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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
22important that the task that you are coding have the full generality
23of being portable, or whether to just get the job done right now.
24This is the hardest choice to be made. The rest is easy, because
25Perl provides many choices, whichever way you want to approach your
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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,
62S<Mac OS>, VMS, etc.), consider writing platform-specific code.
63
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64When the code will run on only two or three operating systems, 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
70portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and
b7df3edc 71built-in perl functions that behave differently on various ports
0a47030a 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
c47ff5f1 78(<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>,
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87and S<Mac OS> uses C<\015>.
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
91means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
92when accessing a file in "text" mode, STDIO translates it to (or
56d7751a 93from) C<\015\012>, depending on whether you're reading or writing.
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94Unix does the same thing on ttys in canonical mode. C<\015\012>
95is commonly referred to as CRLF.
96
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97A common cause of unportable programs is the misuse of chop() to trim
98newlines:
99
100 # XXX UNPORTABLE!
101 while(<FILE>) {
102 chop;
103 @array = split(/:/);
104 #...
105 }
106
107You can get away with this on Unix and MacOS (they have a single
108character end-of-line), but the same program will break under DOSish
109perls because you're only chop()ing half the end-of-line. Instead,
110chomp() should be used to trim newlines. The Dunce::Files module can
111help audit your code for misuses of chop().
112
113When dealing with binary files (or text files in binary mode) be sure
114to explicitly set $/ to the appropriate value for your file format
115before using chomp().
116
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117Because of the "text" mode translation, DOSish perls have limitations
118in using C<seek> and C<tell> on a file accessed in "text" mode.
119Stick to C<seek>-ing to locations you got from C<tell> (and no
120others), and you are usually free to use C<seek> and C<tell> even
121in "text" mode. Using C<seek> or C<tell> or other file operations
122may be non-portable. If you use C<binmode> on a file, however, you
123can usually C<seek> and C<tell> with arbitrary values in safety.
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124
125A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 126everywhere. When using protocols such as common Internet protocols,
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127C<\012> and C<\015> are called for specifically, and the values of
128the logical C<\n> and C<\r> (carriage return) are not reliable.
129
130 print SOCKET "Hi there, client!\r\n"; # WRONG
131 print SOCKET "Hi there, client!\015\012"; # RIGHT
132
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133However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
134and unsightly, as well as confusing to those maintaining the code. As
6ab3f9cb 135such, the Socket module supplies the Right Thing for those who want it.
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136
137 use Socket qw(:DEFAULT :crlf);
138 print SOCKET "Hi there, client!$CRLF" # RIGHT
139
6ab3f9cb 140When reading from a socket, remember that the default input record
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141separator C<$/> is C<\n>, but robust socket code will recognize as
142either C<\012> or C<\015\012> as end of line:
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143
144 while (<SOCKET>) {
145 # ...
146 }
147
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148Because both CRLF and LF end in LF, the input record separator can
149be set to LF and any CR stripped later. Better to write:
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150
151 use Socket qw(:DEFAULT :crlf);
152 local($/) = LF; # not needed if $/ is already \012
153
154 while (<SOCKET>) {
155 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
156 # s/\015?\012/\n/; # same thing
157 }
158
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159This example is preferred over the previous one--even for Unix
160platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
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161(and there was much rejoicing).
162
6ab3f9cb 163Similarly, functions that return text data--such as a function that
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164fetches a web page--should sometimes translate newlines before
165returning the data, if they've not yet been translated to the local
166newline representation. A single line of code will often suffice:
2ee0eb3c 167
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168 $data =~ s/\015?\012/\n/g;
169 return $data;
2ee0eb3c 170
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171Some of this may be confusing. Here's a handy reference to the ASCII CR
172and LF characters. You can print it out and stick it in your wallet.
173
174 LF == \012 == \x0A == \cJ == ASCII 10
175 CR == \015 == \x0D == \cM == ASCII 13
176
177 | Unix | DOS | Mac |
178 ---------------------------
179 \n | LF | LF | CR |
180 \r | CR | CR | LF |
181 \n * | LF | CRLF | CR |
182 \r * | CR | CR | LF |
183 ---------------------------
184 * text-mode STDIO
185
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186The Unix column assumes that you are not accessing a serial line
187(like a tty) in canonical mode. If you are, then CR on input becomes
188"\n", and "\n" on output becomes CRLF.
189
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190These are just the most common definitions of C<\n> and C<\r> in Perl.
191There may well be others.
192
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193=head2 Numbers endianness and Width
194
195Different CPUs store integers and floating point numbers in different
196orders (called I<endianness>) and widths (32-bit and 64-bit being the
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197most common today). This affects your programs when they attempt to transfer
198numbers in binary format from one CPU architecture to another,
199usually either "live" via network connection, or by storing the
200numbers to secondary storage such as a disk file or tape.
322422de 201
b7df3edc 202Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 203little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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204decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2050x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
206Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
207them in big-endian mode. To avoid this problem in network (socket)
208connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
209"network" orders. These are guaranteed to be portable.
322422de 210
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211You can explore the endianness of your platform by unpacking a
212data structure packed in native format such as:
213
214 print unpack("h*", pack("s2", 1, 2)), "\n";
215 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
216 # '00100020' on e.g. Motorola 68040
217
218If you need to distinguish between endian architectures you could use
219either of the variables set like so:
220
221 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 222 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 223
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224Differing widths can cause truncation even between platforms of equal
225endianness. The platform of shorter width loses the upper parts of the
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226number. There is no good solution for this problem except to avoid
227transferring or storing raw binary numbers.
228
b7df3edc 229One can circumnavigate both these problems in two ways. Either
322422de 230transfer and store numbers always in text format, instead of raw
b7df3edc 231binary, or else consider using modules like Data::Dumper (included in
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232the standard distribution as of Perl 5.005) and Storable (included as
233of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 234
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235The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
236how far EBCDIC, or more precisely UTF-EBCDIC will go.
237
433acd8a 238=head2 Files and Filesystems
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239
240Most platforms these days structure files in a hierarchical fashion.
b7df3edc 241So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 242notion of a "path" to uniquely identify a file on the system. How
b7df3edc 243that path is really written, though, differs considerably.
e41182b5 244
4375e838 245Although similar, file path specifications differ between Unix,
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246Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
247Unix, for example, is one of the few OSes that has the elegant idea
248of a single root directory.
322422de 249
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250DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
251as path separator, or in their own idiosyncratic ways (such as having
252several root directories and various "unrooted" device files such NIL:
253and LPT:).
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254
255S<Mac OS> uses C<:> as a path separator instead of C</>.
256
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257The filesystem may support neither hard links (C<link>) nor
258symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 259
6ab3f9cb 260The filesystem may support neither access timestamp nor change
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261timestamp (meaning that about the only portable timestamp is the
262modification timestamp), or one second granularity of any timestamps
263(e.g. the FAT filesystem limits the time granularity to two seconds).
264
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265VOS perl can emulate Unix filenames with C</> as path separator. The
266native pathname characters greater-than, less-than, number-sign, and
267percent-sign are always accepted.
268
6ab3f9cb 269S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 270separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 271signal filesystems and disk names.
e41182b5 272
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273Don't assume UNIX filesystem access semantics: that read, write,
274and execute are all the permissions there are, and even if they exist,
275that their semantics (for example what do r, w, and x mean on
276a directory) are the UNIX ones. The various UNIX/POSIX compatibility
277layers usually try to make interfaces like chmod() work, but sometimes
278there simply is no good mapping.
279
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280If all this is intimidating, have no (well, maybe only a little)
281fear. There are modules that can help. The File::Spec modules
282provide methods to do the Right Thing on whatever platform happens
283to be running the program.
e41182b5 284
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285 use File::Spec::Functions;
286 chdir(updir()); # go up one directory
287 $file = catfile(curdir(), 'temp', 'file.txt');
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288 # on Unix and Win32, './temp/file.txt'
289 # on Mac OS, ':temp:file.txt'
d1e3b762 290 # on VMS, '[.temp]file.txt'
e41182b5 291
b7df3edc 292File::Spec is available in the standard distribution as of version
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2935.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
294and some versions of perl come with version 0.6. If File::Spec
295is not updated to 0.7 or later, you must use the object-oriented
296interface from File::Spec (or upgrade File::Spec).
e41182b5 297
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298In general, production code should not have file paths hardcoded.
299Making them user-supplied or read from a configuration file is
300better, keeping in mind that file path syntax varies on different
301machines.
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302
303This is especially noticeable in scripts like Makefiles and test suites,
304which often assume C</> as a path separator for subdirectories.
305
b7df3edc 306Also of use is File::Basename from the standard distribution, which
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307splits a pathname into pieces (base filename, full path to directory,
308and file suffix).
309
19799a22 310Even when on a single platform (if you can call Unix a single platform),
b7df3edc 311remember not to count on the existence or the contents of particular
3c075c7d 312system-specific files or directories, like F</etc/passwd>,
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313F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
314example, F</etc/passwd> may exist but not contain the encrypted
315passwords, because the system is using some form of enhanced security.
316Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 317If code does need to rely on such a file, include a description of the
b7df3edc 318file and its format in the code's documentation, then make it easy for
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319the user to override the default location of the file.
