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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
174 LF == \012 == \x0A == \cJ == ASCII 10
175 CR == \015 == \x0D == \cM == ASCII 13
176
177 | Unix | DOS | Mac |
178 ---------------------------
179 \n | LF | LF | CR |
180 \r | CR | CR | LF |
181 \n * | LF | CRLF | CR |
182 \r * | CR | CR | LF |
183 ---------------------------
184 * text-mode STDIO
185
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186The Unix column assumes that you are not accessing a serial line
187(like a tty) in canonical mode. If you are, then CR on input becomes
188"\n", and "\n" on output becomes CRLF.
189
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190These are just the most common definitions of C<\n> and C<\r> in Perl.
191There may well be others.
192
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193=head2 Numbers endianness and Width
194
195Different CPUs store integers and floating point numbers in different
196orders (called I<endianness>) and widths (32-bit and 64-bit being the
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197most common today). This affects your programs when they attempt to transfer
198numbers in binary format from one CPU architecture to another,
199usually either "live" via network connection, or by storing the
200numbers to secondary storage such as a disk file or tape.
322422de 201
b7df3edc 202Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 203little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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204decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2050x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
206Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
207them in big-endian mode. To avoid this problem in network (socket)
208connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
209"network" orders. These are guaranteed to be portable.
322422de 210
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211You can explore the endianness of your platform by unpacking a
212data structure packed in native format such as:
213
214 print unpack("h*", pack("s2", 1, 2)), "\n";
215 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
216 # '00100020' on e.g. Motorola 68040
217
218If you need to distinguish between endian architectures you could use
219either of the variables set like so:
220
221 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 222 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 223
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224Differing widths can cause truncation even between platforms of equal
225endianness. The platform of shorter width loses the upper parts of the
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226number. There is no good solution for this problem except to avoid
227transferring or storing raw binary numbers.
228
b7df3edc 229One can circumnavigate both these problems in two ways. Either
322422de 230transfer and store numbers always in text format, instead of raw
b7df3edc 231binary, or else consider using modules like Data::Dumper (included in
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232the standard distribution as of Perl 5.005) and Storable (included as
233of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 234
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235The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
236how far EBCDIC, or more precisely UTF-EBCDIC will go.
237
433acd8a 238=head2 Files and Filesystems
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239
240Most platforms these days structure files in a hierarchical fashion.
b7df3edc 241So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 242notion of a "path" to uniquely identify a file on the system. How
b7df3edc 243that path is really written, though, differs considerably.
e41182b5 244
4375e838 245Although similar, file path specifications differ between Unix,
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246Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
247Unix, for example, is one of the few OSes that has the elegant idea
248of a single root directory.
322422de 249
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250DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
251as path separator, or in their own idiosyncratic ways (such as having
252several root directories and various "unrooted" device files such NIL:
253and LPT:).
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254
255S<Mac OS> uses C<:> as a path separator instead of C</>.
256
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257The filesystem may support neither hard links (C<link>) nor
258symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 259
6ab3f9cb 260The filesystem may support neither access timestamp nor change
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261timestamp (meaning that about the only portable timestamp is the
262modification timestamp), or one second granularity of any timestamps
263(e.g. the FAT filesystem limits the time granularity to two seconds).
264
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265The "inode change timestamp" (the <-C> filetest) may really be the
266"creation timestamp" (which it is not in UNIX).
267
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268VOS perl can emulate Unix filenames with C</> as path separator. The
269native pathname characters greater-than, less-than, number-sign, and
270percent-sign are always accepted.
271
6ab3f9cb 272S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 273separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 274signal filesystems and disk names.
e41182b5 275
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276Don't assume UNIX filesystem access semantics: that read, write,
277and execute are all the permissions there are, and even if they exist,
278that their semantics (for example what do r, w, and x mean on
279a directory) are the UNIX ones. The various UNIX/POSIX compatibility
280layers usually try to make interfaces like chmod() work, but sometimes
281there simply is no good mapping.
282
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283If all this is intimidating, have no (well, maybe only a little)
284fear. There are modules that can help. The File::Spec modules
285provide methods to do the Right Thing on whatever platform happens
286to be running the program.
e41182b5 287
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288 use File::Spec::Functions;
289 chdir(updir()); # go up one directory
290 $file = catfile(curdir(), 'temp', 'file.txt');
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291 # on Unix and Win32, './temp/file.txt'
292 # on Mac OS, ':temp:file.txt'
d1e3b762 293 # on VMS, '[.temp]file.txt'
e41182b5 294
b7df3edc 295File::Spec is available in the standard distribution as of version
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2965.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
297and some versions of perl come with version 0.6. If File::Spec
298is not updated to 0.7 or later, you must use the object-oriented
299interface from File::Spec (or upgrade File::Spec).
e41182b5 300
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301In general, production code should not have file paths hardcoded.
302Making them user-supplied or read from a configuration file is
303better, keeping in mind that file path syntax varies on different
304machines.
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305
306This is especially noticeable in scripts like Makefiles and test suites,
307which often assume C</> as a path separator for subdirectories.
308
b7df3edc 309Also of use is File::Basename from the standard distribution, which
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310splits a pathname into pieces (base filename, full path to directory,
311and file suffix).
312
19799a22 313Even when on a single platform (if you can call Unix a single platform),
b7df3edc 314remember not to count on the existence or the contents of particular
3c075c7d 315system-specific files or directories, like F</etc/passwd>,
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316F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
317example, F</etc/passwd> may exist but not contain the encrypted
318passwords, because the system is using some form of enhanced security.
319Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 320If code does need to rely on such a file, include a description of the
b7df3edc 321file and its format in the code's documentation, then make it easy for
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322the user to override the default location of the file.
323
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324Don't assume a text file will end with a newline. They should,
325but people forget.
e41182b5 326
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327Do not have two files or directories of the same name with different
328case, like F<test.pl> and F<Test.pl>, as many platforms have
329case-insensitive (or at least case-forgiving) filenames. Also, try
330not to have non-word characters (except for C<.>) in the names, and
331keep them to the 8.3 convention, for maximum portability, onerous a
332burden though this may appear.
dd9f0070 333
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334Likewise, when using the AutoSplit module, try to keep your functions to
3358.3 naming and case-insensitive conventions; or, at the least,
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336make it so the resulting files have a unique (case-insensitively)
337first 8 characters.
338
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339Whitespace in filenames is tolerated on most systems, but not all,
340and even on systems where it might be tolerated, some utilities
fe829689 341might become confused by such whitespace.
ec481373 342
b7df3edc 343Many systems (DOS, VMS) cannot have more than one C<.> in their filenames.
433acd8a 344
c47ff5f1 345Don't assume C<< > >> won't be the first character of a filename.
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346Always use C<< < >> explicitly to open a file for reading, or even
347better, use the three-arg version of open, unless you want the user to
348be able to specify a pipe open.
0a47030a 349
fe829689 350 open(FILE, '<', $existing_file) or die $!;
0a47030a 351
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352If filenames might use strange characters, it is safest to open it
353with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 354translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 355be the wrong thing to do. (Sometimes, though, it's the right thing.)
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356Three-arg open can also help protect against this translation in cases
357where it is undesirable.
e41182b5 358
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359Don't use C<:> as a part of a filename since many systems use that for
360their own semantics (MacOS Classic for separating pathname components,
361many networking schemes and utilities for separating the nodename and
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362the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
363C<|>.
ec481373 364
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365Don't assume that in pathnames you can collapse two leading slashes
366C<//> into one: some networking and clustering filesystems have special
367semantics for that. Let the operating system to sort it out.
368
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369The I<portable filename characters> as defined by ANSI C are
370
371 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
372 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
373 0 1 2 3 4 5 6 7 8 9
374 . _ -
375
08fef530 376and the "-" shouldn't be the first character. If you want to be
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377hypercorrect, stay case-insensitive and within the 8.3 naming
378convention (all the files and directories have to be unique within one
379directory if their names are lowercased and truncated to eight
380characters before the C<.>, if any, and to three characters after the
381C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 382
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383=head2 System Interaction
384
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385Not all platforms provide a command line. These are usually platforms
386that rely primarily on a Graphical User Interface (GUI) for user
387interaction. A program requiring a command line interface might
388not work everywhere. This is probably for the user of the program
389to deal with, so don't stay up late worrying about it.
e41182b5 390
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391Some platforms can't delete or rename files held open by the system.
392Remember to C<close> files when you are done with them. Don't
393C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
394file already tied or opened; C<untie> or C<close> it first.
e41182b5 395
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396Don't open the same file more than once at a time for writing, as some
397operating systems put mandatory locks on such files.
398
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399Don't assume that write/modify permission on a directory gives the
400right to add or delete files/directories in that directory. That is
401filesystem specific: in some filesystems you need write/modify
402permission also (or even just) in the file/directory itself. In some
403filesystems (AFS, DFS) the permission to add/delete directory entries
404is a completely separate permission.
