, don't assume that you can control the timezone through
c87488a3
HS
648that variable. Don't assume anything about the three-letter timezone
649abbreviations (for example that MST would be the Mountain Standard Time,
650it's been known to stand for Moscow Standard Time). If you need to
651use timezones, express them in some unambiguous format like the
652exact number of minutes offset from UTC, or the POSIX timezone
653format.
e41182b5 654
322422de 655Don't assume that the epoch starts at 00:00:00, January 1, 1970,
c87488a3
HS
656because that is OS- and implementation-specific. It is better to
657store a date in an unambiguous representation. The ISO 8601 standard
766af94f 658defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH:MM:SS
c87488a3 659(that's a literal "T" separating the date from the time).
91d20606 660Please do use the ISO 8601 instead of making us guess what
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661date 02/03/04 might be. ISO 8601 even sorts nicely as-is.
662A text representation (like "1987-12-18") can be easily converted
83a46a63
LM
663into an OS-specific value using a module like
664L<C<Time::Piece>|Time::Piece> (see L<Time::Piece/Date Parsing>) or
665L<C<Date::Parse>|Date::Parse>. An array of values, such as those
666returned by L<C<localtime>|perlfunc/localtime EXPR>, can be converted to an OS-specific
667representation using L<C<Time::Local>|Time::Local>.
322422de 668
19799a22
GS
669When calculating specific times, such as for tests in time or date modules,
670it may be appropriate to calculate an offset for the epoch.
b7df3edc 671
83a46a63
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672 use Time::Local qw(timegm);
673 my $offset = timegm(0, 0, 0, 1, 0, 70);
b7df3edc 674
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JV
675The value for C<$offset> in Unix will be C<0>, but in Mac OS Classic
676will be some large number. C<$offset> can then be added to a Unix time
677value to get what should be the proper value on any system.
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GS
678
679=head2 Character sets and character encoding
680
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681Assume very little about character sets.
682
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683Assume nothing about numerical values (L<C<ord>|perlfunc/ord EXPR>,
684L<C<chr>|perlfunc/chr NUMBER>) of characters.
eb9df707
KW
685Do not use explicit code point ranges (like C<\xHH-\xHH)>. However,
686starting in Perl v5.22, regular expression pattern bracketed character
f4240379 687class ranges specified like C<qr/[\N{U+HH}-\N{U+HH}]/> are portable,
83a46a63
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688and starting in Perl v5.24, the same ranges are portable in
689L<C<trE<sol>E<sol>E<sol>>|perlop/C<trE<sol>I<SEARCHLIST>E<sol>I<REPLACEMENTLIST>E<sol>cdsr>>.
2c044526 690You can portably use symbolic character classes like C<[:print:]>.
ec481373
JH
691
692Do not assume that the alphabetic characters are encoded contiguously
eb9df707
KW
693(in the numeric sense). There may be gaps. Special coding in Perl,
694however, guarantees that all subsets of C<qr/[A-Z]/>, C<qr/[a-z]/>, and
83a46a63
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695C<qr/[0-9]/> behave as expected.
696L<C<trE<sol>E<sol>E<sol>>|perlop/C<trE<sol>I<SEARCHLIST>E<sol>I<REPLACEMENTLIST>E<sol>cdsr>>
697behaves the same for these ranges. In patterns, any ranges specified with
698end points using the C<\N{...}> notations ensures character set
699portability, but it is a bug in Perl v5.22 that this isn't true of
700L<C<trE<sol>E<sol>E<sol>>|perlop/C<trE<sol>I<SEARCHLIST>E<sol>I<REPLACEMENTLIST>E<sol>cdsr>>,
701fixed in v5.24.
ec481373
JH
702
703Do not assume anything about the ordering of the characters.
704The lowercase letters may come before or after the uppercase letters;
b432a672
AL
705the lowercase and uppercase may be interlaced so that both "a" and "A"
706come before "b"; the accented and other international characters may
707be interlaced so that E<auml> comes before "b".
2c044526 708L<Unicode::Collate> can be used to sort this all out.
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GS
709
710=head2 Internationalisation
711
b7df3edc
GS
712If you may assume POSIX (a rather large assumption), you may read
713more about the POSIX locale system from L<perllocale>. The locale
714system at least attempts to make things a little bit more portable,
715or at least more convenient and native-friendly for non-English
716users. The system affects character sets and encoding, and date
717and time formatting--amongst other things.
e41182b5 718
c87488a3
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719If you really want to be international, you should consider Unicode.
720See L<perluniintro> and L<perlunicode> for more information.
721
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722By default Perl assumes your source code is written in an 8-bit ASCII
723superset. To embed Unicode characters in your strings and regexes, you can
724use the L<C<\x{HH}> or (more portably) C<\N{U+HH}>
725notations|perlop/Quote and Quote-like Operators>. You can also use the
726L<C<utf8>|utf8> pragma and write your code in UTF-8, which lets you use
727Unicode characters directly (not just in quoted constructs but also in
728identifiers).
11264fdb 729
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730=head2 System Resources
731
0a47030a
GS
732If your code is destined for systems with severely constrained (or
733missing!) virtual memory systems then you want to be I<especially> mindful
734of avoiding wasteful constructs such as:
e41182b5 735
ceaffd1d 736 my @lines = <$very_large_file>; # bad
e41182b5 737
ceaffd1d 738 while (<$fh>) {$file .= $_} # sometimes bad
739 my $file = join('', <$fh>); # better
e41182b5 740
b7df3edc
GS
741The last two constructs may appear unintuitive to most people. The
742first repeatedly grows a string, whereas the second allocates a
743large chunk of memory in one go. On some systems, the second is
2c044526 744more efficient than the first.
0a47030a 745
e41182b5
GS
746=head2 Security
747
b7df3edc 748Most multi-user platforms provide basic levels of security, usually
ac036724 749implemented at the filesystem level. Some, however, unfortunately do
750not. Thus the notion of user id, or "home" directory,
b7df3edc
GS
751or even the state of being logged-in, may be unrecognizable on many
752platforms. If you write programs that are security-conscious, it
753is usually best to know what type of system you will be running
754under so that you can write code explicitly for that platform (or
755class of platforms).
0a47030a 756
e1020413 757Don't assume the Unix filesystem access semantics: the operating
a1667ba3 758system or the filesystem may be using some ACL systems, which are
2c044526 759richer languages than the usual C<rwx>. Even if the C<rwx> exist,
a1667ba3
JH
760their semantics might be different.
761
2c044526 762(From the security viewpoint, testing for permissions before attempting to
a1667ba3 763do something is silly anyway: if one tries this, there is potential
ac036724 764for race conditions. Someone or something might change the
a1667ba3
JH
765permissions between the permissions check and the actual operation.
766Just try the operation.)
767
e1020413 768Don't assume the Unix user and group semantics: especially, don't
83a46a63
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769expect L<C<< $< >>|perlvar/$E<lt>> and L<C<< $> >>|perlvar/$E<gt>> (or
770L<C<$(>|perlvar/$(> and L<C<$)>|perlvar/$)>) to work for switching
771identities (or memberships).
a1667ba3 772
83a46a63 773Don't assume set-uid and set-gid semantics. (And even if you do,
a1667ba3
JH
774think twice: set-uid and set-gid are a known can of security worms.)
775
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GS
776=head2 Style
777
778For those times when it is necessary to have platform-specific code,
779consider keeping the platform-specific code in one place, making porting
83a46a63
LM
780to other platforms easier. Use the L<C<Config>|Config> module and the
781special variable L<C<$^O>|perlvar/$^O> to differentiate platforms, as
782described in L</"PLATFORMS">.
e41182b5 783
d4c800c7
JH
784Beware of the "else syndrome":
785
786 if ($^O eq 'MSWin32') {
787 # code that assumes Windows
788 } else {
789 # code that assumes Linux
790 }
791
792The C<else> branch should be used for the really ultimate fallback,
793not for code specific to some platform.
794
b7df3edc
GS
795Be careful in the tests you supply with your module or programs.
796Module code may be fully portable, but its tests might not be. This
797often happens when tests spawn off other processes or call external
798programs to aid in the testing, or when (as noted above) the tests
c87488a3
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799assume certain things about the filesystem and paths. Be careful not
800to depend on a specific output style for errors, such as when checking
83a46a63
LM
801L<C<$!>|perlvar/$!> after a failed system call. Using
802L<C<$!>|perlvar/$!> for anything else than displaying it as output is
803doubtful (though see the L<C<Errno>|Errno> module for testing reasonably
804portably for error value). Some platforms expect a certain output format,
805and Perl on those platforms may have been adjusted accordingly. Most
806specifically, don't anchor a regex when testing an error value.
e41182b5 807
0a47030a 808=head1 CPAN Testers
e41182b5 809
0a47030a
GS
810Modules uploaded to CPAN are tested by a variety of volunteers on
811different platforms. These CPAN testers are notified by mail of each
e41182b5 812new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 813this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
GS
814
815The purpose of the testing is twofold: one, to help developers fix any
0a47030a 816problems in their code that crop up because of lack of testing on other
b7df3edc 817platforms; two, to provide users with information about whether
0a47030a 818a given module works on a given platform.
e41182b5 819
2890cc8c 820Also see:
7ee27b7c 821
e41182b5
GS
822=over 4
823
7ee27b7c
AT
824=item *
825
636280bd 826Mailing list: cpan-testers-discuss@perl.org
7ee27b7c
AT
827
828=item *
e41182b5 829
500f1b69 830Testing results: L<http://www.cpantesters.org/>
e41182b5
GS
831
832=back
833
e41182b5
GS
834=head1 PLATFORMS
835
83a46a63
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836Perl is built with a L<C<$^O>|perlvar/$^O> variable that indicates the
837operating system it was built on. This was implemented
b7df3edc 838to help speed up code that would otherwise have to C<use Config>
83a46a63
LM
839and use the value of L<C<$Config{osname}>|Config/C<osname>>. Of course,
840to get more detailed information about the system, looking into
841L<C<%Config>|Config/DESCRIPTION> is certainly recommended.
e41182b5 842
83a46a63
LM
843L<C<%Config>|Config/DESCRIPTION> cannot always be trusted, however,
844because it was built at compile time. If perl was built in one place,
845then transferred elsewhere, some values may be wrong. The values may
846even have been edited after the fact.
