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1=head1 NAME
2
3perlport - Writing portable Perl
4
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5=head1 DESCRIPTION
6
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7Perl runs on numerous operating systems. While most of them share
8much in common, they also have their own unique features.
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9
10This document is meant to help you to find out what constitutes portable
b7df3edc 11Perl code. That way once you make a decision to write portably,
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12you know where the lines are drawn, and you can stay within them.
13
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14There is a tradeoff between taking full advantage of one particular
15type of computer and taking advantage of a full range of them.
16Naturally, as you broaden your range and become more diverse, the
17common factors drop, and you are left with an increasingly smaller
18area of common ground in which you can operate to accomplish a
19particular task. Thus, when you begin attacking a problem, it is
20important to consider under which part of the tradeoff curve you
21want to operate. Specifically, you must decide whether it is
22important that the task that you are coding have the full generality
23of being portable, or whether to just get the job done right now.
24This is the hardest choice to be made. The rest is easy, because
25Perl provides many choices, whichever way you want to approach your
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26problem.
27
28Looking at it another way, writing portable code is usually about
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29willfully limiting your available choices. Naturally, it takes
30discipline and sacrifice to do that. The product of portability
31and convenience may be a constant. You have been warned.
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32
33Be aware of two important points:
34
35=over 4
36
37=item Not all Perl programs have to be portable
38
b7df3edc 39There is no reason you should not use Perl as a language to glue Unix
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40tools together, or to prototype a Macintosh application, or to manage the
41Windows registry. If it makes no sense to aim for portability for one
42reason or another in a given program, then don't bother.
43
b7df3edc 44=item Nearly all of Perl already I<is> portable
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45
46Don't be fooled into thinking that it is hard to create portable Perl
47code. It isn't. Perl tries its level-best to bridge the gaps between
48what's available on different platforms, and all the means available to
49use those features. Thus almost all Perl code runs on any machine
6ab3f9cb 50without modification. But there are some significant issues in
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51writing portable code, and this document is entirely about those issues.
52
53=back
54
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55Here's the general rule: When you approach a task commonly done
56using a whole range of platforms, think about writing portable
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57code. That way, you don't sacrifice much by way of the implementation
58choices you can avail yourself of, and at the same time you can give
59your users lots of platform choices. On the other hand, when you have to
60take advantage of some unique feature of a particular platform, as is
61often the case with systems programming (whether for Unix, Windows,
62S<Mac OS>, VMS, etc.), consider writing platform-specific code.
63
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64When the code will run on only two or three operating systems, you
65may need to consider only the differences of those particular systems.
66The important thing is to decide where the code will run and to be
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67deliberate in your decision.
68
69The material below is separated into three main sections: main issues of
70portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and
b7df3edc 71built-in perl functions that behave differently on various ports
0a47030a 72(L<"FUNCTION IMPLEMENTATIONS">.
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73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
b7df3edc 76all of which are in a state of constant evolution. Thus, this material
e41182b5 77should be considered a perpetual work in progress
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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97A common cause of unportable programs is the misuse of chop() to trim
98newlines:
99
100 # XXX UNPORTABLE!
101 while(<FILE>) {
102 chop;
103 @array = split(/:/);
104 #...
105 }
106
107You can get away with this on Unix and MacOS (they have a single
108character end-of-line), but the same program will break under DOSish
109perls because you're only chop()ing half the end-of-line. Instead,
110chomp() should be used to trim newlines. The Dunce::Files module can
111help audit your code for misuses of chop().
112
113When dealing with binary files (or text files in binary mode) be sure
114to explicitly set $/ to the appropriate value for your file format
115before using chomp().
116
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117Because of the "text" mode translation, DOSish perls have limitations
118in using C<seek> and C<tell> on a file accessed in "text" mode.
119Stick to C<seek>-ing to locations you got from C<tell> (and no
120others), and you are usually free to use C<seek> and C<tell> even
121in "text" mode. Using C<seek> or C<tell> or other file operations
122may be non-portable. If you use C<binmode> on a file, however, you
123can usually C<seek> and C<tell> with arbitrary values in safety.
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124
125A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 126everywhere. When using protocols such as common Internet protocols,
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127C<\012> and C<\015> are called for specifically, and the values of
128the logical C<\n> and C<\r> (carriage return) are not reliable.
129
130 print SOCKET "Hi there, client!\r\n"; # WRONG
131 print SOCKET "Hi there, client!\015\012"; # RIGHT
132
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133However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
134and unsightly, as well as confusing to those maintaining the code. As
6ab3f9cb 135such, the Socket module supplies the Right Thing for those who want it.
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136
137 use Socket qw(:DEFAULT :crlf);
138 print SOCKET "Hi there, client!$CRLF" # RIGHT
139
6ab3f9cb 140When reading from a socket, remember that the default input record
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141separator C<$/> is C<\n>, but robust socket code will recognize as
142either C<\012> or C<\015\012> as end of line:
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143
144 while (<SOCKET>) {
145 # ...
146 }
147
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148Because both CRLF and LF end in LF, the input record separator can
149be set to LF and any CR stripped later. Better to write:
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150
151 use Socket qw(:DEFAULT :crlf);
152 local($/) = LF; # not needed if $/ is already \012
153
154 while (<SOCKET>) {
155 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
156 # s/\015?\012/\n/; # same thing
157 }
158
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159This example is preferred over the previous one--even for Unix
160platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
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161(and there was much rejoicing).
162
6ab3f9cb 163Similarly, functions that return text data--such as a function that
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164fetches a web page--should sometimes translate newlines before
165returning the data, if they've not yet been translated to the local
166newline representation. A single line of code will often suffice:
2ee0eb3c 167
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168 $data =~ s/\015?\012/\n/g;
169 return $data;
2ee0eb3c 170
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171Some of this may be confusing. Here's a handy reference to the ASCII CR
172and LF characters. You can print it out and stick it in your wallet.
173
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174 LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
175 CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
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176
177 | Unix | DOS | Mac |
178 ---------------------------
179 \n | LF | LF | CR |
180 \r | CR | CR | LF |
181 \n * | LF | CRLF | CR |
182 \r * | CR | CR | LF |
183 ---------------------------
184 * text-mode STDIO
185
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186The Unix column assumes that you are not accessing a serial line
187(like a tty) in canonical mode. If you are, then CR on input becomes
188"\n", and "\n" on output becomes CRLF.
189
6ab3f9cb 190These are just the most common definitions of C<\n> and C<\r> in Perl.
aa7f90d3 191There may well be others. For example, on an EBCDIC implementation such
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192as z/OS or OS/400 the above material is similar to "Unix" but the code
193numbers change:
194
195 LF eq \025 eq \x15 eq chr(21) eq CP-1047 21
196 LF eq \045 eq \x25 eq \cU eq chr(37) eq CP-0037 37
197 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
198 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
199
200 | z/OS | OS/400 |
201 ----------------------
202 \n | LF | LF |
203 \r | CR | CR |
204 \n * | LF | LF |
205 \r * | CR | CR |
206 ----------------------
207 * text-mode STDIO
6ab3f9cb 208
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209=head2 Numbers endianness and Width
210
211Different CPUs store integers and floating point numbers in different
212orders (called I<endianness>) and widths (32-bit and 64-bit being the
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213most common today). This affects your programs when they attempt to transfer
214numbers in binary format from one CPU architecture to another,
215usually either "live" via network connection, or by storing the
216numbers to secondary storage such as a disk file or tape.
322422de 217
b7df3edc 218Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 219little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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220decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2210x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
222Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
223them in big-endian mode. To avoid this problem in network (socket)
224connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
225"network" orders. These are guaranteed to be portable.
322422de 226
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227You can explore the endianness of your platform by unpacking a
228data structure packed in native format such as:
229
230 print unpack("h*", pack("s2", 1, 2)), "\n";
231 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
232 # '00100020' on e.g. Motorola 68040
233
234If you need to distinguish between endian architectures you could use
235either of the variables set like so:
236
237 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 238 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 239
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240Differing widths can cause truncation even between platforms of equal
241endianness. The platform of shorter width loses the upper parts of the
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242number. There is no good solution for this problem except to avoid
243transferring or storing raw binary numbers.
244
b7df3edc 245One can circumnavigate both these problems in two ways. Either
322422de 246transfer and store numbers always in text format, instead of raw
b7df3edc 247binary, or else consider using modules like Data::Dumper (included in
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248the standard distribution as of Perl 5.005) and Storable (included as
249of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 250
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251The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
252how far EBCDIC, or more precisely UTF-EBCDIC will go.
253
433acd8a 254=head2 Files and Filesystems
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255
256Most platforms these days structure files in a hierarchical fashion.
b7df3edc 257So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 258notion of a "path" to uniquely identify a file on the system. How
b7df3edc 259that path is really written, though, differs considerably.
e41182b5 260
4375e838 261Although similar, file path specifications differ between Unix,
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262Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
263Unix, for example, is one of the few OSes that has the elegant idea
264of a single root directory.
322422de 265
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266DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
267as path separator, or in their own idiosyncratic ways (such as having
268several root directories and various "unrooted" device files such NIL:
269and LPT:).
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270
271S<Mac OS> uses C<:> as a path separator instead of C</>.
272
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273The filesystem may support neither hard links (C<link>) nor
274symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 275
6ab3f9cb 276The filesystem may support neither access timestamp nor change
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277timestamp (meaning that about the only portable timestamp is the
278modification timestamp), or one second granularity of any timestamps
279(e.g. the FAT filesystem limits the time granularity to two seconds).