320
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321Don't assume a text file will end with a newline. They should,
322but people forget.
e41182b5 323
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324Do not have two files or directories of the same name with different
325case, like F<test.pl> and F<Test.pl>, as many platforms have
326case-insensitive (or at least case-forgiving) filenames. Also, try
327not to have non-word characters (except for C<.>) in the names, and
328keep them to the 8.3 convention, for maximum portability, onerous a
329burden though this may appear.
dd9f0070 330
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331Likewise, when using the AutoSplit module, try to keep your functions to
3328.3 naming and case-insensitive conventions; or, at the least,
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333make it so the resulting files have a unique (case-insensitively)
334first 8 characters.
335
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336Whitespace in filenames is tolerated on most systems, but not all,
337and even on systems where it might be tolerated, some utilities
fe829689 338might become confused by such whitespace.
ec481373 339
b7df3edc 340Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
433acd8a 341
c47ff5f1 342Don't assume C<< > >> won't be the first character of a filename.
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343Always use C<< < >> explicitly to open a file for reading, or even
344better, use the three-arg version of open, unless you want the user to
345be able to specify a pipe open.
0a47030a 346
fe829689 347 open(FILE, '<', $existing_file) or die $!;
0a47030a 348
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349If filenames might use strange characters, it is safest to open it
350with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 351translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 352be the wrong thing to do. (Sometimes, though, it's the right thing.)
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353Three-arg open can also help protect against this translation in cases
354where it is undesirable.
e41182b5 355
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356Don't use C<:> as a part of a filename since many systems use that for
357their own semantics (MacOS Classic for separating pathname components,
358many networking schemes and utilities for separating the nodename and
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359the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
360C<|>.
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361
362The I<portable filename characters> as defined by ANSI C are
363
364 a b c d e f g h i j k l m n o p q r t u v w x y z
365 A B C D E F G H I J K L M N O P Q R T U V W X Y Z
366 0 1 2 3 4 5 6 7 8 9
367 . _ -
368
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369and the "-" shouldn't be the first character. If you want to be
370hypercorrect, stay within the 8.3 naming convention (all the files and
371directories have to be unique within one directory if their names are
372lowercased and truncated to eight characters before the C<.>, if any,
373and to three characters after the C<.>, if any). (And do not use
374C<.>s in directory names.)
ec481373 375
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376=head2 System Interaction
377
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378Not all platforms provide a command line. These are usually platforms
379that rely primarily on a Graphical User Interface (GUI) for user
380interaction. A program requiring a command line interface might
381not work everywhere. This is probably for the user of the program
382to deal with, so don't stay up late worrying about it.
e41182b5 383
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384Some platforms can't delete or rename files held open by the system.
385Remember to C<close> files when you are done with them. Don't
386C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
387file already tied or opened; C<untie> or C<close> it first.
e41182b5 388
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389Don't open the same file more than once at a time for writing, as some
390operating systems put mandatory locks on such files.
391
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392Don't assume that write/modify permission on a directory gives the
393right to add or delete files/directories in that directory. That is
394filesystem specific: in some filesystems you need write/modify
395permission also (or even just) in the file/directory itself. In some
396filesystems (AFS, DFS) the permission to add/delete directory entries
397is a completely separate permission.
398
399Don't assume that a single C<unlink> completely gets rid of the file:
400some filesystems (most notably the ones in VMS) have versioned
401filesystems, and unlink() removes only the most recent one (it doesn't
402remove all the versions because by default the native tools on those
403platforms remove just the most recent version, too). The portable
404idiom to remove all the versions of a file is
405
94bb614c 406 1 while unlink "file";
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407
408This will terminate if the file is undeleteable for some reason
409(protected, not there, and so on).
410
e41182b5 411Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 412Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 413case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 414if you really have to, make it conditional on C<$^O ne 'VMS'> since in
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415VMS the C<%ENV> table is much more than a per-process key-value string
416table.
e41182b5 417
d1e3b762 418Don't count on signals or C<%SIG> for anything.
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419
420Don't count on filename globbing. Use C<opendir>, C<readdir>, and
421C<closedir> instead.
422
b8099c3d 423Don't count on per-program environment variables, or per-program current
dd9f0070 424directories.
b8099c3d 425
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426Don't count on specific values of C<$!>.
427
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428=head2 Interprocess Communication (IPC)
429
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430In general, don't directly access the system in code meant to be
431portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
432C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
433that makes being a perl hacker worth being.
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434
435Commands that launch external processes are generally supported on
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436most platforms (though many of them do not support any type of
437forking). The problem with using them arises from what you invoke
438them on. External tools are often named differently on different
4375e838 439platforms, may not be available in the same location, might accept
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440different arguments, can behave differently, and often present their
441results in a platform-dependent way. Thus, you should seldom depend
442on them to produce consistent results. (Then again, if you're calling
443I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 444
b7df3edc 445One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 446
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447 open(MAIL, '|/usr/lib/sendmail -t')
448 or die "cannot fork sendmail: $!";
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449
450This is fine for systems programming when sendmail is known to be
451available. But it is not fine for many non-Unix systems, and even
452some Unix systems that may not have sendmail installed. If a portable
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453solution is needed, see the various distributions on CPAN that deal
454with it. Mail::Mailer and Mail::Send in the MailTools distribution are
455commonly used, and provide several mailing methods, including mail,
456sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
457not available. Mail::Sendmail is a standalone module that provides
458simple, platform-independent mailing.
459
460The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
461even on all Unix platforms.
e41182b5 462
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463Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
464bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
465both forms just pack the four bytes into network order. That this
466would be equal to the C language C<in_addr> struct (which is what the
467socket code internally uses) is not guaranteed. To be portable use
468the routines of the Socket extension, such as C<inet_aton()>,
469C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 470
e41182b5 471The rule of thumb for portable code is: Do it all in portable Perl, or
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472use a module (that may internally implement it with platform-specific
473code, but expose a common interface).
e41182b5 474
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475=head2 External Subroutines (XS)
476
b7df3edc 477XS code can usually be made to work with any platform, but dependent
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478libraries, header files, etc., might not be readily available or
479portable, or the XS code itself might be platform-specific, just as Perl
480code might be. If the libraries and headers are portable, then it is
481normally reasonable to make sure the XS code is portable, too.
482
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483A different type of portability issue arises when writing XS code:
484availability of a C compiler on the end-user's system. C brings
485with it its own portability issues, and writing XS code will expose
486you to some of those. Writing purely in Perl is an easier way to
e41182b5
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487achieve portability.
488
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489=head2 Standard Modules
490
491In general, the standard modules work across platforms. Notable
6ab3f9cb 492exceptions are the CPAN module (which currently makes connections to external
e41182b5 493programs that may not be available), platform-specific modules (like
6ab3f9cb 494ExtUtils::MM_VMS), and DBM modules.
e41182b5 495
b7df3edc 496There is no one DBM module available on all platforms.
6ab3f9cb
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497SDBM_File and the others are generally available on all Unix and DOSish
498ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 499available.
e41182b5
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500
501The good news is that at least some DBM module should be available, and
6ab3f9cb 502AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
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503the code needs to be fairly strict, dropping to the greatest common
504factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 505work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 506
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507=head2 Time and Date
508
0a47030a 509The system's notion of time of day and calendar date is controlled in
b7df3edc 510widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a
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511and even if it is, don't assume that you can control the timezone through
512that variable.
e41182b5 513
322422de 514Don't assume that the epoch starts at 00:00:00, January 1, 1970,
6ab3f9cb
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515because that is OS- and implementation-specific. It is better to store a date
516in an unambiguous representation. The ISO-8601 standard defines
517"YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
518can be easily converted into an OS-specific value using a module like
519Date::Parse. An array of values, such as those returned by
322422de 520C<localtime>, can be converted to an OS-specific representation using
6ab3f9cb 521Time::Local.
322422de 522
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523When calculating specific times, such as for tests in time or date modules,
524it may be appropriate to calculate an offset for the epoch.
b7df3edc 525
19799a22
GS
526 require Time::Local;
527 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 528
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529The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
530some large number. C<$offset> can then be added to a Unix time value
531to get what should be the proper value on any system.
322422de
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532
533=head2 Character sets and character encoding
534
ec481373
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535Assume very little about character sets.
536
537Assume nothing about numerical values (C<ord>, C<chr>) of characters.
538Do not use explicit code point ranges (like \xHH-\xHH); use for
539example symbolic character classes like C<[:print:]>.
540
541Do not assume that the alphabetic characters are encoded contiguously
542(in the numeric sense). There may be gaps.
543
544Do not assume anything about the ordering of the characters.
545The lowercase letters may come before or after the uppercase letters;
546the lowercase and uppercase may be interlaced so that both `a' and `A'
547come before `b'; the accented and other international characters may
548be interlaced so that E<auml> comes before `b'.
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549
550=head2 Internationalisation
551
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552If you may assume POSIX (a rather large assumption), you may read
553more about the POSIX locale system from L<perllocale>. The locale
554system at least attempts to make things a little bit more portable,
555or at least more convenient and native-friendly for non-English
556users. The system affects character sets and encoding, and date
557and time formatting--amongst other things.
