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Fix -p function and Fcntl::S_IFIFO constant under Microsoft VC compiler
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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
7ee27b7c 70portability (L<"ISSUES">), platform-specific issues (L<"PLATFORMS">), and
b7df3edc 71built-in perl functions that behave differently on various ports
7ee27b7c 72(L<"FUNCTION IMPLEMENTATIONS">).
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73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
b7df3edc 76all of which are in a state of constant evolution. Thus, this material
e41182b5 77should be considered a perpetual work in progress
cc07ed0b 78(C<< <IMG SRC="yellow_sign.gif" ALT="Under Construction"> >>).
e41182b5 79
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80=head1 ISSUES
81
82=head2 Newlines
83
638bc118 84In most operating systems, lines in files are terminated by newlines.
e41182b5 85Just what is used as a newline may vary from OS to OS. Unix
b7df3edc 86traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>,
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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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97To trim trailing newlines from text lines use chomp(). With default
98settings that function looks for a trailing C<\n> character and thus
99trims in a portable way.
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100
101When dealing with binary files (or text files in binary mode) be sure
102to explicitly set $/ to the appropriate value for your file format
103before using chomp().
104
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105Because of the "text" mode translation, DOSish perls have limitations
106in using C<seek> and C<tell> on a file accessed in "text" mode.
107Stick to C<seek>-ing to locations you got from C<tell> (and no
108others), and you are usually free to use C<seek> and C<tell> even
109in "text" mode. Using C<seek> or C<tell> or other file operations
110may be non-portable. If you use C<binmode> on a file, however, you
111can usually C<seek> and C<tell> with arbitrary values in safety.
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112
113A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 114everywhere. When using protocols such as common Internet protocols,
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115C<\012> and C<\015> are called for specifically, and the values of
116the logical C<\n> and C<\r> (carriage return) are not reliable.
117
118 print SOCKET "Hi there, client!\r\n"; # WRONG
119 print SOCKET "Hi there, client!\015\012"; # RIGHT
120
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121However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
122and unsightly, as well as confusing to those maintaining the code. As
6ab3f9cb 123such, the Socket module supplies the Right Thing for those who want it.
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124
125 use Socket qw(:DEFAULT :crlf);
126 print SOCKET "Hi there, client!$CRLF" # RIGHT
127
6ab3f9cb 128When reading from a socket, remember that the default input record
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129separator C<$/> is C<\n>, but robust socket code will recognize as
130either C<\012> or C<\015\012> as end of line:
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131
132 while (<SOCKET>) {
133 # ...
134 }
135
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136Because both CRLF and LF end in LF, the input record separator can
137be set to LF and any CR stripped later. Better to write:
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138
139 use Socket qw(:DEFAULT :crlf);
140 local($/) = LF; # not needed if $/ is already \012
141
142 while (<SOCKET>) {
143 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
144 # s/\015?\012/\n/; # same thing
145 }
146
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147This example is preferred over the previous one--even for Unix
148platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
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149(and there was much rejoicing).
150
6ab3f9cb 151Similarly, functions that return text data--such as a function that
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152fetches a web page--should sometimes translate newlines before
153returning the data, if they've not yet been translated to the local
154newline representation. A single line of code will often suffice:
2ee0eb3c 155
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156 $data =~ s/\015?\012/\n/g;
157 return $data;
2ee0eb3c 158
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159Some of this may be confusing. Here's a handy reference to the ASCII CR
160and LF characters. You can print it out and stick it in your wallet.
161
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162 LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
163 CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
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164
165 | Unix | DOS | Mac |
166 ---------------------------
167 \n | LF | LF | CR |
168 \r | CR | CR | LF |
169 \n * | LF | CRLF | CR |
170 \r * | CR | CR | LF |
171 ---------------------------
172 * text-mode STDIO
173
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174The Unix column assumes that you are not accessing a serial line
175(like a tty) in canonical mode. If you are, then CR on input becomes
176"\n", and "\n" on output becomes CRLF.
177
6ab3f9cb 178These are just the most common definitions of C<\n> and C<\r> in Perl.
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179There may well be others. For example, on an EBCDIC implementation
180such as z/OS (OS/390) or OS/400 (using the ILE, the PASE is ASCII-based)
181the above material is similar to "Unix" but the code numbers change:
74555b7a 182
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183 LF eq \025 eq \x15 eq \cU eq chr(21) eq CP-1047 21
184 LF eq \045 eq \x25 eq chr(37) eq CP-0037 37
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185 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
186 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
187
188 | z/OS | OS/400 |
189 ----------------------
190 \n | LF | LF |
191 \r | CR | CR |
192 \n * | LF | LF |
193 \r * | CR | CR |
194 ----------------------
195 * text-mode STDIO
6ab3f9cb 196
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197=head2 Numbers endianness and Width
198
199Different CPUs store integers and floating point numbers in different
200orders (called I<endianness>) and widths (32-bit and 64-bit being the
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201most common today). This affects your programs when they attempt to transfer
202numbers in binary format from one CPU architecture to another,
203usually either "live" via network connection, or by storing the
204numbers to secondary storage such as a disk file or tape.
322422de 205
b7df3edc 206Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 207little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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208decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2090x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
210Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
211them in big-endian mode. To avoid this problem in network (socket)
212connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
213"network" orders. These are guaranteed to be portable.
322422de 214
7a4d2905 215As of perl 5.9.2, you can also use the C<E<gt>> and C<E<lt>> modifiers
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216to force big- or little-endian byte-order. This is useful if you want
217to store signed integers or 64-bit integers, for example.
218
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219You can explore the endianness of your platform by unpacking a
220data structure packed in native format such as:
221
222 print unpack("h*", pack("s2", 1, 2)), "\n";
223 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
224 # '00100020' on e.g. Motorola 68040
225
226If you need to distinguish between endian architectures you could use
227either of the variables set like so:
228
229 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 230 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 231
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232Differing widths can cause truncation even between platforms of equal
233endianness. The platform of shorter width loses the upper parts of the
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234number. There is no good solution for this problem except to avoid
235transferring or storing raw binary numbers.
236
b7df3edc 237One can circumnavigate both these problems in two ways. Either
322422de 238transfer and store numbers always in text format, instead of raw
b7df3edc 239binary, or else consider using modules like Data::Dumper (included in
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240the standard distribution as of Perl 5.005) and Storable (included as
241of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 242
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243The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
244how far EBCDIC, or more precisely UTF-EBCDIC will go.
245
433acd8a 246=head2 Files and Filesystems
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247
248Most platforms these days structure files in a hierarchical fashion.
b7df3edc 249So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 250notion of a "path" to uniquely identify a file on the system. How
b7df3edc 251that path is really written, though, differs considerably.
e41182b5 252
4375e838 253Although similar, file path specifications differ between Unix,
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254Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
255Unix, for example, is one of the few OSes that has the elegant idea
256of a single root directory.
322422de 257
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258DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
259as path separator, or in their own idiosyncratic ways (such as having
260several root directories and various "unrooted" device files such NIL:
261and LPT:).
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262
263S<Mac OS> uses C<:> as a path separator instead of C</>.
264
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265The filesystem may support neither hard links (C<link>) nor
266symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 267
6ab3f9cb 268The filesystem may support neither access timestamp nor change
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269timestamp (meaning that about the only portable timestamp is the
270modification timestamp), or one second granularity of any timestamps
271(e.g. the FAT filesystem limits the time granularity to two seconds).
272
74555b7a 273The "inode change timestamp" (the C<-C> filetest) may really be the
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274"creation timestamp" (which it is not in UNIX).
275
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276VOS perl can emulate Unix filenames with C</> as path separator. The
277native pathname characters greater-than, less-than, number-sign, and
278percent-sign are always accepted.
279
6ab3f9cb 280S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 281separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 282signal filesystems and disk names.
e41182b5 283
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284Don't assume UNIX filesystem access semantics: that read, write,
285and execute are all the permissions there are, and even if they exist,
286that their semantics (for example what do r, w, and x mean on
287a directory) are the UNIX ones. The various UNIX/POSIX compatibility
288layers usually try to make interfaces like chmod() work, but sometimes
289there simply is no good mapping.
290
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291If all this is intimidating, have no (well, maybe only a little)
292fear. There are modules that can help. The File::Spec modules
293provide methods to do the Right Thing on whatever platform happens
294to be running the program.
e41182b5 295
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296 use File::Spec::Functions;
297 chdir(updir()); # go up one directory
298 $file = catfile(curdir(), 'temp', 'file.txt');
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299 # on Unix and Win32, './temp/file.txt'
300 # on Mac OS, ':temp:file.txt'
d1e3b762 301 # on VMS, '[.temp]file.txt'
e41182b5 302
b7df3edc 303File::Spec is available in the standard distribution as of version
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3045.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
305and some versions of perl come with version 0.6. If File::Spec
306is not updated to 0.7 or later, you must use the object-oriented
307interface from File::Spec (or upgrade File::Spec).
e41182b5 308
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309In general, production code should not have file paths hardcoded.
310Making them user-supplied or read from a configuration file is
311better, keeping in mind that file path syntax varies on different
312machines.
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313
314This is especially noticeable in scripts like Makefiles and test suites,
315which often assume C</> as a path separator for subdirectories.
316
b7df3edc 317Also of use is File::Basename from the standard distribution, which
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318splits a pathname into pieces (base filename, full path to directory,
319and file suffix).
320
19799a22 321Even when on a single platform (if you can call Unix a single platform),
b7df3edc 322remember not to count on the existence or the contents of particular
3c075c7d 323system-specific files or directories, like F</etc/passwd>,
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324F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
325example, F</etc/passwd> may exist but not contain the encrypted
326passwords, because the system is using some form of enhanced security.
327Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 328If code does need to rely on such a file, include a description of the
b7df3edc 329file and its format in the code's documentation, then make it easy for
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330the user to override the default location of the file.
331
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332Don't assume a text file will end with a newline. They should,
333but people forget.
e41182b5 334
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335Do not have two files or directories of the same name with different
336case, like F<test.pl> and F<Test.pl>, as many platforms have
337case-insensitive (or at least case-forgiving) filenames. Also, try
338not to have non-word characters (except for C<.>) in the names, and
339keep them to the 8.3 convention, for maximum portability, onerous a
340burden though this may appear.
dd9f0070 341
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342Likewise, when using the AutoSplit module, try to keep your functions to
3438.3 naming and case-insensitive conventions; or, at the least,
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344make it so the resulting files have a unique (case-insensitively)
345first 8 characters.
346
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347Whitespace in filenames is tolerated on most systems, but not all,
348and even on systems where it might be tolerated, some utilities
fe829689 349might become confused by such whitespace.
ec481373 350
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351Many systems (DOS, VMS ODS-2) cannot have more than one C<.> in their
352filenames.