280
74555b7a 281The "inode change timestamp" (the C<-C> filetest) may really be the
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282"creation timestamp" (which it is not in UNIX).
283
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284VOS perl can emulate Unix filenames with C</> as path separator. The
285native pathname characters greater-than, less-than, number-sign, and
286percent-sign are always accepted.
287
6ab3f9cb 288S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 289separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 290signal filesystems and disk names.
e41182b5 291
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292Don't assume UNIX filesystem access semantics: that read, write,
293and execute are all the permissions there are, and even if they exist,
294that their semantics (for example what do r, w, and x mean on
295a directory) are the UNIX ones. The various UNIX/POSIX compatibility
296layers usually try to make interfaces like chmod() work, but sometimes
297there simply is no good mapping.
298
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299If all this is intimidating, have no (well, maybe only a little)
300fear. There are modules that can help. The File::Spec modules
301provide methods to do the Right Thing on whatever platform happens
302to be running the program.
e41182b5 303
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304 use File::Spec::Functions;
305 chdir(updir()); # go up one directory
306 $file = catfile(curdir(), 'temp', 'file.txt');
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307 # on Unix and Win32, './temp/file.txt'
308 # on Mac OS, ':temp:file.txt'
d1e3b762 309 # on VMS, '[.temp]file.txt'
e41182b5 310
b7df3edc 311File::Spec is available in the standard distribution as of version
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3125.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
313and some versions of perl come with version 0.6. If File::Spec
314is not updated to 0.7 or later, you must use the object-oriented
315interface from File::Spec (or upgrade File::Spec).
e41182b5 316
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317In general, production code should not have file paths hardcoded.
318Making them user-supplied or read from a configuration file is
319better, keeping in mind that file path syntax varies on different
320machines.
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321
322This is especially noticeable in scripts like Makefiles and test suites,
323which often assume C</> as a path separator for subdirectories.
324
b7df3edc 325Also of use is File::Basename from the standard distribution, which
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326splits a pathname into pieces (base filename, full path to directory,
327and file suffix).
328
19799a22 329Even when on a single platform (if you can call Unix a single platform),
b7df3edc 330remember not to count on the existence or the contents of particular
3c075c7d 331system-specific files or directories, like F</etc/passwd>,
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332F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
333example, F</etc/passwd> may exist but not contain the encrypted
334passwords, because the system is using some form of enhanced security.
335Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 336If code does need to rely on such a file, include a description of the
b7df3edc 337file and its format in the code's documentation, then make it easy for
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338the user to override the default location of the file.
339
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340Don't assume a text file will end with a newline. They should,
341but people forget.
e41182b5 342
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343Do not have two files or directories of the same name with different
344case, like F<test.pl> and F<Test.pl>, as many platforms have
345case-insensitive (or at least case-forgiving) filenames. Also, try
346not to have non-word characters (except for C<.>) in the names, and
347keep them to the 8.3 convention, for maximum portability, onerous a
348burden though this may appear.
dd9f0070 349
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350Likewise, when using the AutoSplit module, try to keep your functions to
3518.3 naming and case-insensitive conventions; or, at the least,
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352make it so the resulting files have a unique (case-insensitively)
353first 8 characters.
354
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355Whitespace in filenames is tolerated on most systems, but not all,
356and even on systems where it might be tolerated, some utilities
fe829689 357might become confused by such whitespace.
ec481373 358
b7df3edc 359Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
433acd8a 360
c47ff5f1 361Don't assume C<< > >> won't be the first character of a filename.
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362Always use C<< < >> explicitly to open a file for reading, or even
363better, use the three-arg version of open, unless you want the user to
364be able to specify a pipe open.
0a47030a 365
fe829689 366 open(FILE, '<', $existing_file) or die $!;
0a47030a 367
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368If filenames might use strange characters, it is safest to open it
369with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 370translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 371be the wrong thing to do. (Sometimes, though, it's the right thing.)
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372Three-arg open can also help protect against this translation in cases
373where it is undesirable.
e41182b5 374
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375Don't use C<:> as a part of a filename since many systems use that for
376their own semantics (MacOS Classic for separating pathname components,
377many networking schemes and utilities for separating the nodename and
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378the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
379C<|>.
ec481373 380
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381Don't assume that in pathnames you can collapse two leading slashes
382C<//> into one: some networking and clustering filesystems have special
383semantics for that. Let the operating system to sort it out.
384
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385The I<portable filename characters> as defined by ANSI C are
386
387 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
388 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
389 0 1 2 3 4 5 6 7 8 9
390 . _ -
391
08fef530 392and the "-" shouldn't be the first character. If you want to be
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393hypercorrect, stay case-insensitive and within the 8.3 naming
394convention (all the files and directories have to be unique within one
395directory if their names are lowercased and truncated to eight
396characters before the C<.>, if any, and to three characters after the
397C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 398
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399=head2 System Interaction
400
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401Not all platforms provide a command line. These are usually platforms
402that rely primarily on a Graphical User Interface (GUI) for user
403interaction. A program requiring a command line interface might
404not work everywhere. This is probably for the user of the program
405to deal with, so don't stay up late worrying about it.
e41182b5 406
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407Some platforms can't delete or rename files held open by the system.
408Remember to C<close> files when you are done with them. Don't
409C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
410file already tied or opened; C<untie> or C<close> it first.
e41182b5 411
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412Don't open the same file more than once at a time for writing, as some
413operating systems put mandatory locks on such files.
414
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415Don't assume that write/modify permission on a directory gives the
416right to add or delete files/directories in that directory. That is
417filesystem specific: in some filesystems you need write/modify
418permission also (or even just) in the file/directory itself. In some
419filesystems (AFS, DFS) the permission to add/delete directory entries
420is a completely separate permission.
421
422Don't assume that a single C<unlink> completely gets rid of the file:
423some filesystems (most notably the ones in VMS) have versioned
424filesystems, and unlink() removes only the most recent one (it doesn't
425remove all the versions because by default the native tools on those
426platforms remove just the most recent version, too). The portable
427idiom to remove all the versions of a file is
428
94bb614c 429 1 while unlink "file";
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430
431This will terminate if the file is undeleteable for some reason
432(protected, not there, and so on).
433
e41182b5 434Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 435Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 436case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 437if you really have to, make it conditional on C<$^O ne 'VMS'> since in
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438VMS the C<%ENV> table is much more than a per-process key-value string
439table.
e41182b5 440
d1e3b762 441Don't count on signals or C<%SIG> for anything.
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442
443Don't count on filename globbing. Use C<opendir>, C<readdir>, and
444C<closedir> instead.
445
b8099c3d 446Don't count on per-program environment variables, or per-program current
dd9f0070 447directories.
b8099c3d 448
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449Don't count on specific values of C<$!>.
450
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451=head2 Interprocess Communication (IPC)
452
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453In general, don't directly access the system in code meant to be
454portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
455C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
456that makes being a perl hacker worth being.
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457
458Commands that launch external processes are generally supported on
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459most platforms (though many of them do not support any type of
460forking). The problem with using them arises from what you invoke
461them on. External tools are often named differently on different
4375e838 462platforms, may not be available in the same location, might accept
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463different arguments, can behave differently, and often present their
464results in a platform-dependent way. Thus, you should seldom depend
465on them to produce consistent results. (Then again, if you're calling
466I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 467
b7df3edc 468One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 469
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470 open(MAIL, '|/usr/lib/sendmail -t')
471 or die "cannot fork sendmail: $!";
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472
473This is fine for systems programming when sendmail is known to be
474available. But it is not fine for many non-Unix systems, and even
475some Unix systems that may not have sendmail installed. If a portable
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476solution is needed, see the various distributions on CPAN that deal
477with it. Mail::Mailer and Mail::Send in the MailTools distribution are
478commonly used, and provide several mailing methods, including mail,
479sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
480not available. Mail::Sendmail is a standalone module that provides
481simple, platform-independent mailing.
482
483The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
484even on all Unix platforms.
e41182b5 485
a81e5e2e
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486Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
487bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
488both forms just pack the four bytes into network order. That this
489would be equal to the C language C<in_addr> struct (which is what the
490socket code internally uses) is not guaranteed. To be portable use
491the routines of the Socket extension, such as C<inet_aton()>,
492C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 493
e41182b5 494The rule of thumb for portable code is: Do it all in portable Perl, or
0a47030a
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495use a module (that may internally implement it with platform-specific
496code, but expose a common interface).
e41182b5 497
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498=head2 External Subroutines (XS)
499
b7df3edc 500XS code can usually be made to work with any platform, but dependent
e41182b5
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501libraries, header files, etc., might not be readily available or
502portable, or the XS code itself might be platform-specific, just as Perl
503code might be. If the libraries and headers are portable, then it is
504normally reasonable to make sure the XS code is portable, too.
505
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506A different type of portability issue arises when writing XS code:
507availability of a C compiler on the end-user's system. C brings
508with it its own portability issues, and writing XS code will expose
509you to some of those. Writing purely in Perl is an easier way to
e41182b5
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510achieve portability.
511
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512=head2 Standard Modules
513
514In general, the standard modules work across platforms. Notable
6ab3f9cb 515exceptions are the CPAN module (which currently makes connections to external
e41182b5 516programs that may not be available), platform-specific modules (like
6ab3f9cb 517ExtUtils::MM_VMS), and DBM modules.
e41182b5 518
b7df3edc 519There is no one DBM module available on all platforms.