405
406Don't assume that a single C<unlink> completely gets rid of the file:
407some filesystems (most notably the ones in VMS) have versioned
408filesystems, and unlink() removes only the most recent one (it doesn't
409remove all the versions because by default the native tools on those
410platforms remove just the most recent version, too). The portable
411idiom to remove all the versions of a file is
412
94bb614c 413 1 while unlink "file";
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414
415This will terminate if the file is undeleteable for some reason
416(protected, not there, and so on).
417
e41182b5 418Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 419Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 420case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 421if you really have to, make it conditional on C<$^O ne 'VMS'> since in
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422VMS the C<%ENV> table is much more than a per-process key-value string
423table.
e41182b5 424
d1e3b762 425Don't count on signals or C<%SIG> for anything.
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426
427Don't count on filename globbing. Use C<opendir>, C<readdir>, and
428C<closedir> instead.
429
b8099c3d 430Don't count on per-program environment variables, or per-program current
dd9f0070 431directories.
b8099c3d 432
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433Don't count on specific values of C<$!>.
434
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435=head2 Interprocess Communication (IPC)
436
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437In general, don't directly access the system in code meant to be
438portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
439C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
440that makes being a perl hacker worth being.
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441
442Commands that launch external processes are generally supported on
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443most platforms (though many of them do not support any type of
444forking). The problem with using them arises from what you invoke
445them on. External tools are often named differently on different
4375e838 446platforms, may not be available in the same location, might accept
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447different arguments, can behave differently, and often present their
448results in a platform-dependent way. Thus, you should seldom depend
449on them to produce consistent results. (Then again, if you're calling
450I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 451
b7df3edc 452One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 453
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454 open(MAIL, '|/usr/lib/sendmail -t')
455 or die "cannot fork sendmail: $!";
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456
457This is fine for systems programming when sendmail is known to be
458available. But it is not fine for many non-Unix systems, and even
459some Unix systems that may not have sendmail installed. If a portable
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460solution is needed, see the various distributions on CPAN that deal
461with it. Mail::Mailer and Mail::Send in the MailTools distribution are
462commonly used, and provide several mailing methods, including mail,
463sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
464not available. Mail::Sendmail is a standalone module that provides
465simple, platform-independent mailing.
466
467The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
468even on all Unix platforms.
e41182b5 469
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470Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
471bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
472both forms just pack the four bytes into network order. That this
473would be equal to the C language C<in_addr> struct (which is what the
474socket code internally uses) is not guaranteed. To be portable use
475the routines of the Socket extension, such as C<inet_aton()>,
476C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 477
e41182b5 478The rule of thumb for portable code is: Do it all in portable Perl, or
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479use a module (that may internally implement it with platform-specific
480code, but expose a common interface).
e41182b5 481
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482=head2 External Subroutines (XS)
483
b7df3edc 484XS code can usually be made to work with any platform, but dependent
e41182b5
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485libraries, header files, etc., might not be readily available or
486portable, or the XS code itself might be platform-specific, just as Perl
487code might be. If the libraries and headers are portable, then it is
488normally reasonable to make sure the XS code is portable, too.
489
b7df3edc
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490A different type of portability issue arises when writing XS code:
491availability of a C compiler on the end-user's system. C brings
492with it its own portability issues, and writing XS code will expose
493you to some of those. Writing purely in Perl is an easier way to
e41182b5
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494achieve portability.
495
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496=head2 Standard Modules
497
498In general, the standard modules work across platforms. Notable
6ab3f9cb 499exceptions are the CPAN module (which currently makes connections to external
e41182b5 500programs that may not be available), platform-specific modules (like
6ab3f9cb 501ExtUtils::MM_VMS), and DBM modules.
e41182b5 502
b7df3edc 503There is no one DBM module available on all platforms.
6ab3f9cb
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504SDBM_File and the others are generally available on all Unix and DOSish
505ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 506available.
e41182b5
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507
508The good news is that at least some DBM module should be available, and
6ab3f9cb 509AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
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510the code needs to be fairly strict, dropping to the greatest common
511factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 512work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 513
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514=head2 Time and Date
515
0a47030a 516The system's notion of time of day and calendar date is controlled in
b7df3edc 517widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a
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518and even if it is, don't assume that you can control the timezone through
519that variable.
e41182b5 520
322422de 521Don't assume that the epoch starts at 00:00:00, January 1, 1970,
6ab3f9cb
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522because that is OS- and implementation-specific. It is better to store a date
523in an unambiguous representation. The ISO-8601 standard defines
524"YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
525can be easily converted into an OS-specific value using a module like
526Date::Parse. An array of values, such as those returned by
322422de 527C<localtime>, can be converted to an OS-specific representation using
6ab3f9cb 528Time::Local.
322422de 529
19799a22
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530When calculating specific times, such as for tests in time or date modules,
531it may be appropriate to calculate an offset for the epoch.
b7df3edc 532
19799a22
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533 require Time::Local;
534 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 535
19799a22
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536The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
537some large number. C<$offset> can then be added to a Unix time value
538to get what should be the proper value on any system.
322422de
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539
540=head2 Character sets and character encoding
541
ec481373
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542Assume very little about character sets.
543
544Assume nothing about numerical values (C<ord>, C<chr>) of characters.
545Do not use explicit code point ranges (like \xHH-\xHH); use for
546example symbolic character classes like C<[:print:]>.
547
548Do not assume that the alphabetic characters are encoded contiguously
549(in the numeric sense). There may be gaps.
550
551Do not assume anything about the ordering of the characters.
552The lowercase letters may come before or after the uppercase letters;
553the lowercase and uppercase may be interlaced so that both `a' and `A'
554come before `b'; the accented and other international characters may
555be interlaced so that E<auml> comes before `b'.
322422de
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556
557=head2 Internationalisation
558
b7df3edc
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559If you may assume POSIX (a rather large assumption), you may read
560more about the POSIX locale system from L<perllocale>. The locale
561system at least attempts to make things a little bit more portable,
562or at least more convenient and native-friendly for non-English
563users. The system affects character sets and encoding, and date
564and time formatting--amongst other things.
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565
566=head2 System Resources
567
0a47030a
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568If your code is destined for systems with severely constrained (or
569missing!) virtual memory systems then you want to be I<especially> mindful
570of avoiding wasteful constructs such as:
e41182b5
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571
572 # NOTE: this is no longer "bad" in perl5.005
573 for (0..10000000) {} # bad
574 for (my $x = 0; $x <= 10000000; ++$x) {} # good
575
576 @lines = <VERY_LARGE_FILE>; # bad
577
578 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 579 $file = join('', <FILE>); # better
e41182b5 580
b7df3edc
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581The last two constructs may appear unintuitive to most people. The
582first repeatedly grows a string, whereas the second allocates a
583large chunk of memory in one go. On some systems, the second is
584more efficient that the first.
0a47030a 585
e41182b5
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586=head2 Security
587
b7df3edc
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588Most multi-user platforms provide basic levels of security, usually
589implemented at the filesystem level. Some, however, do
a1667ba3 590not-- unfortunately. Thus the notion of user id, or "home" directory,
b7df3edc
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591or even the state of being logged-in, may be unrecognizable on many
592platforms. If you write programs that are security-conscious, it
593is usually best to know what type of system you will be running
594under so that you can write code explicitly for that platform (or
595class of platforms).
0a47030a 596
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597Don't assume the UNIX filesystem access semantics: the operating
598system or the filesystem may be using some ACL systems, which are
599richer languages than the usual rwx. Even if the rwx exist,
600their semantics might be different.
601
602(From security viewpoint testing for permissions before attempting to
603do something is silly anyway: if one tries this, there is potential
604for race conditions-- someone or something might change the
605permissions between the permissions check and the actual operation.
606Just try the operation.)
607
608Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 609expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
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610for switching identities (or memberships).
611
612Don't assume set-uid and set-gid semantics. (And even if you do,
613think twice: set-uid and set-gid are a known can of security worms.)
614
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615=head2 Style
616
617For those times when it is necessary to have platform-specific code,
618consider keeping the platform-specific code in one place, making porting
6ab3f9cb 619to other platforms easier. Use the Config module and the special
0a47030a
GS
620variable C<$^O> to differentiate platforms, as described in
621L<"PLATFORMS">.
e41182b5 622
b7df3edc
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623Be careful in the tests you supply with your module or programs.