433acd8a 353
c47ff5f1 354Don't assume C<< > >> won't be the first character of a filename.
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355Always use C<< < >> explicitly to open a file for reading, or even
356better, use the three-arg version of open, unless you want the user to
357be able to specify a pipe open.
0a47030a 358
fe829689 359 open(FILE, '<', $existing_file) or die $!;
0a47030a 360
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361If filenames might use strange characters, it is safest to open it
362with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 363translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 364be the wrong thing to do. (Sometimes, though, it's the right thing.)
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365Three-arg open can also help protect against this translation in cases
366where it is undesirable.
e41182b5 367
ec481373 368Don't use C<:> as a part of a filename since many systems use that for
8939ba94 369their own semantics (Mac OS Classic for separating pathname components,
ec481373 370many networking schemes and utilities for separating the nodename and
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371the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
372C<|>.
ec481373 373
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374Don't assume that in pathnames you can collapse two leading slashes
375C<//> into one: some networking and clustering filesystems have special
376semantics for that. Let the operating system to sort it out.
377
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378The I<portable filename characters> as defined by ANSI C are
379
380 a b c d e f g h i j k l m n o p q r t u v w x y z
381 A B C D E F G H I J K L M N O P Q R T U V W X Y Z
382 0 1 2 3 4 5 6 7 8 9
383 . _ -
384
08fef530 385and the "-" shouldn't be the first character. If you want to be
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386hypercorrect, stay case-insensitive and within the 8.3 naming
387convention (all the files and directories have to be unique within one
388directory if their names are lowercased and truncated to eight
389characters before the C<.>, if any, and to three characters after the
390C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 391
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392=head2 System Interaction
393
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394Not all platforms provide a command line. These are usually platforms
395that rely primarily on a Graphical User Interface (GUI) for user
396interaction. A program requiring a command line interface might
397not work everywhere. This is probably for the user of the program
398to deal with, so don't stay up late worrying about it.
e41182b5 399
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400Some platforms can't delete or rename files held open by the system,
401this limitation may also apply to changing filesystem metainformation
402like file permissions or owners. Remember to C<close> files when you
403are done with them. Don't C<unlink> or C<rename> an open file. Don't
404C<tie> or C<open> a file already tied or opened; C<untie> or C<close>
405it first.
e41182b5 406
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407Don't open the same file more than once at a time for writing, as some
408operating systems put mandatory locks on such files.
409
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410Don't assume that write/modify permission on a directory gives the
411right to add or delete files/directories in that directory. That is
412filesystem specific: in some filesystems you need write/modify
413permission also (or even just) in the file/directory itself. In some
414filesystems (AFS, DFS) the permission to add/delete directory entries
415is a completely separate permission.
416
417Don't assume that a single C<unlink> completely gets rid of the file:
418some filesystems (most notably the ones in VMS) have versioned
419filesystems, and unlink() removes only the most recent one (it doesn't
420remove all the versions because by default the native tools on those
421platforms remove just the most recent version, too). The portable
422idiom to remove all the versions of a file is
423
94bb614c 424 1 while unlink "file";
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425
426This will terminate if the file is undeleteable for some reason
427(protected, not there, and so on).
428
e41182b5 429Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 430Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 431case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 432if you really have to, make it conditional on C<$^O ne 'VMS'> since in
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433VMS the C<%ENV> table is much more than a per-process key-value string
434table.
e41182b5 435
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436On VMS, some entries in the %ENV hash are dynamically created when
437their key is used on a read if they did not previously exist. The
438values for C<$ENV{HOME}>, C<$ENV{TERM}>, C<$ENV{HOME}>, and C<$ENV{USER}>,
439are known to be dynamically generated. The specific names that are
440dynamically generated may vary with the version of the C library on VMS,
441and more may exist than is documented.
442
443On VMS by default, changes to the %ENV hash are persistent after the process
444exits. This can cause unintended issues.
445
d1e3b762 446Don't count on signals or C<%SIG> for anything.
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447
448Don't count on filename globbing. Use C<opendir>, C<readdir>, and
449C<closedir> instead.
450
b8099c3d 451Don't count on per-program environment variables, or per-program current
dd9f0070 452directories.
b8099c3d 453
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454Don't count on specific values of C<$!>, neither numeric nor
455especially the strings values-- users may switch their locales causing
456error messages to be translated into their languages. If you can
457trust a POSIXish environment, you can portably use the symbols defined
458by the Errno module, like ENOENT. And don't trust on the values of C<$!>
459at all except immediately after a failed system call.
3c075c7d 460
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461=head2 Command names versus file pathnames
462
463Don't assume that the name used to invoke a command or program with
464C<system> or C<exec> can also be used to test for the existence of the
465file that holds the executable code for that command or program.
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466First, many systems have "internal" commands that are built-in to the
467shell or OS and while these commands can be invoked, there is no
468corresponding file. Second, some operating systems (e.g., Cygwin,
469DJGPP, OS/2, and VOS) have required suffixes for executable files;
470these suffixes are generally permitted on the command name but are not
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471required. Thus, a command like "perl" might exist in a file named
472"perl", "perl.exe", or "perl.pm", depending on the operating system.
473The variable "_exe" in the Config module holds the executable suffix,
68fb0eb7
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474if any. Third, the VMS port carefully sets up $^X and
475$Config{perlpath} so that no further processing is required. This is
476just as well, because the matching regular expression used below would
477then have to deal with a possible trailing version number in the VMS
478file name.
a10d74f3
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479
480To convert $^X to a file pathname, taking account of the requirements
481of the various operating system possibilities, say:
7ee27b7c 482
a10d74f3 483 use Config;
a10d74f3 484 $thisperl = $^X;
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485 if ($^O ne 'VMS')
486 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3
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487
488To convert $Config{perlpath} to a file pathname, say:
7ee27b7c 489
a10d74f3 490 use Config;
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491 $thisperl = $Config{perlpath};
492 if ($^O ne 'VMS')
493 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3 494
7137b697
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495=head2 Networking
496
497Don't assume that you can reach the public Internet.
498
499Don't assume that there is only one way to get through firewalls
500to the public Internet.
501
932f293e
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502Don't assume that you can reach outside world through any other port
503than 80, or some web proxy. ftp is blocked by many firewalls.
504
dbc6a9ce
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505Don't assume that you can send email by connecting to the local SMTP port.
506
7137b697 507Don't assume that you can reach yourself or any node by the name
dbc6a9ce 508'localhost'. The same goes for '127.0.0.1'. You will have to try both.
932f293e 509
86feb2c5
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510Don't assume that the host has only one network card, or that it
511can't bind to many virtual IP addresses.
932f293e
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512
513Don't assume a particular network device name.
7137b697 514
dbc6a9ce 515Don't assume a particular set of ioctl()s will work.
7137b697
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516
517Don't assume that you can ping hosts and get replies.
518
dbc6a9ce
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519Don't assume that any particular port (service) will respond.
520
7ee27b7c 521Don't assume that Sys::Hostname (or any other API or command)
dbc6a9ce
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522returns either a fully qualified hostname or a non-qualified hostname:
523it all depends on how the system had been configured. Also remember
524things like DHCP and NAT-- the hostname you get back might not be very
525useful.
526
932f293e
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527All the above "don't":s may look daunting, and they are -- but the key
528is to degrade gracefully if one cannot reach the particular network
529service one wants. Croaking or hanging do not look very professional.
530
e41182b5
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531=head2 Interprocess Communication (IPC)
532
b7df3edc
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533In general, don't directly access the system in code meant to be
534portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
535C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
536that makes being a perl hacker worth being.
e41182b5
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537
538Commands that launch external processes are generally supported on
b7df3edc
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539most platforms (though many of them do not support any type of
540forking). The problem with using them arises from what you invoke
541them on. External tools are often named differently on different
4375e838 542platforms, may not be available in the same location, might accept
b7df3edc
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543different arguments, can behave differently, and often present their
544results in a platform-dependent way. Thus, you should seldom depend
545on them to produce consistent results. (Then again, if you're calling
546I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 547
b7df3edc 548One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 549
b7df3edc
GS
550 open(MAIL, '|/usr/lib/sendmail -t')
551 or die "cannot fork sendmail: $!";
e41182b5
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552
553This is fine for systems programming when sendmail is known to be
554available. But it is not fine for many non-Unix systems, and even
555some Unix systems that may not have sendmail installed. If a portable
b7df3edc
GS
556solution is needed, see the various distributions on CPAN that deal
557with it. Mail::Mailer and Mail::Send in the MailTools distribution are
558commonly used, and provide several mailing methods, including mail,
559sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
560not available. Mail::Sendmail is a standalone module that provides
561simple, platform-independent mailing.
562
563The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
564even on all Unix platforms.
e41182b5 565
a81e5e2e
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566Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
567bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
568both forms just pack the four bytes into network order. That this
569would be equal to the C language C<in_addr> struct (which is what the
570socket code internally uses) is not guaranteed. To be portable use
571the routines of the Socket extension, such as C<inet_aton()>,
572C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 573
e41182b5 574The rule of thumb for portable code is: Do it all in portable Perl, or
0a47030a
GS
575use a module (that may internally implement it with platform-specific
576code, but expose a common interface).
e41182b5 577
e41182b5
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578=head2 External Subroutines (XS)
579
b7df3edc 580XS code can usually be made to work with any platform, but dependent
e41182b5
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581libraries, header files, etc., might not be readily available or
582portable, or the XS code itself might be platform-specific, just as Perl
583code might be. If the libraries and headers are portable, then it is
584normally reasonable to make sure the XS code is portable, too.
585
b7df3edc
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586A different type of portability issue arises when writing XS code:
587availability of a C compiler on the end-user's system. C brings
588with it its own portability issues, and writing XS code will expose
589you to some of those. Writing purely in Perl is an easier way to
e41182b5
GS
590achieve portability.
591
e41182b5
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592=head2 Standard Modules
593
594In general, the standard modules work across platforms. Notable
6ab3f9cb 595exceptions are the CPAN module (which currently makes connections to external
e41182b5 596programs that may not be available), platform-specific modules (like
6ab3f9cb 597ExtUtils::MM_VMS), and DBM modules.
e41182b5 598
b7df3edc 599There is no one DBM module available on all platforms.