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558
559=head2 System Resources
560
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561If your code is destined for systems with severely constrained (or
562missing!) virtual memory systems then you want to be I<especially> mindful
563of avoiding wasteful constructs such as:
e41182b5
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564
565 # NOTE: this is no longer "bad" in perl5.005
566 for (0..10000000) {} # bad
567 for (my $x = 0; $x <= 10000000; ++$x) {} # good
568
569 @lines = <VERY_LARGE_FILE>; # bad
570
571 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 572 $file = join('', <FILE>); # better
e41182b5 573
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574The last two constructs may appear unintuitive to most people. The
575first repeatedly grows a string, whereas the second allocates a
576large chunk of memory in one go. On some systems, the second is
577more efficient that the first.
0a47030a 578
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579=head2 Security
580
b7df3edc
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581Most multi-user platforms provide basic levels of security, usually
582implemented at the filesystem level. Some, however, do
a1667ba3 583not-- unfortunately. Thus the notion of user id, or "home" directory,
b7df3edc
GS
584or even the state of being logged-in, may be unrecognizable on many
585platforms. If you write programs that are security-conscious, it
586is usually best to know what type of system you will be running
587under so that you can write code explicitly for that platform (or
588class of platforms).
0a47030a 589
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590Don't assume the UNIX filesystem access semantics: the operating
591system or the filesystem may be using some ACL systems, which are
592richer languages than the usual rwx. Even if the rwx exist,
593their semantics might be different.
594
595(From security viewpoint testing for permissions before attempting to
596do something is silly anyway: if one tries this, there is potential
597for race conditions-- someone or something might change the
598permissions between the permissions check and the actual operation.
599Just try the operation.)
600
601Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 602expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
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603for switching identities (or memberships).
604
605Don't assume set-uid and set-gid semantics. (And even if you do,
606think twice: set-uid and set-gid are a known can of security worms.)
607
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608=head2 Style
609
610For those times when it is necessary to have platform-specific code,
611consider keeping the platform-specific code in one place, making porting
6ab3f9cb 612to other platforms easier. Use the Config module and the special
0a47030a
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613variable C<$^O> to differentiate platforms, as described in
614L<"PLATFORMS">.
e41182b5 615
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616Be careful in the tests you supply with your module or programs.
617Module code may be fully portable, but its tests might not be. This
618often happens when tests spawn off other processes or call external
619programs to aid in the testing, or when (as noted above) the tests
620assume certain things about the filesystem and paths. Be careful
621not to depend on a specific output style for errors, such as when
d1be9408 622checking C<$!> after a system call. Some platforms expect a certain
b7df3edc
GS
623output format, and perl on those platforms may have been adjusted
624accordingly. Most specifically, don't anchor a regex when testing
625an error value.
e41182b5 626
0a47030a 627=head1 CPAN Testers
e41182b5 628
0a47030a
GS
629Modules uploaded to CPAN are tested by a variety of volunteers on
630different platforms. These CPAN testers are notified by mail of each
e41182b5 631new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 632this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
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633
634The purpose of the testing is twofold: one, to help developers fix any
0a47030a 635problems in their code that crop up because of lack of testing on other
b7df3edc 636platforms; two, to provide users with information about whether
0a47030a 637a given module works on a given platform.
e41182b5
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638
639=over 4
640
641=item Mailing list: cpan-testers@perl.org
642
c997b287 643=item Testing results: http://testers.cpan.org/
e41182b5
GS
644
645=back
646
e41182b5
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647=head1 PLATFORMS
648
649As of version 5.002, Perl is built with a C<$^O> variable that
650indicates the operating system it was built on. This was implemented
b7df3edc
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651to help speed up code that would otherwise have to C<use Config>
652and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
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653detailed information about the system, looking into C<%Config> is
654certainly recommended.
655
b7df3edc
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656C<%Config> cannot always be trusted, however, because it was built
657at compile time. If perl was built in one place, then transferred
658elsewhere, some values may be wrong. The values may even have been
659edited after the fact.
6ab3f9cb 660
e41182b5
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661=head2 Unix
662
663Perl works on a bewildering variety of Unix and Unix-like platforms (see
664e.g. most of the files in the F<hints/> directory in the source code kit).
665On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
666too) is determined either by lowercasing and stripping punctuation from the
667first field of the string returned by typing C<uname -a> (or a similar command)
668at the shell prompt or by testing the file system for the presence of
669uniquely named files such as a kernel or header file. Here, for example,
670are a few of the more popular Unix flavors:
e41182b5 671
b7df3edc 672 uname $^O $Config{'archname'}
6ab3f9cb 673 --------------------------------------------
b7df3edc 674 AIX aix aix
6ab3f9cb
GS
675 BSD/OS bsdos i386-bsdos
676 dgux dgux AViiON-dgux
677 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 678 FreeBSD freebsd freebsd-i386
d1e3b762 679 Linux linux arm-linux
b7df3edc 680 Linux linux i386-linux
6ab3f9cb
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681 Linux linux i586-linux
682 Linux linux ppc-linux
b7df3edc
GS
683 HP-UX hpux PA-RISC1.1
684 IRIX irix irix
b787fad4 685 Mac OS X darwin darwin
d1e3b762
GS
686 MachTen PPC machten powerpc-machten
687 NeXT 3 next next-fat
688 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 689 openbsd openbsd i386-openbsd
b7df3edc 690 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
691 reliantunix-n svr4 RM400-svr4
692 SCO_SV sco_sv i386-sco_sv
693 SINIX-N svr4 RM400-svr4
694 sn4609 unicos CRAY_C90-unicos
695 sn6521 unicosmk t3e-unicosmk
696 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
697 SunOS solaris sun4-solaris
698 SunOS solaris i86pc-solaris
699 SunOS4 sunos sun4-sunos
e41182b5 700
b7df3edc
GS
701Because the value of C<$Config{archname}> may depend on the
702hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 703
e41182b5
GS
704=head2 DOS and Derivatives
705
b7df3edc 706Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
707systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
708bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 709Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
710be aware that each of these file specifications may have subtle
711differences:
712
713 $filespec0 = "c:/foo/bar/file.txt";
714 $filespec1 = "c:\\foo\\bar\\file.txt";
715 $filespec2 = 'c:\foo\bar\file.txt';
716 $filespec3 = 'c:\\foo\\bar\\file.txt';
717
b7df3edc
GS
718System calls accept either C</> or C<\> as the path separator.
719However, many command-line utilities of DOS vintage treat C</> as
720the option prefix, so may get confused by filenames containing C</>.
721Aside from calling any external programs, C</> will work just fine,
722and probably better, as it is more consistent with popular usage,
723and avoids the problem of remembering what to backwhack and what
724not to.
e41182b5 725
b7df3edc
GS
726The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
727the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 728filesystems you may have to be careful about case returned with functions
e41182b5
GS
729like C<readdir> or used with functions like C<open> or C<opendir>.
730
b7df3edc
GS
731DOS also treats several filenames as special, such as AUX, PRN,
732NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
733filenames won't even work if you include an explicit directory
734prefix. It is best to avoid such filenames, if you want your code
735to be portable to DOS and its derivatives. It's hard to know what
736these all are, unfortunately.
e41182b5
GS
737
738Users of these operating systems may also wish to make use of
b7df3edc 739scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
740put wrappers around your scripts.
741
742Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
743and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
744will keep C<\n> translated as C<\012> for that filehandle. Since it is a
745no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
746that deals with binary data. That's assuming you realize in advance
747that your data is in binary. General-purpose programs should
748often assume nothing about their data.
e41182b5 749
b7df3edc 750The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
751DOSish perls are as follows:
752
67ac489e
MS
753 OS $^O $Config{archname} ID Version
754 --------------------------------------------------------
755 MS-DOS dos ?
756 PC-DOS dos ?
757 OS/2 os2 ?
758 Windows 3.1 ? ? 0 3 01
759 Windows 95 MSWin32 MSWin32-x86 1 4 00
760 Windows 98 MSWin32 MSWin32-x86 1 4 10
761 Windows ME MSWin32 MSWin32-x86 1 ?
762 Windows NT MSWin32 MSWin32-x86 2 4 xx
763 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
764 Windows NT MSWin32 MSWin32-ppc 2 4 xx
765 Windows 2000 MSWin32 MSWin32-x86 2 5 xx
766 Windows XP MSWin32 MSWin32-x86 2 ?
767 Windows CE MSWin32 ? 3
768 Cygwin cygwin ?
e41182b5 769
34aaaa84
PP
770The various MSWin32 Perl's can distinguish the OS they are running on
771via the value of the fifth element of the list returned from
772Win32::GetOSVersion(). For example:
773
774 if ($^O eq 'MSWin32') {
775 my @os_version_info = Win32::GetOSVersion();
776 print +('3.1','95','NT')[$os_version_info[4]],"\n";
777 }
778
e41182b5
GS
779Also see:
780
781=over 4
782
c997b287 783=item *
e41182b5 784
c997b287
GS
785The djgpp environment for DOS, http://www.delorie.com/djgpp/
786and L<perldos>.
e41182b5 787
c997b287 788=item *
e41182b5 789
c997b287
GS
790The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
791http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
792ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
e41182b5 793
c997b287 794=item *
d1e3b762 795
c997b287
GS
796Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
797in L<perlcygwin>.