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520SDBM_File and the others are generally available on all Unix and DOSish
521ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 522available.
e41182b5
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523
524The good news is that at least some DBM module should be available, and
6ab3f9cb 525AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
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526the code needs to be fairly strict, dropping to the greatest common
527factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 528work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 529
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530=head2 Time and Date
531
0a47030a 532The system's notion of time of day and calendar date is controlled in
b7df3edc 533widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a
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534and even if it is, don't assume that you can control the timezone through
535that variable.
e41182b5 536
322422de 537Don't assume that the epoch starts at 00:00:00, January 1, 1970,
6ab3f9cb
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538because that is OS- and implementation-specific. It is better to store a date
539in an unambiguous representation. The ISO-8601 standard defines
540"YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
541can be easily converted into an OS-specific value using a module like
542Date::Parse. An array of values, such as those returned by
322422de 543C<localtime>, can be converted to an OS-specific representation using
6ab3f9cb 544Time::Local.
322422de 545
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546When calculating specific times, such as for tests in time or date modules,
547it may be appropriate to calculate an offset for the epoch.
b7df3edc 548
19799a22
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549 require Time::Local;
550 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 551
19799a22
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552The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
553some large number. C<$offset> can then be added to a Unix time value
554to get what should be the proper value on any system.
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555
556=head2 Character sets and character encoding
557
ec481373
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558Assume very little about character sets.
559
560Assume nothing about numerical values (C<ord>, C<chr>) of characters.
561Do not use explicit code point ranges (like \xHH-\xHH); use for
562example symbolic character classes like C<[:print:]>.
563
564Do not assume that the alphabetic characters are encoded contiguously
565(in the numeric sense). There may be gaps.
566
567Do not assume anything about the ordering of the characters.
568The lowercase letters may come before or after the uppercase letters;
569the lowercase and uppercase may be interlaced so that both `a' and `A'
570come before `b'; the accented and other international characters may
571be interlaced so that E<auml> comes before `b'.
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572
573=head2 Internationalisation
574
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575If you may assume POSIX (a rather large assumption), you may read
576more about the POSIX locale system from L<perllocale>. The locale
577system at least attempts to make things a little bit more portable,
578or at least more convenient and native-friendly for non-English
579users. The system affects character sets and encoding, and date
580and time formatting--amongst other things.
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581
582=head2 System Resources
583
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584If your code is destined for systems with severely constrained (or
585missing!) virtual memory systems then you want to be I<especially> mindful
586of avoiding wasteful constructs such as:
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587
588 # NOTE: this is no longer "bad" in perl5.005
589 for (0..10000000) {} # bad
590 for (my $x = 0; $x <= 10000000; ++$x) {} # good
591
592 @lines = <VERY_LARGE_FILE>; # bad
593
594 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 595 $file = join('', <FILE>); # better
e41182b5 596
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597The last two constructs may appear unintuitive to most people. The
598first repeatedly grows a string, whereas the second allocates a
599large chunk of memory in one go. On some systems, the second is
600more efficient that the first.
0a47030a 601
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602=head2 Security
603
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604Most multi-user platforms provide basic levels of security, usually
605implemented at the filesystem level. Some, however, do
a1667ba3 606not-- unfortunately. Thus the notion of user id, or "home" directory,
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607or even the state of being logged-in, may be unrecognizable on many
608platforms. If you write programs that are security-conscious, it
609is usually best to know what type of system you will be running
610under so that you can write code explicitly for that platform (or
611class of platforms).
0a47030a 612
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613Don't assume the UNIX filesystem access semantics: the operating
614system or the filesystem may be using some ACL systems, which are
615richer languages than the usual rwx. Even if the rwx exist,
616their semantics might be different.
617
618(From security viewpoint testing for permissions before attempting to
619do something is silly anyway: if one tries this, there is potential
620for race conditions-- someone or something might change the
621permissions between the permissions check and the actual operation.
622Just try the operation.)
623
624Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 625expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
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626for switching identities (or memberships).
627
628Don't assume set-uid and set-gid semantics. (And even if you do,
629think twice: set-uid and set-gid are a known can of security worms.)
630
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631=head2 Style
632
633For those times when it is necessary to have platform-specific code,
634consider keeping the platform-specific code in one place, making porting
6ab3f9cb 635to other platforms easier. Use the Config module and the special
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636variable C<$^O> to differentiate platforms, as described in
637L<"PLATFORMS">.
e41182b5 638
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639Be careful in the tests you supply with your module or programs.
640Module code may be fully portable, but its tests might not be. This
641often happens when tests spawn off other processes or call external
642programs to aid in the testing, or when (as noted above) the tests
643assume certain things about the filesystem and paths. Be careful
644not to depend on a specific output style for errors, such as when
d1be9408 645checking C<$!> after a system call. Some platforms expect a certain
b7df3edc
GS
646output format, and perl on those platforms may have been adjusted
647accordingly. Most specifically, don't anchor a regex when testing
648an error value.
e41182b5 649
0a47030a 650=head1 CPAN Testers
e41182b5 651
0a47030a
GS
652Modules uploaded to CPAN are tested by a variety of volunteers on
653different platforms. These CPAN testers are notified by mail of each
e41182b5 654new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 655this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
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656
657The purpose of the testing is twofold: one, to help developers fix any
0a47030a 658problems in their code that crop up because of lack of testing on other
b7df3edc 659platforms; two, to provide users with information about whether
0a47030a 660a given module works on a given platform.
e41182b5
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661
662=over 4
663
664=item Mailing list: cpan-testers@perl.org
665
c997b287 666=item Testing results: http://testers.cpan.org/
e41182b5
GS
667
668=back
669
e41182b5
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670=head1 PLATFORMS
671
672As of version 5.002, Perl is built with a C<$^O> variable that
673indicates the operating system it was built on. This was implemented
b7df3edc
GS
674to help speed up code that would otherwise have to C<use Config>
675and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
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676detailed information about the system, looking into C<%Config> is
677certainly recommended.
678
b7df3edc
GS
679C<%Config> cannot always be trusted, however, because it was built
680at compile time. If perl was built in one place, then transferred
681elsewhere, some values may be wrong. The values may even have been
682edited after the fact.
6ab3f9cb 683
e41182b5
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684=head2 Unix
685
686Perl works on a bewildering variety of Unix and Unix-like platforms (see
687e.g. most of the files in the F<hints/> directory in the source code kit).
688On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
689too) is determined either by lowercasing and stripping punctuation from the
690first field of the string returned by typing C<uname -a> (or a similar command)
691at the shell prompt or by testing the file system for the presence of
692uniquely named files such as a kernel or header file. Here, for example,
693are a few of the more popular Unix flavors:
e41182b5 694
b7df3edc 695 uname $^O $Config{'archname'}
6ab3f9cb 696 --------------------------------------------
b7df3edc 697 AIX aix aix
6ab3f9cb 698 BSD/OS bsdos i386-bsdos
e1516da7 699 Darwin darwin darwin
6ab3f9cb
GS
700 dgux dgux AViiON-dgux
701 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 702 FreeBSD freebsd freebsd-i386
d1e3b762 703 Linux linux arm-linux
b7df3edc 704 Linux linux i386-linux
6ab3f9cb
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705 Linux linux i586-linux
706 Linux linux ppc-linux
b7df3edc
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707 HP-UX hpux PA-RISC1.1
708 IRIX irix irix
b787fad4 709 Mac OS X darwin darwin
d1e3b762
GS
710 MachTen PPC machten powerpc-machten
711 NeXT 3 next next-fat
712 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 713 openbsd openbsd i386-openbsd
b7df3edc 714 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
715 reliantunix-n svr4 RM400-svr4
716 SCO_SV sco_sv i386-sco_sv
717 SINIX-N svr4 RM400-svr4
718 sn4609 unicos CRAY_C90-unicos
719 sn6521 unicosmk t3e-unicosmk
720 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
721 SunOS solaris sun4-solaris
722 SunOS solaris i86pc-solaris
723 SunOS4 sunos sun4-sunos
e41182b5 724
b7df3edc
GS
725Because the value of C<$Config{archname}> may depend on the
726hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 727
e41182b5
GS
728=head2 DOS and Derivatives
729
b7df3edc 730Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
731systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
732bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 733Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
734be aware that each of these file specifications may have subtle
735differences:
736
737 $filespec0 = "c:/foo/bar/file.txt";
738 $filespec1 = "c:\\foo\\bar\\file.txt";
739 $filespec2 = 'c:\foo\bar\file.txt';
740 $filespec3 = 'c:\\foo\\bar\\file.txt';
741
b7df3edc
GS
742System calls accept either C</> or C<\> as the path separator.
743However, many command-line utilities of DOS vintage treat C</> as
744the option prefix, so may get confused by filenames containing C</>.
745Aside from calling any external programs, C</> will work just fine,
746and probably better, as it is more consistent with popular usage,
747and avoids the problem of remembering what to backwhack and what
748not to.
e41182b5 749
b7df3edc
GS
750The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
751the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 752filesystems you may have to be careful about case returned with functions
e41182b5
GS
753like C<readdir> or used with functions like C<open> or C<opendir>.
754
b7df3edc
GS
755DOS also treats several filenames as special, such as AUX, PRN,
756NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
757filenames won't even work if you include an explicit directory
758prefix. It is best to avoid such filenames, if you want your code
759to be portable to DOS and its derivatives. It's hard to know what
760these all are, unfortunately.
e41182b5
GS
761
762Users of these operating systems may also wish to make use of
b7df3edc 763scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
764put wrappers around your scripts.
