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1=head1 NAME
2
3perlport - Writing portable Perl
4
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5=head1 DESCRIPTION
6
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7Perl runs on numerous operating systems. While most of them share
8much in common, they also have their own unique features.
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9
10This document is meant to help you to find out what constitutes portable
b7df3edc 11Perl code. That way once you make a decision to write portably,
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12you know where the lines are drawn, and you can stay within them.
13
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14There is a tradeoff between taking full advantage of one particular
15type of computer and taking advantage of a full range of them.
16Naturally, as you broaden your range and become more diverse, the
17common factors drop, and you are left with an increasingly smaller
18area of common ground in which you can operate to accomplish a
19particular task. Thus, when you begin attacking a problem, it is
20important to consider under which part of the tradeoff curve you
21want to operate. Specifically, you must decide whether it is
22important that the task that you are coding have the full generality
23of being portable, or whether to just get the job done right now.
24This is the hardest choice to be made. The rest is easy, because
25Perl provides many choices, whichever way you want to approach your
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26problem.
27
28Looking at it another way, writing portable code is usually about
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29willfully limiting your available choices. Naturally, it takes
30discipline and sacrifice to do that. The product of portability
31and convenience may be a constant. You have been warned.
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32
33Be aware of two important points:
34
35=over 4
36
37=item Not all Perl programs have to be portable
38
b7df3edc 39There is no reason you should not use Perl as a language to glue Unix
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40tools together, or to prototype a Macintosh application, or to manage the
41Windows registry. If it makes no sense to aim for portability for one
42reason or another in a given program, then don't bother.
43
b7df3edc 44=item Nearly all of Perl already I<is> portable
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45
46Don't be fooled into thinking that it is hard to create portable Perl
47code. It isn't. Perl tries its level-best to bridge the gaps between
48what's available on different platforms, and all the means available to
49use those features. Thus almost all Perl code runs on any machine
6ab3f9cb 50without modification. But there are some significant issues in
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51writing portable code, and this document is entirely about those issues.
52
53=back
54
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55Here's the general rule: When you approach a task commonly done
56using a whole range of platforms, think about writing portable
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57code. That way, you don't sacrifice much by way of the implementation
58choices you can avail yourself of, and at the same time you can give
59your users lots of platform choices. On the other hand, when you have to
60take advantage of some unique feature of a particular platform, as is
61often the case with systems programming (whether for Unix, Windows,
62S<Mac OS>, VMS, etc.), consider writing platform-specific code.
63
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64When the code will run on only two or three operating systems, you
65may need to consider only the differences of those particular systems.
66The important thing is to decide where the code will run and to be
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67deliberate in your decision.
68
69The material below is separated into three main sections: main issues of
7ee27b7c 70portability (L<"ISSUES">), platform-specific issues (L<"PLATFORMS">), and
b7df3edc 71built-in perl functions that behave differently on various ports
7ee27b7c 72(L<"FUNCTION IMPLEMENTATIONS">).
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73
74This information should not be considered complete; it includes possibly
b8099c3d 75transient information about idiosyncrasies of some of the ports, almost
b7df3edc 76all of which are in a state of constant evolution. Thus, this material
e41182b5 77should be considered a perpetual work in progress
cc07ed0b 78(C<< <IMG SRC="yellow_sign.gif" ALT="Under Construction"> >>).
e41182b5 79
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80=head1 ISSUES
81
82=head2 Newlines
83
638bc118 84In most operating systems, lines in files are terminated by newlines.
e41182b5 85Just what is used as a newline may vary from OS to OS. Unix
b7df3edc 86traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>,
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87and S<Mac OS> uses C<\015>.
88
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89Perl uses C<\n> to represent the "logical" newline, where what is
90logical may depend on the platform in use. In MacPerl, C<\n> always
91means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but
92when accessing a file in "text" mode, STDIO translates it to (or
56d7751a 93from) C<\015\012>, depending on whether you're reading or writing.
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94Unix does the same thing on ttys in canonical mode. C<\015\012>
95is commonly referred to as CRLF.
96
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97To trim trailing newlines from text lines use chomp(). With default
98settings that function looks for a trailing C<\n> character and thus
99trims in a portable way.
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100
101When dealing with binary files (or text files in binary mode) be sure
102to explicitly set $/ to the appropriate value for your file format
103before using chomp().
104
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105Because of the "text" mode translation, DOSish perls have limitations
106in using C<seek> and C<tell> on a file accessed in "text" mode.
107Stick to C<seek>-ing to locations you got from C<tell> (and no
108others), and you are usually free to use C<seek> and C<tell> even
109in "text" mode. Using C<seek> or C<tell> or other file operations
110may be non-portable. If you use C<binmode> on a file, however, you
111can usually C<seek> and C<tell> with arbitrary values in safety.
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112
113A common misconception in socket programming is that C<\n> eq C<\012>
0a47030a 114everywhere. When using protocols such as common Internet protocols,
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115C<\012> and C<\015> are called for specifically, and the values of
116the logical C<\n> and C<\r> (carriage return) are not reliable.
117
118 print SOCKET "Hi there, client!\r\n"; # WRONG
119 print SOCKET "Hi there, client!\015\012"; # RIGHT
120
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121However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
122and unsightly, as well as confusing to those maintaining the code. As
6ab3f9cb 123such, the Socket module supplies the Right Thing for those who want it.
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124
125 use Socket qw(:DEFAULT :crlf);
126 print SOCKET "Hi there, client!$CRLF" # RIGHT
127
6ab3f9cb 128When reading from a socket, remember that the default input record
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129separator C<$/> is C<\n>, but robust socket code will recognize as
130either C<\012> or C<\015\012> as end of line:
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131
132 while (<SOCKET>) {
133 # ...
134 }
135
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136Because both CRLF and LF end in LF, the input record separator can
137be set to LF and any CR stripped later. Better to write:
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138
139 use Socket qw(:DEFAULT :crlf);
140 local($/) = LF; # not needed if $/ is already \012
141
142 while (<SOCKET>) {
143 s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
144 # s/\015?\012/\n/; # same thing
145 }
146
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147This example is preferred over the previous one--even for Unix
148platforms--because now any C<\015>'s (C<\cM>'s) are stripped out
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149(and there was much rejoicing).
150
6ab3f9cb 151Similarly, functions that return text data--such as a function that
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152fetches a web page--should sometimes translate newlines before
153returning the data, if they've not yet been translated to the local
154newline representation. A single line of code will often suffice:
2ee0eb3c 155
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156 $data =~ s/\015?\012/\n/g;
157 return $data;
2ee0eb3c 158
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159Some of this may be confusing. Here's a handy reference to the ASCII CR
160and LF characters. You can print it out and stick it in your wallet.
161
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162 LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
163 CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
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164
165 | Unix | DOS | Mac |
166 ---------------------------
167 \n | LF | LF | CR |
168 \r | CR | CR | LF |
169 \n * | LF | CRLF | CR |
170 \r * | CR | CR | LF |
171 ---------------------------
172 * text-mode STDIO
173
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174The Unix column assumes that you are not accessing a serial line
175(like a tty) in canonical mode. If you are, then CR on input becomes
176"\n", and "\n" on output becomes CRLF.
177
6ab3f9cb 178These are just the most common definitions of C<\n> and C<\r> in Perl.
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179There may well be others. For example, on an EBCDIC implementation
180such as z/OS (OS/390) or OS/400 (using the ILE, the PASE is ASCII-based)
181the above material is similar to "Unix" but the code numbers change:
74555b7a 182
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183 LF eq \025 eq \x15 eq \cU eq chr(21) eq CP-1047 21
184 LF eq \045 eq \x25 eq chr(37) eq CP-0037 37
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185 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
186 CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
187
188 | z/OS | OS/400 |
189 ----------------------
190 \n | LF | LF |
191 \r | CR | CR |
192 \n * | LF | LF |
193 \r * | CR | CR |
194 ----------------------
195 * text-mode STDIO
6ab3f9cb 196
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197=head2 Numbers endianness and Width
198
199Different CPUs store integers and floating point numbers in different
200orders (called I<endianness>) and widths (32-bit and 64-bit being the
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201most common today). This affects your programs when they attempt to transfer
202numbers in binary format from one CPU architecture to another,
203usually either "live" via network connection, or by storing the
204numbers to secondary storage such as a disk file or tape.
322422de 205
b7df3edc 206Conflicting storage orders make utter mess out of the numbers. If a
d1e3b762 207little-endian host (Intel, VAX) stores 0x12345678 (305419896 in
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208decimal), a big-endian host (Motorola, Sparc, PA) reads it as
2090x78563412 (2018915346 in decimal). Alpha and MIPS can be either:
210Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses
211them in big-endian mode. To avoid this problem in network (socket)
212connections use the C<pack> and C<unpack> formats C<n> and C<N>, the
213"network" orders. These are guaranteed to be portable.
322422de 214
7a4d2905 215As of perl 5.9.2, you can also use the C<E<gt>> and C<E<lt>> modifiers
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216to force big- or little-endian byte-order. This is useful if you want
217to store signed integers or 64-bit integers, for example.
218
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219You can explore the endianness of your platform by unpacking a
220data structure packed in native format such as:
221
222 print unpack("h*", pack("s2", 1, 2)), "\n";
223 # '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
224 # '00100020' on e.g. Motorola 68040
225
226If you need to distinguish between endian architectures you could use
227either of the variables set like so:
228
229 $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
4375e838 230 $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
d1e3b762 231
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232Differing widths can cause truncation even between platforms of equal
233endianness. The platform of shorter width loses the upper parts of the
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234number. There is no good solution for this problem except to avoid
235transferring or storing raw binary numbers.
236
b7df3edc 237One can circumnavigate both these problems in two ways. Either
322422de 238transfer and store numbers always in text format, instead of raw
b7df3edc 239binary, or else consider using modules like Data::Dumper (included in
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240the standard distribution as of Perl 5.005) and Storable (included as
241of perl 5.8). Keeping all data as text significantly simplifies matters.
322422de 242
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243The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's
244how far EBCDIC, or more precisely UTF-EBCDIC will go.
245
433acd8a 246=head2 Files and Filesystems
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247
248Most platforms these days structure files in a hierarchical fashion.
b7df3edc 249So, it is reasonably safe to assume that all platforms support the
6ab3f9cb 250notion of a "path" to uniquely identify a file on the system. How
b7df3edc 251that path is really written, though, differs considerably.
e41182b5 252
4375e838 253Although similar, file path specifications differ between Unix,
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254Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others.
255Unix, for example, is one of the few OSes that has the elegant idea
256of a single root directory.
322422de 257
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258DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</>
259as path separator, or in their own idiosyncratic ways (such as having
260several root directories and various "unrooted" device files such NIL:
261and LPT:).
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262
263S<Mac OS> uses C<:> as a path separator instead of C</>.
264
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265The filesystem may support neither hard links (C<link>) nor
266symbolic links (C<symlink>, C<readlink>, C<lstat>).
433acd8a 267
6ab3f9cb 268The filesystem may support neither access timestamp nor change
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269timestamp (meaning that about the only portable timestamp is the
270modification timestamp), or one second granularity of any timestamps
271(e.g. the FAT filesystem limits the time granularity to two seconds).
272
74555b7a 273The "inode change timestamp" (the C<-C> filetest) may really be the
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274"creation timestamp" (which it is not in UNIX).
275
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276VOS perl can emulate Unix filenames with C</> as path separator. The
277native pathname characters greater-than, less-than, number-sign, and
278percent-sign are always accepted.