6ab3f9cb
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600SDBM_File and the others are generally available on all Unix and DOSish
601ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 602available.
e41182b5
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603
604The good news is that at least some DBM module should be available, and
6ab3f9cb 605AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
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606the code needs to be fairly strict, dropping to the greatest common
607factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 608work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 609
e41182b5
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610=head2 Time and Date
611
0a47030a 612The system's notion of time of day and calendar date is controlled in
b7df3edc 613widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a 614and even if it is, don't assume that you can control the timezone through
c87488a3
HS
615that variable. Don't assume anything about the three-letter timezone
616abbreviations (for example that MST would be the Mountain Standard Time,
617it's been known to stand for Moscow Standard Time). If you need to
618use timezones, express them in some unambiguous format like the
619exact number of minutes offset from UTC, or the POSIX timezone
620format.
e41182b5 621
322422de 622Don't assume that the epoch starts at 00:00:00, January 1, 1970,
c87488a3
HS
623because that is OS- and implementation-specific. It is better to
624store a date in an unambiguous representation. The ISO 8601 standard
625defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH-MM-SS
626(that's a literal "T" separating the date from the time).
627Please do use the ISO 8601 instead of making us to guess what
628date 02/03/04 might be. ISO 8601 even sorts nicely as-is.
629A text representation (like "1987-12-18") can be easily converted
630into an OS-specific value using a module like Date::Parse.
631An array of values, such as those returned by C<localtime>, can be
632converted to an OS-specific representation using Time::Local.
322422de 633
19799a22
GS
634When calculating specific times, such as for tests in time or date modules,
635it may be appropriate to calculate an offset for the epoch.
b7df3edc 636
19799a22
GS
637 require Time::Local;
638 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 639
19799a22
GS
640The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
641some large number. C<$offset> can then be added to a Unix time value
642to get what should be the proper value on any system.
322422de
GS
643
644=head2 Character sets and character encoding
645
ec481373
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646Assume very little about character sets.
647
648Assume nothing about numerical values (C<ord>, C<chr>) of characters.
649Do not use explicit code point ranges (like \xHH-\xHH); use for
650example symbolic character classes like C<[:print:]>.
651
652Do not assume that the alphabetic characters are encoded contiguously
653(in the numeric sense). There may be gaps.
654
655Do not assume anything about the ordering of the characters.
656The lowercase letters may come before or after the uppercase letters;
b432a672
AL
657the lowercase and uppercase may be interlaced so that both "a" and "A"
658come before "b"; the accented and other international characters may
659be interlaced so that E<auml> comes before "b".
322422de
GS
660
661=head2 Internationalisation
662
b7df3edc
GS
663If you may assume POSIX (a rather large assumption), you may read
664more about the POSIX locale system from L<perllocale>. The locale
665system at least attempts to make things a little bit more portable,
666or at least more convenient and native-friendly for non-English
667users. The system affects character sets and encoding, and date
668and time formatting--amongst other things.
e41182b5 669
c87488a3
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670If you really want to be international, you should consider Unicode.
671See L<perluniintro> and L<perlunicode> for more information.
672
11264fdb
JH
673If you want to use non-ASCII bytes (outside the bytes 0x00..0x7f) in
674the "source code" of your code, to be portable you have to be explicit
675about what bytes they are. Someone might for example be using your
676code under a UTF-8 locale, in which case random native bytes might be
677illegal ("Malformed UTF-8 ...") This means that for example embedding
678ISO 8859-1 bytes beyond 0x7f into your strings might cause trouble
679later. If the bytes are native 8-bit bytes, you can use the C<bytes>
680pragma. If the bytes are in a string (regular expression being a
681curious string), you can often also use the C<\xHH> notation instead
2575c402
JW
682of embedding the bytes as-is. (If you want to write your code in UTF-8,
683you can use the C<utf8>.) The C<bytes> and C<utf8> pragmata are
684available since Perl 5.6.0.
11264fdb 685
e41182b5
GS
686=head2 System Resources
687
0a47030a
GS
688If your code is destined for systems with severely constrained (or
689missing!) virtual memory systems then you want to be I<especially> mindful
690of avoiding wasteful constructs such as:
e41182b5
GS
691
692 # NOTE: this is no longer "bad" in perl5.005
693 for (0..10000000) {} # bad
694 for (my $x = 0; $x <= 10000000; ++$x) {} # good
695
696 @lines = <VERY_LARGE_FILE>; # bad
697
698 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 699 $file = join('', <FILE>); # better
e41182b5 700
b7df3edc
GS
701The last two constructs may appear unintuitive to most people. The
702first repeatedly grows a string, whereas the second allocates a
703large chunk of memory in one go. On some systems, the second is
704more efficient that the first.
0a47030a 705
e41182b5
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706=head2 Security
707
b7df3edc
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708Most multi-user platforms provide basic levels of security, usually
709implemented at the filesystem level. Some, however, do
a1667ba3 710not-- unfortunately. Thus the notion of user id, or "home" directory,
b7df3edc
GS
711or even the state of being logged-in, may be unrecognizable on many
712platforms. If you write programs that are security-conscious, it
713is usually best to know what type of system you will be running
714under so that you can write code explicitly for that platform (or
715class of platforms).
0a47030a 716
a1667ba3
JH
717Don't assume the UNIX filesystem access semantics: the operating
718system or the filesystem may be using some ACL systems, which are
719richer languages than the usual rwx. Even if the rwx exist,
720their semantics might be different.
721
722(From security viewpoint testing for permissions before attempting to
723do something is silly anyway: if one tries this, there is potential
724for race conditions-- someone or something might change the
725permissions between the permissions check and the actual operation.
726Just try the operation.)
727
728Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 729expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
JH
730for switching identities (or memberships).
731
732Don't assume set-uid and set-gid semantics. (And even if you do,
733think twice: set-uid and set-gid are a known can of security worms.)
734
e41182b5
GS
735=head2 Style
736
737For those times when it is necessary to have platform-specific code,
738consider keeping the platform-specific code in one place, making porting
6ab3f9cb 739to other platforms easier. Use the Config module and the special
0a47030a
GS
740variable C<$^O> to differentiate platforms, as described in
741L<"PLATFORMS">.
e41182b5 742
b7df3edc
GS
743Be careful in the tests you supply with your module or programs.
744Module code may be fully portable, but its tests might not be. This
745often happens when tests spawn off other processes or call external
746programs to aid in the testing, or when (as noted above) the tests
c87488a3
HS
747assume certain things about the filesystem and paths. Be careful not
748to depend on a specific output style for errors, such as when checking
749C<$!> after a failed system call. Using C<$!> for anything else than
750displaying it as output is doubtful (though see the Errno module for
751testing reasonably portably for error value). Some platforms expect
752a certain output format, and Perl on those platforms may have been
753adjusted accordingly. Most specifically, don't anchor a regex when
754testing an error value.
e41182b5 755
0a47030a 756=head1 CPAN Testers
e41182b5 757
0a47030a
GS
758Modules uploaded to CPAN are tested by a variety of volunteers on
759different platforms. These CPAN testers are notified by mail of each
e41182b5 760new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 761this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
GS
762
763The purpose of the testing is twofold: one, to help developers fix any
0a47030a 764problems in their code that crop up because of lack of testing on other
b7df3edc 765platforms; two, to provide users with information about whether
0a47030a 766a given module works on a given platform.
e41182b5 767
7ee27b7c
AT
768Also see:
769
e41182b5
GS
770=over 4
771
7ee27b7c
AT
772=item *
773
774Mailing list: cpan-testers@perl.org
775
776=item *
e41182b5 777
7ee27b7c 778Testing results: http://testers.cpan.org/
e41182b5
GS
779
780=back
781
e41182b5
GS
782=head1 PLATFORMS
783
784As of version 5.002, Perl is built with a C<$^O> variable that
785indicates the operating system it was built on. This was implemented
b7df3edc
GS
786to help speed up code that would otherwise have to C<use Config>
787and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
GS
788detailed information about the system, looking into C<%Config> is
789certainly recommended.
790
b7df3edc
GS
791C<%Config> cannot always be trusted, however, because it was built
792at compile time. If perl was built in one place, then transferred
793elsewhere, some values may be wrong. The values may even have been
794edited after the fact.
6ab3f9cb 795
e41182b5
GS
796=head2 Unix
797
798Perl works on a bewildering variety of Unix and Unix-like platforms (see
799e.g. most of the files in the F<hints/> directory in the source code kit).
800On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
801too) is determined either by lowercasing and stripping punctuation from the
802first field of the string returned by typing C<uname -a> (or a similar command)
803at the shell prompt or by testing the file system for the presence of
804uniquely named files such as a kernel or header file. Here, for example,
805are a few of the more popular Unix flavors:
e41182b5 806
b7df3edc 807 uname $^O $Config{'archname'}
6ab3f9cb 808 --------------------------------------------
b7df3edc 809 AIX aix aix
6ab3f9cb 810 BSD/OS bsdos i386-bsdos
e1516da7 811 Darwin darwin darwin
6ab3f9cb
GS
812 dgux dgux AViiON-dgux
813 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 814 FreeBSD freebsd freebsd-i386
df00ff3b 815 Haiku haiku BePC-haiku
d1e3b762 816 Linux linux arm-linux
b7df3edc 817 Linux linux i386-linux
6ab3f9cb
GS
818 Linux linux i586-linux
819 Linux linux ppc-linux
b7df3edc
GS
820 HP-UX hpux PA-RISC1.1
821 IRIX irix irix
b787fad4 822 Mac OS X darwin darwin
d1e3b762
GS
823 MachTen PPC machten powerpc-machten
824 NeXT 3 next next-fat
825 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 826 openbsd openbsd i386-openbsd
b7df3edc 827 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
828 reliantunix-n svr4 RM400-svr4
829 SCO_SV sco_sv i386-sco_sv
830 SINIX-N svr4 RM400-svr4
831 sn4609 unicos CRAY_C90-unicos
832 sn6521 unicosmk t3e-unicosmk
833 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
834 SunOS solaris sun4-solaris
835 SunOS solaris i86pc-solaris
836 SunOS4 sunos sun4-sunos
e41182b5 837
b7df3edc
GS
838Because the value of C<$Config{archname}> may depend on the
839hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 840
e41182b5
GS
841=head2 DOS and Derivatives
842
b7df3edc 843Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
844systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
845bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 846Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
847be aware that each of these file specifications may have subtle
848differences:
849
850 $filespec0 = "c:/foo/bar/file.txt";
851 $filespec1 = "c:\\foo\\bar\\file.txt";
852 $filespec2 = 'c:\foo\bar\file.txt';
853 $filespec3 = 'c:\\foo\\bar\\file.txt';
854
b7df3edc
GS
855System calls accept either C</> or C<\> as the path separator.
856However, many command-line utilities of DOS vintage treat C</> as
857the option prefix, so may get confused by filenames containing C</>.