765
766Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
767and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
768will keep C<\n> translated as C<\012> for that filehandle. Since it is a
769no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
770that deals with binary data. That's assuming you realize in advance
771that your data is in binary. General-purpose programs should
772often assume nothing about their data.
e41182b5 773
b7df3edc 774The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
775DOSish perls are as follows:
776
67ac489e
MS
777 OS $^O $Config{archname} ID Version
778 --------------------------------------------------------
779 MS-DOS dos ?
780 PC-DOS dos ?
781 OS/2 os2 ?
782 Windows 3.1 ? ? 0 3 01
783 Windows 95 MSWin32 MSWin32-x86 1 4 00
784 Windows 98 MSWin32 MSWin32-x86 1 4 10
785 Windows ME MSWin32 MSWin32-x86 1 ?
786 Windows NT MSWin32 MSWin32-x86 2 4 xx
787 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
788 Windows NT MSWin32 MSWin32-ppc 2 4 xx
789 Windows 2000 MSWin32 MSWin32-x86 2 5 xx
790 Windows XP MSWin32 MSWin32-x86 2 ?
791 Windows CE MSWin32 ? 3
792 Cygwin cygwin ?
e41182b5 793
34aaaa84
PP
794The various MSWin32 Perl's can distinguish the OS they are running on
795via the value of the fifth element of the list returned from
796Win32::GetOSVersion(). For example:
797
798 if ($^O eq 'MSWin32') {
799 my @os_version_info = Win32::GetOSVersion();
800 print +('3.1','95','NT')[$os_version_info[4]],"\n";
801 }
802
e41182b5
GS
803Also see:
804
805=over 4
806
c997b287 807=item *
e41182b5 808
c997b287
GS
809The djgpp environment for DOS, http://www.delorie.com/djgpp/
810and L<perldos>.
e41182b5 811
c997b287 812=item *
e41182b5 813
c997b287
GS
814The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
815http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
f224927c 816ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
e41182b5 817
c997b287 818=item *
d1e3b762 819
c997b287
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820Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
821in L<perlcygwin>.
822
823=item *
824
825The C<Win32::*> modules in L<Win32>.
826
827=item *
828
829The ActiveState Pages, http://www.activestate.com/
830
831=item *
832
833The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 834as L<perlcygwin>), http://www.cygwin.com/
c997b287
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835
836=item *
837
838The U/WIN environment for Win32,
cea6626f 839http://www.research.att.com/sw/tools/uwin/
c997b287 840
cea6626f 841=item *
d1e3b762 842
cea6626f 843Build instructions for OS/2, L<perlos2>
d1e3b762 844
e41182b5
GS
845=back
846
dd9f0070 847=head2 S<Mac OS>
e41182b5
GS
848
849Any module requiring XS compilation is right out for most people, because
850MacPerl is built using non-free (and non-cheap!) compilers. Some XS
851modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 852form on CPAN.
e41182b5
GS
853
854Directories are specified as:
855
856 volume:folder:file for absolute pathnames
857 volume:folder: for absolute pathnames
858 :folder:file for relative pathnames
859 :folder: for relative pathnames
860 :file for relative pathnames
861 file for relative pathnames
862
b7df3edc 863Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 864limited to 31 characters, and may include any character except for
b7df3edc 865null and C<:>, which is reserved as the path separator.
e41182b5 866
0a47030a 867Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 868Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
869
870In the MacPerl application, you can't run a program from the command line;
871programs that expect C<@ARGV> to be populated can be edited with something
872like the following, which brings up a dialog box asking for the command
873line arguments.
874
875 if (!@ARGV) {
876 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
877 }
878
b7df3edc 879A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
880pathnames of the files dropped onto the script.
881
b7df3edc
GS
882Mac users can run programs under a type of command line interface
883under MPW (Macintosh Programmer's Workshop, a free development
884environment from Apple). MacPerl was first introduced as an MPW
885tool, and MPW can be used like a shell:
e41182b5
GS
886
887 perl myscript.plx some arguments
888
889ToolServer is another app from Apple that provides access to MPW tools
0a47030a 890from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
891C<system>, backticks, and piped C<open>.
892
893"S<Mac OS>" is the proper name for the operating system, but the value
894in C<$^O> is "MacOS". To determine architecture, version, or whether
895the application or MPW tool version is running, check:
896
897 $is_app = $MacPerl::Version =~ /App/;
898 $is_tool = $MacPerl::Version =~ /MPW/;
899 ($version) = $MacPerl::Version =~ /^(\S+)/;
900 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
901 $is_68k = $MacPerl::Architecture eq 'Mac68K';
902
b787fad4
JH
903S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
904"Classic" environment. There is no "Carbon" version of MacPerl to run
905under the primary Mac OS X environment. S<Mac OS X> and its Open Source
906version, Darwin, both run Unix perl natively.
6ab3f9cb 907
e41182b5
GS
908Also see:
909
910=over 4
911
c997b287
GS
912=item *
913
862b5365 914MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
915
916=item *
917
862b5365 918The MacPerl Pages, http://www.macperl.com/ .
e41182b5 919
c997b287 920=item *
6ab3f9cb 921
862b5365 922The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5
GS
923
924=back
925
e41182b5
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926=head2 VMS
927
c997b287 928Perl on VMS is discussed in L<perlvms> in the perl distribution.
b7df3edc 929Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
930specifications as in either of the following:
931
932 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
933 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
934
935but not a mixture of both as in:
936
937 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
938 Can't open sys$login:/login.com: file specification syntax error
939
940Interacting with Perl from the Digital Command Language (DCL) shell
941often requires a different set of quotation marks than Unix shells do.
942For example:
943
944 $ perl -e "print ""Hello, world.\n"""
945 Hello, world.
946
b7df3edc 947There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
948you are so inclined. For example:
949
950 $ write sys$output "Hello from DCL!"
951 $ if p1 .eqs. ""
952 $ then perl -x 'f$environment("PROCEDURE")
953 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
954 $ deck/dollars="__END__"
955 #!/usr/bin/perl
956
957 print "Hello from Perl!\n";
958
959 __END__
960 $ endif
961
962Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 963perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5
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964
965Filenames are in the format "name.extension;version". The maximum
966length for filenames is 39 characters, and the maximum length for
967extensions is also 39 characters. Version is a number from 1 to
96832767. Valid characters are C</[A-Z0-9$_-]/>.
969
b7df3edc 970VMS's RMS filesystem is case-insensitive and does not preserve case.
e41182b5 971C<readdir> returns lowercased filenames, but specifying a file for
b7df3edc 972opening remains case-insensitive. Files without extensions have a
e41182b5 973trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
974will return F<a.> (though that file could be opened with
975C<open(FH, 'A')>).
e41182b5 976
f34d0673 977RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
CN
978(allowing 16 levels overall) prior to VMS 7.2. Hence
979C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
980C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
981have to take this into account, but at least they can refer to the former
f34d0673 982as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 983
6ab3f9cb 984The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
985process on VMS, is a pure Perl module that can easily be installed on
986non-VMS platforms and can be helpful for conversions to and from RMS
987native formats.
e41182b5 988
5e12dbfa
PP
989What C<\n> represents depends on the type of file opened. It usually
990represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
991C<\000>, C<\040>, or nothing depending on the file organiztion and
992record format. The VMS::Stdio module provides access to the
993special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
994
995TCP/IP stacks are optional on VMS, so socket routines might not be
996implemented. UDP sockets may not be supported.
997
998The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
999that you are running on without resorting to loading all of C<%Config>
1000you can examine the content of the C<@INC> array like so:
1001
1002 if (grep(/VMS_AXP/, @INC)) {
1003 print "I'm on Alpha!\n";
6ab3f9cb 1004
e41182b5
GS
1005 } elsif (grep(/VMS_VAX/, @INC)) {
1006 print "I'm on VAX!\n";
6ab3f9cb 1007
e41182b5
GS
1008 } else {
1009 print "I'm not so sure about where $^O is...\n";
1010 }
1011
b7df3edc
GS
1012On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
1013logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 1014calls to C<localtime> are adjusted to count offsets from
b7df3edc 101501-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1016
e41182b5
GS
1017Also see:
1018
1019=over 4
1020
c997b287
GS
1021=item *
1022
1023F<README.vms> (installed as L<README_vms>), L<perlvms>
1024
1025=item *
1026
1027vmsperl list, majordomo@perl.org
e41182b5 1028
c997b287 1029(Put the words C<subscribe vmsperl> in message body.)
e41182b5 1030
c997b287 1031=item *
e41182b5 1032
c997b287 1033vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1034
1035=back
1036
495c5fdc
GP
1037=head2 VOS
1038
9a997319
JH
1039Perl on VOS is discussed in F<README.vos> in the perl distribution
1040(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1041Unix-style file specifications as in either of the following:
495c5fdc 1042
cc07ed0b
PG
1043 C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
1044 C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
495c5fdc
GP
1045
1046or even a mixture of both as in:
1047
cc07ed0b 1048 C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
495c5fdc 1049
b7df3edc 1050Even though VOS allows the slash character to appear in object
495c5fdc
GP
1051names, because the VOS port of Perl interprets it as a pathname
1052delimiting character, VOS files, directories, or links whose names
1053contain a slash character cannot be processed. Such files must be
a3dfe201
GS
1054renamed before they can be processed by Perl. Note that VOS limits
1055file names to 32 or fewer characters.
495c5fdc 1056
cc07ed0b
PG
1057Perl on VOS can be built using two different compilers and two different
1058versions of the POSIX runtime. The recommended method for building full
1059Perl is with the GNU C compiler and the generally-available version of
1060VOS POSIX support. See F<README.vos> (installed as L<perlvos>) for
1061restrictions that apply when Perl is built using the VOS Standard C
1062compiler or the alpha version of VOS POSIX support.