798
799=item *
800
801The C<Win32::*> modules in L<Win32>.
802
803=item *
804
805The ActiveState Pages, http://www.activestate.com/
806
807=item *
808
809The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 810as L<perlcygwin>), http://www.cygwin.com/
c997b287
GS
811
812=item *
813
814The U/WIN environment for Win32,
cea6626f 815http://www.research.att.com/sw/tools/uwin/
c997b287 816
cea6626f 817=item *
d1e3b762 818
cea6626f 819Build instructions for OS/2, L<perlos2>
d1e3b762 820
e41182b5
GS
821=back
822
dd9f0070 823=head2 S<Mac OS>
e41182b5
GS
824
825Any module requiring XS compilation is right out for most people, because
826MacPerl is built using non-free (and non-cheap!) compilers. Some XS
827modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 828form on CPAN.
e41182b5
GS
829
830Directories are specified as:
831
832 volume:folder:file for absolute pathnames
833 volume:folder: for absolute pathnames
834 :folder:file for relative pathnames
835 :folder: for relative pathnames
836 :file for relative pathnames
837 file for relative pathnames
838
b7df3edc 839Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 840limited to 31 characters, and may include any character except for
b7df3edc 841null and C<:>, which is reserved as the path separator.
e41182b5 842
0a47030a 843Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 844Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
845
846In the MacPerl application, you can't run a program from the command line;
847programs that expect C<@ARGV> to be populated can be edited with something
848like the following, which brings up a dialog box asking for the command
849line arguments.
850
851 if (!@ARGV) {
852 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
853 }
854
b7df3edc 855A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
856pathnames of the files dropped onto the script.
857
b7df3edc
GS
858Mac users can run programs under a type of command line interface
859under MPW (Macintosh Programmer's Workshop, a free development
860environment from Apple). MacPerl was first introduced as an MPW
861tool, and MPW can be used like a shell:
e41182b5
GS
862
863 perl myscript.plx some arguments
864
865ToolServer is another app from Apple that provides access to MPW tools
0a47030a 866from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
867C<system>, backticks, and piped C<open>.
868
869"S<Mac OS>" is the proper name for the operating system, but the value
870in C<$^O> is "MacOS". To determine architecture, version, or whether
871the application or MPW tool version is running, check:
872
873 $is_app = $MacPerl::Version =~ /App/;
874 $is_tool = $MacPerl::Version =~ /MPW/;
875 ($version) = $MacPerl::Version =~ /^(\S+)/;
876 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
877 $is_68k = $MacPerl::Architecture eq 'Mac68K';
878
b787fad4
JH
879S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
880"Classic" environment. There is no "Carbon" version of MacPerl to run
881under the primary Mac OS X environment. S<Mac OS X> and its Open Source
882version, Darwin, both run Unix perl natively.
6ab3f9cb 883
e41182b5
GS
884Also see:
885
886=over 4
887
c997b287
GS
888=item *
889
862b5365 890MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
891
892=item *
893
862b5365 894The MacPerl Pages, http://www.macperl.com/ .
e41182b5 895
c997b287 896=item *
6ab3f9cb 897
862b5365 898The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5
GS
899
900=back
901
e41182b5
GS
902=head2 VMS
903
c997b287 904Perl on VMS is discussed in L<perlvms> in the perl distribution.
b7df3edc 905Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
906specifications as in either of the following:
907
908 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
909 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
910
911but not a mixture of both as in:
912
913 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
914 Can't open sys$login:/login.com: file specification syntax error
915
916Interacting with Perl from the Digital Command Language (DCL) shell
917often requires a different set of quotation marks than Unix shells do.
918For example:
919
920 $ perl -e "print ""Hello, world.\n"""
921 Hello, world.
922
b7df3edc 923There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
924you are so inclined. For example:
925
926 $ write sys$output "Hello from DCL!"
927 $ if p1 .eqs. ""
928 $ then perl -x 'f$environment("PROCEDURE")
929 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
930 $ deck/dollars="__END__"
931 #!/usr/bin/perl
932
933 print "Hello from Perl!\n";
934
935 __END__
936 $ endif
937
938Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 939perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5
GS
940
941Filenames are in the format "name.extension;version". The maximum
942length for filenames is 39 characters, and the maximum length for
943extensions is also 39 characters. Version is a number from 1 to
94432767. Valid characters are C</[A-Z0-9$_-]/>.
945
b7df3edc 946VMS's RMS filesystem is case-insensitive and does not preserve case.
e41182b5 947C<readdir> returns lowercased filenames, but specifying a file for
b7df3edc 948opening remains case-insensitive. Files without extensions have a
e41182b5 949trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
950will return F<a.> (though that file could be opened with
951C<open(FH, 'A')>).
e41182b5 952
f34d0673 953RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
CN
954(allowing 16 levels overall) prior to VMS 7.2. Hence
955C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
956C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
957have to take this into account, but at least they can refer to the former
f34d0673 958as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 959
6ab3f9cb 960The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
961process on VMS, is a pure Perl module that can easily be installed on
962non-VMS platforms and can be helpful for conversions to and from RMS
963native formats.
e41182b5 964
5e12dbfa
PP
965What C<\n> represents depends on the type of file opened. It usually
966represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
967C<\000>, C<\040>, or nothing depending on the file organiztion and
968record format. The VMS::Stdio module provides access to the
969special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
970
971TCP/IP stacks are optional on VMS, so socket routines might not be
972implemented. UDP sockets may not be supported.
973
974The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
975that you are running on without resorting to loading all of C<%Config>
976you can examine the content of the C<@INC> array like so:
977
978 if (grep(/VMS_AXP/, @INC)) {
979 print "I'm on Alpha!\n";
6ab3f9cb 980
e41182b5
GS
981 } elsif (grep(/VMS_VAX/, @INC)) {
982 print "I'm on VAX!\n";
6ab3f9cb 983
e41182b5
GS
984 } else {
985 print "I'm not so sure about where $^O is...\n";
986 }
987
b7df3edc
GS
988On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
989logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 990calls to C<localtime> are adjusted to count offsets from
b7df3edc 99101-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 992
e41182b5
GS
993Also see:
994
995=over 4
996
c997b287
GS
997=item *
998
999F<README.vms> (installed as L<README_vms>), L<perlvms>
1000
1001=item *
1002
1003vmsperl list, majordomo@perl.org
e41182b5 1004
c997b287 1005(Put the words C<subscribe vmsperl> in message body.)
e41182b5 1006
c997b287 1007=item *
e41182b5 1008
c997b287 1009vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1010
1011=back
1012
495c5fdc
GP
1013=head2 VOS
1014
9a997319
JH
1015Perl on VOS is discussed in F<README.vos> in the perl distribution
1016(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1017Unix-style file specifications as in either of the following:
495c5fdc
GP
1018
1019 $ perl -ne "print if /perl_setup/i" >system>notices
1020 $ perl -ne "print if /perl_setup/i" /system/notices
1021
1022or even a mixture of both as in:
1023
1024 $ perl -ne "print if /perl_setup/i" >system/notices
1025
b7df3edc 1026Even though VOS allows the slash character to appear in object
495c5fdc
GP
1027names, because the VOS port of Perl interprets it as a pathname
1028delimiting character, VOS files, directories, or links whose names
1029contain a slash character cannot be processed. Such files must be
a3dfe201
GS
1030renamed before they can be processed by Perl. Note that VOS limits
1031file names to 32 or fewer characters.
495c5fdc 1032
5b8c1387
JH
1033See F<README.vos> for restrictions that apply when Perl is built
1034with the alpha version of VOS POSIX.1 support.
1035
1036Perl on VOS is built without any extensions and does not support
1037dynamic loading.
495c5fdc
GP
1038
1039The value of C<$^O> on VOS is "VOS". To determine the architecture that
1040you are running on without resorting to loading all of C<%Config> you
c997b287 1041can examine the content of the @INC array like so:
495c5fdc 1042
24e8e380 1043 if ($^O =~ /VOS/) {
495c5fdc
GP
1044 print "I'm on a Stratus box!\n";
1045 } else {
1046 print "I'm not on a Stratus box!\n";
1047 die;
1048 }
1049
1050 if (grep(/860/, @INC)) {
1051 print "This box is a Stratus XA/R!\n";
6ab3f9cb 1052
495c5fdc 1053 } elsif (grep(/7100/, @INC)) {
24e8e380 1054 print "This box is a Stratus HP 7100 or 8xxx!\n";
6ab3f9cb 1055
495c5fdc 1056 } elsif (grep(/8000/, @INC)) {
24e8e380 1057 print "This box is a Stratus HP 8xxx!\n";
6ab3f9cb 1058
495c5fdc 1059 } else {
24e8e380 1060 print "This box is a Stratus 68K!\n";
495c5fdc
GP
1061 }
1062
1063Also see:
1064
1065=over 4
1066
c997b287 1067=item *
495c5fdc 1068
c997b287
GS
1069F<README.vos>
1070
1071=item *
1072
1073The VOS mailing list.
495c5fdc
GP
1074
1075There is no specific mailing list for Perl on VOS. You can post
1076comments to the comp.sys.stratus newsgroup, or subscribe to the general
1077Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
1078the message body to majordomo@list.stratagy.com.