6ab3f9cb 847
e41182b5
GS
848=head2 Unix
849
850Perl works on a bewildering variety of Unix and Unix-like platforms (see
851e.g. most of the files in the F<hints/> directory in the source code kit).
83a46a63
LM
852On most of these systems, the value of L<C<$^O>|perlvar/$^O> (hence
853L<C<$Config{osname}>|Config/C<osname>>, too) is determined either by
854lowercasing and stripping punctuation from the first field of the string
855returned by typing C<uname -a> (or a similar command) at the shell prompt
856or by testing the file system for the presence of uniquely named files
857such as a kernel or header file. Here, for example, are a few of the
858more popular Unix flavors:
859
860 uname $^O $Config{archname}
6ab3f9cb 861 --------------------------------------------
b7df3edc 862 AIX aix aix
6ab3f9cb 863 BSD/OS bsdos i386-bsdos
e1516da7 864 Darwin darwin darwin
6ab3f9cb 865 DYNIX/ptx dynixptx i386-dynixptx
2890cc8c 866 FreeBSD freebsd freebsd-i386
df00ff3b 867 Haiku haiku BePC-haiku
d1e3b762 868 Linux linux arm-linux
56b575b9 869 Linux linux armv5tel-linux
b7df3edc 870 Linux linux i386-linux
6ab3f9cb
GS
871 Linux linux i586-linux
872 Linux linux ppc-linux
b7df3edc
GS
873 HP-UX hpux PA-RISC1.1
874 IRIX irix irix
b787fad4 875 Mac OS X darwin darwin
d1e3b762
GS
876 NeXT 3 next next-fat
877 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 878 openbsd openbsd i386-openbsd
b7df3edc 879 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
880 reliantunix-n svr4 RM400-svr4
881 SCO_SV sco_sv i386-sco_sv
882 SINIX-N svr4 RM400-svr4
883 sn4609 unicos CRAY_C90-unicos
884 sn6521 unicosmk t3e-unicosmk
885 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
886 SunOS solaris sun4-solaris
887 SunOS solaris i86pc-solaris
888 SunOS4 sunos sun4-sunos
e41182b5 889
83a46a63
LM
890Because the value of L<C<$Config{archname}>|Config/C<archname>> may
891depend on the hardware architecture, it can vary more than the value of
892L<C<$^O>|perlvar/$^O>.
6ab3f9cb 893
e41182b5
GS
894=head2 DOS and Derivatives
895
b7df3edc 896Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
897systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
898bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 899Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
900be aware that each of these file specifications may have subtle
901differences:
902
ceaffd1d 903 my $filespec0 = "c:/foo/bar/file.txt";
904 my $filespec1 = "c:\\foo\\bar\\file.txt";
905 my $filespec2 = 'c:\foo\bar\file.txt';
906 my $filespec3 = 'c:\\foo\\bar\\file.txt';
e41182b5 907
b7df3edc
GS
908System calls accept either C</> or C<\> as the path separator.
909However, many command-line utilities of DOS vintage treat C</> as
910the option prefix, so may get confused by filenames containing C</>.
911Aside from calling any external programs, C</> will work just fine,
912and probably better, as it is more consistent with popular usage,
913and avoids the problem of remembering what to backwhack and what
914not to.
e41182b5 915
b7df3edc
GS
916The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
917the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 918filesystems you may have to be careful about case returned with functions
83a46a63
LM
919like L<C<readdir>|perlfunc/readdir DIRHANDLE> or used with functions like
920L<C<open>|perlfunc/open FILEHANDLE,EXPR> or
921L<C<opendir>|perlfunc/opendir DIRHANDLE,EXPR>.
e41182b5 922
83a46a63
LM
923DOS also treats several filenames as special, such as F<AUX>, F<PRN>,
924F<NUL>, F<CON>, F<COM1>, F<LPT1>, F<LPT2>, etc. Unfortunately, sometimes
925these filenames won't even work if you include an explicit directory
926prefix. It is best to avoid such filenames, if you want your code to be
927portable to DOS and its derivatives. It's hard to know what these all
928are, unfortunately.
e41182b5
GS
929
930Users of these operating systems may also wish to make use of
83a46a63
LM
931scripts such as F<pl2bat.bat> to put wrappers around your scripts.
932
933Newline (C<\n>) is translated as C<\015\012> by the I/O system when
934reading from and writing to files (see L</"Newlines">).
935C<binmode($filehandle)> will keep C<\n> translated as C<\012> for that
936filehandle.
937L<C<binmode>|perlfunc/binmode FILEHANDLE> should always be used for code
938that deals with binary data. That's assuming you realize in advance that
939your data is in binary. General-purpose programs should often assume
940nothing about their data.
941
942The L<C<$^O>|perlvar/$^O> variable and the
943L<C<$Config{archname}>|Config/C<archname>> values for various DOSish
944perls are as follows:
945
946 OS $^O $Config{archname} ID Version
947 ---------------------------------------------------------
948 MS-DOS dos ?
949 PC-DOS dos ?
950 OS/2 os2 ?
951 Windows 3.1 ? ? 0 3 01
952 Windows 95 MSWin32 MSWin32-x86 1 4 00
953 Windows 98 MSWin32 MSWin32-x86 1 4 10
954 Windows ME MSWin32 MSWin32-x86 1 ?
955 Windows NT MSWin32 MSWin32-x86 2 4 xx
956 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
957 Windows NT MSWin32 MSWin32-ppc 2 4 xx
958 Windows 2000 MSWin32 MSWin32-x86 2 5 00
959 Windows XP MSWin32 MSWin32-x86 2 5 01
960 Windows 2003 MSWin32 MSWin32-x86 2 5 02
961 Windows Vista MSWin32 MSWin32-x86 2 6 00
962 Windows 7 MSWin32 MSWin32-x86 2 6 01
963 Windows 7 MSWin32 MSWin32-x64 2 6 01
964 Windows 2008 MSWin32 MSWin32-x86 2 6 01
965 Windows 2008 MSWin32 MSWin32-x64 2 6 01
966 Windows CE MSWin32 ? 3
967 Cygwin cygwin cygwin
e41182b5 968
34aaaa84 969The various MSWin32 Perl's can distinguish the OS they are running on
2890cc8c 970via the value of the fifth element of the list returned from
83a46a63 971L<C<Win32::GetOSVersion()>|Win32/Win32::GetOSVersion()>. For example:
34aaaa84
PP
972
973 if ($^O eq 'MSWin32') {
974 my @os_version_info = Win32::GetOSVersion();
975 print +('3.1','95','NT')[$os_version_info[4]],"\n";
976 }
977
83a46a63
LM
978There are also C<Win32::IsWinNT()|Win32/Win32::IsWinNT()>,
979C<Win32::IsWin95()|Win32/Win32::IsWin95()>, and
980L<C<Win32::GetOSName()>|Win32/Win32::GetOSName()>; try
981L<C<perldoc Win32>|Win32>.
982The very portable L<C<POSIX::uname()>|POSIX/C<uname>> will work too:
1d65be3a
JH
983
984 c:\> perl -MPOSIX -we "print join '|', uname"
985 Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86
d99f392e 986
e41182b5
GS
987Also see:
988
989=over 4
990
c997b287 991=item *
e41182b5 992
500f1b69 993The djgpp environment for DOS, L<http://www.delorie.com/djgpp/>
c997b287 994and L<perldos>.
e41182b5 995
c997b287 996=item *
e41182b5 997
c997b287 998The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
500f1b69 999L<ftp://hobbes.nmsu.edu/pub/os2/dev/emx/> Also L<perlos2>.
e41182b5 1000
c997b287 1001=item *
d1e3b762 1002
c997b287 1003Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
2890cc8c 1004in L<perlcygwin>.
c997b287
GS
1005
1006=item *
1007
1008The C<Win32::*> modules in L<Win32>.
1009
1010=item *
1011
500f1b69 1012The ActiveState Pages, L<http://www.activestate.com/>
c997b287
GS
1013
1014=item *
1015
2890cc8c 1016The Cygwin environment for Win32; F<README.cygwin> (installed
500f1b69 1017as L<perlcygwin>), L<http://www.cygwin.com/>
c997b287
GS
1018
1019=item *
1020
1021The U/WIN environment for Win32,
500f1b69 1022L<http://www.research.att.com/sw/tools/uwin/>
c997b287 1023
cea6626f 1024=item *
d1e3b762 1025
cea6626f 1026Build instructions for OS/2, L<perlos2>
d1e3b762 1027
e41182b5
GS
1028=back
1029
e41182b5
GS
1030=head2 VMS
1031
2c044526 1032Perl on VMS is discussed in L<perlvms> in the Perl distribution.
016930a6
JM
1033
1034The official name of VMS as of this writing is OpenVMS.
1035
e41182b5
GS
1036Interacting with Perl from the Digital Command Language (DCL) shell
1037often requires a different set of quotation marks than Unix shells do.
1038For example:
1039
1040 $ perl -e "print ""Hello, world.\n"""
1041 Hello, world.
1042
2c044526 1043There are several ways to wrap your Perl scripts in DCL F<.COM> files, if
e41182b5
GS
1044you are so inclined. For example:
1045
1046 $ write sys$output "Hello from DCL!"