495c5fdc
GP
1063
1064The value of C<$^O> on VOS is "VOS". To determine the architecture that
1065you are running on without resorting to loading all of C<%Config> you
c997b287 1066can examine the content of the @INC array like so:
495c5fdc 1067
24e8e380 1068 if ($^O =~ /VOS/) {
495c5fdc
GP
1069 print "I'm on a Stratus box!\n";
1070 } else {
1071 print "I'm not on a Stratus box!\n";
1072 die;
1073 }
1074
1075 if (grep(/860/, @INC)) {
1076 print "This box is a Stratus XA/R!\n";
6ab3f9cb 1077
495c5fdc 1078 } elsif (grep(/7100/, @INC)) {
24e8e380 1079 print "This box is a Stratus HP 7100 or 8xxx!\n";
6ab3f9cb 1080
495c5fdc 1081 } elsif (grep(/8000/, @INC)) {
24e8e380 1082 print "This box is a Stratus HP 8xxx!\n";
6ab3f9cb 1083
495c5fdc 1084 } else {
24e8e380 1085 print "This box is a Stratus 68K!\n";
495c5fdc
GP
1086 }
1087
1088Also see:
1089
1090=over 4
1091
c997b287 1092=item *
495c5fdc 1093
cc07ed0b 1094F<README.vos> (installed as L<perlvos>)
c997b287
GS
1095
1096=item *
1097
1098The VOS mailing list.
495c5fdc
GP
1099
1100There is no specific mailing list for Perl on VOS. You can post
1101comments to the comp.sys.stratus newsgroup, or subscribe to the general
cc07ed0b 1102Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
495c5fdc
GP
1103the message body to majordomo@list.stratagy.com.
1104
c997b287
GS
1105=item *
1106
cc07ed0b 1107VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
495c5fdc
GP
1108
1109=back
1110
e41182b5
GS
1111=head2 EBCDIC Platforms
1112
1113Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1114AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1115Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1116Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1117systems). On the mainframe perl currently works under the "Unix system
1118services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1119the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
c997b287 1120See L<perlos390> for details.
e41182b5 1121
7c5ffed3
JH
1122As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1123sub-systems do not support the C<#!> shebang trick for script invocation.
1124Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1125similar to the following simple script:
e41182b5
GS
1126
1127 : # use perl
1128 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1129 if 0;
1130 #!/usr/local/bin/perl # just a comment really
1131
1132 print "Hello from perl!\n";
1133
d1e3b762
GS
1134OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1135Calls to C<system> and backticks can use POSIX shell syntax on all
1136S/390 systems.
1137
b7df3edc 1138On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1139to wrap your perl scripts in a CL procedure to invoke them like so:
1140
1141 BEGIN
1142 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1143 ENDPGM
1144
1145This will invoke the perl script F<hello.pl> in the root of the
1146QOpenSys file system. On the AS/400 calls to C<system> or backticks
1147must use CL syntax.
1148
e41182b5 1149On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1150an effect on what happens with some perl functions (such as C<chr>,
1151C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1152well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1153and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1154(see L<"Newlines">).
e41182b5 1155
b7df3edc
GS
1156Fortunately, most web servers for the mainframe will correctly
1157translate the C<\n> in the following statement to its ASCII equivalent
1158(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1159
1160 print "Content-type: text/html\r\n\r\n";
1161
d1e3b762 1162The values of C<$^O> on some of these platforms includes:
e41182b5 1163
d1e3b762
GS
1164 uname $^O $Config{'archname'}
1165 --------------------------------------------
1166 OS/390 os390 os390
1167 OS400 os400 os400
1168 POSIX-BC posix-bc BS2000-posix-bc
1169 VM/ESA vmesa vmesa
3c075c7d 1170
e41182b5
GS
1171Some simple tricks for determining if you are running on an EBCDIC
1172platform could include any of the following (perhaps all):
1173
1174 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1175
1176 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1177
1178 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1179
b7df3edc 1180One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1181of punctuation characters since these may differ from code page to code
1182page (and once your module or script is rumoured to work with EBCDIC,
1183folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1184
1185Also see:
1186
1187=over 4
1188
c997b287
GS
1189=item *
1190
1191*
d1e3b762 1192
dc5c060f 1193L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1194L<perlebcdic>.
c997b287
GS
1195
1196=item *
e41182b5
GS
1197
1198The perl-mvs@perl.org list is for discussion of porting issues as well as
1199general usage issues for all EBCDIC Perls. Send a message body of
1200"subscribe perl-mvs" to majordomo@perl.org.
1201
c997b287
GS
1202=item *
1203
1204AS/400 Perl information at
b1866b2d 1205http://as400.rochester.ibm.com/
d1e3b762 1206as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1207
1208=back
1209
b8099c3d
CN
1210=head2 Acorn RISC OS
1211
b7df3edc
GS
1212Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1213Unix, and because Unix filename emulation is turned on by default,
1214most simple scripts will probably work "out of the box". The native
6ab3f9cb 1215filesystem is modular, and individual filesystems are free to be
0a47030a 1216case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1217native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1218names are silently truncated to fit. Scripts should be aware that the
1219standard filesystem currently has a name length limit of B<10>
1220characters, with up to 77 items in a directory, but other filesystems
0a47030a 1221may not impose such limitations.
b8099c3d
CN
1222
1223Native filenames are of the form
1224
6ab3f9cb 1225 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1226
b8099c3d
CN
1227where
1228
1229 Special_Field is not usually present, but may contain . and $ .
1230 Filesystem =~ m|[A-Za-z0-9_]|
1231 DsicName =~ m|[A-Za-z0-9_/]|
1232 $ represents the root directory
1233 . is the path separator
1234 @ is the current directory (per filesystem but machine global)
1235 ^ is the parent directory
1236 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1237
1238The default filename translation is roughly C<tr|/.|./|;>
1239
6ab3f9cb 1240Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1241the second stage of C<$> interpolation in regular expressions will fall
1242foul of the C<$.> if scripts are not careful.
1243
1244Logical paths specified by system variables containing comma-separated
b7df3edc 1245search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1246filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1247C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1248Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1249C<System$Path> contains a single item list. The filesystem will also
1250expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1251C<< <System$Dir>.Modules >> would look for the file
0a47030a 1252S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1253that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1254be protected when C<open> is used for input.
b8099c3d
CN
1255
1256Because C<.> was in use as a directory separator and filenames could not
1257be assumed to be unique after 10 characters, Acorn implemented the C
1258compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1259filenames specified in source code and store the respective files in
b7df3edc 1260subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1261
1262 foo.h h.foo
1263 C:foo.h C:h.foo (logical path variable)
1264 sys/os.h sys.h.os (C compiler groks Unix-speak)
1265 10charname.c c.10charname
1266 10charname.o o.10charname
1267 11charname_.c c.11charname (assuming filesystem truncates at 10)
1268
1269The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1270that this sort of translation is required, and it allows a user-defined list
1271of known suffixes that it will transpose in this fashion. This may
1272seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1273and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1274C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1275C<.>'s in filenames are translated to C</>.
0a47030a 1276
b7df3edc 1277As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1278the convention is that program specific environment variables are of the
6ab3f9cb
GS
1279form C<Program$Name>. Each filesystem maintains a current directory,
1280and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1281directory. Consequently, sociable programs don't change the current
1282directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1283assume that they can spawn a child process which can change the current
1284directory without affecting its parent (and everyone else for that
1285matter).
1286
b7df3edc
GS
1287Because native operating system filehandles are global and are currently
1288allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1289library emulates Unix filehandles. Consequently, you can't rely on
1290passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1291
1292The desire of users to express filenames of the form
c47ff5f1 1293C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1294too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1295assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1296reference to an environment variable, whereas anything else involving
c47ff5f1 1297C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1298right. Of course, the problem remains that scripts cannot rely on any
1299Unix tools being available, or that any tools found have Unix-like command
1300line arguments.
1301
b7df3edc
GS
1302Extensions and XS are, in theory, buildable by anyone using free
1303tools. In practice, many don't, as users of the Acorn platform are
1304used to binary distributions. MakeMaker does run, but no available
1305make currently copes with MakeMaker's makefiles; even if and when
1306this should be fixed, the lack of a Unix-like shell will cause
1307problems with makefile rules, especially lines of the form C<cd
1308sdbm && make all>, and anything using quoting.
b8099c3d
CN
1309
1310"S<RISC OS>" is the proper name for the operating system, but the value
1311in C<$^O> is "riscos" (because we don't like shouting).
1312
e41182b5
GS
1313=head2 Other perls
1314
b7df3edc
GS
1315Perl has been ported to many platforms that do not fit into any of
1316the categories listed above. Some, such as AmigaOS, Atari MiNT,
1317BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1318into the standard Perl source code kit. You may need to see the
1319F<ports/> directory on CPAN for information, and possibly binaries,
1320for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1321Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1322fall under the Unix category, but we are not a standards body.)
e41182b5 1323
d1e3b762
GS
1324Some approximate operating system names and their C<$^O> values
1325in the "OTHER" category include:
1326
1327 OS $^O $Config{'archname'}
1328 ------------------------------------------
1329 Amiga DOS amigaos m68k-amigos
1330 MPE/iX mpeix PA-RISC1.1
1331
e41182b5
GS
1332See also:
1333
1334=over 4
1335
c997b287
GS
1336=item *
1337
1338Amiga, F<README.amiga> (installed as L<perlamiga>).