279
6ab3f9cb 280S<RISC OS> perl can emulate Unix filenames with C</> as path
322422de 281separator, or go native and use C<.> for path separator and C<:> to
6ab3f9cb 282signal filesystems and disk names.
e41182b5 283
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284Don't assume UNIX filesystem access semantics: that read, write,
285and execute are all the permissions there are, and even if they exist,
286that their semantics (for example what do r, w, and x mean on
287a directory) are the UNIX ones. The various UNIX/POSIX compatibility
288layers usually try to make interfaces like chmod() work, but sometimes
289there simply is no good mapping.
290
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291If all this is intimidating, have no (well, maybe only a little)
292fear. There are modules that can help. The File::Spec modules
293provide methods to do the Right Thing on whatever platform happens
294to be running the program.
e41182b5 295
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296 use File::Spec::Functions;
297 chdir(updir()); # go up one directory
298 $file = catfile(curdir(), 'temp', 'file.txt');
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299 # on Unix and Win32, './temp/file.txt'
300 # on Mac OS, ':temp:file.txt'
d1e3b762 301 # on VMS, '[.temp]file.txt'
e41182b5 302
b7df3edc 303File::Spec is available in the standard distribution as of version
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3045.004_05. File::Spec::Functions is only in File::Spec 0.7 and later,
305and some versions of perl come with version 0.6. If File::Spec
306is not updated to 0.7 or later, you must use the object-oriented
307interface from File::Spec (or upgrade File::Spec).
e41182b5 308
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309In general, production code should not have file paths hardcoded.
310Making them user-supplied or read from a configuration file is
311better, keeping in mind that file path syntax varies on different
312machines.
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313
314This is especially noticeable in scripts like Makefiles and test suites,
315which often assume C</> as a path separator for subdirectories.
316
b7df3edc 317Also of use is File::Basename from the standard distribution, which
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318splits a pathname into pieces (base filename, full path to directory,
319and file suffix).
320
19799a22 321Even when on a single platform (if you can call Unix a single platform),
b7df3edc 322remember not to count on the existence or the contents of particular
3c075c7d 323system-specific files or directories, like F</etc/passwd>,
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324F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
325example, F</etc/passwd> may exist but not contain the encrypted
326passwords, because the system is using some form of enhanced security.
327Or it may not contain all the accounts, because the system is using NIS.
3c075c7d 328If code does need to rely on such a file, include a description of the
b7df3edc 329file and its format in the code's documentation, then make it easy for
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330the user to override the default location of the file.
331
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332Don't assume a text file will end with a newline. They should,
333but people forget.
e41182b5 334
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335Do not have two files or directories of the same name with different
336case, like F<test.pl> and F<Test.pl>, as many platforms have
337case-insensitive (or at least case-forgiving) filenames. Also, try
338not to have non-word characters (except for C<.>) in the names, and
339keep them to the 8.3 convention, for maximum portability, onerous a
340burden though this may appear.
dd9f0070 341
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342Likewise, when using the AutoSplit module, try to keep your functions to
3438.3 naming and case-insensitive conventions; or, at the least,
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344make it so the resulting files have a unique (case-insensitively)
345first 8 characters.
346
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347Whitespace in filenames is tolerated on most systems, but not all,
348and even on systems where it might be tolerated, some utilities
fe829689 349might become confused by such whitespace.
ec481373 350
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351Many systems (DOS, VMS ODS-2) cannot have more than one C<.> in their
352filenames.
433acd8a 353
c47ff5f1 354Don't assume C<< > >> won't be the first character of a filename.
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355Always use C<< < >> explicitly to open a file for reading, or even
356better, use the three-arg version of open, unless you want the user to
357be able to specify a pipe open.
0a47030a 358
fe829689 359 open(FILE, '<', $existing_file) or die $!;
0a47030a 360
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361If filenames might use strange characters, it is safest to open it
362with C<sysopen> instead of C<open>. C<open> is magic and can
c47ff5f1 363translate characters like C<< > >>, C<< < >>, and C<|>, which may
b7df3edc 364be the wrong thing to do. (Sometimes, though, it's the right thing.)
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365Three-arg open can also help protect against this translation in cases
366where it is undesirable.
e41182b5 367
ec481373 368Don't use C<:> as a part of a filename since many systems use that for
8939ba94 369their own semantics (Mac OS Classic for separating pathname components,
ec481373 370many networking schemes and utilities for separating the nodename and
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371the pathname, and so on). For the same reasons, avoid C<@>, C<;> and
372C<|>.
ec481373 373
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374Don't assume that in pathnames you can collapse two leading slashes
375C<//> into one: some networking and clustering filesystems have special
376semantics for that. Let the operating system to sort it out.
377
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378The I<portable filename characters> as defined by ANSI C are
379
380 a b c d e f g h i j k l m n o p q r t u v w x y z
381 A B C D E F G H I J K L M N O P Q R T U V W X Y Z
382 0 1 2 3 4 5 6 7 8 9
383 . _ -
384
08fef530 385and the "-" shouldn't be the first character. If you want to be
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386hypercorrect, stay case-insensitive and within the 8.3 naming
387convention (all the files and directories have to be unique within one
388directory if their names are lowercased and truncated to eight
389characters before the C<.>, if any, and to three characters after the
390C<.>, if any). (And do not use C<.>s in directory names.)
ec481373 391
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392=head2 System Interaction
393
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394Not all platforms provide a command line. These are usually platforms
395that rely primarily on a Graphical User Interface (GUI) for user
396interaction. A program requiring a command line interface might
397not work everywhere. This is probably for the user of the program
398to deal with, so don't stay up late worrying about it.
e41182b5 399
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400Some platforms can't delete or rename files held open by the system,
401this limitation may also apply to changing filesystem metainformation
402like file permissions or owners. Remember to C<close> files when you
403are done with them. Don't C<unlink> or C<rename> an open file. Don't
404C<tie> or C<open> a file already tied or opened; C<untie> or C<close>
405it first.
e41182b5 406
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407Don't open the same file more than once at a time for writing, as some
408operating systems put mandatory locks on such files.
409
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410Don't assume that write/modify permission on a directory gives the
411right to add or delete files/directories in that directory. That is
412filesystem specific: in some filesystems you need write/modify
413permission also (or even just) in the file/directory itself. In some
414filesystems (AFS, DFS) the permission to add/delete directory entries
415is a completely separate permission.
416
417Don't assume that a single C<unlink> completely gets rid of the file:
418some filesystems (most notably the ones in VMS) have versioned
419filesystems, and unlink() removes only the most recent one (it doesn't
420remove all the versions because by default the native tools on those
421platforms remove just the most recent version, too). The portable
422idiom to remove all the versions of a file is
423
94bb614c 424 1 while unlink "file";
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425
426This will terminate if the file is undeleteable for some reason
427(protected, not there, and so on).
428
e41182b5 429Don't count on a specific environment variable existing in C<%ENV>.
0a47030a 430Don't count on C<%ENV> entries being case-sensitive, or even
4a0d0822 431case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or,
6be8f7a6 432if you really have to, make it conditional on C<$^O ne 'VMS'> since in
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433VMS the C<%ENV> table is much more than a per-process key-value string
434table.
e41182b5 435
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436On VMS, some entries in the %ENV hash are dynamically created when
437their key is used on a read if they did not previously exist. The
438values for C<$ENV{HOME}>, C<$ENV{TERM}>, C<$ENV{HOME}>, and C<$ENV{USER}>,
439are known to be dynamically generated. The specific names that are
440dynamically generated may vary with the version of the C library on VMS,
441and more may exist than is documented.
442
443On VMS by default, changes to the %ENV hash are persistent after the process
444exits. This can cause unintended issues.
445
d1e3b762 446Don't count on signals or C<%SIG> for anything.
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447
448Don't count on filename globbing. Use C<opendir>, C<readdir>, and
449C<closedir> instead.
450
b8099c3d 451Don't count on per-program environment variables, or per-program current
dd9f0070 452directories.
b8099c3d 453
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454Don't count on specific values of C<$!>, neither numeric nor
455especially the strings values-- users may switch their locales causing
456error messages to be translated into their languages. If you can
457trust a POSIXish environment, you can portably use the symbols defined
458by the Errno module, like ENOENT. And don't trust on the values of C<$!>
459at all except immediately after a failed system call.
3c075c7d 460
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461=head2 Command names versus file pathnames
462
463Don't assume that the name used to invoke a command or program with
464C<system> or C<exec> can also be used to test for the existence of the
465file that holds the executable code for that command or program.
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466First, many systems have "internal" commands that are built-in to the
467shell or OS and while these commands can be invoked, there is no
468corresponding file. Second, some operating systems (e.g., Cygwin,
469DJGPP, OS/2, and VOS) have required suffixes for executable files;
470these suffixes are generally permitted on the command name but are not
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471required. Thus, a command like "perl" might exist in a file named
472"perl", "perl.exe", or "perl.pm", depending on the operating system.
473The variable "_exe" in the Config module holds the executable suffix,
68fb0eb7
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474if any. Third, the VMS port carefully sets up $^X and
475$Config{perlpath} so that no further processing is required. This is
476just as well, because the matching regular expression used below would
477then have to deal with a possible trailing version number in the VMS
478file name.
a10d74f3
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479
480To convert $^X to a file pathname, taking account of the requirements
481of the various operating system possibilities, say:
7ee27b7c 482
a10d74f3 483 use Config;
a10d74f3 484 $thisperl = $^X;
68fb0eb7
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485 if ($^O ne 'VMS')
486 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3
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487
488To convert $Config{perlpath} to a file pathname, say:
7ee27b7c 489
a10d74f3 490 use Config;
68fb0eb7
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491 $thisperl = $Config{perlpath};
492 if ($^O ne 'VMS')
493 {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
a10d74f3 494
7137b697
JH
495=head2 Networking
496
497Don't assume that you can reach the public Internet.
498
499Don't assume that there is only one way to get through firewalls
500to the public Internet.
501
932f293e
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502Don't assume that you can reach outside world through any other port
503than 80, or some web proxy. ftp is blocked by many firewalls.
504
dbc6a9ce
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505Don't assume that you can send email by connecting to the local SMTP port.
506
7137b697 507Don't assume that you can reach yourself or any node by the name
dbc6a9ce 508'localhost'. The same goes for '127.0.0.1'. You will have to try both.
932f293e 509
86feb2c5
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510Don't assume that the host has only one network card, or that it
511can't bind to many virtual IP addresses.
932f293e
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512
513Don't assume a particular network device name.
7137b697 514
dbc6a9ce 515Don't assume a particular set of ioctl()s will work.
7137b697
JH
516
517Don't assume that you can ping hosts and get replies.
518
dbc6a9ce
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519Don't assume that any particular port (service) will respond.
520
7ee27b7c 521Don't assume that Sys::Hostname (or any other API or command)
dbc6a9ce
JH
522returns either a fully qualified hostname or a non-qualified hostname:
523it all depends on how the system had been configured. Also remember
524things like DHCP and NAT-- the hostname you get back might not be very
525useful.
526
932f293e
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527All the above "don't":s may look daunting, and they are -- but the key
528is to degrade gracefully if one cannot reach the particular network
529service one wants. Croaking or hanging do not look very professional.