1079
c997b287
GS
1080=item *
1081
1082VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
495c5fdc
GP
1083
1084=back
1085
e41182b5
GS
1086=head2 EBCDIC Platforms
1087
1088Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1089AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1090Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1091Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1092systems). On the mainframe perl currently works under the "Unix system
1093services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1094the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
c997b287 1095See L<perlos390> for details.
e41182b5 1096
7c5ffed3
JH
1097As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1098sub-systems do not support the C<#!> shebang trick for script invocation.
1099Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1100similar to the following simple script:
e41182b5
GS
1101
1102 : # use perl
1103 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1104 if 0;
1105 #!/usr/local/bin/perl # just a comment really
1106
1107 print "Hello from perl!\n";
1108
d1e3b762
GS
1109OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1110Calls to C<system> and backticks can use POSIX shell syntax on all
1111S/390 systems.
1112
b7df3edc 1113On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1114to wrap your perl scripts in a CL procedure to invoke them like so:
1115
1116 BEGIN
1117 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1118 ENDPGM
1119
1120This will invoke the perl script F<hello.pl> in the root of the
1121QOpenSys file system. On the AS/400 calls to C<system> or backticks
1122must use CL syntax.
1123
e41182b5 1124On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1125an effect on what happens with some perl functions (such as C<chr>,
1126C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1127well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1128and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1129(see L<"Newlines">).
e41182b5 1130
b7df3edc
GS
1131Fortunately, most web servers for the mainframe will correctly
1132translate the C<\n> in the following statement to its ASCII equivalent
1133(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1134
1135 print "Content-type: text/html\r\n\r\n";
1136
d1e3b762 1137The values of C<$^O> on some of these platforms includes:
e41182b5 1138
d1e3b762
GS
1139 uname $^O $Config{'archname'}
1140 --------------------------------------------
1141 OS/390 os390 os390
1142 OS400 os400 os400
1143 POSIX-BC posix-bc BS2000-posix-bc
1144 VM/ESA vmesa vmesa
3c075c7d 1145
e41182b5
GS
1146Some simple tricks for determining if you are running on an EBCDIC
1147platform could include any of the following (perhaps all):
1148
1149 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1150
1151 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1152
1153 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1154
b7df3edc 1155One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1156of punctuation characters since these may differ from code page to code
1157page (and once your module or script is rumoured to work with EBCDIC,
1158folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1159
1160Also see:
1161
1162=over 4
1163
c997b287
GS
1164=item *
1165
1166*
d1e3b762 1167
dc5c060f 1168L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1169L<perlebcdic>.
c997b287
GS
1170
1171=item *
e41182b5
GS
1172
1173The perl-mvs@perl.org list is for discussion of porting issues as well as
1174general usage issues for all EBCDIC Perls. Send a message body of
1175"subscribe perl-mvs" to majordomo@perl.org.
1176
c997b287
GS
1177=item *
1178
1179AS/400 Perl information at
b1866b2d 1180http://as400.rochester.ibm.com/
d1e3b762 1181as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1182
1183=back
1184
b8099c3d
CN
1185=head2 Acorn RISC OS
1186
b7df3edc
GS
1187Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1188Unix, and because Unix filename emulation is turned on by default,
1189most simple scripts will probably work "out of the box". The native
6ab3f9cb 1190filesystem is modular, and individual filesystems are free to be
0a47030a 1191case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1192native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1193names are silently truncated to fit. Scripts should be aware that the
1194standard filesystem currently has a name length limit of B<10>
1195characters, with up to 77 items in a directory, but other filesystems
0a47030a 1196may not impose such limitations.
b8099c3d
CN
1197
1198Native filenames are of the form
1199
6ab3f9cb 1200 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1201
b8099c3d
CN
1202where
1203
1204 Special_Field is not usually present, but may contain . and $ .
1205 Filesystem =~ m|[A-Za-z0-9_]|
1206 DsicName =~ m|[A-Za-z0-9_/]|
1207 $ represents the root directory
1208 . is the path separator
1209 @ is the current directory (per filesystem but machine global)
1210 ^ is the parent directory
1211 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1212
1213The default filename translation is roughly C<tr|/.|./|;>
1214
6ab3f9cb 1215Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1216the second stage of C<$> interpolation in regular expressions will fall
1217foul of the C<$.> if scripts are not careful.
1218
1219Logical paths specified by system variables containing comma-separated
b7df3edc 1220search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1221filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1222C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1223Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1224C<System$Path> contains a single item list. The filesystem will also
1225expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1226C<< <System$Dir>.Modules >> would look for the file
0a47030a 1227S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1228that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1229be protected when C<open> is used for input.
b8099c3d
CN
1230
1231Because C<.> was in use as a directory separator and filenames could not
1232be assumed to be unique after 10 characters, Acorn implemented the C
1233compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1234filenames specified in source code and store the respective files in
b7df3edc 1235subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1236
1237 foo.h h.foo
1238 C:foo.h C:h.foo (logical path variable)
1239 sys/os.h sys.h.os (C compiler groks Unix-speak)
1240 10charname.c c.10charname
1241 10charname.o o.10charname
1242 11charname_.c c.11charname (assuming filesystem truncates at 10)
1243
1244The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1245that this sort of translation is required, and it allows a user-defined list
1246of known suffixes that it will transpose in this fashion. This may
1247seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1248and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1249C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1250C<.>'s in filenames are translated to C</>.
0a47030a 1251
b7df3edc 1252As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1253the convention is that program specific environment variables are of the
6ab3f9cb
GS
1254form C<Program$Name>. Each filesystem maintains a current directory,
1255and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1256directory. Consequently, sociable programs don't change the current
1257directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1258assume that they can spawn a child process which can change the current
1259directory without affecting its parent (and everyone else for that
1260matter).
1261
b7df3edc
GS
1262Because native operating system filehandles are global and are currently
1263allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1264library emulates Unix filehandles. Consequently, you can't rely on
1265passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1266
1267The desire of users to express filenames of the form
c47ff5f1 1268C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1269too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1270assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1271reference to an environment variable, whereas anything else involving
c47ff5f1 1272C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1273right. Of course, the problem remains that scripts cannot rely on any
1274Unix tools being available, or that any tools found have Unix-like command
1275line arguments.
1276
b7df3edc
GS
1277Extensions and XS are, in theory, buildable by anyone using free
1278tools. In practice, many don't, as users of the Acorn platform are
1279used to binary distributions. MakeMaker does run, but no available
1280make currently copes with MakeMaker's makefiles; even if and when
1281this should be fixed, the lack of a Unix-like shell will cause
1282problems with makefile rules, especially lines of the form C<cd
1283sdbm && make all>, and anything using quoting.
b8099c3d
CN
1284
1285"S<RISC OS>" is the proper name for the operating system, but the value
1286in C<$^O> is "riscos" (because we don't like shouting).
1287
e41182b5
GS
1288=head2 Other perls
1289
b7df3edc
GS
1290Perl has been ported to many platforms that do not fit into any of
1291the categories listed above. Some, such as AmigaOS, Atari MiNT,
1292BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1293into the standard Perl source code kit. You may need to see the
1294F<ports/> directory on CPAN for information, and possibly binaries,
1295for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1296Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1297fall under the Unix category, but we are not a standards body.)
e41182b5 1298
d1e3b762
GS
1299Some approximate operating system names and their C<$^O> values
1300in the "OTHER" category include:
1301
1302 OS $^O $Config{'archname'}
1303 ------------------------------------------
1304 Amiga DOS amigaos m68k-amigos
1305 MPE/iX mpeix PA-RISC1.1
1306
e41182b5
GS
1307See also:
1308
1309=over 4
1310
c997b287
GS
1311=item *
1312
1313Amiga, F<README.amiga> (installed as L<perlamiga>).
1314
1315=item *
d1e3b762 1316
c997b287
GS
1317Atari, F<README.mint> and Guido Flohr's web page
1318http://stud.uni-sb.de/~gufl0000/
e41182b5 1319
c997b287 1320=item *
d1e3b762 1321
c997b287 1322Be OS, F<README.beos>
e41182b5 1323
c997b287
GS
1324=item *
1325
1326HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1327http://www.bixby.org/mark/perlix.html
c997b287
GS
1328
1329=item *
e41182b5 1330
6ab3f9cb 1331A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1332precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1333as well as from CPAN.
e41182b5 1334
13a2d996 1335=item *
c997b287
GS
1336
1337Plan 9, F<README.plan9>
d1e3b762 1338
e41182b5
GS
1339=back
1340
e41182b5
GS
1341=head1 FUNCTION IMPLEMENTATIONS
1342
b7df3edc
GS
1343Listed below are functions that are either completely unimplemented
1344or else have been implemented differently on various platforms.