1047 $ if p1 .eqs. ""
1048 $ then perl -x 'f$environment("PROCEDURE")
1049 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
1050 $ deck/dollars="__END__"
1051 #!/usr/bin/perl
1052
1053 print "Hello from Perl!\n";
1054
1055 __END__
1056 $ endif
1057
1058Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
2c044526 1059Perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5 1060
9e861032
CB
1061The VMS operating system has two filesystems, designated by their
1062on-disk structure (ODS) level: ODS-2 and its successor ODS-5. The
1063initial port of Perl to VMS pre-dates ODS-5, but all current testing and
1064development assumes ODS-5 and its capabilities, including case
1065preservation, extended characters in filespecs, and names up to 8192
1066bytes long.
016930a6 1067
9e861032
CB
1068Perl on VMS can accept either VMS- or Unix-style file
1069specifications as in either of the following:
1089a9e3 1070
9e861032
CB
1071 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
1072 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
1089a9e3 1073
9e861032 1074but not a mixture of both as in:
1089a9e3 1075
9e861032
CB
1076 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
1077 Can't open sys$login:/login.com: file specification syntax error
e41182b5 1078
9e861032
CB
1079In general, the easiest path to portability is always to specify
1080filenames in Unix format unless they will need to be processed by native
1081commands or utilities. Because of this latter consideration, the
83a46a63 1082L<File::Spec> module by default returns native format specifications
9e861032
CB
1083regardless of input format. This default may be reversed so that
1084filenames are always reported in Unix format by specifying the
1085C<DECC$FILENAME_UNIX_REPORT> feature logical in the environment.
1086
1087The file type, or extension, is always present in a VMS-format file
1088specification even if it's zero-length. This means that, by default,
83a46a63
LM
1089L<C<readdir>|perlfunc/readdir DIRHANDLE> will return a trailing dot on a
1090file with no extension, so where you would see C<"a"> on Unix you'll see
1091C<"a."> on VMS. However, the trailing dot may be suppressed by enabling
1092the C<DECC$READDIR_DROPDOTNOTYPE> feature in the environment (see the CRTL
9e861032 1093documentation on feature logical names).
e41182b5 1094
5e12dbfa 1095What C<\n> represents depends on the type of file opened. It usually
2890cc8c
CBW
1096represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
1097C<\000>, C<\040>, or nothing depending on the file organization and
83a46a63
LM
1098record format. The L<C<VMS::Stdio>|VMS::Stdio> module provides access to
1099the special C<fopen()> requirements of files with unusual attributes on
1100VMS.
e41182b5 1101
83a46a63
LM
1102The value of L<C<$^O>|perlvar/$^O> on OpenVMS is "VMS". To determine the
1103architecture that you are running on refer to
1104L<C<$Config{archname}>|Config/C<archname>>.
016930a6 1105
b7df3edc
GS
1106On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
1107logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
83a46a63
LM
1108calls to L<C<localtime>|perlfunc/localtime EXPR> are adjusted to count
1109offsets from 01-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1110
e41182b5
GS
1111Also see:
1112
1113=over 4
1114
c997b287
GS
1115=item *
1116
96090e4f 1117F<README.vms> (installed as F<README_vms>), L<perlvms>
c997b287
GS
1118
1119=item *
1120
1089a9e3 1121vmsperl list, vmsperl-subscribe@perl.org
e41182b5 1122
c997b287 1123=item *
e41182b5 1124
500f1b69 1125vmsperl on the web, L<http://www.sidhe.org/vmsperl/index.html>
e41182b5 1126
9e861032
CB
1127=item *
1128
1129VMS Software Inc. web site, L<http://www.vmssoftware.com>
1130
e41182b5
GS
1131=back
1132
495c5fdc
GP
1133=head2 VOS
1134
10fb90aa 1135Perl on VOS (also known as OpenVOS) is discussed in F<README.vos>
2c044526 1136in the Perl distribution (installed as L<perlvos>). Perl on VOS
10fb90aa
PG
1137can accept either VOS- or Unix-style file specifications as in
1138either of the following:
495c5fdc 1139
ea8b8ad2
VP
1140 $ perl -ne "print if /perl_setup/i" >system>notices
1141 $ perl -ne "print if /perl_setup/i" /system/notices
495c5fdc
GP
1142
1143or even a mixture of both as in:
1144
ea8b8ad2 1145 $ perl -ne "print if /perl_setup/i" >system/notices
495c5fdc 1146
b7df3edc 1147Even though VOS allows the slash character to appear in object
495c5fdc 1148names, because the VOS port of Perl interprets it as a pathname
10fb90aa
PG
1149delimiting character, VOS files, directories, or links whose
1150names contain a slash character cannot be processed. Such files
1151must be renamed before they can be processed by Perl.
1152
1153Older releases of VOS (prior to OpenVOS Release 17.0) limit file
1154names to 32 or fewer characters, prohibit file names from
1155starting with a C<-> character, and prohibit file names from
83a46a63 1156containing C< > (space) or any character from the set C<< !#%&'()*;<=>? >>.
10fb90aa
PG
1157
1158Newer releases of VOS (OpenVOS Release 17.0 or later) support a
1159feature known as extended names. On these releases, file names
1160can contain up to 255 characters, are prohibited from starting
1161with a C<-> character, and the set of prohibited characters is
83a46a63 1162reduced to C<< #%*<>? >>. There are
c69ca1d4 1163restrictions involving spaces and apostrophes: these characters
10fb90aa
PG
1164must not begin or end a name, nor can they immediately precede or
1165follow a period. Additionally, a space must not immediately
1166precede another space or hyphen. Specifically, the following
1167character combinations are prohibited: space-space,
1168space-hyphen, period-space, space-period, period-apostrophe,
1169apostrophe-period, leading or trailing space, and leading or
1170trailing apostrophe. Although an extended file name is limited
1171to 255 characters, a path name is still limited to 256
1172characters.
1173
83a46a63
LM
1174The value of L<C<$^O>|perlvar/$^O> on VOS is "vos". To determine the
1175architecture that you are running on refer to
1176L<C<$Config{archname}>|Config/C<archname>>.
495c5fdc 1177
495c5fdc
GP
1178Also see:
1179
1180=over 4
1181
c997b287 1182=item *
495c5fdc 1183
cc07ed0b 1184F<README.vos> (installed as L<perlvos>)
c997b287
GS
1185
1186=item *
1187
1188The VOS mailing list.
495c5fdc 1189
7d4dfb6d
PG
1190There is no specific mailing list for Perl on VOS. You can contact
1191the Stratus Technologies Customer Assistance Center (CAC) for your
1192region, or you can use the contact information located in the
1193distribution files on the Stratus Anonymous FTP site.
495c5fdc 1194
c997b287
GS
1195=item *
1196
7d4dfb6d
PG
1197Stratus Technologies on the web at L<http://www.stratus.com>
1198
1199=item *
1200
1201VOS Open-Source Software on the web at L<http://ftp.stratus.com/pub/vos/vos.html>
495c5fdc
GP
1202
1203=back
1204
e41182b5
GS
1205=head2 EBCDIC Platforms
1206
6eb53dea
KW
1207v5.22 core Perl runs on z/OS (formerly OS/390). Theoretically it could
1208run on the successors of OS/400 on AS/400 minicomputers as well as
1209VM/ESA, and BS2000 for S/390 Mainframes. Such computers use EBCDIC
83a46a63
LM
1210character sets internally (usually Character Code Set ID 0037 for OS/400
1211and either 1047 or POSIX-BC for S/390 systems).
6eb53dea
KW
1212
1213The rest of this section may need updating, but we don't know what it
1214should say. Please email comments to
1215L<perlbug@perl.org|mailto:perlbug@perl.org>.
1216
1217On the mainframe Perl currently works under the "Unix system
0cc436d0 1218services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
2c044526 1219the BS200 POSIX-BC system (BS2000 is supported in Perl 5.6 and greater).
522b859a 1220See L<perlos390> for details. Note that for OS/400 there is also a port of
1bcbdd38 1221Perl 5.8.1/5.10.0 or later to the PASE which is ASCII-based (as opposed to
2890cc8c 1222ILE which is EBCDIC-based), see L<perlos400>.
e41182b5 1223
7c5ffed3
JH
1224As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1225sub-systems do not support the C<#!> shebang trick for script invocation.
2c044526 1226Hence, on OS/390 and VM/ESA Perl scripts can be executed with a header
7c5ffed3 1227similar to the following simple script:
e41182b5
GS
1228
1229 : # use perl
1230 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1231 if 0;
1232 #!/usr/local/bin/perl # just a comment really
1233
1234 print "Hello from perl!\n";
1235
d1e3b762 1236OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
83a46a63
LM
1237Calls to L<C<system>|perlfunc/system LIST> and backticks can use POSIX
1238shell syntax on all S/390 systems.
d1e3b762 1239
b7df3edc 1240On the AS/400, if PERL5 is in your library list, you may need
2c044526 1241to wrap your Perl scripts in a CL procedure to invoke them like so:
6ab3f9cb
GS
1242
1243 BEGIN
1244 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1245 ENDPGM
1246
2c044526 1247This will invoke the Perl script F<hello.pl> in the root of the
83a46a63
LM
1248QOpenSys file system. On the AS/400 calls to
1249L<C<system>|perlfunc/system LIST> or backticks must use CL syntax.