530
e41182b5
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531=head2 Interprocess Communication (IPC)
532
b7df3edc
GS
533In general, don't directly access the system in code meant to be
534portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>,
535C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things
536that makes being a perl hacker worth being.
e41182b5
GS
537
538Commands that launch external processes are generally supported on
b7df3edc
GS
539most platforms (though many of them do not support any type of
540forking). The problem with using them arises from what you invoke
541them on. External tools are often named differently on different
4375e838 542platforms, may not be available in the same location, might accept
b7df3edc
GS
543different arguments, can behave differently, and often present their
544results in a platform-dependent way. Thus, you should seldom depend
545on them to produce consistent results. (Then again, if you're calling
546I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.)
e41182b5 547
b7df3edc 548One especially common bit of Perl code is opening a pipe to B<sendmail>:
e41182b5 549
b7df3edc
GS
550 open(MAIL, '|/usr/lib/sendmail -t')
551 or die "cannot fork sendmail: $!";
e41182b5
GS
552
553This is fine for systems programming when sendmail is known to be
554available. But it is not fine for many non-Unix systems, and even
555some Unix systems that may not have sendmail installed. If a portable
b7df3edc
GS
556solution is needed, see the various distributions on CPAN that deal
557with it. Mail::Mailer and Mail::Send in the MailTools distribution are
558commonly used, and provide several mailing methods, including mail,
559sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is
560not available. Mail::Sendmail is a standalone module that provides
561simple, platform-independent mailing.
562
563The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available
564even on all Unix platforms.
e41182b5 565
a81e5e2e
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566Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or
567bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses:
568both forms just pack the four bytes into network order. That this
569would be equal to the C language C<in_addr> struct (which is what the
570socket code internally uses) is not guaranteed. To be portable use
571the routines of the Socket extension, such as C<inet_aton()>,
572C<inet_ntoa()>, and C<sockaddr_in()>.
6b2463a0 573
e41182b5 574The rule of thumb for portable code is: Do it all in portable Perl, or
0a47030a
GS
575use a module (that may internally implement it with platform-specific
576code, but expose a common interface).
e41182b5 577
e41182b5
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578=head2 External Subroutines (XS)
579
b7df3edc 580XS code can usually be made to work with any platform, but dependent
e41182b5
GS
581libraries, header files, etc., might not be readily available or
582portable, or the XS code itself might be platform-specific, just as Perl
583code might be. If the libraries and headers are portable, then it is
584normally reasonable to make sure the XS code is portable, too.
585
b7df3edc
GS
586A different type of portability issue arises when writing XS code:
587availability of a C compiler on the end-user's system. C brings
588with it its own portability issues, and writing XS code will expose
589you to some of those. Writing purely in Perl is an easier way to
e41182b5
GS
590achieve portability.
591
e41182b5
GS
592=head2 Standard Modules
593
594In general, the standard modules work across platforms. Notable
6ab3f9cb 595exceptions are the CPAN module (which currently makes connections to external
e41182b5 596programs that may not be available), platform-specific modules (like
6ab3f9cb 597ExtUtils::MM_VMS), and DBM modules.
e41182b5 598
b7df3edc 599There is no one DBM module available on all platforms.
6ab3f9cb
GS
600SDBM_File and the others are generally available on all Unix and DOSish
601ports, but not in MacPerl, where only NBDM_File and DB_File are
0a47030a 602available.
e41182b5
GS
603
604The good news is that at least some DBM module should be available, and
6ab3f9cb 605AnyDBM_File will use whichever module it can find. Of course, then
b7df3edc
GS
606the code needs to be fairly strict, dropping to the greatest common
607factor (e.g., not exceeding 1K for each record), so that it will
6ab3f9cb 608work with any DBM module. See L<AnyDBM_File> for more details.
e41182b5 609
e41182b5
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610=head2 Time and Date
611
0a47030a 612The system's notion of time of day and calendar date is controlled in
b7df3edc 613widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>,
0a47030a 614and even if it is, don't assume that you can control the timezone through
c87488a3
HS
615that variable. Don't assume anything about the three-letter timezone
616abbreviations (for example that MST would be the Mountain Standard Time,
617it's been known to stand for Moscow Standard Time). If you need to
618use timezones, express them in some unambiguous format like the
619exact number of minutes offset from UTC, or the POSIX timezone
620format.
e41182b5 621
322422de 622Don't assume that the epoch starts at 00:00:00, January 1, 1970,
c87488a3
HS
623because that is OS- and implementation-specific. It is better to
624store a date in an unambiguous representation. The ISO 8601 standard
625defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH-MM-SS
626(that's a literal "T" separating the date from the time).
627Please do use the ISO 8601 instead of making us to guess what
628date 02/03/04 might be. ISO 8601 even sorts nicely as-is.
629A text representation (like "1987-12-18") can be easily converted
630into an OS-specific value using a module like Date::Parse.
631An array of values, such as those returned by C<localtime>, can be
632converted to an OS-specific representation using Time::Local.
322422de 633
19799a22
GS
634When calculating specific times, such as for tests in time or date modules,
635it may be appropriate to calculate an offset for the epoch.
b7df3edc 636
19799a22
GS
637 require Time::Local;
638 $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
b7df3edc 639
19799a22
GS
640The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
641some large number. C<$offset> can then be added to a Unix time value
642to get what should be the proper value on any system.
322422de 643
bbac04ed
RGS
644On Windows (at least), you shouldn't pass a negative value to C<gmtime> or
645C<localtime>.
646
322422de
GS
647=head2 Character sets and character encoding
648
ec481373
JH
649Assume very little about character sets.
650
651Assume nothing about numerical values (C<ord>, C<chr>) of characters.
652Do not use explicit code point ranges (like \xHH-\xHH); use for
653example symbolic character classes like C<[:print:]>.
654
655Do not assume that the alphabetic characters are encoded contiguously
656(in the numeric sense). There may be gaps.
657
658Do not assume anything about the ordering of the characters.
659The lowercase letters may come before or after the uppercase letters;
b432a672
AL
660the lowercase and uppercase may be interlaced so that both "a" and "A"
661come before "b"; the accented and other international characters may
662be interlaced so that E<auml> comes before "b".
322422de
GS
663
664=head2 Internationalisation
665
b7df3edc
GS
666If you may assume POSIX (a rather large assumption), you may read
667more about the POSIX locale system from L<perllocale>. The locale
668system at least attempts to make things a little bit more portable,
669or at least more convenient and native-friendly for non-English
670users. The system affects character sets and encoding, and date
671and time formatting--amongst other things.
e41182b5 672
c87488a3
HS
673If you really want to be international, you should consider Unicode.
674See L<perluniintro> and L<perlunicode> for more information.
675
11264fdb
JH
676If you want to use non-ASCII bytes (outside the bytes 0x00..0x7f) in
677the "source code" of your code, to be portable you have to be explicit
678about what bytes they are. Someone might for example be using your
679code under a UTF-8 locale, in which case random native bytes might be
680illegal ("Malformed UTF-8 ...") This means that for example embedding
681ISO 8859-1 bytes beyond 0x7f into your strings might cause trouble
682later. If the bytes are native 8-bit bytes, you can use the C<bytes>
683pragma. If the bytes are in a string (regular expression being a
684curious string), you can often also use the C<\xHH> notation instead
2575c402
JW
685of embedding the bytes as-is. (If you want to write your code in UTF-8,
686you can use the C<utf8>.) The C<bytes> and C<utf8> pragmata are
687available since Perl 5.6.0.
11264fdb 688
e41182b5
GS
689=head2 System Resources
690
0a47030a
GS
691If your code is destined for systems with severely constrained (or
692missing!) virtual memory systems then you want to be I<especially> mindful
693of avoiding wasteful constructs such as:
e41182b5
GS
694
695 # NOTE: this is no longer "bad" in perl5.005
696 for (0..10000000) {} # bad
697 for (my $x = 0; $x <= 10000000; ++$x) {} # good
698
699 @lines = <VERY_LARGE_FILE>; # bad
700
701 while (<FILE>) {$file .= $_} # sometimes bad
0a47030a 702 $file = join('', <FILE>); # better
e41182b5 703
b7df3edc
GS
704The last two constructs may appear unintuitive to most people. The
705first repeatedly grows a string, whereas the second allocates a
706large chunk of memory in one go. On some systems, the second is
707more efficient that the first.
0a47030a 708
e41182b5
GS
709=head2 Security
710
b7df3edc
GS
711Most multi-user platforms provide basic levels of security, usually
712implemented at the filesystem level. Some, however, do
a1667ba3 713not-- unfortunately. Thus the notion of user id, or "home" directory,
b7df3edc
GS
714or even the state of being logged-in, may be unrecognizable on many
715platforms. If you write programs that are security-conscious, it
716is usually best to know what type of system you will be running
717under so that you can write code explicitly for that platform (or
718class of platforms).
0a47030a 719
a1667ba3
JH
720Don't assume the UNIX filesystem access semantics: the operating
721system or the filesystem may be using some ACL systems, which are
722richer languages than the usual rwx. Even if the rwx exist,
723their semantics might be different.
724
725(From security viewpoint testing for permissions before attempting to
726do something is silly anyway: if one tries this, there is potential
727for race conditions-- someone or something might change the
728permissions between the permissions check and the actual operation.
729Just try the operation.)
730
731Don't assume the UNIX user and group semantics: especially, don't
2edcc0d9 732expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
a1667ba3
JH
733for switching identities (or memberships).
734
735Don't assume set-uid and set-gid semantics. (And even if you do,
736think twice: set-uid and set-gid are a known can of security worms.)
737
e41182b5
GS
738=head2 Style
739
740For those times when it is necessary to have platform-specific code,
741consider keeping the platform-specific code in one place, making porting
6ab3f9cb 742to other platforms easier. Use the Config module and the special
0a47030a
GS
743variable C<$^O> to differentiate platforms, as described in
744L<"PLATFORMS">.
e41182b5 745
b7df3edc
GS
746Be careful in the tests you supply with your module or programs.
747Module code may be fully portable, but its tests might not be. This
748often happens when tests spawn off other processes or call external
749programs to aid in the testing, or when (as noted above) the tests
c87488a3
HS
750assume certain things about the filesystem and paths. Be careful not
751to depend on a specific output style for errors, such as when checking
752C<$!> after a failed system call. Using C<$!> for anything else than
753displaying it as output is doubtful (though see the Errno module for
754testing reasonably portably for error value). Some platforms expect
755a certain output format, and Perl on those platforms may have been
756adjusted accordingly. Most specifically, don't anchor a regex when
757testing an error value.
e41182b5 758
0a47030a 759=head1 CPAN Testers
e41182b5 760
0a47030a
GS
761Modules uploaded to CPAN are tested by a variety of volunteers on
762different platforms. These CPAN testers are notified by mail of each
e41182b5 763new upload, and reply to the list with PASS, FAIL, NA (not applicable to
0a47030a 764this platform), or UNKNOWN (unknown), along with any relevant notations.
e41182b5
GS
765
766The purpose of the testing is twofold: one, to help developers fix any
0a47030a 767problems in their code that crop up because of lack of testing on other
b7df3edc 768platforms; two, to provide users with information about whether
0a47030a 769a given module works on a given platform.
e41182b5 770
7ee27b7c
AT
771Also see:
772
e41182b5
GS
773=over 4
774
7ee27b7c
AT
775=item *
776
777Mailing list: cpan-testers@perl.org
778
779=item *
e41182b5 780
7ee27b7c 781Testing results: http://testers.cpan.org/
e41182b5
GS
782
783=back
784
e41182b5
GS
785=head1 PLATFORMS
786
787As of version 5.002, Perl is built with a C<$^O> variable that
788indicates the operating system it was built on. This was implemented
b7df3edc
GS
789to help speed up code that would otherwise have to C<use Config>
790and use the value of C<$Config{osname}>. Of course, to get more
e41182b5
GS
791detailed information about the system, looking into C<%Config> is
792certainly recommended.