624Module code may be fully portable, but its tests might not be. This
625often happens when tests spawn off other processes or call external
626programs to aid in the testing, or when (as noted above) the tests
627assume certain things about the filesystem and paths. Be careful
628not to depend on a specific output style for errors, such as when
d1be9408 629checking C<$!> after a system call. Some platforms expect a certain
b7df3edc
GS
630output format, and perl on those platforms may have been adjusted
631accordingly. Most specifically, don't anchor a regex when testing
632an error value.
e41182b5 633
0a47030a 634=head1 CPAN Testers
e41182b5 635
0a47030a
GS
636Modules uploaded to CPAN are tested by a variety of volunteers on
637different platforms. These CPAN testers are notified by mail of each
e41182b5 638new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 639this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
GS
640
641The purpose of the testing is twofold: one, to help developers fix any
0a47030a 642problems in their code that crop up because of lack of testing on other
b7df3edc 643platforms; two, to provide users with information about whether
0a47030a 644a given module works on a given platform.
e41182b5
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645
646=over 4
647
648=item Mailing list: cpan-testers@perl.org
649
c997b287 650=item Testing results: http://testers.cpan.org/
e41182b5
GS
651
652=back
653
e41182b5
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654=head1 PLATFORMS
655
656As of version 5.002, Perl is built with a C<$^O> variable that
657indicates the operating system it was built on. This was implemented
b7df3edc
GS
658to help speed up code that would otherwise have to C<use Config>
659and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
GS
660detailed information about the system, looking into C<%Config> is
661certainly recommended.
662
b7df3edc
GS
663C<%Config> cannot always be trusted, however, because it was built
664at compile time. If perl was built in one place, then transferred
665elsewhere, some values may be wrong. The values may even have been
666edited after the fact.
6ab3f9cb 667
e41182b5
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668=head2 Unix
669
670Perl works on a bewildering variety of Unix and Unix-like platforms (see
671e.g. most of the files in the F<hints/> directory in the source code kit).
672On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
673too) is determined either by lowercasing and stripping punctuation from the
674first field of the string returned by typing C<uname -a> (or a similar command)
675at the shell prompt or by testing the file system for the presence of
676uniquely named files such as a kernel or header file. Here, for example,
677are a few of the more popular Unix flavors:
e41182b5 678
b7df3edc 679 uname $^O $Config{'archname'}
6ab3f9cb 680 --------------------------------------------
b7df3edc 681 AIX aix aix
6ab3f9cb 682 BSD/OS bsdos i386-bsdos
e1516da7 683 Darwin darwin darwin
6ab3f9cb
GS
684 dgux dgux AViiON-dgux
685 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 686 FreeBSD freebsd freebsd-i386
d1e3b762 687 Linux linux arm-linux
b7df3edc 688 Linux linux i386-linux
6ab3f9cb
GS
689 Linux linux i586-linux
690 Linux linux ppc-linux
b7df3edc
GS
691 HP-UX hpux PA-RISC1.1
692 IRIX irix irix
b787fad4 693 Mac OS X darwin darwin
d1e3b762
GS
694 MachTen PPC machten powerpc-machten
695 NeXT 3 next next-fat
696 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 697 openbsd openbsd i386-openbsd
b7df3edc 698 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
699 reliantunix-n svr4 RM400-svr4
700 SCO_SV sco_sv i386-sco_sv
701 SINIX-N svr4 RM400-svr4
702 sn4609 unicos CRAY_C90-unicos
703 sn6521 unicosmk t3e-unicosmk
704 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
705 SunOS solaris sun4-solaris
706 SunOS solaris i86pc-solaris
707 SunOS4 sunos sun4-sunos
e41182b5 708
b7df3edc
GS
709Because the value of C<$Config{archname}> may depend on the
710hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 711
e41182b5
GS
712=head2 DOS and Derivatives
713
b7df3edc 714Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
715systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
716bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 717Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
718be aware that each of these file specifications may have subtle
719differences:
720
721 $filespec0 = "c:/foo/bar/file.txt";
722 $filespec1 = "c:\\foo\\bar\\file.txt";
723 $filespec2 = 'c:\foo\bar\file.txt';
724 $filespec3 = 'c:\\foo\\bar\\file.txt';
725
b7df3edc
GS
726System calls accept either C</> or C<\> as the path separator.
727However, many command-line utilities of DOS vintage treat C</> as
728the option prefix, so may get confused by filenames containing C</>.
729Aside from calling any external programs, C</> will work just fine,
730and probably better, as it is more consistent with popular usage,
731and avoids the problem of remembering what to backwhack and what
732not to.
e41182b5 733
b7df3edc
GS
734The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
735the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 736filesystems you may have to be careful about case returned with functions
e41182b5
GS
737like C<readdir> or used with functions like C<open> or C<opendir>.
738
b7df3edc
GS
739DOS also treats several filenames as special, such as AUX, PRN,
740NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
741filenames won't even work if you include an explicit directory
742prefix. It is best to avoid such filenames, if you want your code
743to be portable to DOS and its derivatives. It's hard to know what
744these all are, unfortunately.
e41182b5
GS
745
746Users of these operating systems may also wish to make use of
b7df3edc 747scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
748put wrappers around your scripts.
749
750Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
751and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
752will keep C<\n> translated as C<\012> for that filehandle. Since it is a
753no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
754that deals with binary data. That's assuming you realize in advance
755that your data is in binary. General-purpose programs should
756often assume nothing about their data.
e41182b5 757
b7df3edc 758The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
759DOSish perls are as follows:
760
67ac489e
MS
761 OS $^O $Config{archname} ID Version
762 --------------------------------------------------------
763 MS-DOS dos ?
764 PC-DOS dos ?
765 OS/2 os2 ?
766 Windows 3.1 ? ? 0 3 01
767 Windows 95 MSWin32 MSWin32-x86 1 4 00
768 Windows 98 MSWin32 MSWin32-x86 1 4 10
769 Windows ME MSWin32 MSWin32-x86 1 ?
770 Windows NT MSWin32 MSWin32-x86 2 4 xx
771 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
772 Windows NT MSWin32 MSWin32-ppc 2 4 xx
773 Windows 2000 MSWin32 MSWin32-x86 2 5 xx
774 Windows XP MSWin32 MSWin32-x86 2 ?
775 Windows CE MSWin32 ? 3
776 Cygwin cygwin ?
e41182b5 777
34aaaa84
PP
778The various MSWin32 Perl's can distinguish the OS they are running on
779via the value of the fifth element of the list returned from
780Win32::GetOSVersion(). For example:
781
782 if ($^O eq 'MSWin32') {
783 my @os_version_info = Win32::GetOSVersion();
784 print +('3.1','95','NT')[$os_version_info[4]],"\n";
785 }
786
e41182b5
GS
787Also see:
788
789=over 4
790
c997b287 791=item *
e41182b5 792
c997b287
GS
793The djgpp environment for DOS, http://www.delorie.com/djgpp/
794and L<perldos>.
e41182b5 795
c997b287 796=item *
e41182b5 797
c997b287
GS
798The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
799http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
f224927c 800ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
e41182b5 801
c997b287 802=item *
d1e3b762 803
c997b287
GS
804Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
805in L<perlcygwin>.
806
807=item *
808
809The C<Win32::*> modules in L<Win32>.
810
811=item *
812
813The ActiveState Pages, http://www.activestate.com/
814
815=item *
816
817The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 818as L<perlcygwin>), http://www.cygwin.com/
c997b287
GS
819
820=item *
821
822The U/WIN environment for Win32,
cea6626f 823http://www.research.att.com/sw/tools/uwin/
c997b287 824
cea6626f 825=item *
d1e3b762 826
cea6626f 827Build instructions for OS/2, L<perlos2>
d1e3b762 828
e41182b5
GS
829=back
830
dd9f0070 831=head2 S<Mac OS>
e41182b5
GS
832
833Any module requiring XS compilation is right out for most people, because
834MacPerl is built using non-free (and non-cheap!) compilers. Some XS
835modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 836form on CPAN.
e41182b5
GS
837
838Directories are specified as:
839
840 volume:folder:file for absolute pathnames
841 volume:folder: for absolute pathnames
842 :folder:file for relative pathnames
843 :folder: for relative pathnames
844 :file for relative pathnames
845 file for relative pathnames
846
b7df3edc 847Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 848limited to 31 characters, and may include any character except for
b7df3edc 849null and C<:>, which is reserved as the path separator.
e41182b5 850
0a47030a 851Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 852Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
853
854In the MacPerl application, you can't run a program from the command line;
855programs that expect C<@ARGV> to be populated can be edited with something
856like the following, which brings up a dialog box asking for the command
857line arguments.
858
859 if (!@ARGV) {
860 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
861 }
862
b7df3edc 863A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
864pathnames of the files dropped onto the script.
865
b7df3edc
GS
866Mac users can run programs under a type of command line interface
867under MPW (Macintosh Programmer's Workshop, a free development
868environment from Apple). MacPerl was first introduced as an MPW
869tool, and MPW can be used like a shell:
e41182b5
GS
870
871 perl myscript.plx some arguments
872
873ToolServer is another app from Apple that provides access to MPW tools
0a47030a 874from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
875C<system>, backticks, and piped C<open>.