6ab3f9cb 1250
e41182b5 1251On these platforms, bear in mind that the EBCDIC character set may have
83a46a63
LM
1252an effect on what happens with some Perl functions (such as
1253L<C<chr>|perlfunc/chr NUMBER>, L<C<pack>|perlfunc/pack TEMPLATE,LIST>,
1254L<C<print>|perlfunc/print FILEHANDLE LIST>,
1255L<C<printf>|perlfunc/printf FILEHANDLE FORMAT, LIST>,
1256L<C<ord>|perlfunc/ord EXPR>, L<C<sort>|perlfunc/sort SUBNAME LIST>,
1257L<C<sprintf>|perlfunc/sprintf FORMAT, LIST>,
1258L<C<unpack>|perlfunc/unpack TEMPLATE,EXPR>), as
1259well as bit-fiddling with ASCII constants using operators like
1260L<C<^>, C<&> and C<|>|perlop/Bitwise String Operators>, not to mention
1261dealing with socket interfaces to ASCII computers (see L</"Newlines">).
e41182b5 1262
b7df3edc
GS
1263Fortunately, most web servers for the mainframe will correctly
1264translate the C<\n> in the following statement to its ASCII equivalent
2c044526 1265(C<\r> is the same under both Unix and z/OS):
e41182b5
GS
1266
1267 print "Content-type: text/html\r\n\r\n";
1268
83a46a63 1269The values of L<C<$^O>|perlvar/$^O> on some of these platforms include:
e41182b5 1270
83a46a63 1271 uname $^O $Config{archname}
d1e3b762
GS
1272 --------------------------------------------
1273 OS/390 os390 os390
1274 OS400 os400 os400
1275 POSIX-BC posix-bc BS2000-posix-bc
3c075c7d 1276
e41182b5
GS
1277Some simple tricks for determining if you are running on an EBCDIC
1278platform could include any of the following (perhaps all):
1279
83a46a63 1280 if ("\t" eq "\005") { print "EBCDIC may be spoken here!\n"; }
e41182b5
GS
1281
1282 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1283
1284 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1285
b7df3edc 1286One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1287of punctuation characters since these may differ from code page to code
1288page (and once your module or script is rumoured to work with EBCDIC,
1289folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1290
1291Also see:
1292
1293=over 4
1294
c997b287
GS
1295=item *
1296
6eb53dea 1297L<perlos390>, L<perlos400>, L<perlbs2000>, L<perlebcdic>.
c997b287
GS
1298
1299=item *
e41182b5
GS
1300
1301The perl-mvs@perl.org list is for discussion of porting issues as well as
1302general usage issues for all EBCDIC Perls. Send a message body of
1303"subscribe perl-mvs" to majordomo@perl.org.
1304
7ee27b7c 1305=item *
c997b287
GS
1306
1307AS/400 Perl information at
500f1b69 1308L<http://as400.rochester.ibm.com/>
d1e3b762 1309as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1310
1311=back
1312
b8099c3d
CN
1313=head2 Acorn RISC OS
1314
b7df3edc 1315Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
2890cc8c 1316Unix, and because Unix filename emulation is turned on by default,
b7df3edc 1317most simple scripts will probably work "out of the box". The native
6ab3f9cb 1318filesystem is modular, and individual filesystems are free to be
0a47030a 1319case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1320native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1321names are silently truncated to fit. Scripts should be aware that the
1322standard filesystem currently has a name length limit of B<10>
1323characters, with up to 77 items in a directory, but other filesystems
0a47030a 1324may not impose such limitations.
b8099c3d
CN
1325
1326Native filenames are of the form
1327
6ab3f9cb 1328 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1329
b8099c3d
CN
1330where
1331
1332 Special_Field is not usually present, but may contain . and $ .
1333 Filesystem =~ m|[A-Za-z0-9_]|
1334 DsicName =~ m|[A-Za-z0-9_/]|
1335 $ represents the root directory
1336 . is the path separator
1337 @ is the current directory (per filesystem but machine global)
1338 ^ is the parent directory
1339 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1340
83a46a63
LM
1341The default filename translation is roughly C<tr|/.|./|>, swapping dots
1342and slahes.
b8099c3d 1343
6ab3f9cb 1344Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a 1345the second stage of C<$> interpolation in regular expressions will fall
83a46a63 1346foul of the L<C<$.>|perlvar/$.> variable if scripts are not careful.
0a47030a
GS
1347
1348Logical paths specified by system variables containing comma-separated
b7df3edc 1349search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1350filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1351C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1352Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1353C<System$Path> contains a single item list. The filesystem will also
1354expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1355C<< <System$Dir>.Modules >> would look for the file
0a47030a 1356S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
83a46a63
LM
1357that B<fully qualified filenames can start with C<< <> >>> and the
1358three-argument form of L<C<open>|perlfunc/open FILEHANDLE,EXPR> should
1359always be used.
b8099c3d
CN
1360
1361Because C<.> was in use as a directory separator and filenames could not
1362be assumed to be unique after 10 characters, Acorn implemented the C
1363compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1364filenames specified in source code and store the respective files in
b7df3edc 1365subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1366
1367 foo.h h.foo
1368 C:foo.h C:h.foo (logical path variable)
1369 sys/os.h sys.h.os (C compiler groks Unix-speak)
1370 10charname.c c.10charname
1371 10charname.o o.10charname
1372 11charname_.c c.11charname (assuming filesystem truncates at 10)
1373
1374The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1375that this sort of translation is required, and it allows a user-defined list
1376of known suffixes that it will transpose in this fashion. This may
92863ac5 1377seem transparent, but consider that with these rules F<foo/bar/baz.h>
83a46a63
LM
1378and F<foo/bar/h/baz> both map to F<foo.bar.h.baz>, and that
1379L<C<readdir>|perlfunc/readdir DIRHANDLE> and L<C<glob>|perlfunc/glob EXPR>
1380cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1381C<.>'s in filenames are translated to C</>.
0a47030a 1382
83a46a63
LM
1383As implied above, the environment accessed through
1384L<C<%ENV>|perlvar/%ENV> is global, and the convention is that program
1385specific environment variables are of the form C<Program$Name>.
1386Each filesystem maintains a current directory,
6ab3f9cb 1387and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1388directory. Consequently, sociable programs don't change the current
1389directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1390assume that they can spawn a child process which can change the current
1391directory without affecting its parent (and everyone else for that
1392matter).
1393
2890cc8c 1394Because native operating system filehandles are global and are currently
b7df3edc 1395allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1396library emulates Unix filehandles. Consequently, you can't rely on
1397passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1398
1399The desire of users to express filenames of the form
c47ff5f1 1400C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
83a46a63
LM
1401too: L<C<``>|perlop/C<qxE<sol>I<STRING>E<sol>>> command output capture has
1402to perform a guessing game. It assumes that a string C<< <[^<>]+\$[^<>]> >>
1403is a reference to an environment variable, whereas anything else involving
c47ff5f1 1404C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1405right. Of course, the problem remains that scripts cannot rely on any
1406Unix tools being available, or that any tools found have Unix-like command
1407line arguments.
1408
b7df3edc
GS
1409Extensions and XS are, in theory, buildable by anyone using free
1410tools. In practice, many don't, as users of the Acorn platform are
1411used to binary distributions. MakeMaker does run, but no available
1412make currently copes with MakeMaker's makefiles; even if and when
1413this should be fixed, the lack of a Unix-like shell will cause
83a46a63
LM
1414problems with makefile rules, especially lines of the form
1415C<cd sdbm && make all>, and anything using quoting.
b8099c3d 1416
83a46a63
LM
1417S<"RISC OS"> is the proper name for the operating system, but the value
1418in L<C<$^O>|perlvar/$^O> is "riscos" (because we don't like shouting).
b8099c3d 1419
e41182b5
GS
1420=head2 Other perls
1421
b7df3edc 1422Perl has been ported to many platforms that do not fit into any of
b6c36746 1423the categories listed above. Some, such as AmigaOS,
cd86ed9d
JV
1424QNX, Plan 9, and VOS, have been well-integrated into the standard
1425Perl source code kit. You may need to see the F<ports/> directory
1426on CPAN for information, and possibly binaries, for the likes of:
1427aos, Atari ST, lynxos, riscos, Novell Netware, Tandem Guardian,
1428I<etc.> (Yes, we know that some of these OSes may fall under the
1429Unix category, but we are not a standards body.)
e41182b5 1430
83a46a63
LM
1431Some approximate operating system names and their L<C<$^O>|perlvar/$^O>
1432values in the "OTHER" category include:
d1e3b762 1433
83a46a63 1434 OS $^O $Config{archname}
d1e3b762
GS
1435 ------------------------------------------
1436 Amiga DOS amigaos m68k-amigos
d1e3b762 1437
e41182b5
GS
1438See also:
1439
1440=over 4
1441
c997b287
GS
1442=item *
1443
1444Amiga, F<README.amiga> (installed as L<perlamiga>).
1445
1446=item *
d1e3b762 1447
6ab3f9cb 1448A free perl5-based PERL.NLM for Novell Netware is available in
500f1b69 1449precompiled binary and source code form from L<http://www.novell.com/>
6ab3f9cb 1450as well as from CPAN.
e41182b5 1451
13a2d996 1452=item *
c997b287 1453
e6f03d26 1454S<Plan 9>, F<README.plan9>
d1e3b762 1455
e41182b5
GS
1456=back
1457
e41182b5
GS
1458=head1 FUNCTION IMPLEMENTATIONS
1459
b7df3edc
GS
1460Listed below are functions that are either completely unimplemented
1461or else have been implemented differently on various platforms.