793
b7df3edc
GS
794C<%Config> cannot always be trusted, however, because it was built
795at compile time. If perl was built in one place, then transferred
796elsewhere, some values may be wrong. The values may even have been
797edited after the fact.
6ab3f9cb 798
e41182b5
GS
799=head2 Unix
800
801Perl works on a bewildering variety of Unix and Unix-like platforms (see
802e.g. most of the files in the F<hints/> directory in the source code kit).
803On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>,
d1e3b762
GS
804too) is determined either by lowercasing and stripping punctuation from the
805first field of the string returned by typing C<uname -a> (or a similar command)
806at the shell prompt or by testing the file system for the presence of
807uniquely named files such as a kernel or header file. Here, for example,
808are a few of the more popular Unix flavors:
e41182b5 809
b7df3edc 810 uname $^O $Config{'archname'}
6ab3f9cb 811 --------------------------------------------
b7df3edc 812 AIX aix aix
6ab3f9cb 813 BSD/OS bsdos i386-bsdos
e1516da7 814 Darwin darwin darwin
6ab3f9cb
GS
815 dgux dgux AViiON-dgux
816 DYNIX/ptx dynixptx i386-dynixptx
b7df3edc 817 FreeBSD freebsd freebsd-i386
d1e3b762 818 Linux linux arm-linux
b7df3edc 819 Linux linux i386-linux
6ab3f9cb
GS
820 Linux linux i586-linux
821 Linux linux ppc-linux
b7df3edc
GS
822 HP-UX hpux PA-RISC1.1
823 IRIX irix irix
b787fad4 824 Mac OS X darwin darwin
d1e3b762
GS
825 MachTen PPC machten powerpc-machten
826 NeXT 3 next next-fat
827 NeXT 4 next OPENSTEP-Mach
6ab3f9cb 828 openbsd openbsd i386-openbsd
b7df3edc 829 OSF1 dec_osf alpha-dec_osf
6ab3f9cb
GS
830 reliantunix-n svr4 RM400-svr4
831 SCO_SV sco_sv i386-sco_sv
832 SINIX-N svr4 RM400-svr4
833 sn4609 unicos CRAY_C90-unicos
834 sn6521 unicosmk t3e-unicosmk
835 sn9617 unicos CRAY_J90-unicos
b7df3edc
GS
836 SunOS solaris sun4-solaris
837 SunOS solaris i86pc-solaris
838 SunOS4 sunos sun4-sunos
e41182b5 839
b7df3edc
GS
840Because the value of C<$Config{archname}> may depend on the
841hardware architecture, it can vary more than the value of C<$^O>.
6ab3f9cb 842
e41182b5
GS
843=head2 DOS and Derivatives
844
b7df3edc 845Perl has long been ported to Intel-style microcomputers running under
e41182b5
GS
846systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can
847bring yourself to mention (except for Windows CE, if you count that).
b7df3edc 848Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should
e41182b5
GS
849be aware that each of these file specifications may have subtle
850differences:
851
852 $filespec0 = "c:/foo/bar/file.txt";
853 $filespec1 = "c:\\foo\\bar\\file.txt";
854 $filespec2 = 'c:\foo\bar\file.txt';
855 $filespec3 = 'c:\\foo\\bar\\file.txt';
856
b7df3edc
GS
857System calls accept either C</> or C<\> as the path separator.
858However, many command-line utilities of DOS vintage treat C</> as
859the option prefix, so may get confused by filenames containing C</>.
860Aside from calling any external programs, C</> will work just fine,
861and probably better, as it is more consistent with popular usage,
862and avoids the problem of remembering what to backwhack and what
863not to.
e41182b5 864
b7df3edc
GS
865The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
866the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
0a47030a 867filesystems you may have to be careful about case returned with functions
e41182b5
GS
868like C<readdir> or used with functions like C<open> or C<opendir>.
869
b7df3edc
GS
870DOS also treats several filenames as special, such as AUX, PRN,
871NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these
872filenames won't even work if you include an explicit directory
873prefix. It is best to avoid such filenames, if you want your code
874to be portable to DOS and its derivatives. It's hard to know what
875these all are, unfortunately.
e41182b5
GS
876
877Users of these operating systems may also wish to make use of
b7df3edc 878scripts such as I<pl2bat.bat> or I<pl2cmd> to
e41182b5
GS
879put wrappers around your scripts.
880
881Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
6ab3f9cb
GS
882and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
883will keep C<\n> translated as C<\012> for that filehandle. Since it is a
884no-op on other systems, C<binmode> should be used for cross-platform code
b7df3edc
GS
885that deals with binary data. That's assuming you realize in advance
886that your data is in binary. General-purpose programs should
887often assume nothing about their data.
e41182b5 888
b7df3edc 889The C<$^O> variable and the C<$Config{archname}> values for various
e41182b5
GS
890DOSish perls are as follows:
891
67ac489e
MS
892 OS $^O $Config{archname} ID Version
893 --------------------------------------------------------
894 MS-DOS dos ?
895 PC-DOS dos ?
896 OS/2 os2 ?
897 Windows 3.1 ? ? 0 3 01
898 Windows 95 MSWin32 MSWin32-x86 1 4 00
899 Windows 98 MSWin32 MSWin32-x86 1 4 10
900 Windows ME MSWin32 MSWin32-x86 1 ?
901 Windows NT MSWin32 MSWin32-x86 2 4 xx
902 Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
903 Windows NT MSWin32 MSWin32-ppc 2 4 xx
7ee27b7c
AT
904 Windows 2000 MSWin32 MSWin32-x86 2 5 00
905 Windows XP MSWin32 MSWin32-x86 2 5 01
906 Windows 2003 MSWin32 MSWin32-x86 2 5 02
67ac489e 907 Windows CE MSWin32 ? 3
7ee27b7c 908 Cygwin cygwin cygwin
e41182b5 909
34aaaa84
PP
910The various MSWin32 Perl's can distinguish the OS they are running on
911via the value of the fifth element of the list returned from
912Win32::GetOSVersion(). For example:
913
914 if ($^O eq 'MSWin32') {
915 my @os_version_info = Win32::GetOSVersion();
916 print +('3.1','95','NT')[$os_version_info[4]],"\n";
917 }
918
7939d86b
JH
919There are also Win32::IsWinNT() and Win32::IsWin95(), try C<perldoc Win32>,
920and as of libwin32 0.19 (not part of the core Perl distribution)
921Win32::GetOSName(). The very portable POSIX::uname() will work too:
1d65be3a
JH
922
923 c:\> perl -MPOSIX -we "print join '|', uname"
924 Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86
d99f392e 925
e41182b5
GS
926Also see:
927
928=over 4
929
c997b287 930=item *
e41182b5 931
c997b287
GS
932The djgpp environment for DOS, http://www.delorie.com/djgpp/
933and L<perldos>.
e41182b5 934
c997b287 935=item *
e41182b5 936
c997b287
GS
937The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
938http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
f224927c 939ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
e41182b5 940
c997b287 941=item *
d1e3b762 942
c997b287
GS
943Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment
944in L<perlcygwin>.
945
946=item *
947
948The C<Win32::*> modules in L<Win32>.
949
950=item *
951
952The ActiveState Pages, http://www.activestate.com/
953
954=item *
955
956The Cygwin environment for Win32; F<README.cygwin> (installed
47dafe4d 957as L<perlcygwin>), http://www.cygwin.com/
c997b287
GS
958
959=item *
960
961The U/WIN environment for Win32,
cea6626f 962http://www.research.att.com/sw/tools/uwin/
c997b287 963
cea6626f 964=item *
d1e3b762 965
cea6626f 966Build instructions for OS/2, L<perlos2>
d1e3b762 967
e41182b5
GS
968=back
969
dd9f0070 970=head2 S<Mac OS>
e41182b5
GS
971
972Any module requiring XS compilation is right out for most people, because
973MacPerl is built using non-free (and non-cheap!) compilers. Some XS
974modules that can work with MacPerl are built and distributed in binary
6ab3f9cb 975form on CPAN.
e41182b5
GS
976
977Directories are specified as:
978
979 volume:folder:file for absolute pathnames
980 volume:folder: for absolute pathnames
981 :folder:file for relative pathnames
982 :folder: for relative pathnames
983 :file for relative pathnames
984 file for relative pathnames
985
b7df3edc 986Files are stored in the directory in alphabetical order. Filenames are
6ab3f9cb 987limited to 31 characters, and may include any character except for
b7df3edc 988null and C<:>, which is reserved as the path separator.
e41182b5 989
0a47030a 990Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
6ab3f9cb 991Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
e41182b5
GS
992
993In the MacPerl application, you can't run a program from the command line;
994programs that expect C<@ARGV> to be populated can be edited with something
995like the following, which brings up a dialog box asking for the command
996line arguments.
997
998 if (!@ARGV) {
999 @ARGV = split /\s+/, MacPerl::Ask('Arguments?');
1000 }
1001
b7df3edc 1002A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
e41182b5
GS
1003pathnames of the files dropped onto the script.
1004
b7df3edc
GS
1005Mac users can run programs under a type of command line interface
1006under MPW (Macintosh Programmer's Workshop, a free development
1007environment from Apple). MacPerl was first introduced as an MPW
1008tool, and MPW can be used like a shell:
e41182b5
GS
1009
1010 perl myscript.plx some arguments
1011
1012ToolServer is another app from Apple that provides access to MPW tools
0a47030a 1013from MPW and the MacPerl app, which allows MacPerl programs to use
e41182b5
GS
1014C<system>, backticks, and piped C<open>.
1015
1016"S<Mac OS>" is the proper name for the operating system, but the value
1017in C<$^O> is "MacOS". To determine architecture, version, or whether
1018the application or MPW tool version is running, check:
1019
1020 $is_app = $MacPerl::Version =~ /App/;
1021 $is_tool = $MacPerl::Version =~ /MPW/;
1022 ($version) = $MacPerl::Version =~ /^(\S+)/;
1023 $is_ppc = $MacPerl::Architecture eq 'MacPPC';
1024 $is_68k = $MacPerl::Architecture eq 'Mac68K';
1025
b787fad4
JH
1026S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
1027"Classic" environment. There is no "Carbon" version of MacPerl to run
1028under the primary Mac OS X environment. S<Mac OS X> and its Open Source
1029version, Darwin, both run Unix perl natively.
6ab3f9cb 1030
e41182b5
GS
1031Also see:
1032
1033=over 4
1034
c997b287
GS
1035=item *
1036
862b5365 1037MacPerl Development, http://dev.macperl.org/ .
c997b287
GS
1038
1039=item *
1040
862b5365 1041The MacPerl Pages, http://www.macperl.com/ .
e41182b5 1042
c997b287 1043=item *
6ab3f9cb 1044
862b5365 1045The MacPerl mailing lists, http://lists.perl.org/ .
e41182b5 1046
7ee27b7c
AT
1047=item *
1048
1049MPW, ftp://ftp.apple.com/developer/Tool_Chest/Core_Mac_OS_Tools/
1050
e41182b5
GS
1051=back
1052
e41182b5
GS
1053=head2 VMS
1054
c997b287 1055Perl on VMS is discussed in L<perlvms> in the perl distribution.
016930a6
JM
1056
1057The official name of VMS as of this writing is OpenVMS.