876
877"S<Mac OS>" is the proper name for the operating system, but the value
878in C<$^O> is "MacOS". To determine architecture, version, or whether
879the application or MPW tool version is running, check:
880
881 $is_app = $MacPerl::Version =~ /App/;
882 $is_tool = $MacPerl::Version =~ /MPW/;
883 ($version) = $MacPerl::Version =~ /^(\S+)/;
884 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
885 $is_68k = $MacPerl::Architecture eq 'Mac68K';
886
b787fad4
JH
887S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
888"Classic" environment. There is no "Carbon" version of MacPerl to run
889under the primary Mac OS X environment. S<Mac OS X> and its Open Source
890version, Darwin, both run Unix perl natively.
6ab3f9cb 891
e41182b5
GS
892Also see:
893
894=over 4
895
c997b287
GS
896=item *
897
862b5365 898MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
899
900=item *
901
862b5365 902The MacPerl Pages, http://www.macperl.com/ .
e41182b5 903
c997b287 904=item *
6ab3f9cb 905
862b5365 906The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5
GS
907
908=back
909
e41182b5
GS
910=head2 VMS
911
c997b287 912Perl on VMS is discussed in L<perlvms> in the perl distribution.
b7df3edc 913Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
914specifications as in either of the following:
915
916 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
917 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
918
919but not a mixture of both as in:
920
921 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
922 Can't open sys$login:/login.com: file specification syntax error
923
924Interacting with Perl from the Digital Command Language (DCL) shell
925often requires a different set of quotation marks than Unix shells do.
926For example:
927
928 $ perl -e "print ""Hello, world.\n"""
929 Hello, world.
930
b7df3edc 931There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
932you are so inclined. For example:
933
934 $ write sys$output "Hello from DCL!"
935 $ if p1 .eqs. ""
936 $ then perl -x 'f$environment("PROCEDURE")
937 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
938 $ deck/dollars="__END__"
939 #!/usr/bin/perl
940
941 print "Hello from Perl!\n";
942
943 __END__
944 $ endif
945
946Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 947perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5
GS
948
949Filenames are in the format "name.extension;version". The maximum
950length for filenames is 39 characters, and the maximum length for
951extensions is also 39 characters. Version is a number from 1 to
95232767. Valid characters are C</[A-Z0-9$_-]/>.
953
b7df3edc 954VMS's RMS filesystem is case-insensitive and does not preserve case.
e41182b5 955C<readdir> returns lowercased filenames, but specifying a file for
b7df3edc 956opening remains case-insensitive. Files without extensions have a
e41182b5 957trailing period on them, so doing a C<readdir> with a file named F<A.;5>
0a47030a
GS
958will return F<a.> (though that file could be opened with
959C<open(FH, 'A')>).
e41182b5 960
f34d0673 961RMS had an eight level limit on directory depths from any rooted logical
dd9f0070
CN
962(allowing 16 levels overall) prior to VMS 7.2. Hence
963C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but
964C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might
965have to take this into account, but at least they can refer to the former
f34d0673 966as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
e41182b5 967
6ab3f9cb 968The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
969process on VMS, is a pure Perl module that can easily be installed on
970non-VMS platforms and can be helpful for conversions to and from RMS
971native formats.
e41182b5 972
5e12dbfa
PP
973What C<\n> represents depends on the type of file opened. It usually
974represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
975C<\000>, C<\040>, or nothing depending on the file organiztion and
976record format. The VMS::Stdio module provides access to the
977special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
978
979TCP/IP stacks are optional on VMS, so socket routines might not be
980implemented. UDP sockets may not be supported.
981
982The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
983that you are running on without resorting to loading all of C<%Config>
984you can examine the content of the C<@INC> array like so:
985
986 if (grep(/VMS_AXP/, @INC)) {
987 print "I'm on Alpha!\n";
6ab3f9cb 988
e41182b5
GS
989 } elsif (grep(/VMS_VAX/, @INC)) {
990 print "I'm on VAX!\n";
6ab3f9cb 991
e41182b5
GS
992 } else {
993 print "I'm not so sure about where $^O is...\n";
994 }
995
b7df3edc
GS
996On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
997logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 998calls to C<localtime> are adjusted to count offsets from
b7df3edc 99901-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1000
e41182b5
GS
1001Also see:
1002
1003=over 4
1004
c997b287
GS
1005=item *
1006
1007F<README.vms> (installed as L<README_vms>), L<perlvms>
1008
1009=item *
1010
1011vmsperl list, majordomo@perl.org
e41182b5 1012
c997b287 1013(Put the words C<subscribe vmsperl> in message body.)
e41182b5 1014
c997b287 1015=item *
e41182b5 1016
c997b287 1017vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1018
1019=back
1020
495c5fdc
PG
1021=head2 VOS
1022
9a997319
JH
1023Perl on VOS is discussed in F<README.vos> in the perl distribution
1024(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1025Unix-style file specifications as in either of the following:
495c5fdc 1026
cc07ed0b
PG
1027 C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
1028 C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
495c5fdc
PG
1029
1030or even a mixture of both as in:
1031
cc07ed0b 1032 C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
495c5fdc 1033
b7df3edc 1034Even though VOS allows the slash character to appear in object
495c5fdc
PG
1035names, because the VOS port of Perl interprets it as a pathname
1036delimiting character, VOS files, directories, or links whose names
1037contain a slash character cannot be processed. Such files must be
a3dfe201
GS
1038renamed before they can be processed by Perl. Note that VOS limits
1039file names to 32 or fewer characters.
495c5fdc 1040
cc07ed0b
PG
1041Perl on VOS can be built using two different compilers and two different
1042versions of the POSIX runtime. The recommended method for building full
1043Perl is with the GNU C compiler and the generally-available version of
1044VOS POSIX support. See F<README.vos> (installed as L<perlvos>) for
1045restrictions that apply when Perl is built using the VOS Standard C
1046compiler or the alpha version of VOS POSIX support.
495c5fdc
PG
1047
1048The value of C<$^O> on VOS is "VOS". To determine the architecture that
1049you are running on without resorting to loading all of C<%Config> you
c997b287 1050can examine the content of the @INC array like so:
495c5fdc 1051
24e8e380 1052 if ($^O =~ /VOS/) {
495c5fdc
PG
1053 print "I'm on a Stratus box!\n";
1054 } else {
1055 print "I'm not on a Stratus box!\n";
1056 die;
1057 }
1058
1059 if (grep(/860/, @INC)) {
1060 print "This box is a Stratus XA/R!\n";
6ab3f9cb 1061
495c5fdc 1062 } elsif (grep(/7100/, @INC)) {
24e8e380 1063 print "This box is a Stratus HP 7100 or 8xxx!\n";
6ab3f9cb 1064
495c5fdc 1065 } elsif (grep(/8000/, @INC)) {
24e8e380 1066 print "This box is a Stratus HP 8xxx!\n";
6ab3f9cb 1067
495c5fdc 1068 } else {
24e8e380 1069 print "This box is a Stratus 68K!\n";
495c5fdc
PG
1070 }
1071
1072Also see:
1073
1074=over 4
1075
c997b287 1076=item *
495c5fdc 1077
cc07ed0b 1078F<README.vos> (installed as L<perlvos>)
c997b287
GS
1079
1080=item *
1081
1082The VOS mailing list.
495c5fdc
PG
1083
1084There is no specific mailing list for Perl on VOS. You can post
1085comments to the comp.sys.stratus newsgroup, or subscribe to the general
cc07ed0b 1086Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
495c5fdc
PG
1087the message body to majordomo@list.stratagy.com.
1088
c997b287
GS
1089=item *
1090
cc07ed0b 1091VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
495c5fdc
PG
1092
1093=back
1094
e41182b5
GS
1095=head2 EBCDIC Platforms
1096
1097Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1098AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1099Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1100Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1101systems). On the mainframe perl currently works under the "Unix system
1102services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1103the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
c997b287 1104See L<perlos390> for details.
e41182b5 1105
7c5ffed3
JH
1106As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1107sub-systems do not support the C<#!> shebang trick for script invocation.
1108Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1109similar to the following simple script:
e41182b5
GS
1110
1111 : # use perl
1112 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1113 if 0;
1114 #!/usr/local/bin/perl # just a comment really
1115
1116 print "Hello from perl!\n";
1117
d1e3b762
GS
1118OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1119Calls to C<system> and backticks can use POSIX shell syntax on all
1120S/390 systems.
1121
b7df3edc 1122On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1123to wrap your perl scripts in a CL procedure to invoke them like so:
1124
1125 BEGIN
1126 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1127 ENDPGM
1128
1129This will invoke the perl script F<hello.pl> in the root of the
1130QOpenSys file system. On the AS/400 calls to C<system> or backticks
1131must use CL syntax.