858Aside from calling any external programs, C</> will work just fine,
859and probably better, as it is more consistent with popular usage,
860and avoids the problem of remembering what to backwhack and what
861not to.
e41182b5 862
b7df3edc
GS
863The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
864the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 865filesystems you may have to be careful about case returned with functions
e41182b5
GS
866like C<readdir> or used with functions like C<open> or C<opendir>.
867
b7df3edc
GS
868DOS also treats several filenames as special, such as AUX, PRN,
869NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
870filenames won't even work if you include an explicit directory
871prefix. It is best to avoid such filenames, if you want your code
872to be portable to DOS and its derivatives. It's hard to know what
873these all are, unfortunately.
e41182b5
GS
874
875Users of these operating systems may also wish to make use of
b7df3edc 876scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
877put wrappers around your scripts.
878
879Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
880and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
881will keep C<\n> translated as C<\012> for that filehandle. Since it is a
882no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
883that deals with binary data. That's assuming you realize in advance
884that your data is in binary. General-purpose programs should
885often assume nothing about their data.
e41182b5 886
b7df3edc 887The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
888DOSish perls are as follows:
889
67ac489e
MS
890 OS $^O $Config{archname} ID Version
891 --------------------------------------------------------
892 MS-DOS dos ?
893 PC-DOS dos ?
894 OS/2 os2 ?
895 Windows 3.1 ? ? 0 3 01
896 Windows 95 MSWin32 MSWin32-x86 1 4 00
897 Windows 98 MSWin32 MSWin32-x86 1 4 10
898 Windows ME MSWin32 MSWin32-x86 1 ?
899 Windows NT MSWin32 MSWin32-x86 2 4 xx
900 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
901 Windows NT MSWin32 MSWin32-ppc 2 4 xx
7ee27b7c
AT
902 Windows 2000 MSWin32 MSWin32-x86 2 5 00
903 Windows XP MSWin32 MSWin32-x86 2 5 01
904 Windows 2003 MSWin32 MSWin32-x86 2 5 02
67ac489e 905 Windows CE MSWin32 ? 3
7ee27b7c 906 Cygwin cygwin cygwin
e41182b5 907
34aaaa84
PP
908The various MSWin32 Perl's can distinguish the OS they are running on
909via the value of the fifth element of the list returned from
910Win32::GetOSVersion(). For example:
911
912 if ($^O eq 'MSWin32') {
913 my @os_version_info = Win32::GetOSVersion();
914 print +('3.1','95','NT')[$os_version_info[4]],"\n";
915 }
916
7939d86b
JH
917There are also Win32::IsWinNT() and Win32::IsWin95(), try C<perldoc Win32>,
918and as of libwin32 0.19 (not part of the core Perl distribution)
919Win32::GetOSName(). The very portable POSIX::uname() will work too:
1d65be3a
JH
920
921 c:\> perl -MPOSIX -we "print join '|', uname"
922 Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86
d99f392e 923
e41182b5
GS
924Also see:
925
926=over 4
927
c997b287 928=item *
e41182b5 929
c997b287
GS
930The djgpp environment for DOS, http://www.delorie.com/djgpp/
931and L<perldos>.
e41182b5 932
c997b287 933=item *
e41182b5 934
c997b287
GS
935The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
936http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
f224927c 937ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
e41182b5 938
c997b287 939=item *
d1e3b762 940
c997b287
GS
941Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
942in L<perlcygwin>.
943
944=item *
945
946The C<Win32::*> modules in L<Win32>.
947
948=item *
949
950The ActiveState Pages, http://www.activestate.com/
951
952=item *
953
954The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 955as L<perlcygwin>), http://www.cygwin.com/
c997b287
GS
956
957=item *
958
959The U/WIN environment for Win32,
cea6626f 960http://www.research.att.com/sw/tools/uwin/
c997b287 961
cea6626f 962=item *
d1e3b762 963
cea6626f 964Build instructions for OS/2, L<perlos2>
d1e3b762 965
e41182b5
GS
966=back
967
dd9f0070 968=head2 S<Mac OS>
e41182b5
GS
969
970Any module requiring XS compilation is right out for most people, because
971MacPerl is built using non-free (and non-cheap!) compilers. Some XS
972modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 973form on CPAN.
e41182b5
GS
974
975Directories are specified as:
976
977 volume:folder:file for absolute pathnames
978 volume:folder: for absolute pathnames
979 :folder:file for relative pathnames
980 :folder: for relative pathnames
981 :file for relative pathnames
982 file for relative pathnames
983
b7df3edc 984Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 985limited to 31 characters, and may include any character except for
b7df3edc 986null and C<:>, which is reserved as the path separator.
e41182b5 987
0a47030a 988Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 989Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
990
991In the MacPerl application, you can't run a program from the command line;
992programs that expect C<@ARGV> to be populated can be edited with something
993like the following, which brings up a dialog box asking for the command
994line arguments.
995
996 if (!@ARGV) {
997 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
998 }
999
b7df3edc 1000A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
1001pathnames of the files dropped onto the script.
1002
b7df3edc
GS
1003Mac users can run programs under a type of command line interface
1004under MPW (Macintosh Programmer's Workshop, a free development
1005environment from Apple). MacPerl was first introduced as an MPW
1006tool, and MPW can be used like a shell:
e41182b5
GS
1007
1008 perl myscript.plx some arguments
1009
1010ToolServer is another app from Apple that provides access to MPW tools
0a47030a 1011from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
1012C<system>, backticks, and piped C<open>.
1013
1014"S<Mac OS>" is the proper name for the operating system, but the value
1015in C<$^O> is "MacOS". To determine architecture, version, or whether
1016the application or MPW tool version is running, check:
1017
1018 $is_app = $MacPerl::Version =~ /App/;
1019 $is_tool = $MacPerl::Version =~ /MPW/;
1020 ($version) = $MacPerl::Version =~ /^(\S+)/;
1021 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
1022 $is_68k = $MacPerl::Architecture eq 'Mac68K';
1023
b787fad4
JH
1024S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
1025"Classic" environment. There is no "Carbon" version of MacPerl to run
1026under the primary Mac OS X environment. S<Mac OS X> and its Open Source
1027version, Darwin, both run Unix perl natively.
6ab3f9cb 1028
e41182b5
GS
1029Also see:
1030
1031=over 4
1032
c997b287
GS
1033=item *
1034
862b5365 1035MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
1036
1037=item *
1038
862b5365 1039The MacPerl Pages, http://www.macperl.com/ .
e41182b5 1040
c997b287 1041=item *
6ab3f9cb 1042
862b5365 1043The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5 1044
7ee27b7c
AT
1045=item *
1046
1047MPW, ftp://ftp.apple.com/developer/Tool_Chest/Core_Mac_OS_Tools/
1048
e41182b5
GS
1049=back
1050
e41182b5
GS
1051=head2 VMS
1052
c997b287 1053Perl on VMS is discussed in L<perlvms> in the perl distribution.
016930a6
JM
1054
1055The official name of VMS as of this writing is OpenVMS.
1056
b7df3edc 1057Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
1058specifications as in either of the following:
1059
1060 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
1061 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
1062
1063but not a mixture of both as in:
1064
1065 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
1066 Can't open sys$login:/login.com: file specification syntax error
1067
1068Interacting with Perl from the Digital Command Language (DCL) shell
1069often requires a different set of quotation marks than Unix shells do.
1070For example:
1071
1072 $ perl -e "print ""Hello, world.\n"""
1073 Hello, world.
1074
b7df3edc 1075There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
1076you are so inclined. For example:
1077
1078 $ write sys$output "Hello from DCL!"
1079 $ if p1 .eqs. ""
1080 $ then perl -x 'f$environment("PROCEDURE")
1081 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
1082 $ deck/dollars="__END__"
1083 #!/usr/bin/perl
1084
1085 print "Hello from Perl!\n";
1086
1087 __END__
1088 $ endif
1089
1090Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 1091perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5 1092
016930a6
JM
1093The VMS operating system has two filesystems, known as ODS-2 and ODS-5.
1094
1095For ODS-2, filenames are in the format "name.extension;version". The
1096maximum length for filenames is 39 characters, and the maximum length for
e41182b5
GS
1097extensions is also 39 characters. Version is a number from 1 to
109832767. Valid characters are C</[A-Z0-9$_-]/>.
1099
016930a6
JM
1100The ODS-2 filesystem is case-insensitive and does not preserve case.
1101Perl simulates this by converting all filenames to lowercase internally.
1102
1103For ODS-5, filenames may have almost any character in them and can include
1104Unicode characters. Characters that could be misinterpreted by the DCL
1105shell or file parsing utilities need to be prefixed with the C<^>
1106character, or replaced with hexadecimal characters prefixed with the
1107C<^> character. Such prefixing is only needed with the pathnames are
1108in VMS format in applications. Programs that can accept the UNIX format
1109of pathnames do not need the escape characters. The maximum length for
1110filenames is 255 characters. The ODS-5 file system can handle both
1111a case preserved and a case sensitive mode.
1112
1113ODS-5 is only available on the OpenVMS for 64 bit platforms.
1114
1115Support for the extended file specifications is being done as optional
1116settings to preserve backward compatibility with Perl scripts that
1117assume the previous VMS limitations.
1118
1119In general routines on VMS that get a UNIX format file specification
1120should return it in a UNIX format, and when they get a VMS format
1121specification they should return a VMS format unless they are documented
1122to do a conversion.
1123
1124For routines that generate return a file specification, VMS allows setting
1125if the C library which Perl is built on if it will be returned in VMS
1126format or in UNIX format.
1127
1128With the ODS-2 file system, there is not much difference in syntax of
1129filenames without paths for VMS or UNIX. With the extended character
1130set available with ODS-5 there can be a significant difference.
1131
1132Because of this, existing Perl scripts written for VMS were sometimes
1133treating VMS and UNIX filenames interchangeably. Without the extended
1134character set enabled, this behavior will mostly be maintained for
1135backwards compatibility.
1136
1137When extended characters are enabled with ODS-5, the handling of
1138UNIX formatted file specifications is to that of a UNIX system.
1139
1140VMS file specifications without extensions have a trailing dot. An
1141equivalent UNIX file specification should not show the trailing dot.
1142
1143The result of all of this, is that for VMS, for portable scripts, you
1144can not depend on Perl to present the filenames in lowercase, to be
1145case sensitive, and that the filenames could be returned in either
1146UNIX or VMS format.
1147
1148And if a routine returns a file specification, unless it is intended to
1149convert it, it should return it in the same format as it found it.
1150
1151C<readdir> by default has traditionally returned lowercased filenames.
1152When the ODS-5 support is enabled, it will return the exact case of the
1153filename on the disk.