1058
b7df3edc 1059Perl on VMS can accept either VMS- or Unix-style file
e41182b5
GS
1060specifications as in either of the following:
1061
1062 $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
1063 $ perl -ne "print if /perl_setup/i" /sys$login/login.com
1064
1065but not a mixture of both as in:
1066
1067 $ perl -ne "print if /perl_setup/i" sys$login:/login.com
1068 Can't open sys$login:/login.com: file specification syntax error
1069
1070Interacting with Perl from the Digital Command Language (DCL) shell
1071often requires a different set of quotation marks than Unix shells do.
1072For example:
1073
1074 $ perl -e "print ""Hello, world.\n"""
1075 Hello, world.
1076
b7df3edc 1077There are several ways to wrap your perl scripts in DCL F<.COM> files, if
e41182b5
GS
1078you are so inclined. For example:
1079
1080 $ write sys$output "Hello from DCL!"
1081 $ if p1 .eqs. ""
1082 $ then perl -x 'f$environment("PROCEDURE")
1083 $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
1084 $ deck/dollars="__END__"
1085 #!/usr/bin/perl
1086
1087 print "Hello from Perl!\n";
1088
1089 __END__
1090 $ endif
1091
1092Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your
c47ff5f1 1093perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
e41182b5 1094
016930a6
JM
1095The VMS operating system has two filesystems, known as ODS-2 and ODS-5.
1096
1097For ODS-2, filenames are in the format "name.extension;version". The
1098maximum length for filenames is 39 characters, and the maximum length for
e41182b5
GS
1099extensions is also 39 characters. Version is a number from 1 to
110032767. Valid characters are C</[A-Z0-9$_-]/>.
1101
016930a6
JM
1102The ODS-2 filesystem is case-insensitive and does not preserve case.
1103Perl simulates this by converting all filenames to lowercase internally.
1104
1105For ODS-5, filenames may have almost any character in them and can include
1106Unicode characters. Characters that could be misinterpreted by the DCL
1107shell or file parsing utilities need to be prefixed with the C<^>
1108character, or replaced with hexadecimal characters prefixed with the
1109C<^> character. Such prefixing is only needed with the pathnames are
1110in VMS format in applications. Programs that can accept the UNIX format
1111of pathnames do not need the escape characters. The maximum length for
1112filenames is 255 characters. The ODS-5 file system can handle both
1113a case preserved and a case sensitive mode.
1114
1115ODS-5 is only available on the OpenVMS for 64 bit platforms.
1116
1117Support for the extended file specifications is being done as optional
1118settings to preserve backward compatibility with Perl scripts that
1119assume the previous VMS limitations.
1120
1121In general routines on VMS that get a UNIX format file specification
1122should return it in a UNIX format, and when they get a VMS format
1123specification they should return a VMS format unless they are documented
1124to do a conversion.
1125
1126For routines that generate return a file specification, VMS allows setting
1127if the C library which Perl is built on if it will be returned in VMS
1128format or in UNIX format.
1129
1130With the ODS-2 file system, there is not much difference in syntax of
1131filenames without paths for VMS or UNIX. With the extended character
1132set available with ODS-5 there can be a significant difference.
1133
1134Because of this, existing Perl scripts written for VMS were sometimes
1135treating VMS and UNIX filenames interchangeably. Without the extended
1136character set enabled, this behavior will mostly be maintained for
1137backwards compatibility.
1138
1139When extended characters are enabled with ODS-5, the handling of
1140UNIX formatted file specifications is to that of a UNIX system.
1141
1142VMS file specifications without extensions have a trailing dot. An
1143equivalent UNIX file specification should not show the trailing dot.
1144
1145The result of all of this, is that for VMS, for portable scripts, you
1146can not depend on Perl to present the filenames in lowercase, to be
1147case sensitive, and that the filenames could be returned in either
1148UNIX or VMS format.
1149
1150And if a routine returns a file specification, unless it is intended to
1151convert it, it should return it in the same format as it found it.
1152
1153C<readdir> by default has traditionally returned lowercased filenames.
1154When the ODS-5 support is enabled, it will return the exact case of the
1155filename on the disk.
1156
1157Files without extensions have a trailing period on them, so doing a
1158C<readdir> in the default mode with a file named F<A.;5> will
1159return F<a.> when VMS is (though that file could be opened with
0a47030a 1160C<open(FH, 'A')>).
e41182b5 1161
016930a6
JM
1162With support for extended file specifications and if C<opendir> was
1163given a UNIX format directory, a file named F<A.;5> will return F<a>
1164and optionally in the exact case on the disk. When C<opendir> is given
1165a VMS format directory, then C<readdir> should return F<a.>, and
1166again with the optionally the exact case.
1167
f34d0673 1168RMS had an eight level limit on directory depths from any rooted logical
1089a9e3
CB
1169(allowing 16 levels overall) prior to VMS 7.2, and even with versions of
1170VMS on VAX up through 7.3. Hence C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a
1171valid directory specification but C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is
1172not. F<Makefile.PL> authors might have to take this into account, but at
1173least they can refer to the former as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>.
1174
1175Pumpkings and module integrators can easily see whether files with too many
1176directory levels have snuck into the core by running the following in the
1177top-level source directory:
1178
1179 $ perl -ne "$_=~s/\s+.*//; print if scalar(split /\//) > 8;" < MANIFEST
1180
e41182b5 1181
6ab3f9cb 1182The VMS::Filespec module, which gets installed as part of the build
0a47030a
GS
1183process on VMS, is a pure Perl module that can easily be installed on
1184non-VMS platforms and can be helpful for conversions to and from RMS
016930a6
JM
1185native formats. It is also now the only way that you should check to
1186see if VMS is in a case sensitive mode.
e41182b5 1187
5e12dbfa
PP
1188What C<\n> represents depends on the type of file opened. It usually
1189represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>,
fa11829f 1190C<\000>, C<\040>, or nothing depending on the file organization and
5e12dbfa
PP
1191record format. The VMS::Stdio module provides access to the
1192special fopen() requirements of files with unusual attributes on VMS.
e41182b5
GS
1193
1194TCP/IP stacks are optional on VMS, so socket routines might not be
1195implemented. UDP sockets may not be supported.
1196
016930a6
JM
1197The TCP/IP library support for all current versions of VMS is dynamically
1198loaded if present, so even if the routines are configured, they may
1199return a status indicating that they are not implemented.
1200
e41182b5
GS
1201The value of C<$^O> on OpenVMS is "VMS". To determine the architecture
1202that you are running on without resorting to loading all of C<%Config>
1203you can examine the content of the C<@INC> array like so:
1204
1205 if (grep(/VMS_AXP/, @INC)) {
1206 print "I'm on Alpha!\n";
6ab3f9cb 1207
e41182b5
GS
1208 } elsif (grep(/VMS_VAX/, @INC)) {
1209 print "I'm on VAX!\n";
6ab3f9cb 1210
016930a6
JM
1211 } elsif (grep(/VMS_IA64/, @INC)) {
1212 print "I'm on IA64!\n";
1213
e41182b5
GS
1214 } else {
1215 print "I'm not so sure about where $^O is...\n";
1216 }
1217
016930a6
JM
1218In general, the significant differences should only be if Perl is running
1219on VMS_VAX or one of the 64 bit OpenVMS platforms.
1220
b7df3edc
GS
1221On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL>
1222logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
6ab3f9cb 1223calls to C<localtime> are adjusted to count offsets from
b7df3edc 122401-JAN-1970 00:00:00.00, just like Unix.
6ab3f9cb 1225
e41182b5
GS
1226Also see:
1227
1228=over 4
1229
c997b287
GS
1230=item *
1231
1232F<README.vms> (installed as L<README_vms>), L<perlvms>
1233
1234=item *
1235
1089a9e3 1236vmsperl list, vmsperl-subscribe@perl.org
e41182b5 1237
c997b287 1238=item *
e41182b5 1239
c997b287 1240vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
e41182b5
GS
1241
1242=back
1243
495c5fdc
PG
1244=head2 VOS
1245
9a997319
JH
1246Perl on VOS is discussed in F<README.vos> in the perl distribution
1247(installed as L<perlvos>). Perl on VOS can accept either VOS- or
1248Unix-style file specifications as in either of the following:
495c5fdc 1249
cc07ed0b
PG
1250 C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
1251 C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
495c5fdc
PG
1252
1253or even a mixture of both as in:
1254
cc07ed0b 1255 C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
495c5fdc 1256
b7df3edc 1257Even though VOS allows the slash character to appear in object
495c5fdc
PG
1258names, because the VOS port of Perl interprets it as a pathname
1259delimiting character, VOS files, directories, or links whose names
1260contain a slash character cannot be processed. Such files must be
a3dfe201 1261renamed before they can be processed by Perl. Note that VOS limits
b449fc5b
NC
1262file names to 32 or fewer characters, file names cannot start with a
1263C<-> character, or contain any character matching C<< tr/ !%&'()*+;<>?// >>
495c5fdc 1264
495c5fdc
PG
1265The value of C<$^O> on VOS is "VOS". To determine the architecture that
1266you are running on without resorting to loading all of C<%Config> you
c997b287 1267can examine the content of the @INC array like so:
495c5fdc 1268
24e8e380 1269 if ($^O =~ /VOS/) {
495c5fdc
PG
1270 print "I'm on a Stratus box!\n";
1271 } else {
1272 print "I'm not on a Stratus box!\n";
1273 die;
1274 }
1275
495c5fdc
PG
1276Also see:
1277
1278=over 4
1279
c997b287 1280=item *
495c5fdc 1281
cc07ed0b 1282F<README.vos> (installed as L<perlvos>)
c997b287
GS
1283
1284=item *
1285
1286The VOS mailing list.
495c5fdc
PG
1287
1288There is no specific mailing list for Perl on VOS. You can post
1289comments to the comp.sys.stratus newsgroup, or subscribe to the general
cc07ed0b 1290Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
495c5fdc
PG
1291the message body to majordomo@list.stratagy.com.
1292
c997b287
GS
1293=item *
1294
cc07ed0b 1295VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
495c5fdc
PG
1296
1297=back
1298
e41182b5
GS
1299=head2 EBCDIC Platforms
1300
1301Recent versions of Perl have been ported to platforms such as OS/400 on
d1e3b762
GS
1302AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
1303Mainframes. Such computers use EBCDIC character sets internally (usually
0cc436d0
GS
1304Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
1305systems). On the mainframe perl currently works under the "Unix system
1306services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or
1307the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
522b859a
JH
1308See L<perlos390> for details. Note that for OS/400 there is also a port of
1309Perl 5.8.1/5.9.0 or later to the PASE which is ASCII-based (as opposed to
1310ILE which is EBCDIC-based), see L<perlos400>.
e41182b5 1311
7c5ffed3
JH
1312As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix
1313sub-systems do not support the C<#!> shebang trick for script invocation.
1314Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
1315similar to the following simple script:
e41182b5
GS
1316
1317 : # use perl
1318 eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
1319 if 0;
1320 #!/usr/local/bin/perl # just a comment really
1321
1322 print "Hello from perl!\n";
1323
d1e3b762
GS
1324OS/390 will support the C<#!> shebang trick in release 2.8 and beyond.
1325Calls to C<system> and backticks can use POSIX shell syntax on all
1326S/390 systems.
1327
b7df3edc 1328On the AS/400, if PERL5 is in your library list, you may need
6ab3f9cb
GS
1329to wrap your perl scripts in a CL procedure to invoke them like so:
1330
1331 BEGIN
1332 CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
1333 ENDPGM
1334
1335This will invoke the perl script F<hello.pl> in the root of the
1336QOpenSys file system. On the AS/400 calls to C<system> or backticks
1337must use CL syntax.