1132
e41182b5 1133On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1134an effect on what happens with some perl functions (such as C<chr>,
1135C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1136well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1137and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1138(see L<"Newlines">).
e41182b5 1139
b7df3edc
GS
1140Fortunately, most web servers for the mainframe will correctly
1141translate the C<\n> in the following statement to its ASCII equivalent
1142(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1143
1144 print "Content-type: text/html\r\n\r\n";
1145
d1e3b762 1146The values of C<$^O> on some of these platforms includes:
e41182b5 1147
d1e3b762
GS
1148 uname $^O $Config{'archname'}
1149 --------------------------------------------
1150 OS/390 os390 os390
1151 OS400 os400 os400
1152 POSIX-BC posix-bc BS2000-posix-bc
1153 VM/ESA vmesa vmesa
3c075c7d 1154
e41182b5
GS
1155Some simple tricks for determining if you are running on an EBCDIC
1156platform could include any of the following (perhaps all):
1157
1158 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1159
1160 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1161
1162 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1163
b7df3edc 1164One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1165of punctuation characters since these may differ from code page to code
1166page (and once your module or script is rumoured to work with EBCDIC,
1167folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1168
1169Also see:
1170
1171=over 4
1172
c997b287
GS
1173=item *
1174
1175*
d1e3b762 1176
dc5c060f 1177L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1178L<perlebcdic>.
c997b287
GS
1179
1180=item *
e41182b5
GS
1181
1182The perl-mvs@perl.org list is for discussion of porting issues as well as
1183general usage issues for all EBCDIC Perls. Send a message body of
1184"subscribe perl-mvs" to majordomo@perl.org.
1185
c997b287
GS
1186=item *
1187
1188AS/400 Perl information at
b1866b2d 1189http://as400.rochester.ibm.com/
d1e3b762 1190as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1191
1192=back
1193
b8099c3d
CN
1194=head2 Acorn RISC OS
1195
b7df3edc
GS
1196Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1197Unix, and because Unix filename emulation is turned on by default,
1198most simple scripts will probably work "out of the box". The native
6ab3f9cb 1199filesystem is modular, and individual filesystems are free to be
0a47030a 1200case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1201native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1202names are silently truncated to fit. Scripts should be aware that the
1203standard filesystem currently has a name length limit of B<10>
1204characters, with up to 77 items in a directory, but other filesystems
0a47030a 1205may not impose such limitations.
b8099c3d
CN
1206
1207Native filenames are of the form
1208
6ab3f9cb 1209 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1210
b8099c3d
CN
1211where
1212
1213 Special_Field is not usually present, but may contain . and $ .
1214 Filesystem =~ m|[A-Za-z0-9_]|
1215 DsicName =~ m|[A-Za-z0-9_/]|
1216 $ represents the root directory
1217 . is the path separator
1218 @ is the current directory (per filesystem but machine global)
1219 ^ is the parent directory
1220 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1221
1222The default filename translation is roughly C<tr|/.|./|;>
1223
6ab3f9cb 1224Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1225the second stage of C<$> interpolation in regular expressions will fall
1226foul of the C<$.> if scripts are not careful.
1227
1228Logical paths specified by system variables containing comma-separated
b7df3edc 1229search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1230filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1231C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1232Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1233C<System$Path> contains a single item list. The filesystem will also
1234expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1235C<< <System$Dir>.Modules >> would look for the file
0a47030a 1236S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1237that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1238be protected when C<open> is used for input.
b8099c3d
CN
1239
1240Because C<.> was in use as a directory separator and filenames could not
1241be assumed to be unique after 10 characters, Acorn implemented the C
1242compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1243filenames specified in source code and store the respective files in
b7df3edc 1244subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1245
1246 foo.h h.foo
1247 C:foo.h C:h.foo (logical path variable)
1248 sys/os.h sys.h.os (C compiler groks Unix-speak)
1249 10charname.c c.10charname
1250 10charname.o o.10charname
1251 11charname_.c c.11charname (assuming filesystem truncates at 10)
1252
1253The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1254that this sort of translation is required, and it allows a user-defined list
1255of known suffixes that it will transpose in this fashion. This may
1256seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1257and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1258C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1259C<.>'s in filenames are translated to C</>.
0a47030a 1260
b7df3edc 1261As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1262the convention is that program specific environment variables are of the
6ab3f9cb
GS
1263form C<Program$Name>. Each filesystem maintains a current directory,
1264and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1265directory. Consequently, sociable programs don't change the current
1266directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1267assume that they can spawn a child process which can change the current
1268directory without affecting its parent (and everyone else for that
1269matter).
1270
b7df3edc
GS
1271Because native operating system filehandles are global and are currently
1272allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1273library emulates Unix filehandles. Consequently, you can't rely on
1274passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1275
1276The desire of users to express filenames of the form
c47ff5f1 1277C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1278too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1279assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1280reference to an environment variable, whereas anything else involving
c47ff5f1 1281C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1282right. Of course, the problem remains that scripts cannot rely on any
1283Unix tools being available, or that any tools found have Unix-like command
1284line arguments.
1285
b7df3edc
GS
1286Extensions and XS are, in theory, buildable by anyone using free
1287tools. In practice, many don't, as users of the Acorn platform are
1288used to binary distributions. MakeMaker does run, but no available
1289make currently copes with MakeMaker's makefiles; even if and when
1290this should be fixed, the lack of a Unix-like shell will cause
1291problems with makefile rules, especially lines of the form C<cd
1292sdbm && make all>, and anything using quoting.
b8099c3d
CN
1293
1294"S<RISC OS>" is the proper name for the operating system, but the value
1295in C<$^O> is "riscos" (because we don't like shouting).
1296
e41182b5
GS
1297=head2 Other perls
1298
b7df3edc
GS
1299Perl has been ported to many platforms that do not fit into any of
1300the categories listed above. Some, such as AmigaOS, Atari MiNT,
1301BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1302into the standard Perl source code kit. You may need to see the
1303F<ports/> directory on CPAN for information, and possibly binaries,
1304for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1305Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1306fall under the Unix category, but we are not a standards body.)
e41182b5 1307
d1e3b762
GS
1308Some approximate operating system names and their C<$^O> values
1309in the "OTHER" category include:
1310
1311 OS $^O $Config{'archname'}
1312 ------------------------------------------
1313 Amiga DOS amigaos m68k-amigos
1314 MPE/iX mpeix PA-RISC1.1
1315
e41182b5
GS
1316See also:
1317
1318=over 4
1319
c997b287
GS
1320=item *
1321
1322Amiga, F<README.amiga> (installed as L<perlamiga>).
1323
1324=item *
d1e3b762 1325
c997b287
GS
1326Atari, F<README.mint> and Guido Flohr's web page
1327http://stud.uni-sb.de/~gufl0000/
e41182b5 1328
c997b287 1329=item *
d1e3b762 1330
c997b287 1331Be OS, F<README.beos>
e41182b5 1332
c997b287
GS
1333=item *
1334
1335HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1336http://www.bixby.org/mark/perlix.html
c997b287
GS
1337
1338=item *
e41182b5 1339
6ab3f9cb 1340A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1341precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1342as well as from CPAN.
e41182b5 1343
13a2d996 1344=item *
c997b287
GS
1345
1346Plan 9, F<README.plan9>
d1e3b762 1347
e41182b5
GS
1348=back
1349
e41182b5
GS
1350=head1 FUNCTION IMPLEMENTATIONS
1351
b7df3edc
GS
1352Listed below are functions that are either completely unimplemented
1353or else have been implemented differently on various platforms.
1354Following each description will be, in parentheses, a list of
1355platforms that the description applies to.
e41182b5 1356
b7df3edc
GS
1357The list may well be incomplete, or even wrong in some places. When
1358in doubt, consult the platform-specific README files in the Perl
1359source distribution, and any other documentation resources accompanying
1360a given port.
e41182b5 1361
0a47030a 1362Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1363
b7df3edc
GS
1364For many functions, you can also query C<%Config>, exported by
1365default from the Config module. For example, to check whether the
1366platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1367L<Config> for a full description of available variables.
e41182b5
GS
1368
1369=head2 Alphabetical Listing of Perl Functions
1370
1371=over 8
1372
1373=item -X FILEHANDLE
1374
1375=item -X EXPR
1376
1377=item -X
1378
b7df3edc 1379C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1380and applications are executable, and there are no uid/gid
b7df3edc 1381considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1382
b7df3edc
GS
1383C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1384which may not reflect UIC-based file protections. (VMS)
e41182b5 1385
b8099c3d
CN
1386C<-s> returns the size of the data fork, not the total size of data fork
1387plus resource fork. (S<Mac OS>).
1388
1389C<-s> by name on an open file will return the space reserved on disk,
1390rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1391current size. (S<RISC OS>)
b8099c3d 1392
e41182b5 1393C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1394C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1395
1396C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1397(S<Mac OS>)
1398
1399C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1400(Win32, VMS, S<RISC OS>)
e41182b5
GS
1401
1402C<-d> is true if passed a device spec without an explicit directory.
1403(VMS)
1404
1405C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1406with foreign characters; this is the case will all platforms, but may
b7df3edc 1407affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1408
1409C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1410suffixes. C<-S> is meaningless. (Win32)
e41182b5 1411
b8099c3d
CN
1412C<-x> (or C<-X>) determine if a file has an executable file type.