1462Following each description will be, in parentheses, a list of
1463platforms that the description applies to.
e41182b5 1464
b7df3edc
GS
1465The list may well be incomplete, or even wrong in some places. When
1466in doubt, consult the platform-specific README files in the Perl
1467source distribution, and any other documentation resources accompanying
1468a given port.
e41182b5 1469
0a47030a 1470Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1471
83a46a63
LM
1472For many functions, you can also query L<C<%Config>|Config/DESCRIPTION>,
1473exported by default from the L<C<Config>|Config> module. For example, to
1474check whether the platform has the L<C<lstat>|perlfunc/lstat FILEHANDLE>
1475call, check L<C<$Config{d_lstat}>|Config/C<d_lstat>>. See L<Config> for a
1476full description of available variables.
e41182b5
GS
1477
1478=head2 Alphabetical Listing of Perl Functions
1479
1480=over 8
1481
e41182b5
GS
1482=item -X
1483
038ae9a4
SH
1484C<-w> only inspects the read-only file attribute (FILE_ATTRIBUTE_READONLY),
1485which determines whether the directory can be deleted, not whether it can
1486be written to. Directories always have read and write access unless denied
83a46a63 1487by discretionary access control lists (DACLs). (Win32)
038ae9a4 1488
b7df3edc
GS
1489C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1490which may not reflect UIC-based file protections. (VMS)
e41182b5 1491
b8099c3d
CN
1492C<-s> by name on an open file will return the space reserved on disk,
1493rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1494current size. (S<RISC OS>)
b8099c3d 1495
e41182b5 1496C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
83a46a63 1497C<-x>, C<-o>. (Win32, VMS, S<RISC OS>)
e41182b5 1498
287a962e 1499C<-g>, C<-k>, C<-l>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1500(Win32, VMS, S<RISC OS>)
e41182b5 1501
83a46a63 1502C<-p> is not particularly meaningful. (VMS, S<RISC OS>)
287a962e 1503
e41182b5
GS
1504C<-d> is true if passed a device spec without an explicit directory.
1505(VMS)
1506
e41182b5 1507C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1508suffixes. C<-S> is meaningless. (Win32)
e41182b5 1509
b8099c3d
CN
1510C<-x> (or C<-X>) determine if a file has an executable file type.
1511(S<RISC OS>)
1512
aca72608
JD
1513=item alarm
1514
1515Emulated using timers that must be explicitly polled whenever Perl
1516wants to dispatch "safe signals" and therefore cannot interrupt
1517blocking system calls. (Win32)
1518
47cd99a4 1519=item atan2
519bc777
RGS
1520
1521Due to issues with various CPUs, math libraries, compilers, and standards,
83a46a63 1522results for C<atan2> may vary depending on any combination of the above.
519bc777 1523Perl attempts to conform to the Open Group/IEEE standards for the results
83a46a63 1524returned from C<atan2>, but cannot force the issue if the system Perl is
2890cc8c 1525run on does not allow it. (Tru64, HP-UX 10.20)
519bc777 1526
83a46a63 1527The current version of the standards for C<atan2> is available at
519bc777
RGS
1528L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.
1529
47cd99a4 1530=item binmode
e41182b5 1531
204ad8d5 1532Meaningless. (S<RISC OS>)
e41182b5
GS
1533
1534Reopens file and restores pointer; if function fails, underlying
1535filehandle may be closed, or pointer may be in a different position.
1536(VMS)
1537
83a46a63
LM
1538The value returned by L<C<tell>|perlfunc/tell FILEHANDLE> may be affected
1539after the call, and the filehandle may be flushed. (Win32)
e41182b5 1540
47cd99a4 1541=item chmod
e41182b5 1542
83a46a63
LM
1543Only good for changing "owner" read-write access; "group" and "other"
1544bits are meaningless. (Win32)
e41182b5 1545
83a46a63 1546Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
b8099c3d 1547
83a46a63 1548Access permissions are mapped onto VOS access-control list changes. (VOS)
495c5fdc 1549
83a46a63 1550The actual permissions set depend on the value of the C<CYGWIN> variable
789f0d36 1551in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1552
2c044526 1553Setting the exec bit on some locations (generally F</sdcard>) will return true
83a46a63 1554but not actually set the bit. (Android)
43b08d74 1555
47cd99a4 1556=item chown
e41182b5 1557
83a46a63 1558Not implemented. (S<Plan 9>, S<RISC OS>)
e41182b5 1559
83a46a63 1560Does nothing, but won't fail. (Win32)
e41182b5 1561
83a46a63 1562A little funky, because VOS's notion of ownership is a little funky. (VOS)
3fd80bd6 1563
e41182b5
GS
1564=item chroot
1565
83a46a63 1566Not implemented. (Win32, VMS, S<Plan 9>, S<RISC OS>, VOS)
e41182b5 1567
47cd99a4 1568=item crypt
e41182b5
GS
1569
1570May not be available if library or source was not provided when building
83a46a63 1571perl. (Win32)
e41182b5 1572
83a46a63 1573Not implemented. (Android)
43b08d74 1574
47cd99a4 1575=item dbmclose
e41182b5 1576
83a46a63 1577Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1578
47cd99a4 1579=item dbmopen
e41182b5 1580
83a46a63 1581Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1582
47cd99a4 1583=item dump
e41182b5 1584
83a46a63 1585Not useful. (S<RISC OS>)
e41182b5 1586
83a46a63 1587Not supported. (Cygwin, Win32)
e41182b5 1588
83a46a63 1589Invokes VMS debugger. (VMS)
e41182b5 1590
47cd99a4 1591=item exec
e41182b5 1592
94d4006a 1593C<exec LIST> without the use of indirect object syntax (C<exec PROGRAM LIST>)
2c044526 1594may fall back to trying the shell if the first C<spawn()> fails. (Win32)
94d4006a 1595
0f897271
GS
1596Does not automatically flush output handles on some platforms.
1597(SunOS, Solaris, HP-UX)
1598
83a46a63 1599Not supported. (Symbian OS)
af8bb25a 1600
fe12c0e8
MS
1601=item exit
1602
83a46a63 1603Emulates Unix C<exit> (which considers C<exit 1> to indicate an error) by
2c044526 1604mapping the C<1> to C<SS$_ABORT> (C<44>). This behavior may be overridden
83a46a63
LM
1605with the pragma L<C<use vmsish 'exit'>|vmsish/C<vmsish exit>>. As with
1606the CRTL's C<exit()> function, C<exit 0> is also mapped to an exit status
1607of C<SS$_NORMAL> (C<1>); this mapping cannot be overridden. Any other
1608argument to C<exit>
016930a6
JM
1609is used directly as Perl's exit status. On VMS, unless the future
1610POSIX_EXIT mode is enabled, the exit code should always be a valid
1611VMS exit code and not a generic number. When the POSIX_EXIT mode is
1612enabled, a generic number will be encoded in a method compatible with
1613the C library _POSIX_EXIT macro so that it can be decoded by other
1614programs, particularly ones written in C, like the GNV package. (VMS)
fe12c0e8 1615
83a46a63
LM
1616C<exit> resets file pointers, which is a problem when called
1617from a child process (created by L<C<fork>|perlfunc/fork>) in
1618L<C<BEGIN>|perlmod/BEGIN, UNITCHECK, CHECK, INIT and END>.
1619A workaround is to use L<C<POSIX::_exit>|POSIX/C<_exit>>. (Solaris)
bef2c191
RB
1620
1621 exit unless $Config{archname} =~ /\bsolaris\b/;
83a46a63
LM
1622 require POSIX;
1623 POSIX::_exit(0);
bef2c191 1624
47cd99a4 1625=item fcntl
e41182b5 1626
83a46a63 1627Not implemented. (Win32)
6a065175 1628
83a46a63 1629Some functions available based on the version of VMS. (VMS)
e41182b5 1630
47cd99a4 1631=item flock
e41182b5 1632
83a46a63 1633Not implemented (VMS, S<RISC OS>, VOS).
e41182b5 1634
e41182b5
GS
1635=item fork
1636
83a46a63 1637Not implemented. (AmigaOS, S<RISC OS>, VMS)
0f897271
GS
1638
1639Emulated using multiple interpreters. See L<perlfork>. (Win32)
1640
1641Does not automatically flush output handles on some platforms.