1338
e41182b5 1339On these platforms, bear in mind that the EBCDIC character set may have
0a47030a
GS
1340an effect on what happens with some perl functions (such as C<chr>,
1341C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
1342well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
1343and C<|>, not to mention dealing with socket interfaces to ASCII computers
6ab3f9cb 1344(see L<"Newlines">).
e41182b5 1345
b7df3edc
GS
1346Fortunately, most web servers for the mainframe will correctly
1347translate the C<\n> in the following statement to its ASCII equivalent
1348(C<\r> is the same under both Unix and OS/390 & VM/ESA):
e41182b5
GS
1349
1350 print "Content-type: text/html\r\n\r\n";
1351
d1e3b762 1352The values of C<$^O> on some of these platforms includes:
e41182b5 1353
d1e3b762
GS
1354 uname $^O $Config{'archname'}
1355 --------------------------------------------
1356 OS/390 os390 os390
1357 OS400 os400 os400
1358 POSIX-BC posix-bc BS2000-posix-bc
1359 VM/ESA vmesa vmesa
3c075c7d 1360
e41182b5
GS
1361Some simple tricks for determining if you are running on an EBCDIC
1362platform could include any of the following (perhaps all):
1363
1364 if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
1365
1366 if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
1367
1368 if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
1369
b7df3edc 1370One thing you may not want to rely on is the EBCDIC encoding
0a47030a
GS
1371of punctuation characters since these may differ from code page to code
1372page (and once your module or script is rumoured to work with EBCDIC,
1373folks will want it to work with all EBCDIC character sets).
e41182b5
GS
1374
1375Also see:
1376
1377=over 4
1378
c997b287
GS
1379=item *
1380
dc5c060f 1381L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>,
bb462878 1382L<perlebcdic>.
c997b287
GS
1383
1384=item *
e41182b5
GS
1385
1386The perl-mvs@perl.org list is for discussion of porting issues as well as
1387general usage issues for all EBCDIC Perls. Send a message body of
1388"subscribe perl-mvs" to majordomo@perl.org.
1389
7ee27b7c 1390=item *
c997b287
GS
1391
1392AS/400 Perl information at
b1866b2d 1393http://as400.rochester.ibm.com/
d1e3b762 1394as well as on CPAN in the F<ports/> directory.
e41182b5
GS
1395
1396=back
1397
b8099c3d
CN
1398=head2 Acorn RISC OS
1399
b7df3edc
GS
1400Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
1401Unix, and because Unix filename emulation is turned on by default,
1402most simple scripts will probably work "out of the box". The native
6ab3f9cb 1403filesystem is modular, and individual filesystems are free to be
0a47030a 1404case-sensitive or insensitive, and are usually case-preserving. Some
b7df3edc 1405native filesystems have name length limits, which file and directory
6ab3f9cb
GS
1406names are silently truncated to fit. Scripts should be aware that the
1407standard filesystem currently has a name length limit of B<10>
1408characters, with up to 77 items in a directory, but other filesystems
0a47030a 1409may not impose such limitations.
b8099c3d
CN
1410
1411Native filenames are of the form
1412
6ab3f9cb 1413 Filesystem#Special_Field::DiskName.$.Directory.Directory.File
dd9f0070 1414
b8099c3d
CN
1415where
1416
1417 Special_Field is not usually present, but may contain . and $ .
1418 Filesystem =~ m|[A-Za-z0-9_]|
1419 DsicName =~ m|[A-Za-z0-9_/]|
1420 $ represents the root directory
1421 . is the path separator
1422 @ is the current directory (per filesystem but machine global)
1423 ^ is the parent directory
1424 Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+|
1425
1426The default filename translation is roughly C<tr|/.|./|;>
1427
6ab3f9cb 1428Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that
0a47030a
GS
1429the second stage of C<$> interpolation in regular expressions will fall
1430foul of the C<$.> if scripts are not careful.
1431
1432Logical paths specified by system variables containing comma-separated
b7df3edc 1433search lists are also allowed; hence C<System:Modules> is a valid
0a47030a 1434filename, and the filesystem will prefix C<Modules> with each section of
6ab3f9cb 1435C<System$Path> until a name is made that points to an object on disk.
b7df3edc 1436Writing to a new file C<System:Modules> would be allowed only if
0a47030a
GS
1437C<System$Path> contains a single item list. The filesystem will also
1438expand system variables in filenames if enclosed in angle brackets, so
c47ff5f1 1439C<< <System$Dir>.Modules >> would look for the file
0a47030a 1440S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is
c47ff5f1 1441that B<fully qualified filenames can start with C<< <> >>> and should
0a47030a 1442be protected when C<open> is used for input.
b8099c3d
CN
1443
1444Because C<.> was in use as a directory separator and filenames could not
1445be assumed to be unique after 10 characters, Acorn implemented the C
1446compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from
1447filenames specified in source code and store the respective files in
b7df3edc 1448subdirectories named after the suffix. Hence files are translated:
b8099c3d
CN
1449
1450 foo.h h.foo
1451 C:foo.h C:h.foo (logical path variable)
1452 sys/os.h sys.h.os (C compiler groks Unix-speak)
1453 10charname.c c.10charname
1454 10charname.o o.10charname
1455 11charname_.c c.11charname (assuming filesystem truncates at 10)
1456
1457The Unix emulation library's translation of filenames to native assumes
b7df3edc
GS
1458that this sort of translation is required, and it allows a user-defined list
1459of known suffixes that it will transpose in this fashion. This may
1460seem transparent, but consider that with these rules C<foo/bar/baz.h>
0a47030a
GS
1461and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
1462C<glob> cannot and do not attempt to emulate the reverse mapping. Other
6ab3f9cb 1463C<.>'s in filenames are translated to C</>.
0a47030a 1464
b7df3edc 1465As implied above, the environment accessed through C<%ENV> is global, and
0a47030a 1466the convention is that program specific environment variables are of the
6ab3f9cb
GS
1467form C<Program$Name>. Each filesystem maintains a current directory,
1468and the current filesystem's current directory is the B<global> current
b7df3edc
GS
1469directory. Consequently, sociable programs don't change the current
1470directory but rely on full pathnames, and programs (and Makefiles) cannot
0a47030a
GS
1471assume that they can spawn a child process which can change the current
1472directory without affecting its parent (and everyone else for that
1473matter).
1474
b7df3edc
GS
1475Because native operating system filehandles are global and are currently
1476allocated down from 255, with 0 being a reserved value, the Unix emulation
0a47030a
GS
1477library emulates Unix filehandles. Consequently, you can't rely on
1478passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children.
1479
1480The desire of users to express filenames of the form
c47ff5f1 1481C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems,
0a47030a 1482too: C<``> command output capture has to perform a guessing game. It
c47ff5f1 1483assumes that a string C<< <[^<>]+\$[^<>]> >> is a
0a47030a 1484reference to an environment variable, whereas anything else involving
c47ff5f1 1485C<< < >> or C<< > >> is redirection, and generally manages to be 99%
0a47030a
GS
1486right. Of course, the problem remains that scripts cannot rely on any
1487Unix tools being available, or that any tools found have Unix-like command
1488line arguments.
1489
b7df3edc
GS
1490Extensions and XS are, in theory, buildable by anyone using free
1491tools. In practice, many don't, as users of the Acorn platform are
1492used to binary distributions. MakeMaker does run, but no available
1493make currently copes with MakeMaker's makefiles; even if and when
1494this should be fixed, the lack of a Unix-like shell will cause
1495problems with makefile rules, especially lines of the form C<cd
1496sdbm && make all>, and anything using quoting.
b8099c3d
CN
1497
1498"S<RISC OS>" is the proper name for the operating system, but the value
1499in C<$^O> is "riscos" (because we don't like shouting).
1500
e41182b5
GS
1501=head2 Other perls
1502
b7df3edc
GS
1503Perl has been ported to many platforms that do not fit into any of
1504the categories listed above. Some, such as AmigaOS, Atari MiNT,
1505BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
1506into the standard Perl source code kit. You may need to see the
1507F<ports/> directory on CPAN for information, and possibly binaries,
1508for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware,
1509Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may
1510fall under the Unix category, but we are not a standards body.)
e41182b5 1511
d1e3b762
GS
1512Some approximate operating system names and their C<$^O> values
1513in the "OTHER" category include:
1514
1515 OS $^O $Config{'archname'}
1516 ------------------------------------------
1517 Amiga DOS amigaos m68k-amigos
cec2c193 1518 BeOS beos
d1e3b762
GS
1519 MPE/iX mpeix PA-RISC1.1
1520
e41182b5
GS
1521See also:
1522
1523=over 4
1524
c997b287
GS
1525=item *
1526
1527Amiga, F<README.amiga> (installed as L<perlamiga>).
1528
1529=item *
d1e3b762 1530
c997b287
GS
1531Atari, F<README.mint> and Guido Flohr's web page
1532http://stud.uni-sb.de/~gufl0000/
e41182b5 1533
c997b287 1534=item *
d1e3b762 1535
c997b287 1536Be OS, F<README.beos>
e41182b5 1537
c997b287
GS
1538=item *
1539
1540HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
34aaaa84 1541http://www.bixby.org/mark/perlix.html
c997b287
GS
1542
1543=item *
e41182b5 1544
6ab3f9cb 1545A free perl5-based PERL.NLM for Novell Netware is available in
c997b287 1546precompiled binary and source code form from http://www.novell.com/
6ab3f9cb 1547as well as from CPAN.
e41182b5 1548
13a2d996 1549=item *
c997b287 1550
e6f03d26 1551S<Plan 9>, F<README.plan9>
d1e3b762 1552
e41182b5
GS
1553=back
1554
e41182b5
GS
1555=head1 FUNCTION IMPLEMENTATIONS
1556
b7df3edc
GS
1557Listed below are functions that are either completely unimplemented
1558or else have been implemented differently on various platforms.
1559Following each description will be, in parentheses, a list of
1560platforms that the description applies to.
e41182b5 1561
b7df3edc
GS
1562The list may well be incomplete, or even wrong in some places. When
1563in doubt, consult the platform-specific README files in the Perl
1564source distribution, and any other documentation resources accompanying
1565a given port.
e41182b5 1566
0a47030a 1567Be aware, moreover, that even among Unix-ish systems there are variations.
e41182b5 1568
b7df3edc
GS
1569For many functions, you can also query C<%Config>, exported by
1570default from the Config module. For example, to check whether the
1571platform has the C<lstat> call, check C<$Config{d_lstat}>. See
1572L<Config> for a full description of available variables.
e41182b5
GS
1573
1574=head2 Alphabetical Listing of Perl Functions
1575
1576=over 8
1577
e41182b5
GS
1578=item -X
1579
b7df3edc 1580C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
e41182b5 1581and applications are executable, and there are no uid/gid
b7df3edc 1582considerations. C<-o> is not supported. (S<Mac OS>)
e41182b5 1583
b7df3edc
GS
1584C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible,
1585which may not reflect UIC-based file protections. (VMS)
e41182b5 1586
b8099c3d
CN
1587C<-s> returns the size of the data fork, not the total size of data fork
1588plus resource fork. (S<Mac OS>).
1589
1590C<-s> by name on an open file will return the space reserved on disk,
1591rather than the current extent. C<-s> on an open filehandle returns the
b7df3edc 1592current size. (S<RISC OS>)
b8099c3d 1593
e41182b5 1594C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>,
b8099c3d 1595C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1596
1597C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
1598(S<Mac OS>)
1599
1600C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
b8099c3d 1601(Win32, VMS, S<RISC OS>)
e41182b5
GS
1602
1603C<-d> is true if passed a device spec without an explicit directory.