1413(S<RISC OS>)
1414
63f87e49
GS
1415=item alarm SECONDS
1416
1417=item alarm
1418
1419Not implemented. (Win32)
1420
e41182b5
GS
1421=item binmode FILEHANDLE
1422
b7df3edc 1423Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1424
1425Reopens file and restores pointer; if function fails, underlying
1426filehandle may be closed, or pointer may be in a different position.
1427(VMS)
1428
1429The value returned by C<tell> may be affected after the call, and
1430the filehandle may be flushed. (Win32)
1431
1432=item chmod LIST
1433
b7df3edc 1434Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1435locking/unlocking the file. (S<Mac OS>)
1436
1437Only good for changing "owner" read-write access, "group", and "other"
1438bits are meaningless. (Win32)
1439
b8099c3d
CN
1440Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1441
495c5fdc
PG
1442Access permissions are mapped onto VOS access-control list changes. (VOS)
1443
4e51f8e4 1444The actual permissions set depend on the value of the C<CYGWIN>
789f0d36 1445in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1446
e41182b5
GS
1447=item chown LIST
1448
495c5fdc 1449Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1450
1451Does nothing, but won't fail. (Win32)
1452
1453=item chroot FILENAME
1454
1455=item chroot
1456
7c5ffed3 1457Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1458
1459=item crypt PLAINTEXT,SALT
1460
1461May not be available if library or source was not provided when building
b8099c3d 1462perl. (Win32)
e41182b5 1463
495c5fdc
PG
1464Not implemented. (VOS)
1465
e41182b5
GS
1466=item dbmclose HASH
1467
495c5fdc 1468Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1469
1470=item dbmopen HASH,DBNAME,MODE
1471
495c5fdc 1472Not implemented. (VMS, Plan9, VOS)
e41182b5
GS
1473
1474=item dump LABEL
1475
b8099c3d 1476Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1477
1478Not implemented. (Win32)
1479
b8099c3d 1480Invokes VMS debugger. (VMS)
e41182b5
GS
1481
1482=item exec LIST
1483
1484Not implemented. (S<Mac OS>)
1485
7c5ffed3 1486Implemented via Spawn. (VM/ESA)
3c075c7d 1487
0f897271
GS
1488Does not automatically flush output handles on some platforms.
1489(SunOS, Solaris, HP-UX)
1490
fe12c0e8
MS
1491=item exit EXPR
1492
1493=item exit
1494
1495Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1496mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1497with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1498function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1499(C<1>); this mapping cannot be overridden. Any other argument to exit()
1500is used directly as Perl's exit status. (VMS)
1501
e41182b5
GS
1502=item fcntl FILEHANDLE,FUNCTION,SCALAR
1503
1504Not implemented. (Win32, VMS)
1505
1506=item flock FILEHANDLE,OPERATION
1507
495c5fdc 1508Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1509
1510Available only on Windows NT (not on Windows 95). (Win32)
1511
1512=item fork
1513
0f897271
GS
1514Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
1515
1516Emulated using multiple interpreters. See L<perlfork>. (Win32)
1517
1518Does not automatically flush output handles on some platforms.
1519(SunOS, Solaris, HP-UX)
e41182b5
GS
1520
1521=item getlogin
1522
b8099c3d 1523Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1524
1525=item getpgrp PID
1526
495c5fdc 1527Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1528
1529=item getppid
1530
b8099c3d 1531Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1532
1533=item getpriority WHICH,WHO
1534
7c5ffed3 1535Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1536
1537=item getpwnam NAME
1538
1539Not implemented. (S<Mac OS>, Win32)
1540
b8099c3d
CN
1541Not useful. (S<RISC OS>)
1542
e41182b5
GS
1543=item getgrnam NAME
1544
b8099c3d 1545Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1546
1547=item getnetbyname NAME
1548
1549Not implemented. (S<Mac OS>, Win32, Plan9)
1550
1551=item getpwuid UID
1552
1553Not implemented. (S<Mac OS>, Win32)
1554
b8099c3d
CN
1555Not useful. (S<RISC OS>)
1556
e41182b5
GS
1557=item getgrgid GID
1558
b8099c3d 1559Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1560
1561=item getnetbyaddr ADDR,ADDRTYPE
1562
1563Not implemented. (S<Mac OS>, Win32, Plan9)
1564
1565=item getprotobynumber NUMBER
1566
1567Not implemented. (S<Mac OS>)
1568
1569=item getservbyport PORT,PROTO
1570
1571Not implemented. (S<Mac OS>)
1572
1573=item getpwent
1574
7c5ffed3 1575Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1576
1577=item getgrent
1578
7c5ffed3 1579Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5
GS
1580
1581=item gethostent
1582
1583Not implemented. (S<Mac OS>, Win32)
1584
1585=item getnetent
1586
1587Not implemented. (S<Mac OS>, Win32, Plan9)
1588
1589=item getprotoent
1590
1591Not implemented. (S<Mac OS>, Win32, Plan9)
1592
1593=item getservent
1594
1595Not implemented. (Win32, Plan9)
1596
1597=item setpwent
1598
b8099c3d 1599Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5
GS
1600
1601=item setgrent
1602
b8099c3d 1603Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1604
1605=item sethostent STAYOPEN
1606
b8099c3d 1607Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1608
1609=item setnetent STAYOPEN
1610
b8099c3d 1611Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1612
1613=item setprotoent STAYOPEN
1614
b8099c3d 1615Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
e41182b5
GS
1616
1617=item setservent STAYOPEN
1618
b8099c3d 1619Not implemented. (Plan9, Win32, S<RISC OS>)
e41182b5
GS
1620
1621=item endpwent
1622
a3dfe201 1623Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1624
1625=item endgrent
1626
a3dfe201 1627Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1628
1629=item endhostent
1630
1631Not implemented. (S<Mac OS>, Win32)
1632
1633=item endnetent
1634
1635Not implemented. (S<Mac OS>, Win32, Plan9)
1636
1637=item endprotoent
1638
1639Not implemented. (S<Mac OS>, Win32, Plan9)
1640
1641=item endservent
1642
1643Not implemented. (Plan9, Win32)
1644
1645=item getsockopt SOCKET,LEVEL,OPTNAME
1646
97c10e77 1647Not implemented. (Plan9)
e41182b5
GS
1648
1649=item glob EXPR
1650
1651=item glob
1652
63f87e49
GS
1653This operator is implemented via the File::Glob extension on most
1654platforms. See L<File::Glob> for portability information.
b8099c3d 1655
e41182b5
GS
1656=item ioctl FILEHANDLE,FUNCTION,SCALAR
1657
1658Not implemented. (VMS)
1659
1660Available only for socket handles, and it does what the ioctlsocket() call
1661in the Winsock API does. (Win32)
1662
b8099c3d
CN
1663Available only for socket handles. (S<RISC OS>)
1664
b350dd2f 1665=item kill SIGNAL, LIST
e41182b5 1666
862b5365
JH
1667C<kill(0, LIST)> is implemented for the sake of taint checking;
1668use with other signals is unimplemented. (S<Mac OS>)
1669
1670Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1671
63f87e49
GS
1672C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1673a signal to the identified process like it does on Unix platforms.
1674Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1675and makes it exit immediately with exit status $sig. As in Unix, if
1676$sig is 0 and the specified process exists, it returns true without
1677actually terminating it. (Win32)
e41182b5
GS
1678
1679=item link OLDFILE,NEWFILE
1680
a3dfe201 1681Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
e41182b5 1682
433acd8a
JH
1683Link count not updated because hard links are not quite that hard
1684(They are sort of half-way between hard and soft links). (AmigaOS)
1685
a3dfe201
GS
1686Hard links are implemented on Win32 (Windows NT and Windows 2000)
1687under NTFS only.