1642(SunOS, Solaris, HP-UX)
e41182b5
GS
1643
1644=item getlogin
1645
83a46a63 1646Not implemented. (S<RISC OS>)
e41182b5 1647
47cd99a4 1648=item getpgrp
e41182b5 1649
83a46a63 1650Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1651
1652=item getppid
1653
83a46a63 1654Not implemented. (Win32, S<RISC OS>)
e41182b5 1655
47cd99a4 1656=item getpriority
e41182b5 1657
83a46a63 1658Not implemented. (Win32, VMS, S<RISC OS>, VOS)
e41182b5 1659
47cd99a4 1660=item getpwnam
e41182b5 1661
83a46a63 1662Not implemented. (Win32)
e41182b5 1663
83a46a63 1664Not useful. (S<RISC OS>)
b8099c3d 1665
47cd99a4 1666=item getgrnam
e41182b5 1667
83a46a63 1668Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1669
47cd99a4 1670=item getnetbyname
e41182b5 1671
83a46a63 1672Not implemented. (Android, Win32, S<Plan 9>)
e41182b5 1673
47cd99a4 1674=item getpwuid
e41182b5 1675
83a46a63 1676Not implemented. (Win32)
e41182b5 1677
83a46a63 1678Not useful. (S<RISC OS>)
b8099c3d 1679
47cd99a4 1680=item getgrgid
e41182b5 1681
83a46a63 1682Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1683
47cd99a4 1684=item getnetbyaddr
e41182b5 1685
83a46a63 1686Not implemented. (Android, Win32, S<Plan 9>)
e41182b5 1687
47cd99a4 1688=item getprotobynumber
e41182b5 1689
83a46a63 1690Not implemented. (Android)
43b08d74 1691
e41182b5
GS
1692=item getpwent
1693
83a46a63 1694Not implemented. (Android, Win32)
e41182b5
GS
1695
1696=item getgrent
1697
83a46a63 1698Not implemented. (Android, Win32, VMS)
e41182b5 1699
ef5a6dd7
JH
1700=item gethostbyname
1701
1702C<gethostbyname('localhost')> does not work everywhere: you may have
83a46a63 1703to use C<gethostbyname('127.0.0.1')>. (S<Irix 5>)
ef5a6dd7 1704
e41182b5
GS
1705=item gethostent
1706
83a46a63 1707Not implemented. (Win32)
e41182b5
GS
1708
1709=item getnetent
1710
83a46a63 1711Not implemented. (Android, Win32, S<Plan 9>)
e41182b5
GS
1712
1713=item getprotoent
1714
83a46a63 1715Not implemented. (Android, Win32, S<Plan 9>)
e41182b5
GS
1716
1717=item getservent
1718
83a46a63 1719Not implemented. (Win32, S<Plan 9>)
e41182b5 1720
43b08d74
BF
1721=item seekdir
1722
83a46a63 1723Not implemented. (Android)
43b08d74 1724
47cd99a4 1725=item sethostent
e41182b5 1726
83a46a63 1727Not implemented. (Android, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1728
47cd99a4 1729=item setnetent
e41182b5 1730
83a46a63 1731Not implemented. (Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1732
47cd99a4 1733=item setprotoent
e41182b5 1734
83a46a63 1735Not implemented. (Android, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1736
47cd99a4 1737=item setservent
e41182b5 1738
83a46a63 1739Not implemented. (S<Plan 9>, Win32, S<RISC OS>)
e41182b5
GS
1740
1741=item endpwent
1742
83a46a63 1743Not implemented. (Win32)
e41182b5 1744
83a46a63 1745Either not implemented or a no-op. (Android)
43b08d74 1746
e41182b5
GS
1747=item endgrent
1748
83a46a63 1749Not implemented. (Android, S<RISC OS>, VMS, Win32)
e41182b5
GS
1750
1751=item endhostent
1752
83a46a63 1753Not implemented. (Android, Win32)
e41182b5
GS
1754
1755=item endnetent
1756
83a46a63 1757Not implemented. (Android, Win32, S<Plan 9>)
e41182b5
GS
1758
1759=item endprotoent
1760
83a46a63 1761Not implemented. (Android, Win32, S<Plan 9>)
e41182b5
GS
1762
1763=item endservent
1764
83a46a63 1765Not implemented. (S<Plan 9>, Win32)
e41182b5 1766
1096c54b 1767=item getsockopt
e41182b5 1768
83a46a63 1769Not implemented. (S<Plan 9>)
e41182b5 1770
e41182b5
GS
1771=item glob
1772
83a46a63
LM
1773This operator is implemented via the L<C<File::Glob>|File::Glob> extension
1774on most platforms. See L<File::Glob> for portability information.
b8099c3d 1775
62aa5637
MS
1776=item gmtime
1777
83a46a63
LM
1778In theory, C<gmtime> is reliable from -2**63 to 2**63-1. However,
1779because work-arounds in the implementation use floating point numbers,
461d5a49
MS
1780it will become inaccurate as the time gets larger. This is a bug and
1781will be fixed in the future.
62aa5637 1782
83a46a63 1783Time values are 32-bit quantities. (VOS)
10fb90aa 1784
1096c54b 1785=item ioctl
e41182b5 1786
83a46a63 1787Not implemented. (VMS)
e41182b5 1788
2c044526 1789Available only for socket handles, and it does what the C<ioctlsocket()> call
83a46a63 1790in the Winsock API does. (Win32)
e41182b5 1791
83a46a63 1792Available only for socket handles. (S<RISC OS>)
b8099c3d 1793
47cd99a4 1794=item kill
e41182b5 1795
83a46a63 1796Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1797
83a46a63
LM
1798C<kill> doesn't send a signal to the identified process like it does on
1799Unix platforms. Instead C<kill($sig, $pid)> terminates the process
1800identified by C<$pid>, and makes it exit immediately with exit status
1801C<$sig>. As in Unix, if C<$sig> is 0 and the specified process exists, it
1802returns true without actually terminating it. (Win32)
e41182b5 1803
2c044526 1804C<kill(-9, $pid)> will terminate the process specified by C<$pid> and
d0302514
JD
1805recursively all child processes owned by it. This is different from
1806the Unix semantics, where the signal will be delivered to all
1807processes in the same process group as the process specified by
83a46a63 1808C<$pid>. (Win32)
d0302514 1809
96f902ff 1810A pid of -1 indicating all processes on the system is not currently
83a46a63 1811supported. (VMS)
016930a6 1812
47cd99a4 1813=item link
e41182b5 1814
83a46a63 1815Not implemented. (S<RISC OS>, VOS)
e41182b5 1816
433acd8a 1817Link count not updated because hard links are not quite that hard
83a46a63 1818(They are sort of half-way between hard and soft links). (AmigaOS)
433acd8a 1819
63d6c08b
JD
1820Hard links are implemented on Win32 under NTFS only. They are
1821natively supported on Windows 2000 and later. On Windows NT they
1822are implemented using the Windows POSIX subsystem support and the
1823Perl process will need Administrator or Backup Operator privileges
83a46a63 1824to create hard links. (Win32)
a3dfe201 1825
016930a6
JM
1826Available on 64 bit OpenVMS 8.2 and later. (VMS)
1827
62aa5637
MS
1828=item localtime
1829
83a46a63
LM
1830C<localtime> has the same range as L</gmtime>, but because time zone
1831rules change, its accuracy for historical and future times may degrade
dc164757 1832but usually by no more than an hour.
62aa5637 1833
e41182b5
GS
1834=item lstat
1835
83a46a63 1836Not implemented. (S<RISC OS>)
e41182b5 1837
83a46a63 1838Return values (especially for device and inode) may be bogus. (Win32)
e41182b5 1839
47cd99a4 1840=item msgctl
e41182b5 1841
47cd99a4 1842=item msgget
e41182b5 1843
47cd99a4 1844=item msgsnd
e41182b5 1845
47cd99a4 1846=item msgrcv
e41182b5 1847
83a46a63 1848Not implemented. (Android, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS)
e41182b5 1849
47cd99a4 1850=item open
e41182b5 1851
83a46a63 1852Open modes C<|-> and C<-|> are unsupported. (Win32, S<RISC OS>)
e41182b5 1853
0f897271
GS
1854Opening a process does not automatically flush output handles on some
1855platforms. (SunOS, Solaris, HP-UX)
1856
e41182b5
GS
1857=item readlink
1858
83a46a63 1859Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1860
47cd99a4 1861=item rename
c9b2b9d4 1862
83a46a63 1863Can't move directories between directories on different logical volumes. (Win32)
c9b2b9d4 1864
3ba4b5c1
JD
1865=item rewinddir
1866
83a46a63
LM
1867Will not cause L<C<readdir>|perlfunc/readdir DIRHANDLE> to re-read the
1868directory stream. The entries already read before the C<rewinddir> call
1869will just be returned again from a cache buffer. (Win32)
3ba4b5c1 1870
47cd99a4 1871=item select
e41182b5 1872
83a46a63 1873Only implemented on sockets. (Win32, VMS)
e41182b5 1874
83a46a63 1875Only reliable on sockets. (S<RISC OS>)
b8099c3d 1876
83a46a63
LM
1877Note that the L<C<select FILEHANDLE>|perlfunc/select FILEHANDLE> form is
1878generally portable.
63f87e49 1879
47cd99a4 1880=item semctl
e41182b5 1881
47cd99a4 1882=item semget
e41182b5 1883
47cd99a4 1884=item semop
e41182b5 1885
83a46a63 1886Not implemented. (Android, Win32, VMS, S<RISC OS>)
e41182b5 1887
a3dfe201
GS
1888=item setgrent
1889
83a46a63 1890Not implemented. (Android, VMS, Win32, S<RISC OS>)
a3dfe201 1891
47cd99a4 1892=item setpgrp
e41182b5 1893
83a46a63 1894Not implemented. (Win32, VMS, S<RISC OS>, VOS)
e41182b5 1895
47cd99a4 1896=item setpriority
e41182b5 1897
83a46a63 1898Not implemented. (Win32, VMS, S<RISC OS>, VOS)
e41182b5 1899
a3dfe201
GS
1900=item setpwent
1901
83a46a63 1902Not implemented. (Android, Win32, S<RISC OS>)
a3dfe201 1903
47cd99a4 1904=item setsockopt
e41182b5 1905
83a46a63 1906Not implemented. (S<Plan 9>)
e41182b5 1907
47cd99a4 1908=item shmctl
e41182b5 1909
47cd99a4 1910=item shmget
e41182b5 1911
47cd99a4 1912=item shmread
e41182b5 1913
47cd99a4 1914=item shmwrite
e41182b5 1915
83a46a63 1916Not implemented. (Android, Win32, VMS, S<RISC OS>)
e41182b5 1917
001e9f89
DD
1918=item sleep
1919
3cd50447 1920Emulated using synchronization functions such that it can be
83a46a63
LM
1921interrupted by L<C<alarm>|perlfunc/alarm SECONDS>, and limited to a
1922maximum of 4294967 seconds, approximately 49 days. (Win32)
80cbd5ad 1923
47cd99a4 1924=item socketpair
e41182b5 1925
83a46a63 1926Not implemented. (S<RISC OS>)
10fb90aa 1927
016930a6 1928Available on 64 bit OpenVMS 8.2 and later. (VMS)
e41182b5 1929
e41182b5
GS
1930=item stat
1931
83a46a63
LM
1932Platforms that do not have C<rdev>, C<blksize>, or C<blocks> will return
1933these as C<''>, so numeric comparison or manipulation of these fields may
1934cause 'not numeric' warnings.
d62e1b7f 1935
83a46a63 1936C<ctime> not supported on UFS. (S<Mac OS X>)
e41182b5 1937
83a46a63 1938C<ctime> is creation time instead of inode change time. (Win32)
95a3fe12 1939
83a46a63 1940C<dev> and C<ino> are not meaningful. (Win32)
e41182b5 1941
83a46a63 1942C<dev> and C<ino> are not necessarily reliable. (VMS)
e41182b5 1943
83a46a63
LM
1944C<mtime>, C<atime> and C<ctime> all return the last modification time.