1154
1155Files without extensions have a trailing period on them, so doing a
1156C<readdir> in the default mode with a file named F<A.;5> will
1157return F<a.> when VMS is (though that file could be opened with
0a47030a 1158C<open(FH, 'A')>).
e41182b5 1159
016930a6
JM
1160With support for extended file specifications and if C<opendir> was
1161given a UNIX format directory, a file named F<A.;5> will return F<a>
1162and optionally in the exact case on the disk. When C<opendir> is given
1163a VMS format directory, then C<readdir> should return F<a.>, and
1164again with the optionally the exact case.
1165
f34d0673 1166RMS had an eight level limit on directory depths from any rooted logical
1089a9e3
CB
1167(allowing 16 levels overall) prior to VMS 7.2, and even with versions of
1168VMS on VAX up through 7.3. Hence C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a
1169valid directory specification but C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is
1170not. F<Makefile.PL> authors might have to take this into account, but at
1171least they can refer to the former as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
1172
1173Pumpkings and module integrators can easily see whether files with too many
1174directory levels have snuck into the core by running the following in the
1175top-level source directory:
1176
1177 $ perl -ne "$_=~s/\s+.*//; print if scalar(split /\//) > 8;" < MANIFEST
1178
e41182b5 1179
6ab3f9cb 1180The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
1181process on VMS, is a pure Perl module that can easily be installed on
1182non-VMS platforms and can be helpful for conversions to and from RMS
016930a6
JM
1183native formats. It is also now the only way that you should check to
1184see if VMS is in a case sensitive mode.
e41182b5 1185
5e12dbfa
PP
1186What C<\n> represents depends on the type of file opened. It usually
1187represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
fa11829f 1188C<\000>, C<\040>, or nothing depending on the file organization and
5e12dbfa
PP
1189record format. The VMS::Stdio module provides access to the
1190special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
1191
1192TCP/IP stacks are optional on VMS, so socket routines might not be
1193implemented. UDP sockets may not be supported.
1194
016930a6
JM
1195The TCP/IP library support for all current versions of VMS is dynamically
1196loaded if present, so even if the routines are configured, they may
1197return a status indicating that they are not implemented.
1198
e41182b5
GS
1199The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
1200that you are running on without resorting to loading all of C<%Config>
1201you can examine the content of the C<@INC> array like so:
1202
1203 if (grep(/VMS_AXP/, @INC)) {
1204 print "I'm on Alpha!\n";
6ab3f9cb 1205
e41182b5
GS
1206 } elsif (grep(/VMS_VAX/, @INC)) {
1207 print "I'm on VAX!\n";
6ab3f9cb 1208
016930a6
JM
1209 } elsif (grep(/VMS_IA64/, @INC)) {
1210 print "I'm on IA64!\n";
1211
e41182b5
GS
1212 } else {
1213 print "I'm not so sure about where $^O is...\n";
1214 }
1215
016930a6
JM
1216In general, the significant differences should only be if Perl is running
1217on VMS_VAX or one of the 64 bit OpenVMS platforms.
1218
b7df3edc
GS
1219On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
1220logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 1221calls to C<localtime> are adjusted to count offsets from
b7df3edc 122201-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1223
e41182b5
GS
1224Also see:
1225
1226=over 4
1227
c997b287
GS
1228=item *
1229
1230F<README.vms> (installed as L<README_vms>), L<perlvms>
1231
1232=item *
1233
1089a9e3 1234vmsperl list, vmsperl-subscribe@perl.org
e41182b5 1235
c997b287 1236=item *
e41182b5 1237
c997b287 1238vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1239
1240=back
1241
495c5fdc
GP
1242=head2 VOS
1243
9a997319
JH
1244Perl on VOS is discussed in F<README.vos> in the perl distribution
1245(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1246Unix-style file specifications as in either of the following:
495c5fdc 1247
cc07ed0b
PG
1248 C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
1249 C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
495c5fdc
GP
1250
1251or even a mixture of both as in:
1252
cc07ed0b 1253 C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
495c5fdc 1254
b7df3edc 1255Even though VOS allows the slash character to appear in object
495c5fdc
GP
1256names, because the VOS port of Perl interprets it as a pathname
1257delimiting character, VOS files, directories, or links whose names
1258contain a slash character cannot be processed. Such files must be
a3dfe201 1259renamed before they can be processed by Perl. Note that VOS limits
b449fc5b
NC
1260file names to 32 or fewer characters, file names cannot start with a
1261C<-> character, or contain any character matching C<< tr/ !%&'()*+;<>?// >>
495c5fdc 1262
495c5fdc
GP
1263The value of C<$^O> on VOS is "VOS". To determine the architecture that
1264you are running on without resorting to loading all of C<%Config> you
c997b287 1265can examine the content of the @INC array like so:
495c5fdc 1266
24e8e380 1267 if ($^O =~ /VOS/) {
495c5fdc
GP
1268 print "I'm on a Stratus box!\n";
1269 } else {
1270 print "I'm not on a Stratus box!\n";
1271 die;
1272 }
1273
495c5fdc
GP
1274Also see:
1275
1276=over 4
1277
c997b287 1278=item *
495c5fdc 1279
cc07ed0b 1280F<README.vos> (installed as L<perlvos>)
c997b287
GS
1281
1282=item *
1283
1284The VOS mailing list.
495c5fdc
GP
1285
1286There is no specific mailing list for Perl on VOS. You can post
1287comments to the comp.sys.stratus newsgroup, or subscribe to the general
cc07ed0b 1288Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
495c5fdc
GP
1289the message body to majordomo@list.stratagy.com.
1290
c997b287
GS
1291=item *
1292
cc07ed0b 1293VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
495c5fdc
GP
1294
1295=back
1296
e41182b5
GS
1297=head2 EBCDIC Platforms
1298
1299Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1300AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1301Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1302Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1303systems). On the mainframe perl currently works under the "Unix system
1304services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1305the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
522b859a
JH
1306See L<perlos390> for details. Note that for OS/400 there is also a port of
1307Perl 5.8.1/5.9.0 or later to the PASE which is ASCII-based (as opposed to
1308ILE which is EBCDIC-based), see L<perlos400>.
e41182b5 1309
7c5ffed3
JH
1310As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1311sub-systems do not support the C<#!> shebang trick for script invocation.
1312Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1313similar to the following simple script:
e41182b5
GS
1314
1315 : # use perl
1316 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1317 if 0;
1318 #!/usr/local/bin/perl # just a comment really
1319
1320 print "Hello from perl!\n";
1321
d1e3b762
GS
1322OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1323Calls to C<system> and backticks can use POSIX shell syntax on all
1324S/390 systems.
1325
b7df3edc 1326On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1327to wrap your perl scripts in a CL procedure to invoke them like so:
1328
1329 BEGIN
1330 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1331 ENDPGM
1332
1333This will invoke the perl script F<hello.pl> in the root of the
1334QOpenSys file system. On the AS/400 calls to C<system> or backticks
1335must use CL syntax.
1336
e41182b5 1337On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1338an effect on what happens with some perl functions (such as C<chr>,
1339C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1340well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1341and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1342(see L<"Newlines">).
e41182b5 1343
b7df3edc
GS
1344Fortunately, most web servers for the mainframe will correctly
1345translate the C<\n> in the following statement to its ASCII equivalent
1346(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1347
1348 print "Content-type: text/html\r\n\r\n";
1349
d1e3b762 1350The values of C<$^O> on some of these platforms includes:
e41182b5 1351
d1e3b762
GS
1352 uname $^O $Config{'archname'}
1353 --------------------------------------------
1354 OS/390 os390 os390
1355 OS400 os400 os400
1356 POSIX-BC posix-bc BS2000-posix-bc
1357 VM/ESA vmesa vmesa
3c075c7d 1358
e41182b5
GS
1359Some simple tricks for determining if you are running on an EBCDIC
1360platform could include any of the following (perhaps all):
1361
1362 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1363
1364 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1365
1366 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1367
b7df3edc 1368One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1369of punctuation characters since these may differ from code page to code
1370page (and once your module or script is rumoured to work with EBCDIC,
1371folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1372
1373Also see:
1374
1375=over 4
1376
c997b287
GS
1377=item *
1378
dc5c060f 1379L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1380L<perlebcdic>.
c997b287
GS
1381
1382=item *
e41182b5
GS
1383
1384The perl-mvs@perl.org list is for discussion of porting issues as well as
1385general usage issues for all EBCDIC Perls. Send a message body of
1386"subscribe perl-mvs" to majordomo@perl.org.
1387
7ee27b7c 1388=item *
c997b287
GS
1389
1390AS/400 Perl information at
b1866b2d 1391http://as400.rochester.ibm.com/
d1e3b762 1392as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1393
1394=back
1395
b8099c3d
CN
1396=head2 Acorn RISC OS
1397
b7df3edc
GS
1398Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1399Unix, and because Unix filename emulation is turned on by default,
1400most simple scripts will probably work "out of the box". The native
6ab3f9cb 1401filesystem is modular, and individual filesystems are free to be
0a47030a 1402case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1403native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1404names are silently truncated to fit. Scripts should be aware that the
1405standard filesystem currently has a name length limit of B<10>
1406characters, with up to 77 items in a directory, but other filesystems
0a47030a 1407may not impose such limitations.
b8099c3d
CN
1408
1409Native filenames are of the form
1410
6ab3f9cb 1411 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1412
b8099c3d
CN
1413where
1414
1415 Special_Field is not usually present, but may contain . and $ .
1416 Filesystem =~ m|[A-Za-z0-9_]|
1417 DsicName =~ m|[A-Za-z0-9_/]|
1418 $ represents the root directory
1419 . is the path separator
1420 @ is the current directory (per filesystem but machine global)
1421 ^ is the parent directory
1422 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1423
1424The default filename translation is roughly C<tr|/.|./|;>
1425
6ab3f9cb 1426Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1427the second stage of C<$> interpolation in regular expressions will fall
1428foul of the C<$.> if scripts are not careful.
1429
1430Logical paths specified by system variables containing comma-separated
b7df3edc 1431search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1432filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1433C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1434Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1435C<System$Path> contains a single item list. The filesystem will also
1436expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1437C<< <System$Dir>.Modules >> would look for the file
0a47030a 1438S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1439that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1440be protected when C<open> is used for input.
b8099c3d
CN
1441
1442Because C<.> was in use as a directory separator and filenames could not
1443be assumed to be unique after 10 characters, Acorn implemented the C
1444compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1445filenames specified in source code and store the respective files in
b7df3edc 1446subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1447
1448 foo.h h.foo
1449 C:foo.h C:h.foo (logical path variable)
1450 sys/os.h sys.h.os (C compiler groks Unix-speak)
1451 10charname.c c.10charname
1452 10charname.o o.10charname
1453 11charname_.c c.11charname (assuming filesystem truncates at 10)
1454
1455The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1456that this sort of translation is required, and it allows a user-defined list
1457of known suffixes that it will transpose in this fashion. This may
1458seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1459and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1460C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1461C<.>'s in filenames are translated to C</>.