1688
e41182b5
GS
1689=item lstat FILEHANDLE
1690
1691=item lstat EXPR
1692
1693=item lstat
1694
b8099c3d 1695Not implemented. (VMS, S<RISC OS>)
e41182b5 1696
63f87e49 1697Return values (especially for device and inode) may be bogus. (Win32)
e41182b5
GS
1698
1699=item msgctl ID,CMD,ARG
1700
1701=item msgget KEY,FLAGS
1702
1703=item msgsnd ID,MSG,FLAGS
1704
1705=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
1706
495c5fdc 1707Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
e41182b5
GS
1708
1709=item open FILEHANDLE,EXPR
1710
1711=item open FILEHANDLE
1712
b7df3edc 1713The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1714(S<Mac OS>)
1715
c47ff5f1 1716open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1717
0f897271
GS
1718Opening a process does not automatically flush output handles on some
1719platforms. (SunOS, Solaris, HP-UX)
1720
e41182b5
GS
1721=item pipe READHANDLE,WRITEHANDLE
1722
433acd8a
JH
1723Very limited functionality. (MiNT)
1724
e41182b5
GS
1725=item readlink EXPR
1726
1727=item readlink
1728
b8099c3d 1729Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1730
1731=item select RBITS,WBITS,EBITS,TIMEOUT
1732
689c5c24 1733Only implemented on sockets. (Win32, VMS)
e41182b5 1734
b8099c3d
CN
1735Only reliable on sockets. (S<RISC OS>)
1736
76e05f0b 1737Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1738
e41182b5
GS
1739=item semctl ID,SEMNUM,CMD,ARG
1740
1741=item semget KEY,NSEMS,FLAGS
1742
1743=item semop KEY,OPSTRING
1744
495c5fdc 1745Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1746
a3dfe201
GS
1747=item setgrent
1748
1749Not implemented. (MPE/iX, Win32)
1750
e41182b5
GS
1751=item setpgrp PID,PGRP
1752
495c5fdc 1753Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5
GS
1754
1755=item setpriority WHICH,WHO,PRIORITY
1756
495c5fdc 1757Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1758
a3dfe201
GS
1759=item setpwent
1760
1761Not implemented. (MPE/iX, Win32)
1762
e41182b5
GS
1763=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
1764
97c10e77 1765Not implemented. (Plan9)
e41182b5
GS
1766
1767=item shmctl ID,CMD,ARG
1768
1769=item shmget KEY,SIZE,FLAGS
1770
1771=item shmread ID,VAR,POS,SIZE
1772
1773=item shmwrite ID,STRING,POS,SIZE
1774
495c5fdc 1775Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1776
80cbd5ad
JH
1777=item sockatmark SOCKET
1778
1779A relatively recent addition to socket functions, may not
1780be implemented even in UNIX platforms.
1781
e41182b5
GS
1782=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
1783
862b5365 1784Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5
GS
1785
1786=item stat FILEHANDLE
1787
1788=item stat EXPR
1789
1790=item stat
1791
d62e1b7f
JH
1792Platforms that do not have rdev, blksize, or blocks will return these
1793as '', so numeric comparison or manipulation of these fields may cause
1794'not numeric' warnings.
1795
e41182b5 1796mtime and atime are the same thing, and ctime is creation time instead of
3f1f789b
JH
1797inode change time. (S<Mac OS>).
1798
1799ctime not supported on UFS (S<Mac OS X>).
e41182b5 1800
95a3fe12
MS
1801ctime is creation time instead of inode change time (Win32).
1802
e41182b5
GS
1803device and inode are not meaningful. (Win32)
1804
1805device and inode are not necessarily reliable. (VMS)
1806
b8099c3d
CN
1807mtime, atime and ctime all return the last modification time. Device and
1808inode are not necessarily reliable. (S<RISC OS>)
1809
d62e1b7f
JH
1810dev, rdev, blksize, and blocks are not available. inode is not
1811meaningful and will differ between stat calls on the same file. (os2)
1812
73e9292c
JH
1813some versions of cygwin when doing a stat("foo") and if not finding it
1814may then attempt to stat("foo.exe") (Cygwin)
1815
e41182b5
GS
1816=item symlink OLDFILE,NEWFILE
1817
b8099c3d 1818Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5
GS
1819
1820=item syscall LIST
1821
7c5ffed3 1822Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1823
f34d0673
GS
1824=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
1825
dd9f0070 1826The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
1827numeric values on some systems. The flags exported by C<Fcntl>
1828(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 1829OS>, OS/390, VM/ESA)
f34d0673 1830
e41182b5
GS
1831=item system LIST
1832
9d6eb86e 1833In general, do not assume the UNIX/POSIX semantics that you can shift
7717d0e7 1834C<$?> right by eight to get the exit value, or that C<$? & 127>
9d6eb86e
JH
1835would give you the number of the signal that terminated the program,
1836or that C<$? & 128> would test true if the program was terminated by a
1837coredump. Instead, use the POSIX W*() interfaces: for example, use
1838WIFEXITED($?) an WEXITVALUE($?) to test for a normal exit and the exit
1839value, and WIFSIGNALED($?) and WTERMSIG($?) for a signal exit and the
7717d0e7 1840signal. Core dumping is not a portable concept, so there's no portable
9d6eb86e
JH
1841way to test for that.
1842
e41182b5
GS
1843Only implemented if ToolServer is installed. (S<Mac OS>)
1844
1845As an optimization, may not call the command shell specified in
b7df3edc 1846C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
1847process and immediately returns its process designator, without
1848waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
1849in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
1850by setting $? to "255 << 8". C<$?> is set in a way compatible with
1851Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
1852as described in the documentation). (Win32)
e41182b5 1853
b8099c3d
CN
1854There is no shell to process metacharacters, and the native standard is
1855to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 1856program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
1857the run time library of the spawned program. C<system> I<list> will call
1858the Unix emulation library's C<exec> emulation, which attempts to provide
1859emulation of the stdin, stdout, stderr in force in the parent, providing
1860the child program uses a compatible version of the emulation library.
1861I<scalar> will call the native command line direct and no such emulation
1862of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
1863
433acd8a
JH
1864Far from being POSIX compliant. Because there may be no underlying
1865/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 1866first token in its argument string. Handles basic redirection
c47ff5f1 1867("<" or ">") on its own behalf. (MiNT)
433acd8a 1868
0f897271
GS
1869Does not automatically flush output handles on some platforms.
1870(SunOS, Solaris, HP-UX)
1871
9bc98430
CB
1872The return value is POSIX-like (shifted up by 8 bits), which only allows
1873room for a made-up value derived from the severity bits of the native
187432-bit condition code (unless overridden by C<use vmsish 'status'>).
1875For more details see L<perlvms/$?>. (VMS)
1876
e41182b5
GS
1877=item times
1878
1879Only the first entry returned is nonzero. (S<Mac OS>)
1880
63f87e49
GS
1881"cumulative" times will be bogus. On anything other than Windows NT
1882or Windows 2000, "system" time will be bogus, and "user" time is
1883actually the time returned by the clock() function in the C runtime
1884library. (Win32)
e41182b5 1885
b8099c3d
CN
1886Not useful. (S<RISC OS>)
1887
e41182b5
GS
1888=item truncate FILEHANDLE,LENGTH
1889
1890=item truncate EXPR,LENGTH
1891
6d738113 1892Not implemented. (Older versions of VMS)
e41182b5 1893
495c5fdc
PG
1894Truncation to zero-length only. (VOS)
1895
4cfdb94f 1896If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 1897mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
1898or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
1899should not be held open elsewhere. (Win32)
1900
e41182b5
GS
1901=item umask EXPR
1902
1903=item umask
1904
1905Returns undef where unavailable, as of version 5.005.
1906
b7df3edc
GS
1907C<umask> works but the correct permissions are set only when the file
1908is finally closed. (AmigaOS)
433acd8a 1909
e41182b5
GS
1910=item utime LIST
1911
15c65113 1912Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 1913
322422de
GS
1914May not behave as expected. Behavior depends on the C runtime
1915library's implementation of utime(), and the filesystem being
1916used. The FAT filesystem typically does not support an "access
1917time" field, and it may limit timestamps to a granularity of
1918two seconds. (Win32)
e41182b5
GS
1919
1920=item wait
1921
1922=item waitpid PID,FLAGS
1923
495c5fdc 1924Not implemented. (S<Mac OS>, VOS)
e41182b5
GS
1925
1926Can only be applied to process handles returned for processes spawned
a6f858fb 1927using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 1928
b8099c3d
CN
1929Not useful. (S<RISC OS>)
1930
e41182b5
GS
1931=back
1932
b8099c3d
CN
1933=head1 CHANGES
1934
1935=over 4
1936
fd46a41b
JH
1937=item v1.48, 02 February 2001
1938
1939Various updates from perl5-porters over the past year, supported
1940platforms update from Jarkko Hietaniemi.
1941
c997b287
GS
1942=item v1.47, 22 March 2000
1943
1944Various cleanups from Tom Christiansen, including migration of
1945long platform listings from L<perl>.
1946
56d7751a
GS
1947=item v1.46, 12 February 2000
1948
1949Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
1950
0cc436d0
GS
1951=item v1.45, 20 December 1999
1952
1953Small changes from 5.005_63 distribution, more changes to EBCDIC info.
1954
d1e3b762
GS
1955=item v1.44, 19 July 1999
1956
1957A bunch of updates from Peter Prymmer for C<$^O> values,
1958endianness, File::Spec, VMS, BS2000, OS/400.
1959
b7df3edc
GS
1960=item v1.43, 24 May 1999
1961
1962Added a lot of cleaning up from Tom Christiansen.
1963
19799a22 1964=item v1.42, 22 May 1999
b7df3edc 1965
19799a22 1966Added notes about tests, sprintf/printf, and epoch offsets.
b7df3edc 1967
6ab3f9cb
GS
1968=item v1.41, 19 May 1999
1969
1970Lots more little changes to formatting and content.