1345Following each description will be, in parentheses, a list of
1346platforms that the description applies to.
e41182b5 1347
b7df3edc
GS
1348The list may well be incomplete, or even wrong in some places. When
1349in doubt, consult the platform-specific README files in the Perl
1350source distribution, and any other documentation resources accompanying
1351a given port.
e41182b5 1352
0a47030a 1353Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1354
b7df3edc
GS
1355For many functions, you can also query C<%Config>, exported by
1356default from the Config module. For example, to check whether the
1357platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1358L<Config> for a full description of available variables.
e41182b5
GS
1359
1360=head2 Alphabetical Listing of Perl Functions
1361
1362=over 8
1363
1364=item -X FILEHANDLE
1365
1366=item -X EXPR
1367
1368=item -X
1369
b7df3edc 1370C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1371and applications are executable, and there are no uid/gid
b7df3edc 1372considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1373
b7df3edc
GS
1374C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1375which may not reflect UIC-based file protections. (VMS)
e41182b5 1376
b8099c3d
CN
1377C<-s> returns the size of the data fork, not the total size of data fork
1378plus resource fork. (S<Mac OS>).
1379
1380C<-s> by name on an open file will return the space reserved on disk,
1381rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1382current size. (S<RISC OS>)
b8099c3d 1383
e41182b5 1384C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1385C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1386
1387C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1388(S<Mac OS>)
1389
1390C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1391(Win32, VMS, S<RISC OS>)
e41182b5
GS
1392
1393C<-d> is true if passed a device spec without an explicit directory.
1394(VMS)
1395
1396C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1397with foreign characters; this is the case will all platforms, but may
b7df3edc 1398affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1399
1400C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1401suffixes. C<-S> is meaningless. (Win32)
e41182b5 1402
b8099c3d
CN
1403C<-x> (or C<-X>) determine if a file has an executable file type.
1404(S<RISC OS>)
1405
63f87e49
GS
1406=item alarm SECONDS
1407
1408=item alarm
1409
1410Not implemented. (Win32)
1411
e41182b5
GS
1412=item binmode FILEHANDLE
1413
b7df3edc 1414Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1415
1416Reopens file and restores pointer; if function fails, underlying
1417filehandle may be closed, or pointer may be in a different position.
1418(VMS)
1419
1420The value returned by C<tell> may be affected after the call, and
1421the filehandle may be flushed. (Win32)
1422
1423=item chmod LIST
1424
b7df3edc 1425Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1426locking/unlocking the file. (S<Mac OS>)
1427
1428Only good for changing "owner" read-write access, "group", and "other"
1429bits are meaningless. (Win32)
1430
b8099c3d
CN
1431Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1432
495c5fdc
GP
1433Access permissions are mapped onto VOS access-control list changes. (VOS)
1434
e41182b5
GS
1435=item chown LIST
1436
495c5fdc 1437Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1438
1439Does nothing, but won't fail. (Win32)
1440
1441=item chroot FILENAME
1442
1443=item chroot
1444
7c5ffed3 1445Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1446
1447=item crypt PLAINTEXT,SALT
1448
1449May not be available if library or source was not provided when building
b8099c3d 1450perl. (Win32)
e41182b5 1451
495c5fdc
GP
1452Not implemented. (VOS)
1453
e41182b5
GS
1454=item dbmclose HASH
1455
495c5fdc 1456Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1457
1458=item dbmopen HASH,DBNAME,MODE
1459
495c5fdc 1460Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1461
1462=item dump LABEL
1463
b8099c3d 1464Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1465
1466Not implemented. (Win32)
1467
b8099c3d 1468Invokes VMS debugger. (VMS)
e41182b5
GS
1469
1470=item exec LIST
1471
1472Not implemented. (S<Mac OS>)
1473
7c5ffed3 1474Implemented via Spawn. (VM/ESA)
3c075c7d 1475
0f897271
GS
1476Does not automatically flush output handles on some platforms.
1477(SunOS, Solaris, HP-UX)
1478
fe12c0e8
MS
1479=item exit EXPR
1480
1481=item exit
1482
1483Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1484mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1485with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1486function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1487(C<1>); this mapping cannot be overridden. Any other argument to exit()
1488is used directly as Perl's exit status. (VMS)
1489
e41182b5
GS
1490=item fcntl FILEHANDLE,FUNCTION,SCALAR
1491
1492Not implemented. (Win32, VMS)
1493
1494=item flock FILEHANDLE,OPERATION
1495
495c5fdc 1496Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1497
1498Available only on Windows NT (not on Windows 95). (Win32)
1499
1500=item fork
1501
0f897271
GS
1502Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1503
1504Emulated using multiple interpreters. See L<perlfork>. (Win32)
1505
1506Does not automatically flush output handles on some platforms.
1507(SunOS, Solaris, HP-UX)
e41182b5
GS
1508
1509=item getlogin
1510
b8099c3d 1511Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1512
1513=item getpgrp PID
1514
495c5fdc 1515Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1516
1517=item getppid
1518
b8099c3d 1519Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1520
1521=item getpriority WHICH,WHO
1522
7c5ffed3 1523Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1524
1525=item getpwnam NAME
1526
1527Not implemented. (S<Mac OS>, Win32)
1528
b8099c3d
CN
1529Not useful. (S<RISC OS>)
1530
e41182b5
GS
1531=item getgrnam NAME
1532
b8099c3d 1533Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1534
1535=item getnetbyname NAME
1536
1537Not implemented. (S<Mac OS>, Win32, Plan9)
1538
1539=item getpwuid UID
1540
1541Not implemented. (S<Mac OS>, Win32)
1542
b8099c3d
CN
1543Not useful. (S<RISC OS>)
1544
e41182b5
GS
1545=item getgrgid GID
1546
b8099c3d 1547Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1548
1549=item getnetbyaddr ADDR,ADDRTYPE
1550
1551Not implemented. (S<Mac OS>, Win32, Plan9)
1552
1553=item getprotobynumber NUMBER
1554
1555Not implemented. (S<Mac OS>)
1556
1557=item getservbyport PORT,PROTO
1558
1559Not implemented. (S<Mac OS>)
1560
1561=item getpwent
1562
7c5ffed3 1563Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1564
1565=item getgrent
1566
7c5ffed3 1567Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5
GS
1568
1569=item gethostent
1570
1571Not implemented. (S<Mac OS>, Win32)
1572
1573=item getnetent
1574
1575Not implemented. (S<Mac OS>, Win32, Plan9)
1576
1577=item getprotoent
1578
1579Not implemented. (S<Mac OS>, Win32, Plan9)
1580
1581=item getservent
1582
1583Not implemented. (Win32, Plan9)
1584
1585=item setpwent
1586
b8099c3d 1587Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1588
1589=item setgrent
1590
b8099c3d 1591Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1592
1593=item sethostent STAYOPEN
1594
b8099c3d 1595Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1596
1597=item setnetent STAYOPEN
1598
b8099c3d 1599Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1600
1601=item setprotoent STAYOPEN
1602
b8099c3d 1603Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1604
1605=item setservent STAYOPEN
1606
b8099c3d 1607Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1608
1609=item endpwent
1610
a3dfe201 1611Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1612
1613=item endgrent
1614
a3dfe201 1615Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1616
1617=item endhostent
1618
1619Not implemented. (S<Mac OS>, Win32)
1620
1621=item endnetent
1622
1623Not implemented. (S<Mac OS>, Win32, Plan9)
1624
1625=item endprotoent
1626
1627Not implemented. (S<Mac OS>, Win32, Plan9)
1628
1629=item endservent
1630
1631Not implemented. (Plan9, Win32)
1632
1633=item getsockopt SOCKET,LEVEL,OPTNAME
1634
97c10e77 1635Not implemented. (Plan9)
e41182b5
GS
1636
1637=item glob EXPR
1638
1639=item glob
1640
63f87e49
GS
1641This operator is implemented via the File::Glob extension on most
1642platforms. See L<File::Glob> for portability information.
b8099c3d 1643
e41182b5
GS
1644=item ioctl FILEHANDLE,FUNCTION,SCALAR
1645
1646Not implemented. (VMS)
1647
1648Available only for socket handles, and it does what the ioctlsocket() call
1649in the Winsock API does. (Win32)
1650
b8099c3d
CN
1651Available only for socket handles. (S<RISC OS>)
1652
b350dd2f 1653=item kill SIGNAL, LIST
e41182b5 1654
862b5365
JH
1655C<kill(0, LIST)> is implemented for the sake of taint checking;
1656use with other signals is unimplemented. (S<Mac OS>)
1657
1658Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1659
63f87e49
GS
1660C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1661a signal to the identified process like it does on Unix platforms.
1662Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1663and makes it exit immediately with exit status $sig. As in Unix, if
1664$sig is 0 and the specified process exists, it returns true without
1665actually terminating it. (Win32)
e41182b5
GS
1666
1667=item link OLDFILE,NEWFILE
1668
a3dfe201 1669Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
e41182b5 1670
433acd8a
JH
1671Link count not updated because hard links are not quite that hard
1672(They are sort of half-way between hard and soft links). (AmigaOS)
1673
a3dfe201
GS
1674Hard links are implemented on Win32 (Windows NT and Windows 2000)
1675under NTFS only.