0a47030a 1462
b7df3edc 1463As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1464the convention is that program specific environment variables are of the
6ab3f9cb
GS
1465form C<Program$Name>. Each filesystem maintains a current directory,
1466and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1467directory. Consequently, sociable programs don't change the current
1468directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1469assume that they can spawn a child process which can change the current
1470directory without affecting its parent (and everyone else for that
1471matter).
1472
b7df3edc
GS
1473Because native operating system filehandles are global and are currently
1474allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1475library emulates Unix filehandles. Consequently, you can't rely on
1476passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1477
1478The desire of users to express filenames of the form
c47ff5f1 1479C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1480too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1481assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1482reference to an environment variable, whereas anything else involving
c47ff5f1 1483C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1484right. Of course, the problem remains that scripts cannot rely on any
1485Unix tools being available, or that any tools found have Unix-like command
1486line arguments.
1487
b7df3edc
GS
1488Extensions and XS are, in theory, buildable by anyone using free
1489tools. In practice, many don't, as users of the Acorn platform are
1490used to binary distributions. MakeMaker does run, but no available
1491make currently copes with MakeMaker's makefiles; even if and when
1492this should be fixed, the lack of a Unix-like shell will cause
1493problems with makefile rules, especially lines of the form C<cd
1494sdbm && make all>, and anything using quoting.
b8099c3d
CN
1495
1496"S<RISC OS>" is the proper name for the operating system, but the value
1497in C<$^O> is "riscos" (because we don't like shouting).
1498
e41182b5
GS
1499=head2 Other perls
1500
b7df3edc
GS
1501Perl has been ported to many platforms that do not fit into any of
1502the categories listed above. Some, such as AmigaOS, Atari MiNT,
1503BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1504into the standard Perl source code kit. You may need to see the
1505F<ports/> directory on CPAN for information, and possibly binaries,
1506for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1507Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1508fall under the Unix category, but we are not a standards body.)
e41182b5 1509
d1e3b762
GS
1510Some approximate operating system names and their C<$^O> values
1511in the "OTHER" category include:
1512
1513 OS $^O $Config{'archname'}
1514 ------------------------------------------
1515 Amiga DOS amigaos m68k-amigos
cec2c193 1516 BeOS beos
d1e3b762
GS
1517 MPE/iX mpeix PA-RISC1.1
1518
e41182b5
GS
1519See also:
1520
1521=over 4
1522
c997b287
GS
1523=item *
1524
1525Amiga, F<README.amiga> (installed as L<perlamiga>).
1526
1527=item *
d1e3b762 1528
c997b287
GS
1529Atari, F<README.mint> and Guido Flohr's web page
1530http://stud.uni-sb.de/~gufl0000/
e41182b5 1531
c997b287 1532=item *
d1e3b762 1533
c997b287 1534Be OS, F<README.beos>
e41182b5 1535
c997b287
GS
1536=item *
1537
1538HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1539http://www.bixby.org/mark/perlix.html
c997b287
GS
1540
1541=item *
e41182b5 1542
6ab3f9cb 1543A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1544precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1545as well as from CPAN.
e41182b5 1546
13a2d996 1547=item *
c997b287 1548
e6f03d26 1549S<Plan 9>, F<README.plan9>
d1e3b762 1550
e41182b5
GS
1551=back
1552
e41182b5
GS
1553=head1 FUNCTION IMPLEMENTATIONS
1554
b7df3edc
GS
1555Listed below are functions that are either completely unimplemented
1556or else have been implemented differently on various platforms.
1557Following each description will be, in parentheses, a list of
1558platforms that the description applies to.
e41182b5 1559
b7df3edc
GS
1560The list may well be incomplete, or even wrong in some places. When
1561in doubt, consult the platform-specific README files in the Perl
1562source distribution, and any other documentation resources accompanying
1563a given port.
e41182b5 1564
0a47030a 1565Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1566
b7df3edc
GS
1567For many functions, you can also query C<%Config>, exported by
1568default from the Config module. For example, to check whether the
1569platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1570L<Config> for a full description of available variables.
e41182b5
GS
1571
1572=head2 Alphabetical Listing of Perl Functions
1573
1574=over 8
1575
e41182b5
GS
1576=item -X
1577
b7df3edc 1578C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1579and applications are executable, and there are no uid/gid
b7df3edc 1580considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1581
038ae9a4
SH
1582C<-w> only inspects the read-only file attribute (FILE_ATTRIBUTE_READONLY),
1583which determines whether the directory can be deleted, not whether it can
1584be written to. Directories always have read and write access unless denied
1585by discretionary access control lists (DACLs). (S<Win32>)
1586
b7df3edc
GS
1587C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1588which may not reflect UIC-based file protections. (VMS)
e41182b5 1589
b8099c3d
CN
1590C<-s> returns the size of the data fork, not the total size of data fork
1591plus resource fork. (S<Mac OS>).
1592
1593C<-s> by name on an open file will return the space reserved on disk,
1594rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1595current size. (S<RISC OS>)
b8099c3d 1596
e41182b5 1597C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1598C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1599
1600C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1601(S<Mac OS>)
1602
287a962e 1603C<-g>, C<-k>, C<-l>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1604(Win32, VMS, S<RISC OS>)
e41182b5 1605
287a962e
JD
1606C<-p> is not particularly meaningful. (VMS, S<RISC OS>)
1607
e41182b5
GS
1608C<-d> is true if passed a device spec without an explicit directory.
1609(VMS)
1610
1611C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1612with foreign characters; this is the case will all platforms, but may
b7df3edc 1613affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1614
1615C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1616suffixes. C<-S> is meaningless. (Win32)
e41182b5 1617
b8099c3d
CN
1618C<-x> (or C<-X>) determine if a file has an executable file type.
1619(S<RISC OS>)
1620
47cd99a4 1621=item atan2
519bc777
RGS
1622
1623Due to issues with various CPUs, math libraries, compilers, and standards,
1624results for C<atan2()> may vary depending on any combination of the above.
1625Perl attempts to conform to the Open Group/IEEE standards for the results
1626returned from C<atan2()>, but cannot force the issue if the system Perl is
1627run on does not allow it. (Tru64, HP-UX 10.20)
1628
1629The current version of the standards for C<atan2()> is available at
1630L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.
1631
47cd99a4 1632=item binmode
e41182b5 1633
b7df3edc 1634Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1635
1636Reopens file and restores pointer; if function fails, underlying
1637filehandle may be closed, or pointer may be in a different position.
1638(VMS)
1639
1640The value returned by C<tell> may be affected after the call, and
1641the filehandle may be flushed. (Win32)
1642
47cd99a4 1643=item chmod
e41182b5 1644
b7df3edc 1645Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1646locking/unlocking the file. (S<Mac OS>)
1647
1648Only good for changing "owner" read-write access, "group", and "other"
1649bits are meaningless. (Win32)
1650
b8099c3d
CN
1651Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1652
495c5fdc
GP
1653Access permissions are mapped onto VOS access-control list changes. (VOS)
1654
4e51f8e4 1655The actual permissions set depend on the value of the C<CYGWIN>
789f0d36 1656in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1657
47cd99a4 1658=item chown
e41182b5 1659
3fd80bd6 1660Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5
GS
1661
1662Does nothing, but won't fail. (Win32)
1663
3fd80bd6
PG
1664A little funky, because VOS's notion of ownership is a little funky (VOS).
1665
e41182b5
GS
1666=item chroot
1667
e6f03d26 1668Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS, VM/ESA)
e41182b5 1669
47cd99a4 1670=item crypt
e41182b5
GS
1671
1672May not be available if library or source was not provided when building
b8099c3d 1673perl. (Win32)
e41182b5 1674
47cd99a4 1675=item dbmclose
e41182b5 1676
e6f03d26 1677Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1678
47cd99a4 1679=item dbmopen
e41182b5 1680
e6f03d26 1681Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1682
47cd99a4 1683=item dump
e41182b5 1684
b8099c3d 1685Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5 1686
84d78eb7 1687Not supported. (Cygwin, Win32)
e41182b5 1688
b8099c3d 1689Invokes VMS debugger. (VMS)
e41182b5 1690
47cd99a4 1691=item exec
e41182b5
GS
1692
1693Not implemented. (S<Mac OS>)
1694
7c5ffed3 1695Implemented via Spawn. (VM/ESA)
3c075c7d 1696
0f897271
GS
1697Does not automatically flush output handles on some platforms.
1698(SunOS, Solaris, HP-UX)
1699
fe12c0e8
MS
1700=item exit
1701
1702Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1703mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1704with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1705function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1706(C<1>); this mapping cannot be overridden. Any other argument to exit()
016930a6
JM
1707is used directly as Perl's exit status. On VMS, unless the future
1708POSIX_EXIT mode is enabled, the exit code should always be a valid
1709VMS exit code and not a generic number. When the POSIX_EXIT mode is
1710enabled, a generic number will be encoded in a method compatible with
1711the C library _POSIX_EXIT macro so that it can be decoded by other
1712programs, particularly ones written in C, like the GNV package. (VMS)
fe12c0e8 1713
47cd99a4 1714=item fcntl
e41182b5 1715
016930a6
JM
1716Not implemented. (Win32)
1717Some functions available based on the version of VMS. (VMS)
e41182b5 1718
47cd99a4 1719=item flock
e41182b5 1720
495c5fdc 1721Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1722
1723Available only on Windows NT (not on Windows 95). (Win32)
1724
1725=item fork
1726
3fd80bd6 1727Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VM/ESA, VMS)
0f897271
GS
1728
1729Emulated using multiple interpreters. See L<perlfork>. (Win32)
1730
1731Does not automatically flush output handles on some platforms.