1339
1340=item *
d1e3b762 1341
c997b287
GS
1342Atari, F<README.mint> and Guido Flohr's web page
1343http://stud.uni-sb.de/~gufl0000/
e41182b5 1344
c997b287 1345=item *
d1e3b762 1346
c997b287 1347Be OS, F<README.beos>
e41182b5 1348
c997b287
GS
1349=item *
1350
1351HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1352http://www.bixby.org/mark/perlix.html
c997b287
GS
1353
1354=item *
e41182b5 1355
6ab3f9cb 1356A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1357precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1358as well as from CPAN.
e41182b5 1359
13a2d996 1360=item *
c997b287
GS
1361
1362Plan 9, F<README.plan9>
d1e3b762 1363
e41182b5
GS
1364=back
1365
e41182b5
GS
1366=head1 FUNCTION IMPLEMENTATIONS
1367
b7df3edc
GS
1368Listed below are functions that are either completely unimplemented
1369or else have been implemented differently on various platforms.
1370Following each description will be, in parentheses, a list of
1371platforms that the description applies to.
e41182b5 1372
b7df3edc
GS
1373The list may well be incomplete, or even wrong in some places. When
1374in doubt, consult the platform-specific README files in the Perl
1375source distribution, and any other documentation resources accompanying
1376a given port.
e41182b5 1377
0a47030a 1378Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1379
b7df3edc
GS
1380For many functions, you can also query C<%Config>, exported by
1381default from the Config module. For example, to check whether the
1382platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1383L<Config> for a full description of available variables.
e41182b5
GS
1384
1385=head2 Alphabetical Listing of Perl Functions
1386
1387=over 8
1388
1389=item -X FILEHANDLE
1390
1391=item -X EXPR
1392
1393=item -X
1394
b7df3edc 1395C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1396and applications are executable, and there are no uid/gid
b7df3edc 1397considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1398
b7df3edc
GS
1399C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1400which may not reflect UIC-based file protections. (VMS)
e41182b5 1401
b8099c3d
CN
1402C<-s> returns the size of the data fork, not the total size of data fork
1403plus resource fork. (S<Mac OS>).
1404
1405C<-s> by name on an open file will return the space reserved on disk,
1406rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1407current size. (S<RISC OS>)
b8099c3d 1408
e41182b5 1409C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1410C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1411
1412C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1413(S<Mac OS>)
1414
1415C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1416(Win32, VMS, S<RISC OS>)
e41182b5
GS
1417
1418C<-d> is true if passed a device spec without an explicit directory.
1419(VMS)
1420
1421C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1422with foreign characters; this is the case will all platforms, but may
b7df3edc 1423affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1424
1425C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1426suffixes. C<-S> is meaningless. (Win32)
e41182b5 1427
b8099c3d
CN
1428C<-x> (or C<-X>) determine if a file has an executable file type.
1429(S<RISC OS>)
1430
63f87e49
GS
1431=item alarm SECONDS
1432
1433=item alarm
1434
1435Not implemented. (Win32)
1436
e41182b5
GS
1437=item binmode FILEHANDLE
1438
b7df3edc 1439Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1440
1441Reopens file and restores pointer; if function fails, underlying
1442filehandle may be closed, or pointer may be in a different position.
1443(VMS)
1444
1445The value returned by C<tell> may be affected after the call, and
1446the filehandle may be flushed. (Win32)
1447
1448=item chmod LIST
1449
b7df3edc 1450Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1451locking/unlocking the file. (S<Mac OS>)
1452
1453Only good for changing "owner" read-write access, "group", and "other"
1454bits are meaningless. (Win32)
1455
b8099c3d
CN
1456Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1457
495c5fdc
GP
1458Access permissions are mapped onto VOS access-control list changes. (VOS)
1459
4e51f8e4 1460The actual permissions set depend on the value of the C<CYGWIN>
789f0d36 1461in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1462
e41182b5
GS
1463=item chown LIST
1464
495c5fdc 1465Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1466
1467Does nothing, but won't fail. (Win32)
1468
1469=item chroot FILENAME
1470
1471=item chroot
1472
7c5ffed3 1473Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1474
1475=item crypt PLAINTEXT,SALT
1476
1477May not be available if library or source was not provided when building
b8099c3d 1478perl. (Win32)
e41182b5 1479
495c5fdc
GP
1480Not implemented. (VOS)
1481
e41182b5
GS
1482=item dbmclose HASH
1483
495c5fdc 1484Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1485
1486=item dbmopen HASH,DBNAME,MODE
1487
495c5fdc 1488Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1489
1490=item dump LABEL
1491
b8099c3d 1492Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1493
1494Not implemented. (Win32)
1495
b8099c3d 1496Invokes VMS debugger. (VMS)
e41182b5
GS
1497
1498=item exec LIST
1499
1500Not implemented. (S<Mac OS>)
1501
7c5ffed3 1502Implemented via Spawn. (VM/ESA)
3c075c7d 1503
0f897271
GS
1504Does not automatically flush output handles on some platforms.
1505(SunOS, Solaris, HP-UX)
1506
fe12c0e8
MS
1507=item exit EXPR
1508
1509=item exit
1510
1511Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1512mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1513with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1514function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1515(C<1>); this mapping cannot be overridden. Any other argument to exit()
1516is used directly as Perl's exit status. (VMS)
1517
e41182b5
GS
1518=item fcntl FILEHANDLE,FUNCTION,SCALAR
1519
1520Not implemented. (Win32, VMS)
1521
1522=item flock FILEHANDLE,OPERATION
1523
495c5fdc 1524Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1525
1526Available only on Windows NT (not on Windows 95). (Win32)
1527
1528=item fork
1529
0f897271
GS
1530Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1531
1532Emulated using multiple interpreters. See L<perlfork>. (Win32)
1533
1534Does not automatically flush output handles on some platforms.
1535(SunOS, Solaris, HP-UX)
e41182b5
GS
1536
1537=item getlogin
1538
b8099c3d 1539Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1540
1541=item getpgrp PID
1542
495c5fdc 1543Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1544
1545=item getppid
1546
b8099c3d 1547Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1548
1549=item getpriority WHICH,WHO
1550
7c5ffed3 1551Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1552
1553=item getpwnam NAME
1554
1555Not implemented. (S<Mac OS>, Win32)
1556
b8099c3d
CN
1557Not useful. (S<RISC OS>)
1558
e41182b5
GS
1559=item getgrnam NAME
1560
b8099c3d 1561Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1562
1563=item getnetbyname NAME
1564
1565Not implemented. (S<Mac OS>, Win32, Plan9)
1566
1567=item getpwuid UID
1568
1569Not implemented. (S<Mac OS>, Win32)
1570
b8099c3d
CN
1571Not useful. (S<RISC OS>)
1572
e41182b5
GS
1573=item getgrgid GID
1574
b8099c3d 1575Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1576
1577=item getnetbyaddr ADDR,ADDRTYPE
1578
1579Not implemented. (S<Mac OS>, Win32, Plan9)
1580
1581=item getprotobynumber NUMBER
1582
1583Not implemented. (S<Mac OS>)
1584
1585=item getservbyport PORT,PROTO
1586
1587Not implemented. (S<Mac OS>)
1588
1589=item getpwent
1590
7c5ffed3 1591Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1592
1593=item getgrent
1594
7c5ffed3 1595Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5
GS
1596
1597=item gethostent
1598
1599Not implemented. (S<Mac OS>, Win32)
1600
1601=item getnetent
1602
1603Not implemented. (S<Mac OS>, Win32, Plan9)
1604
1605=item getprotoent
1606
1607Not implemented. (S<Mac OS>, Win32, Plan9)
1608
1609=item getservent
1610
1611Not implemented. (Win32, Plan9)
1612
e41182b5
GS
1613=item sethostent STAYOPEN
1614
b8099c3d 1615Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1616
1617=item setnetent STAYOPEN
1618
b8099c3d 1619Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1620
1621=item setprotoent STAYOPEN
1622
b8099c3d 1623Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1624
1625=item setservent STAYOPEN
1626
b8099c3d 1627Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1628
1629=item endpwent
1630
a3dfe201 1631Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1632
1633=item endgrent
1634
a3dfe201 1635Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1636
1637=item endhostent
1638
1639Not implemented. (S<Mac OS>, Win32)
1640
1641=item endnetent
1642
1643Not implemented. (S<Mac OS>, Win32, Plan9)
1644
1645=item endprotoent
1646
1647Not implemented. (S<Mac OS>, Win32, Plan9)
1648
1649=item endservent
1650
1651Not implemented. (Plan9, Win32)
1652
1653=item getsockopt SOCKET,LEVEL,OPTNAME
1654
97c10e77 1655Not implemented. (Plan9)
e41182b5
GS
1656
1657=item glob EXPR
1658
1659=item glob
1660
63f87e49
GS
1661This operator is implemented via the File::Glob extension on most
1662platforms. See L<File::Glob> for portability information.
b8099c3d 1663
e41182b5
GS
1664=item ioctl FILEHANDLE,FUNCTION,SCALAR
1665
1666Not implemented. (VMS)
1667
1668Available only for socket handles, and it does what the ioctlsocket() call
1669in the Winsock API does. (Win32)
1670
b8099c3d
CN
1671Available only for socket handles. (S<RISC OS>)
1672
b350dd2f 1673=item kill SIGNAL, LIST
e41182b5 1674
862b5365
JH
1675C<kill(0, LIST)> is implemented for the sake of taint checking;
1676use with other signals is unimplemented. (S<Mac OS>)
1677
1678Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1679
63f87e49
GS
1680C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1681a signal to the identified process like it does on Unix platforms.