1676
e41182b5
GS
1677=item lstat FILEHANDLE
1678
1679=item lstat EXPR
1680
1681=item lstat
1682
b8099c3d 1683Not implemented. (VMS, S<RISC OS>)
e41182b5 1684
63f87e49 1685Return values (especially for device and inode) may be bogus. (Win32)
e41182b5
GS
1686
1687=item msgctl ID,CMD,ARG
1688
1689=item msgget KEY,FLAGS
1690
1691=item msgsnd ID,MSG,FLAGS
1692
1693=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1694
495c5fdc 1695Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1696
1697=item open FILEHANDLE,EXPR
1698
1699=item open FILEHANDLE
1700
b7df3edc 1701The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1702(S<Mac OS>)
1703
c47ff5f1 1704open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1705
0f897271
GS
1706Opening a process does not automatically flush output handles on some
1707platforms. (SunOS, Solaris, HP-UX)
1708
e41182b5
GS
1709=item pipe READHANDLE,WRITEHANDLE
1710
433acd8a
JH
1711Very limited functionality. (MiNT)
1712
e41182b5
GS
1713=item readlink EXPR
1714
1715=item readlink
1716
b8099c3d 1717Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1718
1719=item select RBITS,WBITS,EBITS,TIMEOUT
1720
689c5c24 1721Only implemented on sockets. (Win32, VMS)
e41182b5 1722
b8099c3d
CN
1723Only reliable on sockets. (S<RISC OS>)
1724
76e05f0b 1725Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1726
e41182b5
GS
1727=item semctl ID,SEMNUM,CMD,ARG
1728
1729=item semget KEY,NSEMS,FLAGS
1730
1731=item semop KEY,OPSTRING
1732
495c5fdc 1733Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1734
a3dfe201
GS
1735=item setgrent
1736
1737Not implemented. (MPE/iX, Win32)
1738
e41182b5
GS
1739=item setpgrp PID,PGRP
1740
495c5fdc 1741Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1742
1743=item setpriority WHICH,WHO,PRIORITY
1744
495c5fdc 1745Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1746
a3dfe201
GS
1747=item setpwent
1748
1749Not implemented. (MPE/iX, Win32)
1750
e41182b5
GS
1751=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1752
97c10e77 1753Not implemented. (Plan9)
e41182b5
GS
1754
1755=item shmctl ID,CMD,ARG
1756
1757=item shmget KEY,SIZE,FLAGS
1758
1759=item shmread ID,VAR,POS,SIZE
1760
1761=item shmwrite ID,STRING,POS,SIZE
1762
495c5fdc 1763Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1764
80cbd5ad
JH
1765=item sockatmark SOCKET
1766
1767A relatively recent addition to socket functions, may not
1768be implemented even in UNIX platforms.
1769
e41182b5
GS
1770=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1771
862b5365 1772Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1773
1774=item stat FILEHANDLE
1775
1776=item stat EXPR
1777
1778=item stat
1779
d62e1b7f
JH
1780Platforms that do not have rdev, blksize, or blocks will return these
1781as '', so numeric comparison or manipulation of these fields may cause
1782'not numeric' warnings.
1783
e41182b5
GS
1784mtime and atime are the same thing, and ctime is creation time instead of
1785inode change time. (S<Mac OS>)
1786
1787device and inode are not meaningful. (Win32)
1788
1789device and inode are not necessarily reliable. (VMS)
1790
b8099c3d
CN
1791mtime, atime and ctime all return the last modification time. Device and
1792inode are not necessarily reliable. (S<RISC OS>)
1793
d62e1b7f
JH
1794dev, rdev, blksize, and blocks are not available. inode is not
1795meaningful and will differ between stat calls on the same file. (os2)
1796
73e9292c
JH
1797some versions of cygwin when doing a stat("foo") and if not finding it
1798may then attempt to stat("foo.exe") (Cygwin)
1799
e41182b5
GS
1800=item symlink OLDFILE,NEWFILE
1801
b8099c3d 1802Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1803
1804=item syscall LIST
1805
7c5ffed3 1806Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1807
f34d0673
GS
1808=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1809
dd9f0070 1810The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1811numeric values on some systems. The flags exported by C<Fcntl>
1812(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 1813OS>, OS/390, VM/ESA)
f34d0673 1814
e41182b5
GS
1815=item system LIST
1816
9d6eb86e 1817In general, do not assume the UNIX/POSIX semantics that you can shift
7717d0e7 1818C<$?> right by eight to get the exit value, or that C<$? & 127>
9d6eb86e
JH
1819would give you the number of the signal that terminated the program,
1820or that C<$? & 128> would test true if the program was terminated by a
1821coredump. Instead, use the POSIX W*() interfaces: for example, use
1822WIFEXITED($?) an WEXITVALUE($?) to test for a normal exit and the exit
1823value, and WIFSIGNALED($?) and WTERMSIG($?) for a signal exit and the
7717d0e7 1824signal. Core dumping is not a portable concept, so there's no portable
9d6eb86e
JH
1825way to test for that.
1826
e41182b5
GS
1827Only implemented if ToolServer is installed. (S<Mac OS>)
1828
1829As an optimization, may not call the command shell specified in
b7df3edc 1830C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
1831process and immediately returns its process designator, without
1832waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
1833in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1834by setting $? to "255 << 8". C<$?> is set in a way compatible with
1835Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1836as described in the documentation). (Win32)
e41182b5 1837
b8099c3d
CN
1838There is no shell to process metacharacters, and the native standard is
1839to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 1840program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
1841the run time library of the spawned program. C<system> I<list> will call
1842the Unix emulation library's C<exec> emulation, which attempts to provide
1843emulation of the stdin, stdout, stderr in force in the parent, providing
1844the child program uses a compatible version of the emulation library.
1845I<scalar> will call the native command line direct and no such emulation
1846of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1847
433acd8a
JH
1848Far from being POSIX compliant. Because there may be no underlying
1849/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 1850first token in its argument string. Handles basic redirection
c47ff5f1 1851("<" or ">") on its own behalf. (MiNT)
433acd8a 1852
0f897271
GS
1853Does not automatically flush output handles on some platforms.
1854(SunOS, Solaris, HP-UX)
1855
9bc98430
CB
1856The return value is POSIX-like (shifted up by 8 bits), which only allows
1857room for a made-up value derived from the severity bits of the native
185832-bit condition code (unless overridden by C<use vmsish 'status'>).
1859For more details see L<perlvms/$?>. (VMS)
1860
e41182b5
GS
1861=item times
1862
1863Only the first entry returned is nonzero. (S<Mac OS>)
1864
63f87e49
GS
1865"cumulative" times will be bogus. On anything other than Windows NT
1866or Windows 2000, "system" time will be bogus, and "user" time is
1867actually the time returned by the clock() function in the C runtime
1868library. (Win32)
e41182b5 1869
b8099c3d
CN
1870Not useful. (S<RISC OS>)
1871
e41182b5
GS
1872=item truncate FILEHANDLE,LENGTH
1873
1874=item truncate EXPR,LENGTH
1875
6d738113 1876Not implemented. (Older versions of VMS)
e41182b5 1877
495c5fdc
GP
1878Truncation to zero-length only. (VOS)
1879
4cfdb94f 1880If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 1881mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
1882or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1883should not be held open elsewhere. (Win32)
1884
e41182b5
GS
1885=item umask EXPR
1886
1887=item umask
1888
1889Returns undef where unavailable, as of version 5.005.
1890
b7df3edc
GS
1891C<umask> works but the correct permissions are set only when the file
1892is finally closed. (AmigaOS)
433acd8a 1893
e41182b5
GS
1894=item utime LIST
1895
15c65113 1896Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1897
322422de
GS
1898May not behave as expected. Behavior depends on the C runtime
1899library's implementation of utime(), and the filesystem being
1900used. The FAT filesystem typically does not support an "access
1901time" field, and it may limit timestamps to a granularity of
1902two seconds. (Win32)
e41182b5
GS
1903
1904=item wait
1905
1906=item waitpid PID,FLAGS
1907
495c5fdc 1908Not implemented. (S<Mac OS>, VOS)
e41182b5
GS
1909
1910Can only be applied to process handles returned for processes spawned
a6f858fb 1911using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 1912
b8099c3d
CN
1913Not useful. (S<RISC OS>)
1914
e41182b5
GS
1915=back
1916
b8099c3d
CN
1917=head1 CHANGES
1918
1919=over 4
1920
fd46a41b
JH
1921=item v1.48, 02 February 2001
1922
1923Various updates from perl5-porters over the past year, supported
1924platforms update from Jarkko Hietaniemi.
1925
c997b287
GS
1926=item v1.47, 22 March 2000
1927
1928Various cleanups from Tom Christiansen, including migration of
1929long platform listings from L<perl>.
1930
56d7751a
GS
1931=item v1.46, 12 February 2000
1932
1933Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1934
0cc436d0
GS
1935=item v1.45, 20 December 1999
1936
1937Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1938
d1e3b762
GS
1939=item v1.44, 19 July 1999
1940
1941A bunch of updates from Peter Prymmer for C<$^O> values,
1942endianness, File::Spec, VMS, BS2000, OS/400.
1943
b7df3edc
GS
1944=item v1.43, 24 May 1999
1945
1946Added a lot of cleaning up from Tom Christiansen.
1947
19799a22 1948=item v1.42, 22 May 1999
b7df3edc 1949
19799a22 1950Added notes about tests, sprintf/printf, and epoch offsets.
b7df3edc 1951
6ab3f9cb
GS
1952=item v1.41, 19 May 1999
1953
1954Lots more little changes to formatting and content.