1732(SunOS, Solaris, HP-UX)
e41182b5
GS
1733
1734=item getlogin
1735
b8099c3d 1736Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5 1737
47cd99a4 1738=item getpgrp
e41182b5 1739
3fd80bd6 1740Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1741
1742=item getppid
1743
41cbbefa 1744Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1745
47cd99a4 1746=item getpriority
e41182b5 1747
7c5ffed3 1748Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1749
47cd99a4 1750=item getpwnam
e41182b5
GS
1751
1752Not implemented. (S<Mac OS>, Win32)
1753
b8099c3d
CN
1754Not useful. (S<RISC OS>)
1755
47cd99a4 1756=item getgrnam
e41182b5 1757
b8099c3d 1758Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1759
47cd99a4 1760=item getnetbyname
e41182b5 1761
e6f03d26 1762Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1763
47cd99a4 1764=item getpwuid
e41182b5
GS
1765
1766Not implemented. (S<Mac OS>, Win32)
1767
b8099c3d
CN
1768Not useful. (S<RISC OS>)
1769
47cd99a4 1770=item getgrgid
e41182b5 1771
b8099c3d 1772Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1773
47cd99a4 1774=item getnetbyaddr
e41182b5 1775
e6f03d26 1776Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1777
47cd99a4 1778=item getprotobynumber
e41182b5
GS
1779
1780Not implemented. (S<Mac OS>)
1781
47cd99a4 1782=item getservbyport
e41182b5
GS
1783
1784Not implemented. (S<Mac OS>)
1785
1786=item getpwent
1787
7c5ffed3 1788Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1789
1790=item getgrent
1791
7c5ffed3 1792Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5 1793
ef5a6dd7
JH
1794=item gethostbyname
1795
1796C<gethostbyname('localhost')> does not work everywhere: you may have
1797to use C<gethostbyname('127.0.0.1')>. (S<Mac OS>, S<Irix 5>)
1798
e41182b5
GS
1799=item gethostent
1800
1801Not implemented. (S<Mac OS>, Win32)
1802
1803=item getnetent
1804
e6f03d26 1805Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1806
1807=item getprotoent
1808
e6f03d26 1809Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1810
1811=item getservent
1812
e6f03d26 1813Not implemented. (Win32, S<Plan 9>)
e41182b5 1814
47cd99a4 1815=item sethostent
e41182b5 1816
e6f03d26 1817Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1818
47cd99a4 1819=item setnetent
e41182b5 1820
e6f03d26 1821Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1822
47cd99a4 1823=item setprotoent
e41182b5 1824
e6f03d26 1825Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1826
47cd99a4 1827=item setservent
e41182b5 1828
e6f03d26 1829Not implemented. (S<Plan 9>, Win32, S<RISC OS>)
e41182b5
GS
1830
1831=item endpwent
1832
a3dfe201 1833Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1834
1835=item endgrent
1836
a3dfe201 1837Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1838
1839=item endhostent
1840
1841Not implemented. (S<Mac OS>, Win32)
1842
1843=item endnetent
1844
e6f03d26 1845Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1846
1847=item endprotoent
1848
e6f03d26 1849Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1850
1851=item endservent
1852
e6f03d26 1853Not implemented. (S<Plan 9>, Win32)
e41182b5
GS
1854
1855=item getsockopt SOCKET,LEVEL,OPTNAME
1856
e6f03d26 1857Not implemented. (S<Plan 9>)
e41182b5 1858
e41182b5
GS
1859=item glob
1860
63f87e49
GS
1861This operator is implemented via the File::Glob extension on most
1862platforms. See L<File::Glob> for portability information.
b8099c3d 1863
62aa5637
MS
1864=item gmtime
1865
461d5a49
MS
1866In theory, gmtime() is reliable from -2**63 to 2**63-1. However,
1867because work arounds in the implementation use floating point numbers,
1868it will become inaccurate as the time gets larger. This is a bug and
1869will be fixed in the future.
62aa5637 1870
e41182b5
GS
1871=item ioctl FILEHANDLE,FUNCTION,SCALAR
1872
1873Not implemented. (VMS)
1874
1875Available only for socket handles, and it does what the ioctlsocket() call
1876in the Winsock API does. (Win32)
1877
b8099c3d
CN
1878Available only for socket handles. (S<RISC OS>)
1879
47cd99a4 1880=item kill
e41182b5 1881
862b5365
JH
1882C<kill(0, LIST)> is implemented for the sake of taint checking;
1883use with other signals is unimplemented. (S<Mac OS>)
1884
1885Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1886
63f87e49
GS
1887C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1888a signal to the identified process like it does on Unix platforms.
1889Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1890and makes it exit immediately with exit status $sig. As in Unix, if
1891$sig is 0 and the specified process exists, it returns true without
1892actually terminating it. (Win32)
e41182b5 1893
d0302514
JD
1894C<kill(-9, $pid)> will terminate the process specified by $pid and
1895recursively all child processes owned by it. This is different from
1896the Unix semantics, where the signal will be delivered to all
1897processes in the same process group as the process specified by
1898$pid. (Win32)
1899
016930a6
JM
1900Is not supported for process identification number of 0 or negative
1901numbers. (VMS)
1902
47cd99a4 1903=item link
e41182b5 1904
016930a6 1905Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>)
e41182b5 1906
433acd8a
JH
1907Link count not updated because hard links are not quite that hard
1908(They are sort of half-way between hard and soft links). (AmigaOS)
1909
63d6c08b
JD
1910Hard links are implemented on Win32 under NTFS only. They are
1911natively supported on Windows 2000 and later. On Windows NT they
1912are implemented using the Windows POSIX subsystem support and the
1913Perl process will need Administrator or Backup Operator privileges
1914to create hard links.
a3dfe201 1915
016930a6
JM
1916Available on 64 bit OpenVMS 8.2 and later. (VMS)
1917
62aa5637
MS
1918=item localtime
1919
dc164757
MS
1920localtime() has the same range as L<gmtime>, but because time zone
1921rules change its accuracy for historical and future times may degrade
1922but usually by no more than an hour.
62aa5637 1923
e41182b5
GS
1924=item lstat
1925
016930a6 1926Not implemented. (S<RISC OS>)
e41182b5 1927
63f87e49 1928Return values (especially for device and inode) may be bogus. (Win32)
e41182b5 1929
47cd99a4 1930=item msgctl
e41182b5 1931
47cd99a4 1932=item msgget
e41182b5 1933
47cd99a4 1934=item msgsnd
e41182b5 1935
47cd99a4 1936=item msgrcv
e41182b5 1937
e6f03d26 1938Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS)
e41182b5 1939
47cd99a4 1940=item open
e41182b5 1941
b7df3edc 1942The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1943(S<Mac OS>)
1944
c47ff5f1 1945open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1946
0f897271
GS
1947Opening a process does not automatically flush output handles on some
1948platforms. (SunOS, Solaris, HP-UX)
1949
47cd99a4 1950=item pipe
e41182b5 1951
433acd8a
JH
1952Very limited functionality. (MiNT)
1953
e41182b5
GS
1954=item readlink
1955
b8099c3d 1956Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1957
47cd99a4 1958=item rename
c9b2b9d4
SS
1959
1960Can't move directories between directories on different logical volumes. (Win32)
1961
47cd99a4 1962=item select
e41182b5 1963
689c5c24 1964Only implemented on sockets. (Win32, VMS)
e41182b5 1965
b8099c3d
CN
1966Only reliable on sockets. (S<RISC OS>)
1967
76e05f0b 1968Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1969
47cd99a4 1970=item semctl
e41182b5 1971
47cd99a4 1972=item semget
e41182b5 1973
47cd99a4 1974=item semop
e41182b5 1975
495c5fdc 1976Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1977
a3dfe201
GS
1978=item setgrent
1979
3fd80bd6 1980Not implemented. (S<Mac OS>, MPE/iX, VMS, Win32, S<RISC OS>, VOS)
a3dfe201 1981
47cd99a4 1982=item setpgrp
e41182b5 1983
495c5fdc 1984Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1985
47cd99a4 1986=item setpriority
e41182b5 1987
495c5fdc 1988Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1989
a3dfe201
GS
1990=item setpwent
1991
3fd80bd6 1992Not implemented. (S<Mac OS>, MPE/iX, Win32, S<RISC OS>, VOS)
a3dfe201 1993
47cd99a4 1994=item setsockopt
e41182b5 1995
e6f03d26 1996Not implemented. (S<Plan 9>)
e41182b5 1997
47cd99a4 1998=item shmctl
e41182b5 1999
47cd99a4 2000=item shmget
e41182b5 2001
47cd99a4 2002=item shmread
e41182b5 2003
47cd99a4 2004=item shmwrite
e41182b5 2005
495c5fdc 2006Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 2007
47cd99a4 2008=item sockatmark
80cbd5ad
JH
2009
2010A relatively recent addition to socket functions, may not
2011be implemented even in UNIX platforms.
2012
47cd99a4 2013=item socketpair
e41182b5 2014
f38e12df 2015Not implemented. (S<RISC OS>, VOS, VM/ESA)
016930a6
JM
2016
2017Available on 64 bit OpenVMS 8.2 and later. (VMS)
e41182b5 2018
e41182b5
GS
2019=item stat
2020
d62e1b7f
JH
2021Platforms that do not have rdev, blksize, or blocks will return these
2022as '', so numeric comparison or manipulation of these fields may cause
2023'not numeric' warnings.
2024
e41182b5 2025mtime and atime are the same thing, and ctime is creation time instead of
3f1f789b
JH
2026inode change time. (S<Mac OS>).
2027
2028ctime not supported on UFS (S<Mac OS X>).
e41182b5 2029
95a3fe12
MS
2030ctime is creation time instead of inode change time (Win32).
2031
e41182b5
GS
2032device and inode are not meaningful. (Win32)
2033
2034device and inode are not necessarily reliable. (VMS)
2035
b8099c3d
CN
2036mtime, atime and ctime all return the last modification time. Device and
2037inode are not necessarily reliable. (S<RISC OS>)
2038
d62e1b7f
JH
2039dev, rdev, blksize, and blocks are not available. inode is not
2040meaningful and will differ between stat calls on the same file. (os2)
2041
73e9292c
JH
2042some versions of cygwin when doing a stat("foo") and if not finding it
2043may then attempt to stat("foo.exe") (Cygwin)
2044
1fafdf34
JD
2045On Win32 stat() needs to open the file to determine the link count
2046and update attributes that may have been changed through hard links.
2047Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up stat() by
2048not performing this operation. (Win32)
2049
47cd99a4 2050=item symlink
e41182b5 2051
c73b03b7
JM
2052Not implemented. (Win32, S<RISC OS>)
2053
2054Implemented on 64 bit VMS 8.3. VMS requires the symbolic link to be in Unix
2055syntax if it is intended to resolve to a valid path.
e41182b5 2056
47cd99a4 2057=item syscall
e41182b5 2058
7c5ffed3 2059Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 2060
47cd99a4 2061=item sysopen
f34d0673 2062
dd9f0070 2063The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
2064numeric values on some systems. The flags exported by C<Fcntl>
2065(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 2066OS>, OS/390, VM/ESA)
f34d0673 2067
47cd99a4 2068=item system
e41182b5
GS
2069
2070Only implemented if ToolServer is installed. (S<Mac OS>)
2071
2072As an optimization, may not call the command shell specified in
b7df3edc 2073C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
2074process and immediately returns its process designator, without
2075waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
2076in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
2077by setting $? to "255 << 8". C<$?> is set in a way compatible with
2078Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
2079as described in the documentation). (Win32)
e41182b5 2080
b8099c3d
CN
2081There is no shell to process metacharacters, and the native standard is
2082to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 2083program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
2084the run time library of the spawned program. C<system> I<list> will call
2085the Unix emulation library's C<exec> emulation, which attempts to provide
2086emulation of the stdin, stdout, stderr in force in the parent, providing
2087the child program uses a compatible version of the emulation library.