1682Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1683and makes it exit immediately with exit status $sig. As in Unix, if
1684$sig is 0 and the specified process exists, it returns true without
1685actually terminating it. (Win32)
e41182b5
GS
1686
1687=item link OLDFILE,NEWFILE
1688
a3dfe201 1689Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
e41182b5 1690
433acd8a
JH
1691Link count not updated because hard links are not quite that hard
1692(They are sort of half-way between hard and soft links). (AmigaOS)
1693
a3dfe201
GS
1694Hard links are implemented on Win32 (Windows NT and Windows 2000)
1695under NTFS only.
1696
e41182b5
GS
1697=item lstat FILEHANDLE
1698
1699=item lstat EXPR
1700
1701=item lstat
1702
b8099c3d 1703Not implemented. (VMS, S<RISC OS>)
e41182b5 1704
63f87e49 1705Return values (especially for device and inode) may be bogus. (Win32)
e41182b5
GS
1706
1707=item msgctl ID,CMD,ARG
1708
1709=item msgget KEY,FLAGS
1710
1711=item msgsnd ID,MSG,FLAGS
1712
1713=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1714
495c5fdc 1715Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1716
1717=item open FILEHANDLE,EXPR
1718
1719=item open FILEHANDLE
1720
b7df3edc 1721The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1722(S<Mac OS>)
1723
c47ff5f1 1724open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1725
0f897271
GS
1726Opening a process does not automatically flush output handles on some
1727platforms. (SunOS, Solaris, HP-UX)
1728
e41182b5
GS
1729=item pipe READHANDLE,WRITEHANDLE
1730
433acd8a
JH
1731Very limited functionality. (MiNT)
1732
e41182b5
GS
1733=item readlink EXPR
1734
1735=item readlink
1736
b8099c3d 1737Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1738
1739=item select RBITS,WBITS,EBITS,TIMEOUT
1740
689c5c24 1741Only implemented on sockets. (Win32, VMS)
e41182b5 1742
b8099c3d
CN
1743Only reliable on sockets. (S<RISC OS>)
1744
76e05f0b 1745Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1746
e41182b5
GS
1747=item semctl ID,SEMNUM,CMD,ARG
1748
1749=item semget KEY,NSEMS,FLAGS
1750
1751=item semop KEY,OPSTRING
1752
495c5fdc 1753Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1754
a3dfe201
GS
1755=item setgrent
1756
74555b7a 1757Not implemented. (S<Mac OS>, MPE/iX, VMS, Win32, VMS, S<RISC OS>)
a3dfe201 1758
e41182b5
GS
1759=item setpgrp PID,PGRP
1760
495c5fdc 1761Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1762
1763=item setpriority WHICH,WHO,PRIORITY
1764
495c5fdc 1765Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1766
a3dfe201
GS
1767=item setpwent
1768
74555b7a 1769Not implemented. (S<Mac OS>, MPE/iX, Win32, S<RISC OS>)
a3dfe201 1770
e41182b5
GS
1771=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1772
97c10e77 1773Not implemented. (Plan9)
e41182b5
GS
1774
1775=item shmctl ID,CMD,ARG
1776
1777=item shmget KEY,SIZE,FLAGS
1778
1779=item shmread ID,VAR,POS,SIZE
1780
1781=item shmwrite ID,STRING,POS,SIZE
1782
495c5fdc 1783Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1784
80cbd5ad
JH
1785=item sockatmark SOCKET
1786
1787A relatively recent addition to socket functions, may not
1788be implemented even in UNIX platforms.
1789
e41182b5
GS
1790=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1791
862b5365 1792Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1793
1794=item stat FILEHANDLE
1795
1796=item stat EXPR
1797
1798=item stat
1799
d62e1b7f
JH
1800Platforms that do not have rdev, blksize, or blocks will return these
1801as '', so numeric comparison or manipulation of these fields may cause
1802'not numeric' warnings.
1803
e41182b5 1804mtime and atime are the same thing, and ctime is creation time instead of
3f1f789b
JH
1805inode change time. (S<Mac OS>).
1806
1807ctime not supported on UFS (S<Mac OS X>).
e41182b5 1808
95a3fe12
MS
1809ctime is creation time instead of inode change time (Win32).
1810
e41182b5
GS
1811device and inode are not meaningful. (Win32)
1812
1813device and inode are not necessarily reliable. (VMS)
1814
b8099c3d
CN
1815mtime, atime and ctime all return the last modification time. Device and
1816inode are not necessarily reliable. (S<RISC OS>)
1817
d62e1b7f
JH
1818dev, rdev, blksize, and blocks are not available. inode is not
1819meaningful and will differ between stat calls on the same file. (os2)
1820
73e9292c
JH
1821some versions of cygwin when doing a stat("foo") and if not finding it
1822may then attempt to stat("foo.exe") (Cygwin)
1823
e41182b5
GS
1824=item symlink OLDFILE,NEWFILE
1825
b8099c3d 1826Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1827
1828=item syscall LIST
1829
7c5ffed3 1830Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1831
f34d0673
GS
1832=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1833
dd9f0070 1834The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1835numeric values on some systems. The flags exported by C<Fcntl>
1836(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 1837OS>, OS/390, VM/ESA)
f34d0673 1838
e41182b5
GS
1839=item system LIST
1840
9d6eb86e 1841In general, do not assume the UNIX/POSIX semantics that you can shift
7717d0e7 1842C<$?> right by eight to get the exit value, or that C<$? & 127>
9d6eb86e
JH
1843would give you the number of the signal that terminated the program,
1844or that C<$? & 128> would test true if the program was terminated by a
1845coredump. Instead, use the POSIX W*() interfaces: for example, use
74555b7a
PP
1846WIFEXITED($?) and WEXITVALUE($?) to test for a normal exit and the exit
1847value, WIFSIGNALED($?) and WTERMSIG($?) for a signal exit and the
7717d0e7 1848signal. Core dumping is not a portable concept, so there's no portable
9d6eb86e
JH
1849way to test for that.
1850
e41182b5
GS
1851Only implemented if ToolServer is installed. (S<Mac OS>)
1852
1853As an optimization, may not call the command shell specified in
b7df3edc 1854C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
1855process and immediately returns its process designator, without
1856waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
1857in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1858by setting $? to "255 << 8". C<$?> is set in a way compatible with
1859Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1860as described in the documentation). (Win32)
e41182b5 1861
b8099c3d
CN
1862There is no shell to process metacharacters, and the native standard is
1863to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 1864program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
1865the run time library of the spawned program. C<system> I<list> will call
1866the Unix emulation library's C<exec> emulation, which attempts to provide
1867emulation of the stdin, stdout, stderr in force in the parent, providing
1868the child program uses a compatible version of the emulation library.
1869I<scalar> will call the native command line direct and no such emulation
1870of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1871
433acd8a
JH
1872Far from being POSIX compliant. Because there may be no underlying
1873/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 1874first token in its argument string. Handles basic redirection
c47ff5f1 1875("<" or ">") on its own behalf. (MiNT)
433acd8a 1876
0f897271
GS
1877Does not automatically flush output handles on some platforms.
1878(SunOS, Solaris, HP-UX)
1879
9bc98430
CB
1880The return value is POSIX-like (shifted up by 8 bits), which only allows
1881room for a made-up value derived from the severity bits of the native
188232-bit condition code (unless overridden by C<use vmsish 'status'>).
1883For more details see L<perlvms/$?>. (VMS)
1884
e41182b5
GS
1885=item times
1886
1887Only the first entry returned is nonzero. (S<Mac OS>)
1888
63f87e49
GS
1889"cumulative" times will be bogus. On anything other than Windows NT
1890or Windows 2000, "system" time will be bogus, and "user" time is
1891actually the time returned by the clock() function in the C runtime
1892library. (Win32)
e41182b5 1893
b8099c3d
CN
1894Not useful. (S<RISC OS>)
1895
e41182b5
GS
1896=item truncate FILEHANDLE,LENGTH
1897
1898=item truncate EXPR,LENGTH
1899
6d738113 1900Not implemented. (Older versions of VMS)
e41182b5 1901
495c5fdc
GP
1902Truncation to zero-length only. (VOS)
1903
4cfdb94f 1904If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 1905mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
1906or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1907should not be held open elsewhere. (Win32)
1908
e41182b5
GS
1909=item umask EXPR
1910
1911=item umask
1912
1913Returns undef where unavailable, as of version 5.005.
1914
b7df3edc
GS
1915C<umask> works but the correct permissions are set only when the file
1916is finally closed. (AmigaOS)
433acd8a 1917
e41182b5
GS
1918=item utime LIST
1919
15c65113 1920Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1921
322422de
GS
1922May not behave as expected. Behavior depends on the C runtime
1923library's implementation of utime(), and the filesystem being
1924used. The FAT filesystem typically does not support an "access
1925time" field, and it may limit timestamps to a granularity of
1926two seconds. (Win32)
e41182b5
GS
1927
1928=item wait
1929
1930=item waitpid PID,FLAGS
1931
495c5fdc 1932Not implemented. (S<Mac OS>, VOS)
e41182b5
GS
1933
1934Can only be applied to process handles returned for processes spawned
a6f858fb 1935using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 1936
b8099c3d
CN
1937Not useful. (S<RISC OS>)
1938
e41182b5
GS
1939=back
1940
b8099c3d
CN
1941=head1 CHANGES
1942
1943=over 4
1944
fd46a41b
JH
1945=item v1.48, 02 February 2001
1946
1947Various updates from perl5-porters over the past year, supported
1948platforms update from Jarkko Hietaniemi.
1949
c997b287
GS
1950=item v1.47, 22 March 2000
1951
1952Various cleanups from Tom Christiansen, including migration of
1953long platform listings from L<perl>.