1955
d1e3b762 1956Added a bunch of C<$^O> and related values
6ab3f9cb
GS
1957for various platforms; fixed mail and web addresses, and added
1958and changed miscellaneous notes. (Peter Prymmer)
1959
1960=item v1.40, 11 April 1999
1961
1962Miscellaneous changes.
1963
1964=item v1.39, 11 February 1999
2ee0eb3c
CN
1965
1966Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1967note about newlines added.
1968
9b63e9ec
CN
1969=item v1.38, 31 December 1998
1970
1971More changes from Jarkko.
1972
3c075c7d
CN
1973=item v1.37, 19 December 1998
1974
1975More minor changes. Merge two separate version 1.35 documents.
1976
1977=item v1.36, 9 September 1998
1978
1979Updated for Stratus VOS. Also known as version 1.35.
1980
1981=item v1.35, 13 August 1998
495c5fdc 1982
3c075c7d
CN
1983Integrate more minor changes, plus addition of new sections under
1984L<"ISSUES">: L<"Numbers endianness and Width">,
1985L<"Character sets and character encoding">,
1986L<"Internationalisation">.
495c5fdc 1987
3c075c7d 1988=item v1.33, 06 August 1998
0a47030a
GS
1989
1990Integrate more minor changes.
1991
3c075c7d 1992=item v1.32, 05 August 1998
dd9f0070
CN
1993
1994Integrate more minor changes.
1995
3c075c7d 1996=item v1.30, 03 August 1998
b8099c3d
CN
1997
1998Major update for RISC OS, other minor changes.
1999
3c075c7d 2000=item v1.23, 10 July 1998
b8099c3d
CN
2001
2002First public release with perl5.005.
2003
2004=back
e41182b5 2005
ba58ab26
JH
2006=head1 Supported Platforms
2007
9ca74005
JH
2008As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
2009platforms are able to build Perl from the standard source code
a93751fa 2010distribution available at http://www.cpan.org/src/index.html
ba58ab26
JH
2011
2012 AIX
fd46a41b 2013 AmigaOS
b787fad4 2014 Darwin (Mac OS X)
fd46a41b 2015 DG/UX
ba58ab26 2016 DOS DJGPP 1)
fd46a41b 2017 DYNIX/ptx
6ba81f13 2018 EPOC
ba58ab26
JH
2019 FreeBSD
2020 HP-UX
2021 IRIX
2022 Linux
ba58ab26 2023 MachTen
fd46a41b
JH
2024 MacOS Classic 2)
2025 NonStop-UX
2026 ReliantUNIX (SINIX)
ba58ab26 2027 OpenBSD
fd46a41b 2028 OpenVMS (VMS)
ba58ab26 2029 OS/2
fd46a41b 2030 OS X
ba58ab26 2031 QNX
ba58ab26 2032 Solaris
fd46a41b 2033 Tru64 UNIX (DEC OSF/1, Digital UNIX)
ba58ab26
JH
2034 UNICOS
2035 UNICOS/mk
ba58ab26 2036 VOS
fd46a41b 2037 Win32/NT/2K 3)
ba58ab26
JH
2038
2039 1) in DOS mode either the DOS or OS/2 ports can be used
fd46a41b
JH
2040 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
2041 the source does work with 5.6.1, but additional MacOS specific
862b5365
JH
2042 source code is needed for a complete build. See the web
2043 site http://dev.macperl.org/ for more information.
fd46a41b 2044 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
ba58ab26 2045
9ca74005
JH
2046The following platforms worked for the previous releases (5.6.0 and 5.7.0),
2047but we did not manage to test these in time for the 5.7.1 release.
2048There is a very good chance that these will work fine with the 5.7.1.
ba58ab26 2049
ba58ab26
JH
2050 DomainOS
2051 Hurd
fd46a41b
JH
2052 LynxOS
2053 MinGW
2054 MPE/iX
2055 NetBSD
ba58ab26 2056 PowerMAX
fd46a41b 2057 SCO SV
ba58ab26 2058 SunOS
fd46a41b
JH
2059 SVR4
2060 Unixware
2061 Windows 3.1
2062 Windows 95
2063 Windows 98
2064 Windows Me
ba58ab26 2065
fd46a41b 2066The following platform worked for the 5.005_03 major release but not
9ca74005
JH
2067for 5.6.0. Standardization on UTF-8 as the internal string
2068representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
2069EBCDIC platform. While Perl 5.7.1 will build on this platform some
fd46a41b 2070regression tests may fail and the C<use utf8;> pragma typically
9ca74005 2071introduces text handling errors.
ba58ab26 2072
fd46a41b 2073 OS/390 1)
ba58ab26 2074
fd46a41b 2075 1) previously known as MVS, about to become z/OS.
ba58ab26 2076
fd46a41b 2077Strongly related to the OS/390 platform by also being EBCDIC-based
ba58ab26
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2078mainframe platforms are the following platforms:
2079
fd46a41b 2080 POSIX-BC (BS2000)
ba58ab26
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2081 VM/ESA
2082
fd46a41b
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2083These are also expected to work, albeit with no UTF-8 support, under 5.6.1
2084for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
2085for more details.
ba58ab26
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2086
2087The following platforms have been known to build Perl from source in
fd46a41b
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2088the past (5.005_03 and earlier), but we haven't been able to verify
2089their status for the current release, either because the
2090hardware/software platforms are rare or because we don't have an
2091active champion on these platforms--or both. They used to work,
2092though, so go ahead and try compiling them, and let perlbug@perl.org
2093of any trouble.
ba58ab26
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2094
2095 3b1
fd46a41b
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2096 A/UX
2097 BeOS
2098 BSD/OS
ba58ab26
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2099 ConvexOS
2100 CX/UX
2101 DC/OSx
2102 DDE SMES
2103 DOS EMX
2104 Dynix
2105 EP/IX
2106 ESIX
2107 FPS
2108 GENIX
2109 Greenhills
2110 ISC
2111 MachTen 68k
2112 MiNT
2113 MPC
2114 NEWS-OS
fd46a41b
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2115 NextSTEP
2116 OpenSTEP
ba58ab26
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2117 Opus
2118 Plan 9
2119 PowerUX
2120 RISC/os
fd46a41b 2121 SCO ODT/OSR
ba58ab26
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2122 Stellar
2123 SVR2
2124 TI1500
2125 TitanOS
fd46a41b 2126 Ultrix
ba58ab26
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2127 Unisys Dynix
2128 Unixware
fd46a41b 2129 UTS
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2130
2131Support for the following platform is planned for a future Perl release:
2132
2133 Netware
2134
2135The following platforms have their own source code distributions and
a93751fa 2136binaries available via http://www.cpan.org/ports/index.html:
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2137
2138 Perl release
2139
ba58ab26 2140 Netware 5.003_07
fd46a41b 2141 OS/400 5.005_02
ba58ab26
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2142 Tandem Guardian 5.004
2143
2144The following platforms have only binaries available via
a93751fa 2145http://www.cpan.org/ports/index.html :
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2146
2147 Perl release
2148
2149 Acorn RISCOS 5.005_02
2150 AOS 5.002
2151 LynxOS 5.004_02
2152
2153Although we do suggest that you always build your own Perl from
2154the source code, both for maximal configurability and for security,
2155in case you are in a hurry you can check
a93751fa 2156http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2157
c997b287
GS
2158=head1 SEE ALSO
2159
a83b6f46 2160L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
a1f19229 2161L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
a83b6f46 2162L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
9038e305
JH
2163L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
2164L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
2165L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
c997b287 2166
e41182b5
GS
2167=head1 AUTHORS / CONTRIBUTORS
2168
06e9666b 2169Abigail <abigail@foad.org>,
c47ff5f1
GS
2170Charles Bailey <bailey@newman.upenn.edu>,
2171Graham Barr <gbarr@pobox.com>,
2172Tom Christiansen <tchrist@perl.com>,
06e9666b 2173Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2174Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2175Andy Dougherty <doughera@lafayette.edu>,
2176Dominic Dunlop <domo@computer.org>,
2177Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1
GS
2178David J. Fiander <davidf@mks.com>,
2179Paul Green <Paul_Green@stratus.com>,
06e9666b 2180M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2181Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2182Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2183Nick Ing-Simmons <nick@ing-simmons.net>,
2184Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2185Markus Laker <mlaker@contax.co.uk>,
2186Andrew M. Langmead <aml@world.std.com>,
2187Larry Moore <ljmoore@freespace.net>,
2188Paul Moore <Paul.Moore@uk.origin-it.com>,
2189Chris Nandor <pudge@pobox.com>,
2190Matthias Neeracher <neeri@iis.ee.ethz.ch>,
e71a7dc8 2191Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2192Gary Ng <71564.1743@CompuServe.COM>,
2193Tom Phoenix <rootbeer@teleport.com>,
2194AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2195Peter Prymmer <pvhp@forte.com>,
2196Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2197Gurusamy Sarathy <gsar@activestate.com>,
2198Paul J. Schinder <schinder@pobox.com>,
2199Michael G Schwern <schwern@pobox.com>,
06e9666b 2200Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2201Nathan Torkington <gnat@frii.com>.
e41182b5 2202
e41182b5
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2203=head1 VERSION
2204
b787fad4 2205Version 1.50, last modified 10 Jul 2001