1945C<dev> and C<ino> are not necessarily reliable. (S<RISC OS>)
b8099c3d 1946
83a46a63
LM
1947C<dev>, C<rdev>, C<blksize>, and C<blocks> are not available. C<ino> is not
1948meaningful and will differ between stat calls on the same file. (OS/2)
d62e1b7f 1949
83a46a63
LM
1950Some versions of cygwin when doing a C<stat("foo")> and not finding it
1951may then attempt to C<stat("foo.exe")>. (Cygwin)
73e9292c 1952
83a46a63 1953C<stat> needs to open the file to determine the link count
1fafdf34 1954and update attributes that may have been changed through hard links.
83a46a63
LM
1955Setting L<C<${^WIN32_SLOPPY_STAT}>|perlvar/${^WIN32_SLOPPY_STAT}> to a
1956true value speeds up C<stat> by not performing this operation. (Win32)
1fafdf34 1957
47cd99a4 1958=item symlink
e41182b5 1959
83a46a63 1960Not implemented. (Win32, S<RISC OS>)
c73b03b7
JM
1961
1962Implemented on 64 bit VMS 8.3. VMS requires the symbolic link to be in Unix
83a46a63 1963syntax if it is intended to resolve to a valid path. (VMS)
e41182b5 1964
47cd99a4 1965=item syscall
e41182b5 1966
83a46a63 1967Not implemented. (Win32, VMS, S<RISC OS>, VOS)
e41182b5 1968
47cd99a4 1969=item sysopen
f34d0673 1970
83a46a63
LM
1971The traditional C<0>, C<1>, and C<2> MODEs are implemented with different
1972numeric values on some systems. The flags exported by L<C<Fcntl>|Fcntl>
1973(C<O_RDONLY>, C<O_WRONLY>, C<O_RDWR>) should work everywhere though.
1974(S<Mac OS>, OS/390)
f34d0673 1975
47cd99a4 1976=item system
e41182b5 1977
e41182b5 1978As an optimization, may not call the command shell specified in
b7df3edc 1979C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
1980process and immediately returns its process designator, without
1981waiting for it to terminate. Return value may be used subsequently
83a46a63
LM
1982in L<C<wait>|perlfunc/wait> or L<C<waitpid>|perlfunc/waitpid PID,FLAGS>.
1983Failure to C<spawn()> a subprocess is indicated by setting
1984L<C<$?>|perlvar/$?> to C<<< 255 << 8 >>>. L<C<$?>|perlvar/$?> is set in a
1985way compatible with Unix (i.e. the exit status of the subprocess is
1986obtained by C<<< $? >> 8 >>>, as described in the documentation). (Win32)
e41182b5 1987
b8099c3d
CN
1988There is no shell to process metacharacters, and the native standard is
1989to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 1990program. Redirection such as C<< > foo >> is performed (if at all) by
83a46a63
LM
1991the run time library of the spawned program. C<system LIST> will call
1992the Unix emulation library's L<C<exec>|perlfunc/exec LIST> emulation,
1993which attempts to provide emulation of the stdin, stdout, stderr in force
1994in the parent, provided the child program uses a compatible version of the
1995emulation library. C<system SCALAR> will call the native command line
1996directly and no such emulation of a child Unix program will occur.
1997Mileage B<will> vary. (S<RISC OS>)
b8099c3d 1998
94d4006a 1999C<system LIST> without the use of indirect object syntax (C<system PROGRAM LIST>)
2c044526 2000may fall back to trying the shell if the first C<spawn()> fails. (Win32)
94d4006a 2001
0f897271
GS
2002Does not automatically flush output handles on some platforms.
2003(SunOS, Solaris, HP-UX)
2004
9bc98430
CB
2005The return value is POSIX-like (shifted up by 8 bits), which only allows
2006room for a made-up value derived from the severity bits of the native
83a46a63
LM
200732-bit condition code (unless overridden by
2008L<C<use vmsish 'status'>|vmsish/C<vmsish status>>). If the native
2009condition code is one that has a POSIX value encoded, the POSIX value will
2010be decoded to extract the expected exit value. For more details see
2011L<perlvms/$?>. (VMS)
9bc98430 2012
43b08d74
BF
2013=item telldir
2014
83a46a63 2015Not implemented. (Android)
43b08d74 2016
e41182b5
GS
2017=item times
2018
83a46a63 2019"Cumulative" times will be bogus. On anything other than Windows NT
63f87e49 2020or Windows 2000, "system" time will be bogus, and "user" time is
83a46a63
LM
2021actually the time returned by the L<C<clock()>|clock(3)> function in the C
2022runtime library. (Win32)
e41182b5 2023
83a46a63 2024Not useful. (S<RISC OS>)
b8099c3d 2025
47cd99a4 2026=item truncate
e41182b5 2027
83a46a63 2028Not implemented. (Older versions of VMS)
e41182b5 2029
83a46a63 2030Truncation to same-or-shorter lengths only. (VOS)
495c5fdc 2031
4cfdb94f 2032If a FILEHANDLE is supplied, it must be writable and opened in append
83a46a63
LM
2033mode (i.e., use C<<< open(my $fh, '>>', 'filename') >>>
2034or C<sysopen(my $fh, ..., O_APPEND|O_RDWR)>. If a filename is supplied, it
2035should not be held open elsewhere. (Win32)
4cfdb94f 2036
e41182b5
GS
2037=item umask
2038
83a46a63 2039Returns C<undef> where unavailable.
e41182b5 2040
b7df3edc 2041C<umask> works but the correct permissions are set only when the file
83a46a63 2042is finally closed. (AmigaOS)
433acd8a 2043
47cd99a4 2044=item utime
e41182b5 2045
83a46a63 2046Only the modification time is updated. (VMS, S<RISC OS>)
e41182b5 2047
322422de 2048May not behave as expected. Behavior depends on the C runtime
83a46a63
LM
2049library's implementation of L<C<utime()>|utime(2)>, and the filesystem
2050being used. The FAT filesystem typically does not support an "access
2051time" field, and it may limit timestamps to a granularity of two seconds.
2052(Win32)
e41182b5
GS
2053
2054=item wait
2055
47cd99a4 2056=item waitpid
e41182b5 2057
e41182b5 2058Can only be applied to process handles returned for processes spawned
83a46a63
LM
2059using C<system(1, ...)> or pseudo processes created with
2060L<C<fork>|perlfunc/fork>. (Win32)
e41182b5 2061
83a46a63 2062Not useful. (S<RISC OS>)
b8099c3d 2063
e41182b5
GS
2064=back
2065
2066
7c35b6af 2067=head1 Supported Platforms
ba58ab26 2068
7c35b6af
RGS
2069The following platforms are known to build Perl 5.12 (as of April 2010,
2070its release date) from the standard source code distribution available
500f1b69 2071at L<http://www.cpan.org/src>
bb377ba2 2072
bb377ba2
JV
2073=over
2074
2075=item Linux (x86, ARM, IA64)
2076
e0d9a2c8 2077=item HP-UX
bb377ba2
JV
2078
2079=item AIX
2080
2081=item Win32
2082
2083=over
2084
2085=item Windows 2000
2086
2087=item Windows XP
2088
2089=item Windows Server 2003
2090
2091=item Windows Vista
2092
2093=item Windows Server 2008
2094
3b665c47
JD
2095=item Windows 7
2096
bb377ba2
JV
2097=back
2098
2d9ede6e
JH
2099=item Cygwin
2100
67e52905
TC
2101Some tests are known to fail:
2102
2103=over
2104
2105=item *
2106
cb0ee57a 2107F<ext/XS-APItest/t/call_checker.t> - see
67e52905
TC
2108L<https://rt.perl.org/Ticket/Display.html?id=78502>
2109
2110=item *
2111
2112F<dist/I18N-Collate/t/I18N-Collate.t>
2113
2114=item *
2115
2116F<ext/Win32CORE/t/win32core.t> - may fail on recent cygwin installs.
2117
2118=back
2119
bb377ba2
JV
2120=item Solaris (x86, SPARC)
2121
1b0ab010
JV
2122=item OpenVMS
2123
2124=over
2125
2126=item Alpha (7.2 and later)
2127
2128=item I64 (8.2 and later)
2129
2130=back
bb377ba2
JV
2131
2132=item Symbian
2133
2134=item NetBSD
2135
2136=item FreeBSD
2137
2d8e9a35
CBW
2138=item Debian GNU/kFreeBSD
2139
bb377ba2
JV
2140=item Haiku
2141
2142=item Irix (6.5. What else?)
2143
2144=item OpenBSD
2145
2146=item Dragonfly BSD
2147
b60fc215
CBW
2148=item Midnight BSD
2149
a62bfce3
CBW
2150=item QNX Neutrino RTOS (6.5.0)
2151
bb377ba2
JV
2152=item MirOS BSD
2153
7d4dfb6d
PG
2154=item Stratus OpenVOS (17.0 or later)
2155
bb377ba2
JV
2156Caveats:
2157
2158=over
2159
2160=item time_t issues that may or may not be fixed
2161
2162=back
2163
bb377ba2
JV
2164=item Symbian (Series 60 v3, 3.2 and 5 - what else?)