1971
d1e3b762 1972Added a bunch of C<$^O> and related values
6ab3f9cb
GS
1973for various platforms; fixed mail and web addresses, and added
1974and changed miscellaneous notes. (Peter Prymmer)
1975
1976=item v1.40, 11 April 1999
1977
1978Miscellaneous changes.
1979
1980=item v1.39, 11 February 1999
2ee0eb3c
CN
1981
1982Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
1983note about newlines added.
1984
9b63e9ec
CN
1985=item v1.38, 31 December 1998
1986
1987More changes from Jarkko.
1988
3c075c7d
CN
1989=item v1.37, 19 December 1998
1990
1991More minor changes. Merge two separate version 1.35 documents.
1992
1993=item v1.36, 9 September 1998
1994
1995Updated for Stratus VOS. Also known as version 1.35.
1996
1997=item v1.35, 13 August 1998
495c5fdc 1998
3c075c7d
CN
1999Integrate more minor changes, plus addition of new sections under
2000L<"ISSUES">: L<"Numbers endianness and Width">,
2001L<"Character sets and character encoding">,
2002L<"Internationalisation">.
495c5fdc 2003
3c075c7d 2004=item v1.33, 06 August 1998
0a47030a
GS
2005
2006Integrate more minor changes.
2007
3c075c7d 2008=item v1.32, 05 August 1998
dd9f0070
CN
2009
2010Integrate more minor changes.
2011
3c075c7d 2012=item v1.30, 03 August 1998
b8099c3d
CN
2013
2014Major update for RISC OS, other minor changes.
2015
3c075c7d 2016=item v1.23, 10 July 1998
b8099c3d
CN
2017
2018First public release with perl5.005.
2019
2020=back
e41182b5 2021
ba58ab26
JH
2022=head1 Supported Platforms
2023
9ca74005
JH
2024As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
2025platforms are able to build Perl from the standard source code
a93751fa 2026distribution available at http://www.cpan.org/src/index.html
ba58ab26
JH
2027
2028 AIX
fd46a41b 2029 AmigaOS
b787fad4 2030 Darwin (Mac OS X)
fd46a41b 2031 DG/UX
ba58ab26 2032 DOS DJGPP 1)
fd46a41b 2033 DYNIX/ptx
2585f9a3 2034 EPOC R5
ba58ab26
JH
2035 FreeBSD
2036 HP-UX
2037 IRIX
2038 Linux
ba58ab26 2039 MachTen
fd46a41b
JH
2040 MacOS Classic 2)
2041 NonStop-UX
2042 ReliantUNIX (SINIX)
ba58ab26 2043 OpenBSD
fd46a41b 2044 OpenVMS (VMS)
ba58ab26 2045 OS/2
fd46a41b 2046 OS X
ba58ab26 2047 QNX
ba58ab26 2048 Solaris
fd46a41b 2049 Tru64 UNIX (DEC OSF/1, Digital UNIX)
ba58ab26
JH
2050 UNICOS
2051 UNICOS/mk
ba58ab26 2052 VOS
fd46a41b 2053 Win32/NT/2K 3)
ba58ab26
JH
2054
2055 1) in DOS mode either the DOS or OS/2 ports can be used
fd46a41b
JH
2056 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
2057 the source does work with 5.6.1, but additional MacOS specific
862b5365
JH
2058 source code is needed for a complete build. See the web
2059 site http://dev.macperl.org/ for more information.
fd46a41b 2060 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
ba58ab26 2061
9ca74005
JH
2062The following platforms worked for the previous releases (5.6.0 and 5.7.0),
2063but we did not manage to test these in time for the 5.7.1 release.
2064There is a very good chance that these will work fine with the 5.7.1.
ba58ab26 2065
ba58ab26
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2066 DomainOS
2067 Hurd
fd46a41b
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2068 LynxOS
2069 MinGW
2070 MPE/iX
2071 NetBSD
ba58ab26 2072 PowerMAX
fd46a41b 2073 SCO SV
ba58ab26 2074 SunOS
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2075 SVR4
2076 Unixware
2077 Windows 3.1
2078 Windows 95
2079 Windows 98
2080 Windows Me
ba58ab26 2081
fd46a41b 2082The following platform worked for the 5.005_03 major release but not
9ca74005
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2083for 5.6.0. Standardization on UTF-8 as the internal string
2084representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
2085EBCDIC platform. While Perl 5.7.1 will build on this platform some
fd46a41b 2086regression tests may fail and the C<use utf8;> pragma typically
9ca74005 2087introduces text handling errors.
ba58ab26 2088
fd46a41b 2089 OS/390 1)
ba58ab26 2090
fd46a41b 2091 1) previously known as MVS, about to become z/OS.
ba58ab26 2092
fd46a41b 2093Strongly related to the OS/390 platform by also being EBCDIC-based
ba58ab26
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2094mainframe platforms are the following platforms:
2095
fd46a41b 2096 POSIX-BC (BS2000)
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2097 VM/ESA
2098
fd46a41b
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2099These are also expected to work, albeit with no UTF-8 support, under 5.6.1
2100for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
2101for more details.
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2102
2103The following platforms have been known to build Perl from source in
fd46a41b
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2104the past (5.005_03 and earlier), but we haven't been able to verify
2105their status for the current release, either because the
2106hardware/software platforms are rare or because we don't have an
2107active champion on these platforms--or both. They used to work,
2108though, so go ahead and try compiling them, and let perlbug@perl.org
2109of any trouble.
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2110
2111 3b1
fd46a41b
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2112 A/UX
2113 BeOS
2114 BSD/OS
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2115 ConvexOS
2116 CX/UX
2117 DC/OSx
2118 DDE SMES
2119 DOS EMX
2120 Dynix
2121 EP/IX
2122 ESIX
2123 FPS
2124 GENIX
2125 Greenhills
2126 ISC
2127 MachTen 68k
2128 MiNT
2129 MPC
2130 NEWS-OS
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2131 NextSTEP
2132 OpenSTEP
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2133 Opus
2134 Plan 9
2135 PowerUX
2136 RISC/os
fd46a41b 2137 SCO ODT/OSR
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2138 Stellar
2139 SVR2
2140 TI1500
2141 TitanOS
fd46a41b 2142 Ultrix
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2143 Unisys Dynix
2144 Unixware
fd46a41b 2145 UTS
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2146
2147Support for the following platform is planned for a future Perl release:
2148
2149 Netware
2150
2151The following platforms have their own source code distributions and
1577cd80 2152binaries available via http://www.cpan.org/ports/
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2153
2154 Perl release
2155
ba58ab26 2156 Netware 5.003_07
fd46a41b 2157 OS/400 5.005_02
ba58ab26
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2158 Tandem Guardian 5.004
2159
2160The following platforms have only binaries available via
a93751fa 2161http://www.cpan.org/ports/index.html :
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2162
2163 Perl release
2164
2165 Acorn RISCOS 5.005_02
2166 AOS 5.002
2167 LynxOS 5.004_02
2168
2169Although we do suggest that you always build your own Perl from
2170the source code, both for maximal configurability and for security,
2171in case you are in a hurry you can check
a93751fa 2172http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2173
c997b287
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2174=head1 SEE ALSO
2175
a83b6f46 2176L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
a1f19229 2177L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
a83b6f46 2178L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
9038e305
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2179L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
2180L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
2181L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
c997b287 2182
e41182b5
GS
2183=head1 AUTHORS / CONTRIBUTORS
2184
06e9666b 2185Abigail <abigail@foad.org>,
c47ff5f1
GS
2186Charles Bailey <bailey@newman.upenn.edu>,
2187Graham Barr <gbarr@pobox.com>,
2188Tom Christiansen <tchrist@perl.com>,
06e9666b 2189Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2190Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2191Andy Dougherty <doughera@lafayette.edu>,
2192Dominic Dunlop <domo@computer.org>,
2193Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1
GS
2194David J. Fiander <davidf@mks.com>,
2195Paul Green <Paul_Green@stratus.com>,
06e9666b 2196M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2197Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2198Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2199Nick Ing-Simmons <nick@ing-simmons.net>,
2200Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2201Markus Laker <mlaker@contax.co.uk>,
2202Andrew M. Langmead <aml@world.std.com>,
2203Larry Moore <ljmoore@freespace.net>,
2204Paul Moore <Paul.Moore@uk.origin-it.com>,
2205Chris Nandor <pudge@pobox.com>,
1afc07ec 2206Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2207Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2208Gary Ng <71564.1743@CompuServe.COM>,
2209Tom Phoenix <rootbeer@teleport.com>,
2210AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2211Peter Prymmer <pvhp@forte.com>,
2212Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2213Gurusamy Sarathy <gsar@activestate.com>,
2214Paul J. Schinder <schinder@pobox.com>,
2215Michael G Schwern <schwern@pobox.com>,
06e9666b 2216Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2217Nathan Torkington <gnat@frii.com>.
e41182b5 2218