1954
56d7751a
GS
1955=item v1.46, 12 February 2000
1956
1957Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1958
0cc436d0
GS
1959=item v1.45, 20 December 1999
1960
1961Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1962
d1e3b762
GS
1963=item v1.44, 19 July 1999
1964
1965A bunch of updates from Peter Prymmer for C<$^O> values,
1966endianness, File::Spec, VMS, BS2000, OS/400.
1967
b7df3edc
GS
1968=item v1.43, 24 May 1999
1969
1970Added a lot of cleaning up from Tom Christiansen.
1971
19799a22 1972=item v1.42, 22 May 1999
b7df3edc 1973
19799a22 1974Added notes about tests, sprintf/printf, and epoch offsets.
b7df3edc 1975
6ab3f9cb
GS
1976=item v1.41, 19 May 1999
1977
1978Lots more little changes to formatting and content.
1979
d1e3b762 1980Added a bunch of C<$^O> and related values
6ab3f9cb
GS
1981for various platforms; fixed mail and web addresses, and added
1982and changed miscellaneous notes. (Peter Prymmer)
1983
1984=item v1.40, 11 April 1999
1985
1986Miscellaneous changes.
1987
1988=item v1.39, 11 February 1999
2ee0eb3c
CN
1989
1990Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1991note about newlines added.
1992
9b63e9ec
CN
1993=item v1.38, 31 December 1998
1994
1995More changes from Jarkko.
1996
3c075c7d
CN
1997=item v1.37, 19 December 1998
1998
1999More minor changes. Merge two separate version 1.35 documents.
2000
2001=item v1.36, 9 September 1998
2002
2003Updated for Stratus VOS. Also known as version 1.35.
2004
2005=item v1.35, 13 August 1998
495c5fdc 2006
3c075c7d
CN
2007Integrate more minor changes, plus addition of new sections under
2008L<"ISSUES">: L<"Numbers endianness and Width">,
2009L<"Character sets and character encoding">,
2010L<"Internationalisation">.
495c5fdc 2011
3c075c7d 2012=item v1.33, 06 August 1998
0a47030a
GS
2013
2014Integrate more minor changes.
2015
3c075c7d 2016=item v1.32, 05 August 1998
dd9f0070
CN
2017
2018Integrate more minor changes.
2019
3c075c7d 2020=item v1.30, 03 August 1998
b8099c3d
CN
2021
2022Major update for RISC OS, other minor changes.
2023
3c075c7d 2024=item v1.23, 10 July 1998
b8099c3d
CN
2025
2026First public release with perl5.005.
2027
2028=back
e41182b5 2029
ba58ab26
JH
2030=head1 Supported Platforms
2031
9ca74005
JH
2032As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
2033platforms are able to build Perl from the standard source code
a93751fa 2034distribution available at http://www.cpan.org/src/index.html
ba58ab26
JH
2035
2036 AIX
fd46a41b 2037 AmigaOS
b787fad4 2038 Darwin (Mac OS X)
fd46a41b 2039 DG/UX
ba58ab26 2040 DOS DJGPP 1)
fd46a41b 2041 DYNIX/ptx
2585f9a3 2042 EPOC R5
ba58ab26
JH
2043 FreeBSD
2044 HP-UX
2045 IRIX
2046 Linux
ba58ab26 2047 MachTen
fd46a41b
JH
2048 MacOS Classic 2)
2049 NonStop-UX
2050 ReliantUNIX (SINIX)
ba58ab26 2051 OpenBSD
fd46a41b 2052 OpenVMS (VMS)
ba58ab26 2053 OS/2
fd46a41b 2054 OS X
ba58ab26 2055 QNX
ba58ab26 2056 Solaris
fd46a41b 2057 Tru64 UNIX (DEC OSF/1, Digital UNIX)
ba58ab26
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2058 UNICOS
2059 UNICOS/mk
ba58ab26 2060 VOS
fd46a41b 2061 Win32/NT/2K 3)
ba58ab26
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2062
2063 1) in DOS mode either the DOS or OS/2 ports can be used
fd46a41b
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2064 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
2065 the source does work with 5.6.1, but additional MacOS specific
862b5365
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2066 source code is needed for a complete build. See the web
2067 site http://dev.macperl.org/ for more information.
fd46a41b 2068 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
ba58ab26 2069
9ca74005
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2070The following platforms worked for the previous releases (5.6.0 and 5.7.0),
2071but we did not manage to test these in time for the 5.7.1 release.
2072There is a very good chance that these will work fine with the 5.7.1.
ba58ab26 2073
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2074 DomainOS
2075 Hurd
fd46a41b
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2076 LynxOS
2077 MinGW
2078 MPE/iX
2079 NetBSD
ba58ab26 2080 PowerMAX
fd46a41b 2081 SCO SV
ba58ab26 2082 SunOS
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2083 SVR4
2084 Unixware
2085 Windows 3.1
2086 Windows 95
2087 Windows 98
2088 Windows Me
ba58ab26 2089
fd46a41b 2090The following platform worked for the 5.005_03 major release but not
9ca74005
JH
2091for 5.6.0. Standardization on UTF-8 as the internal string
2092representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
2093EBCDIC platform. While Perl 5.7.1 will build on this platform some
fd46a41b 2094regression tests may fail and the C<use utf8;> pragma typically
9ca74005 2095introduces text handling errors.
ba58ab26 2096
fd46a41b 2097 OS/390 1)
ba58ab26 2098
fd46a41b 2099 1) previously known as MVS, about to become z/OS.
ba58ab26 2100
fd46a41b 2101Strongly related to the OS/390 platform by also being EBCDIC-based
ba58ab26
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2102mainframe platforms are the following platforms:
2103
fd46a41b 2104 POSIX-BC (BS2000)
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2105 VM/ESA
2106
fd46a41b
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2107These are also expected to work, albeit with no UTF-8 support, under 5.6.1
2108for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
2109for more details.
ba58ab26
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2110
2111The following platforms have been known to build Perl from source in
fd46a41b
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2112the past (5.005_03 and earlier), but we haven't been able to verify
2113their status for the current release, either because the
2114hardware/software platforms are rare or because we don't have an
2115active champion on these platforms--or both. They used to work,
2116though, so go ahead and try compiling them, and let perlbug@perl.org
2117of any trouble.
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2118
2119 3b1
fd46a41b
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2120 A/UX
2121 BeOS
2122 BSD/OS
ba58ab26
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2123 ConvexOS
2124 CX/UX
2125 DC/OSx
2126 DDE SMES
2127 DOS EMX
2128 Dynix
2129 EP/IX
2130 ESIX
2131 FPS
2132 GENIX
2133 Greenhills
2134 ISC
2135 MachTen 68k
2136 MiNT
2137 MPC
2138 NEWS-OS
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2139 NextSTEP
2140 OpenSTEP
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2141 Opus
2142 Plan 9
2143 PowerUX
2144 RISC/os
fd46a41b 2145 SCO ODT/OSR
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2146 Stellar
2147 SVR2
2148 TI1500
2149 TitanOS
fd46a41b 2150 Ultrix
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2151 Unisys Dynix
2152 Unixware
fd46a41b 2153 UTS
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2154
2155Support for the following platform is planned for a future Perl release:
2156
2157 Netware
2158
2159The following platforms have their own source code distributions and
1577cd80 2160binaries available via http://www.cpan.org/ports/
ba58ab26
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2161
2162 Perl release
2163
ba58ab26 2164 Netware 5.003_07
fd46a41b 2165 OS/400 5.005_02
ba58ab26
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2166 Tandem Guardian 5.004
2167
2168The following platforms have only binaries available via
a93751fa 2169http://www.cpan.org/ports/index.html :
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2170
2171 Perl release
2172
2173 Acorn RISCOS 5.005_02
2174 AOS 5.002
2175 LynxOS 5.004_02
2176
2177Although we do suggest that you always build your own Perl from
2178the source code, both for maximal configurability and for security,
2179in case you are in a hurry you can check
a93751fa 2180http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2181
c997b287
GS
2182=head1 SEE ALSO
2183
a83b6f46 2184L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
a1f19229 2185L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
a83b6f46 2186L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
9038e305
JH
2187L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
2188L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
2189L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
c997b287 2190
e41182b5
GS
2191=head1 AUTHORS / CONTRIBUTORS
2192
06e9666b 2193Abigail <abigail@foad.org>,
c47ff5f1
GS
2194Charles Bailey <bailey@newman.upenn.edu>,
2195Graham Barr <gbarr@pobox.com>,
2196Tom Christiansen <tchrist@perl.com>,
06e9666b 2197Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2198Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2199Andy Dougherty <doughera@lafayette.edu>,
2200Dominic Dunlop <domo@computer.org>,
2201Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1
GS
2202David J. Fiander <davidf@mks.com>,
2203Paul Green <Paul_Green@stratus.com>,
06e9666b 2204M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2205Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2206Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2207Nick Ing-Simmons <nick@ing-simmons.net>,
2208Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2209Markus Laker <mlaker@contax.co.uk>,
2210Andrew M. Langmead <aml@world.std.com>,
2211Larry Moore <ljmoore@freespace.net>,
2212Paul Moore <Paul.Moore@uk.origin-it.com>,
2213Chris Nandor <pudge@pobox.com>,
1afc07ec 2214Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2215Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2216Gary Ng <71564.1743@CompuServe.COM>,
2217Tom Phoenix <rootbeer@teleport.com>,
2218AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2219Peter Prymmer <pvhp@forte.com>,
2220Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2221Gurusamy Sarathy <gsar@activestate.com>,
2222Paul J. Schinder <schinder@pobox.com>,
2223Michael G Schwern <schwern@pobox.com>,
06e9666b 2224Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2225Nathan Torkington <gnat@frii.com>.
e41182b5 2226