1604(VMS)
1605
1606C<-T> and C<-B> are implemented, but might misclassify Mac text files
0a47030a 1607with foreign characters; this is the case will all platforms, but may
b7df3edc 1608affect S<Mac OS> often. (S<Mac OS>)
e41182b5
GS
1609
1610C<-x> (or C<-X>) determine if a file ends in one of the executable
b7df3edc 1611suffixes. C<-S> is meaningless. (Win32)
e41182b5 1612
b8099c3d
CN
1613C<-x> (or C<-X>) determine if a file has an executable file type.
1614(S<RISC OS>)
1615
47cd99a4 1616=item atan2
519bc777
RGS
1617
1618Due to issues with various CPUs, math libraries, compilers, and standards,
1619results for C<atan2()> may vary depending on any combination of the above.
1620Perl attempts to conform to the Open Group/IEEE standards for the results
1621returned from C<atan2()>, but cannot force the issue if the system Perl is
1622run on does not allow it. (Tru64, HP-UX 10.20)
1623
1624The current version of the standards for C<atan2()> is available at
1625L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.
1626
47cd99a4 1627=item binmode
e41182b5 1628
b7df3edc 1629Meaningless. (S<Mac OS>, S<RISC OS>)
e41182b5
GS
1630
1631Reopens file and restores pointer; if function fails, underlying
1632filehandle may be closed, or pointer may be in a different position.
1633(VMS)
1634
1635The value returned by C<tell> may be affected after the call, and
1636the filehandle may be flushed. (Win32)
1637
47cd99a4 1638=item chmod
e41182b5 1639
b7df3edc 1640Only limited meaning. Disabling/enabling write permission is mapped to
e41182b5
GS
1641locking/unlocking the file. (S<Mac OS>)
1642
1643Only good for changing "owner" read-write access, "group", and "other"
1644bits are meaningless. (Win32)
1645
b8099c3d
CN
1646Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
1647
495c5fdc
PG
1648Access permissions are mapped onto VOS access-control list changes. (VOS)
1649
4e51f8e4 1650The actual permissions set depend on the value of the C<CYGWIN>
789f0d36 1651in the SYSTEM environment settings. (Cygwin)
4e51f8e4 1652
47cd99a4 1653=item chown
e41182b5 1654
3fd80bd6 1655Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5
GS
1656
1657Does nothing, but won't fail. (Win32)
1658
3fd80bd6
PG
1659A little funky, because VOS's notion of ownership is a little funky (VOS).
1660
e41182b5
GS
1661=item chroot
1662
e6f03d26 1663Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS, VM/ESA)
e41182b5 1664
47cd99a4 1665=item crypt
e41182b5
GS
1666
1667May not be available if library or source was not provided when building
b8099c3d 1668perl. (Win32)
e41182b5 1669
47cd99a4 1670=item dbmclose
e41182b5 1671
e6f03d26 1672Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1673
47cd99a4 1674=item dbmopen
e41182b5 1675
e6f03d26 1676Not implemented. (VMS, S<Plan 9>, VOS)
e41182b5 1677
47cd99a4 1678=item dump
e41182b5 1679
b8099c3d 1680Not useful. (S<Mac OS>, S<RISC OS>)
e41182b5 1681
84d78eb7 1682Not supported. (Cygwin, Win32)
e41182b5 1683
b8099c3d 1684Invokes VMS debugger. (VMS)
e41182b5 1685
47cd99a4 1686=item exec
e41182b5
GS
1687
1688Not implemented. (S<Mac OS>)
1689
7c5ffed3 1690Implemented via Spawn. (VM/ESA)
3c075c7d 1691
0f897271
GS
1692Does not automatically flush output handles on some platforms.
1693(SunOS, Solaris, HP-UX)
1694
fe12c0e8
MS
1695=item exit
1696
1697Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
1698mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden
1699with the pragma C<use vmsish 'exit'>. As with the CRTL's exit()
1700function, C<exit 0> is also mapped to an exit status of SS$_NORMAL
1701(C<1>); this mapping cannot be overridden. Any other argument to exit()
016930a6
JM
1702is used directly as Perl's exit status. On VMS, unless the future
1703POSIX_EXIT mode is enabled, the exit code should always be a valid
1704VMS exit code and not a generic number. When the POSIX_EXIT mode is
1705enabled, a generic number will be encoded in a method compatible with
1706the C library _POSIX_EXIT macro so that it can be decoded by other
1707programs, particularly ones written in C, like the GNV package. (VMS)
fe12c0e8 1708
47cd99a4 1709=item fcntl
e41182b5 1710
016930a6
JM
1711Not implemented. (Win32)
1712Some functions available based on the version of VMS. (VMS)
e41182b5 1713
47cd99a4 1714=item flock
e41182b5 1715
495c5fdc 1716Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
e41182b5
GS
1717
1718Available only on Windows NT (not on Windows 95). (Win32)
1719
1720=item fork
1721
3fd80bd6 1722Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VM/ESA, VMS)
0f897271
GS
1723
1724Emulated using multiple interpreters. See L<perlfork>. (Win32)
1725
1726Does not automatically flush output handles on some platforms.
1727(SunOS, Solaris, HP-UX)
e41182b5
GS
1728
1729=item getlogin
1730
b8099c3d 1731Not implemented. (S<Mac OS>, S<RISC OS>)
e41182b5 1732
47cd99a4 1733=item getpgrp
e41182b5 1734
3fd80bd6 1735Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5
GS
1736
1737=item getppid
1738
41cbbefa 1739Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1740
47cd99a4 1741=item getpriority
e41182b5 1742
7c5ffed3 1743Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 1744
47cd99a4 1745=item getpwnam
e41182b5
GS
1746
1747Not implemented. (S<Mac OS>, Win32)
1748
b8099c3d
CN
1749Not useful. (S<RISC OS>)
1750
47cd99a4 1751=item getgrnam
e41182b5 1752
b8099c3d 1753Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1754
47cd99a4 1755=item getnetbyname
e41182b5 1756
e6f03d26 1757Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1758
47cd99a4 1759=item getpwuid
e41182b5
GS
1760
1761Not implemented. (S<Mac OS>, Win32)
1762
b8099c3d
CN
1763Not useful. (S<RISC OS>)
1764
47cd99a4 1765=item getgrgid
e41182b5 1766
b8099c3d 1767Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
e41182b5 1768
47cd99a4 1769=item getnetbyaddr
e41182b5 1770
e6f03d26 1771Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5 1772
47cd99a4 1773=item getprotobynumber
e41182b5
GS
1774
1775Not implemented. (S<Mac OS>)
1776
47cd99a4 1777=item getservbyport
e41182b5
GS
1778
1779Not implemented. (S<Mac OS>)
1780
1781=item getpwent
1782
7c5ffed3 1783Not implemented. (S<Mac OS>, Win32, VM/ESA)
e41182b5
GS
1784
1785=item getgrent
1786
7c5ffed3 1787Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
e41182b5 1788
ef5a6dd7
JH
1789=item gethostbyname
1790
1791C<gethostbyname('localhost')> does not work everywhere: you may have
1792to use C<gethostbyname('127.0.0.1')>. (S<Mac OS>, S<Irix 5>)
1793
e41182b5
GS
1794=item gethostent
1795
1796Not implemented. (S<Mac OS>, Win32)
1797
1798=item getnetent
1799
e6f03d26 1800Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1801
1802=item getprotoent
1803
e6f03d26 1804Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1805
1806=item getservent
1807
e6f03d26 1808Not implemented. (Win32, S<Plan 9>)
e41182b5 1809
47cd99a4 1810=item sethostent
e41182b5 1811
e6f03d26 1812Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1813
47cd99a4 1814=item setnetent
e41182b5 1815
e6f03d26 1816Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1817
47cd99a4 1818=item setprotoent
e41182b5 1819
e6f03d26 1820Not implemented. (S<Mac OS>, Win32, S<Plan 9>, S<RISC OS>)
e41182b5 1821
47cd99a4 1822=item setservent
e41182b5 1823
e6f03d26 1824Not implemented. (S<Plan 9>, Win32, S<RISC OS>)
e41182b5
GS
1825
1826=item endpwent
1827
a3dfe201 1828Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
e41182b5
GS
1829
1830=item endgrent
1831
a3dfe201 1832Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
e41182b5
GS
1833
1834=item endhostent
1835
1836Not implemented. (S<Mac OS>, Win32)
1837
1838=item endnetent
1839
e6f03d26 1840Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1841
1842=item endprotoent
1843
e6f03d26 1844Not implemented. (S<Mac OS>, Win32, S<Plan 9>)
e41182b5
GS
1845
1846=item endservent
1847
e6f03d26 1848Not implemented. (S<Plan 9>, Win32)
e41182b5
GS
1849
1850=item getsockopt SOCKET,LEVEL,OPTNAME
1851
e6f03d26 1852Not implemented. (S<Plan 9>)
e41182b5 1853
e41182b5
GS
1854=item glob
1855
63f87e49
GS
1856This operator is implemented via the File::Glob extension on most
1857platforms. See L<File::Glob> for portability information.
b8099c3d 1858
62aa5637
MS
1859=item gmtime
1860
1861Same portability caveats as L<localtime>.
1862
e41182b5
GS
1863=item ioctl FILEHANDLE,FUNCTION,SCALAR
1864
1865Not implemented. (VMS)
1866
1867Available only for socket handles, and it does what the ioctlsocket() call
1868in the Winsock API does. (Win32)
1869
b8099c3d
CN
1870Available only for socket handles. (S<RISC OS>)
1871
47cd99a4 1872=item kill
e41182b5 1873
862b5365
JH
1874C<kill(0, LIST)> is implemented for the sake of taint checking;
1875use with other signals is unimplemented. (S<Mac OS>)
1876
1877Not implemented, hence not useful for taint checking. (S<RISC OS>)
e41182b5 1878
63f87e49
GS
1879C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
1880a signal to the identified process like it does on Unix platforms.
1881Instead C<kill($sig, $pid)> terminates the process identified by $pid,
1882and makes it exit immediately with exit status $sig. As in Unix, if
1883$sig is 0 and the specified process exists, it returns true without
1884actually terminating it. (Win32)
e41182b5 1885
d0302514
JD
1886C<kill(-9, $pid)> will terminate the process specified by $pid and
1887recursively all child processes owned by it. This is different from
1888the Unix semantics, where the signal will be delivered to all
1889processes in the same process group as the process specified by
1890$pid. (Win32)
1891
016930a6
JM
1892Is not supported for process identification number of 0 or negative
1893numbers. (VMS)
1894
47cd99a4 1895=item link
e41182b5 1896
016930a6 1897Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>)
e41182b5 1898
433acd8a
JH
1899Link count not updated because hard links are not quite that hard
1900(They are sort of half-way between hard and soft links). (AmigaOS)
1901
63d6c08b
JD
1902Hard links are implemented on Win32 under NTFS only. They are
1903natively supported on Windows 2000 and later. On Windows NT they
1904are implemented using the Windows POSIX subsystem support and the
1905Perl process will need Administrator or Backup Operator privileges
1906to create hard links.
a3dfe201 1907
016930a6
JM
1908Available on 64 bit OpenVMS 8.2 and later. (VMS)
1909
62aa5637
MS
1910=item localtime
1911
1912Because Perl currently relies on the native standard C localtime()
1913function, it is only safe to use times between 0 and (2**31)-1. Times
1914outside this range may result in unexpected behavior depending on your
1915operating system's implementation of localtime().