2088I<scalar> will call the native command line direct and no such emulation
2089of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
2090
433acd8a
JH
2091Far from being POSIX compliant. Because there may be no underlying
2092/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 2093first token in its argument string. Handles basic redirection
c47ff5f1 2094("<" or ">") on its own behalf. (MiNT)
433acd8a 2095
0f897271
GS
2096Does not automatically flush output handles on some platforms.
2097(SunOS, Solaris, HP-UX)
2098
9bc98430
CB
2099The return value is POSIX-like (shifted up by 8 bits), which only allows
2100room for a made-up value derived from the severity bits of the native
210132-bit condition code (unless overridden by C<use vmsish 'status'>).
016930a6
JM
2102If the native condition code is one that has a POSIX value encoded, the
2103POSIX value will be decoded to extract the expected exit value.
9bc98430
CB
2104For more details see L<perlvms/$?>. (VMS)
2105
e41182b5
GS
2106=item times
2107
2108Only the first entry returned is nonzero. (S<Mac OS>)
2109
63f87e49
GS
2110"cumulative" times will be bogus. On anything other than Windows NT
2111or Windows 2000, "system" time will be bogus, and "user" time is
2112actually the time returned by the clock() function in the C runtime
2113library. (Win32)
e41182b5 2114
b8099c3d
CN
2115Not useful. (S<RISC OS>)
2116
47cd99a4 2117=item truncate
e41182b5 2118
6d738113 2119Not implemented. (Older versions of VMS)
e41182b5 2120
3fd80bd6 2121Truncation to same-or-shorter lengths only. (VOS)
495c5fdc 2122
4cfdb94f 2123If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 2124mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
2125or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
2126should not be held open elsewhere. (Win32)
2127
e41182b5
GS
2128=item umask
2129
2130Returns undef where unavailable, as of version 5.005.
2131
b7df3edc
GS
2132C<umask> works but the correct permissions are set only when the file
2133is finally closed. (AmigaOS)
433acd8a 2134
47cd99a4 2135=item utime
e41182b5 2136
15c65113 2137Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 2138
322422de
GS
2139May not behave as expected. Behavior depends on the C runtime
2140library's implementation of utime(), and the filesystem being
2141used. The FAT filesystem typically does not support an "access
2142time" field, and it may limit timestamps to a granularity of
2143two seconds. (Win32)
e41182b5
GS
2144
2145=item wait
2146
47cd99a4 2147=item waitpid
e41182b5 2148
3fd80bd6 2149Not implemented. (S<Mac OS>)
e41182b5
GS
2150
2151Can only be applied to process handles returned for processes spawned
a6f858fb 2152using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 2153
b8099c3d
CN
2154Not useful. (S<RISC OS>)
2155
e41182b5
GS
2156=back
2157
2158
ba58ab26
JH
2159=head1 Supported Platforms
2160
522b859a 2161As of July 2002 (the Perl release 5.8.0), the following platforms are
cec2c193
JH
2162able to build Perl from the standard source code distribution
2163available at http://www.cpan.org/src/index.html
2164
2165 AIX
2166 BeOS
6f683aa2 2167 BSD/OS (BSDi)
cec2c193
JH
2168 Cygwin
2169 DG/UX
811b48f2 2170 DOS DJGPP 1)
cec2c193
JH
2171 DYNIX/ptx
2172 EPOC R5
2173 FreeBSD
6f683aa2 2174 HI-UXMPP (Hitachi) (5.8.0 worked but we didn't know it)
cec2c193
JH
2175 HP-UX
2176 IRIX
2177 Linux
8939ba94 2178 Mac OS Classic
6f683aa2 2179 Mac OS X (Darwin)
cec2c193
JH
2180 MPE/iX
2181 NetBSD
2182 NetWare
2183 NonStop-UX
6f683aa2 2184 ReliantUNIX (formerly SINIX)
cec2c193 2185 OpenBSD
6f683aa2 2186 OpenVMS (formerly VMS)
3ebac25b 2187 Open UNIX (Unixware) (since Perl 5.8.1/5.9.0)
cec2c193 2188 OS/2
522b859a 2189 OS/400 (using the PASE) (since Perl 5.8.1/5.9.0)
70de81db 2190 PowerUX
6f683aa2 2191 POSIX-BC (formerly BS2000)
cec2c193
JH
2192 QNX
2193 Solaris
70de81db 2194 SunOS 4
6f683aa2
JH
2195 SUPER-UX (NEC)
2196 Tru64 UNIX (formerly DEC OSF/1, Digital UNIX)
cec2c193
JH
2197 UNICOS
2198 UNICOS/mk
2199 UTS
2200 VOS
811b48f2 2201 Win95/98/ME/2K/XP 2)
c40b5d1d 2202 WinCE
6f683aa2 2203 z/OS (formerly OS/390)
cec2c193 2204 VM/ESA
ba58ab26 2205
811b48f2
JH
2206 1) in DOS mode either the DOS or OS/2 ports can be used
2207 2) compilers: Borland, MinGW (GCC), VC6
cec2c193 2208
c40b5d1d 2209The following platforms worked with the previous releases (5.6 and
cec2c193
JH
22105.7), but we did not manage either to fix or to test these in time
2211for the 5.8.0 release. There is a very good chance that many of these
70de81db 2212will work fine with the 5.8.0.
cec2c193 2213
8da2b1be 2214 BSD/OS
cec2c193
JH
2215 DomainOS
2216 Hurd
2217 LynxOS
2218 MachTen
2219 PowerMAX
2220 SCO SV
cec2c193
JH
2221 SVR4
2222 Unixware
2223 Windows 3.1
ba58ab26 2224
70de81db
JH
2225Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used):
2226
2227 AmigaOS
2228
ba58ab26 2229The following platforms have been known to build Perl from source in
fd46a41b
JH
2230the past (5.005_03 and earlier), but we haven't been able to verify
2231their status for the current release, either because the
2232hardware/software platforms are rare or because we don't have an
2233active champion on these platforms--or both. They used to work,
2234though, so go ahead and try compiling them, and let perlbug@perl.org
2235of any trouble.
ba58ab26 2236
cec2c193
JH
2237 3b1
2238 A/UX
cec2c193
JH
2239 ConvexOS
2240 CX/UX
2241 DC/OSx
2242 DDE SMES
2243 DOS EMX
2244 Dynix
2245 EP/IX
2246 ESIX
2247 FPS
2248 GENIX
2249 Greenhills
2250 ISC
2251 MachTen 68k
2252 MiNT
2253 MPC
2254 NEWS-OS
2255 NextSTEP
2256 OpenSTEP
2257 Opus
2258 Plan 9
cec2c193 2259 RISC/os
8da2b1be 2260 SCO ODT/OSR
cec2c193
JH
2261 Stellar
2262 SVR2
2263 TI1500
2264 TitanOS
2265 Ultrix
2266 Unisys Dynix
ba58ab26
JH
2267
2268The following platforms have their own source code distributions and
1577cd80 2269binaries available via http://www.cpan.org/ports/
ba58ab26 2270
cec2c193 2271 Perl release
ba58ab26 2272
522b859a 2273 OS/400 (ILE) 5.005_02
cec2c193 2274 Tandem Guardian 5.004
ba58ab26
JH
2275
2276The following platforms have only binaries available via
a93751fa 2277http://www.cpan.org/ports/index.html :
ba58ab26 2278
cec2c193 2279 Perl release
ba58ab26 2280
cec2c193
JH
2281 Acorn RISCOS 5.005_02
2282 AOS 5.002
2283 LynxOS 5.004_02
ba58ab26
JH
2284
2285Although we do suggest that you always build your own Perl from
2286the source code, both for maximal configurability and for security,
2287in case you are in a hurry you can check
a93751fa 2288http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2289
c997b287
GS
2290=head1 SEE ALSO
2291
cec2c193 2292L<perlaix>, L<perlamiga>, L<perlapollo>, L<perlbeos>, L<perlbs2000>,
18a271bd 2293L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>,
469e7be4 2294L<perlebcdic>, L<perlfreebsd>, L<perlhurd>, L<perlhpux>, L<perlirix>,
0d53b15f 2295L<perlmachten>, L<perlmacos>, L<perlmacosx>, L<perlmint>, L<perlmpeix>,
522b859a
JH
2296L<perlnetware>, L<perlos2>, L<perlos390>, L<perlos400>,
2297L<perlplan9>, L<perlqnx>, L<perlsolaris>, L<perltru64>,
2298L<perlunicode>, L<perlvmesa>, L<perlvms>, L<perlvos>,
2299L<perlwin32>, and L<Win32>.
c997b287 2300
e41182b5
GS
2301=head1 AUTHORS / CONTRIBUTORS
2302
06e9666b 2303Abigail <abigail@foad.org>,
c47ff5f1
GS
2304Charles Bailey <bailey@newman.upenn.edu>,
2305Graham Barr <gbarr@pobox.com>,
2306Tom Christiansen <tchrist@perl.com>,
06e9666b 2307Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2308Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2309Andy Dougherty <doughera@lafayette.edu>,
2310Dominic Dunlop <domo@computer.org>,
2311Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1 2312David J. Fiander <davidf@mks.com>,
3fd80bd6 2313Paul Green <Paul.Green@stratus.com>,
06e9666b 2314M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2315Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2316Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2317Nick Ing-Simmons <nick@ing-simmons.net>,
2318Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2319Markus Laker <mlaker@contax.co.uk>,
2320Andrew M. Langmead <aml@world.std.com>,
2321Larry Moore <ljmoore@freespace.net>,
2322Paul Moore <Paul.Moore@uk.origin-it.com>,
2323Chris Nandor <pudge@pobox.com>,
1afc07ec 2324Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2325Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2326Gary Ng <71564.1743@CompuServe.COM>,
2327Tom Phoenix <rootbeer@teleport.com>,
2328AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2329Peter Prymmer <pvhp@forte.com>,
2330Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2331Gurusamy Sarathy <gsar@activestate.com>,
2332Paul J. Schinder <schinder@pobox.com>,
2333Michael G Schwern <schwern@pobox.com>,
06e9666b 2334Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2335Nathan Torkington <gnat@frii.com>.
016930a6 2336John Malmberg <wb8tyw@qsl.net>