2165
10fb90aa 2166=item Stratus VOS / OpenVOS
bb377ba2
JV
2167
2168=item AIX
2169
25be0a81
BF
2170=item Android
2171
dcfa7505
TC
2172=item FreeMINT
2173
2174Perl now builds with FreeMiNT/Atari. It fails a few tests, that needs
2175some investigation.
2176
2177The FreeMiNT port uses GNU dld for loadable module capabilities. So
2178ensure you have that library installed when building perl.
2179
bb377ba2
JV
2180=back
2181
2890cc8c 2182=head1 EOL Platforms
7b0e9f13
AD
2183
2184=head2 (Perl 5.20)
bb377ba2
JV
2185
2186The following platforms were supported by a previous version of
2187Perl but have been officially removed from Perl's source code
7b0e9f13 2188as of 5.20:
bb377ba2
JV
2189
2190=over
2191
7b0e9f13 2192=item AT&T 3b1
bb377ba2
JV
2193
2194=back
2195
7b0e9f13
AD
2196=head2 (Perl 5.14)
2197
8cbe99e5
JD
2198The following platforms were supported up to 5.10. They may still
2199have worked in 5.12, but supporting code has been removed for 5.14:
bb377ba2
JV
2200
2201=over
2202
2203=item Windows 95
2204
2205=item Windows 98
2206
2207=item Windows ME
2208
2209=item Windows NT4
2210
2211=back
2212
7b0e9f13
AD
2213=head2 (Perl 5.12)
2214
2215The following platforms were supported by a previous version of
2216Perl but have been officially removed from Perl's source code
2217as of 5.12:
2218
2219=over
2220
2221=item Atari MiNT
2222
2223=item Apollo Domain/OS
2224
2225=item Apple Mac OS 8/9
2226
2227=item Tenon Machten
2228
2229=back
2230
2231
bb377ba2
JV
2232=head1 Supported Platforms (Perl 5.8)
2233
2234As of July 2002 (the Perl release 5.8.0), the following platforms were
cec2c193 2235able to build Perl from the standard source code distribution
500f1b69 2236available at L<http://www.cpan.org/src/>
cec2c193
JH
2237
2238 AIX
2239 BeOS
6f683aa2 2240 BSD/OS (BSDi)
cec2c193 2241 Cygwin
ea297d26 2242 DG/UX
811b48f2 2243 DOS DJGPP 1)
cec2c193
JH
2244 DYNIX/ptx
2245 EPOC R5
2246 FreeBSD
6f683aa2 2247 HI-UXMPP (Hitachi) (5.8.0 worked but we didn't know it)
cec2c193
JH
2248 HP-UX
2249 IRIX
2250 Linux
8939ba94 2251 Mac OS Classic
6f683aa2 2252 Mac OS X (Darwin)
cec2c193
JH
2253 MPE/iX
2254 NetBSD
2255 NetWare
2256 NonStop-UX
6f683aa2 2257 ReliantUNIX (formerly SINIX)
cec2c193 2258 OpenBSD
6f683aa2 2259 OpenVMS (formerly VMS)
3ebac25b 2260 Open UNIX (Unixware) (since Perl 5.8.1/5.9.0)
cec2c193 2261 OS/2
522b859a 2262 OS/400 (using the PASE) (since Perl 5.8.1/5.9.0)
70de81db 2263 PowerUX
6f683aa2 2264 POSIX-BC (formerly BS2000)
cec2c193
JH
2265 QNX
2266 Solaris
70de81db 2267 SunOS 4
6f683aa2
JH
2268 SUPER-UX (NEC)
2269 Tru64 UNIX (formerly DEC OSF/1, Digital UNIX)
cec2c193
JH
2270 UNICOS
2271 UNICOS/mk
2272 UTS
7d4dfb6d 2273 VOS / OpenVOS
811b48f2 2274 Win95/98/ME/2K/XP 2)
c40b5d1d 2275 WinCE
6f683aa2 2276 z/OS (formerly OS/390)
cec2c193 2277 VM/ESA
ba58ab26 2278
811b48f2
JH
2279 1) in DOS mode either the DOS or OS/2 ports can be used
2280 2) compilers: Borland, MinGW (GCC), VC6
cec2c193 2281
c40b5d1d 2282The following platforms worked with the previous releases (5.6 and
cec2c193
JH
22835.7), but we did not manage either to fix or to test these in time
2284for the 5.8.0 release. There is a very good chance that many of these
70de81db 2285will work fine with the 5.8.0.
cec2c193 2286
8da2b1be 2287 BSD/OS
cec2c193
JH
2288 DomainOS
2289 Hurd
2290 LynxOS
2291 MachTen
2292 PowerMAX
2293 SCO SV
cec2c193
JH
2294 SVR4
2295 Unixware
2296 Windows 3.1
ba58ab26 2297
70de81db
JH
2298Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used):
2299
61988e87 2300 AmigaOS 3
70de81db 2301
ba58ab26 2302The following platforms have been known to build Perl from source in
fd46a41b
JH
2303the past (5.005_03 and earlier), but we haven't been able to verify
2304their status for the current release, either because the
2305hardware/software platforms are rare or because we don't have an
2306active champion on these platforms--or both. They used to work,
2307though, so go ahead and try compiling them, and let perlbug@perl.org
2308of any trouble.
ba58ab26 2309
cec2c193
JH
2310 3b1
2311 A/UX
cec2c193
JH
2312 ConvexOS
2313 CX/UX
2314 DC/OSx
2315 DDE SMES
2316 DOS EMX
2317 Dynix
2318 EP/IX
2319 ESIX
2320 FPS
2321 GENIX
2322 Greenhills
2323 ISC
2324 MachTen 68k
cec2c193
JH
2325 MPC
2326 NEWS-OS
2327 NextSTEP
2328 OpenSTEP
2329 Opus
2330 Plan 9
cec2c193 2331 RISC/os
8da2b1be 2332 SCO ODT/OSR
cec2c193
JH
2333 Stellar
2334 SVR2
2335 TI1500
2336 TitanOS
2337 Ultrix
2338 Unisys Dynix
ba58ab26
JH
2339
2340The following platforms have their own source code distributions and
500f1b69 2341binaries available via L<http://www.cpan.org/ports/>
ba58ab26 2342
cec2c193 2343 Perl release
ba58ab26 2344
522b859a 2345 OS/400 (ILE) 5.005_02
cec2c193 2346 Tandem Guardian 5.004
ba58ab26
JH
2347
2348The following platforms have only binaries available via
500f1b69 2349L<http://www.cpan.org/ports/index.html> :
ba58ab26 2350
cec2c193 2351 Perl release
ba58ab26 2352
cec2c193
JH
2353 Acorn RISCOS 5.005_02
2354 AOS 5.002
2355 LynxOS 5.004_02
ba58ab26
JH
2356
2357Although we do suggest that you always build your own Perl from
2358the source code, both for maximal configurability and for security,
2359in case you are in a hurry you can check
500f1b69 2360L<http://www.cpan.org/ports/index.html> for binary distributions.
ba58ab26 2361
c997b287
GS
2362=head1 SEE ALSO
2363
b6c36746 2364L<perlaix>, L<perlamiga>, L<perlbs2000>,
8d87852b 2365L<perlce>, L<perlcygwin>, L<perldos>,
469e7be4 2366L<perlebcdic>, L<perlfreebsd>, L<perlhurd>, L<perlhpux>, L<perlirix>,
b5afd346 2367L<perlmacos>, L<perlmacosx>,
522b859a
JH
2368L<perlnetware>, L<perlos2>, L<perlos390>, L<perlos400>,
2369L<perlplan9>, L<perlqnx>, L<perlsolaris>, L<perltru64>,
043fec90 2370L<perlunicode>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
c997b287 2371
e41182b5
GS
2372=head1 AUTHORS / CONTRIBUTORS
2373
06e9666b 2374Abigail <abigail@foad.org>,
c47ff5f1
GS
2375Charles Bailey <bailey@newman.upenn.edu>,
2376Graham Barr <gbarr@pobox.com>,
2377Tom Christiansen <tchrist@perl.com>,
06e9666b 2378Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2379Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2380Andy Dougherty <doughera@lafayette.edu>,
2381Dominic Dunlop <domo@computer.org>,
2382Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1 2383David J. Fiander <davidf@mks.com>,
3fd80bd6 2384Paul Green <Paul.Green@stratus.com>,
06e9666b 2385M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2386Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2387Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2388Nick Ing-Simmons <nick@ing-simmons.net>,
2389Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2390Markus Laker <mlaker@contax.co.uk>,
2391Andrew M. Langmead <aml@world.std.com>,
83a46a63 2392Lukas Mai <l.mai@web.de>,
c47ff5f1
GS
2393Larry Moore <ljmoore@freespace.net>,
2394Paul Moore <Paul.Moore@uk.origin-it.com>,
2395Chris Nandor <pudge@pobox.com>,
1afc07ec 2396Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2397Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2398Gary Ng <71564.1743@CompuServe.COM>,
2399Tom Phoenix <rootbeer@teleport.com>,
2400AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2401Peter Prymmer <pvhp@forte.com>,
2402Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2403Gurusamy Sarathy <gsar@activestate.com>,
2404Paul J. Schinder <schinder@pobox.com>,
2405Michael G Schwern <schwern@pobox.com>,
06e9666b 2406Dan Sugalski <dan@sidhe.org>,
bbe548ff 2407Nathan Torkington <gnat@frii.com>,
016930a6 2408John Malmberg <wb8tyw@qsl.net>