1916
e41182b5
GS
1917=item lstat
1918
016930a6 1919Not implemented. (S<RISC OS>)
e41182b5 1920
63f87e49 1921Return values (especially for device and inode) may be bogus. (Win32)
e41182b5 1922
47cd99a4 1923=item msgctl
e41182b5 1924
47cd99a4 1925=item msgget
e41182b5 1926
47cd99a4 1927=item msgsnd
e41182b5 1928
47cd99a4 1929=item msgrcv
e41182b5 1930
e6f03d26 1931Not implemented. (S<Mac OS>, Win32, VMS, S<Plan 9>, S<RISC OS>, VOS)
e41182b5 1932
47cd99a4 1933=item open
e41182b5 1934
b7df3edc 1935The C<|> variants are supported only if ToolServer is installed.
e41182b5
GS
1936(S<Mac OS>)
1937
c47ff5f1 1938open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
e41182b5 1939
0f897271
GS
1940Opening a process does not automatically flush output handles on some
1941platforms. (SunOS, Solaris, HP-UX)
1942
47cd99a4 1943=item pipe
e41182b5 1944
433acd8a
JH
1945Very limited functionality. (MiNT)
1946
e41182b5
GS
1947=item readlink
1948
b8099c3d 1949Not implemented. (Win32, VMS, S<RISC OS>)
e41182b5 1950
47cd99a4 1951=item rename
c9b2b9d4
SS
1952
1953Can't move directories between directories on different logical volumes. (Win32)
1954
47cd99a4 1955=item select
e41182b5 1956
689c5c24 1957Only implemented on sockets. (Win32, VMS)
e41182b5 1958
b8099c3d
CN
1959Only reliable on sockets. (S<RISC OS>)
1960
76e05f0b 1961Note that the C<select FILEHANDLE> form is generally portable.
63f87e49 1962
47cd99a4 1963=item semctl
e41182b5 1964
47cd99a4 1965=item semget
e41182b5 1966
47cd99a4 1967=item semop
e41182b5 1968
495c5fdc 1969Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1970
a3dfe201
GS
1971=item setgrent
1972
3fd80bd6 1973Not implemented. (S<Mac OS>, MPE/iX, VMS, Win32, S<RISC OS>, VOS)
a3dfe201 1974
47cd99a4 1975=item setpgrp
e41182b5 1976
495c5fdc 1977Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1978
47cd99a4 1979=item setpriority
e41182b5 1980
495c5fdc 1981Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 1982
a3dfe201
GS
1983=item setpwent
1984
3fd80bd6 1985Not implemented. (S<Mac OS>, MPE/iX, Win32, S<RISC OS>, VOS)
a3dfe201 1986
47cd99a4 1987=item setsockopt
e41182b5 1988
e6f03d26 1989Not implemented. (S<Plan 9>)
e41182b5 1990
47cd99a4 1991=item shmctl
e41182b5 1992
47cd99a4 1993=item shmget
e41182b5 1994
47cd99a4 1995=item shmread
e41182b5 1996
47cd99a4 1997=item shmwrite
e41182b5 1998
495c5fdc 1999Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
e41182b5 2000
47cd99a4 2001=item sockatmark
80cbd5ad
JH
2002
2003A relatively recent addition to socket functions, may not
2004be implemented even in UNIX platforms.
2005
47cd99a4 2006=item socketpair
e41182b5 2007
f38e12df 2008Not implemented. (S<RISC OS>, VOS, VM/ESA)
016930a6
JM
2009
2010Available on 64 bit OpenVMS 8.2 and later. (VMS)
e41182b5 2011
e41182b5
GS
2012=item stat
2013
d62e1b7f
JH
2014Platforms that do not have rdev, blksize, or blocks will return these
2015as '', so numeric comparison or manipulation of these fields may cause
2016'not numeric' warnings.
2017
e41182b5 2018mtime and atime are the same thing, and ctime is creation time instead of
3f1f789b
JH
2019inode change time. (S<Mac OS>).
2020
2021ctime not supported on UFS (S<Mac OS X>).
e41182b5 2022
95a3fe12
MS
2023ctime is creation time instead of inode change time (Win32).
2024
e41182b5
GS
2025device and inode are not meaningful. (Win32)
2026
2027device and inode are not necessarily reliable. (VMS)
2028
b8099c3d
CN
2029mtime, atime and ctime all return the last modification time. Device and
2030inode are not necessarily reliable. (S<RISC OS>)
2031
d62e1b7f
JH
2032dev, rdev, blksize, and blocks are not available. inode is not
2033meaningful and will differ between stat calls on the same file. (os2)
2034
73e9292c
JH
2035some versions of cygwin when doing a stat("foo") and if not finding it
2036may then attempt to stat("foo.exe") (Cygwin)
2037
1fafdf34
JD
2038On Win32 stat() needs to open the file to determine the link count
2039and update attributes that may have been changed through hard links.
2040Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up stat() by
2041not performing this operation. (Win32)
2042
47cd99a4 2043=item symlink
e41182b5 2044
c73b03b7
JM
2045Not implemented. (Win32, S<RISC OS>)
2046
2047Implemented on 64 bit VMS 8.3. VMS requires the symbolic link to be in Unix
2048syntax if it is intended to resolve to a valid path.
e41182b5 2049
47cd99a4 2050=item syscall
e41182b5 2051
7c5ffed3 2052Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
e41182b5 2053
47cd99a4 2054=item sysopen
f34d0673 2055
dd9f0070 2056The traditional "0", "1", and "2" MODEs are implemented with different
322422de
GS
2057numeric values on some systems. The flags exported by C<Fcntl>
2058(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
7c5ffed3 2059OS>, OS/390, VM/ESA)
f34d0673 2060
47cd99a4 2061=item system
e41182b5
GS
2062
2063Only implemented if ToolServer is installed. (S<Mac OS>)
2064
2065As an optimization, may not call the command shell specified in
b7df3edc 2066C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
e41182b5
GS
2067process and immediately returns its process designator, without
2068waiting for it to terminate. Return value may be used subsequently
63f87e49
GS
2069in C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated
2070by setting $? to "255 << 8". C<$?> is set in a way compatible with
2071Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8",
2072as described in the documentation). (Win32)
e41182b5 2073
b8099c3d
CN
2074There is no shell to process metacharacters, and the native standard is
2075to pass a command line terminated by "\n" "\r" or "\0" to the spawned
c47ff5f1 2076program. Redirection such as C<< > foo >> is performed (if at all) by
b8099c3d
CN
2077the run time library of the spawned program. C<system> I<list> will call
2078the Unix emulation library's C<exec> emulation, which attempts to provide
2079emulation of the stdin, stdout, stderr in force in the parent, providing
2080the child program uses a compatible version of the emulation library.
2081I<scalar> will call the native command line direct and no such emulation
2082of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
2083
433acd8a
JH
2084Far from being POSIX compliant. Because there may be no underlying
2085/bin/sh tries to work around the problem by forking and execing the
9b63e9ec 2086first token in its argument string. Handles basic redirection
c47ff5f1 2087("<" or ">") on its own behalf. (MiNT)
433acd8a 2088
0f897271
GS
2089Does not automatically flush output handles on some platforms.
2090(SunOS, Solaris, HP-UX)
2091
9bc98430
CB
2092The return value is POSIX-like (shifted up by 8 bits), which only allows
2093room for a made-up value derived from the severity bits of the native
209432-bit condition code (unless overridden by C<use vmsish 'status'>).
016930a6
JM
2095If the native condition code is one that has a POSIX value encoded, the
2096POSIX value will be decoded to extract the expected exit value.
9bc98430
CB
2097For more details see L<perlvms/$?>. (VMS)
2098
e41182b5
GS
2099=item times
2100
2101Only the first entry returned is nonzero. (S<Mac OS>)
2102
63f87e49
GS
2103"cumulative" times will be bogus. On anything other than Windows NT
2104or Windows 2000, "system" time will be bogus, and "user" time is
2105actually the time returned by the clock() function in the C runtime
2106library. (Win32)
e41182b5 2107
b8099c3d
CN
2108Not useful. (S<RISC OS>)
2109
47cd99a4 2110=item truncate
e41182b5 2111
6d738113 2112Not implemented. (Older versions of VMS)
e41182b5 2113
3fd80bd6 2114Truncation to same-or-shorter lengths only. (VOS)
495c5fdc 2115
4cfdb94f 2116If a FILEHANDLE is supplied, it must be writable and opened in append
e71a7dc8 2117mode (i.e., use C<<< open(FH, '>>filename') >>>
4cfdb94f
GS
2118or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it
2119should not be held open elsewhere. (Win32)
2120
e41182b5
GS
2121=item umask
2122
2123Returns undef where unavailable, as of version 5.005.
2124
b7df3edc
GS
2125C<umask> works but the correct permissions are set only when the file
2126is finally closed. (AmigaOS)
433acd8a 2127
47cd99a4 2128=item utime
e41182b5 2129
15c65113 2130Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
e41182b5 2131
322422de
GS
2132May not behave as expected. Behavior depends on the C runtime
2133library's implementation of utime(), and the filesystem being
2134used. The FAT filesystem typically does not support an "access
2135time" field, and it may limit timestamps to a granularity of
2136two seconds. (Win32)
e41182b5
GS
2137
2138=item wait
2139
47cd99a4 2140=item waitpid
e41182b5 2141
3fd80bd6 2142Not implemented. (S<Mac OS>)
e41182b5
GS
2143
2144Can only be applied to process handles returned for processes spawned
a6f858fb 2145using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
e41182b5 2146
b8099c3d
CN
2147Not useful. (S<RISC OS>)
2148
e41182b5
GS
2149=back
2150
2151
ba58ab26
JH
2152=head1 Supported Platforms
2153
522b859a 2154As of July 2002 (the Perl release 5.8.0), the following platforms are
cec2c193
JH
2155able to build Perl from the standard source code distribution
2156available at http://www.cpan.org/src/index.html
2157
2158 AIX
2159 BeOS
6f683aa2 2160 BSD/OS (BSDi)
cec2c193
JH
2161 Cygwin
2162 DG/UX
811b48f2 2163 DOS DJGPP 1)
cec2c193
JH
2164 DYNIX/ptx
2165 EPOC R5
2166 FreeBSD
6f683aa2 2167 HI-UXMPP (Hitachi) (5.8.0 worked but we didn't know it)
cec2c193
JH
2168 HP-UX
2169 IRIX
2170 Linux
8939ba94 2171 Mac OS Classic
6f683aa2 2172 Mac OS X (Darwin)
cec2c193
JH
2173 MPE/iX
2174 NetBSD
2175 NetWare
2176 NonStop-UX
6f683aa2 2177 ReliantUNIX (formerly SINIX)
cec2c193 2178 OpenBSD
6f683aa2 2179 OpenVMS (formerly VMS)
3ebac25b 2180 Open UNIX (Unixware) (since Perl 5.8.1/5.9.0)
cec2c193 2181 OS/2
522b859a 2182 OS/400 (using the PASE) (since Perl 5.8.1/5.9.0)
70de81db 2183 PowerUX
6f683aa2 2184 POSIX-BC (formerly BS2000)
cec2c193
JH
2185 QNX
2186 Solaris
70de81db 2187 SunOS 4
6f683aa2
JH
2188 SUPER-UX (NEC)
2189 Tru64 UNIX (formerly DEC OSF/1, Digital UNIX)
cec2c193
JH
2190 UNICOS
2191 UNICOS/mk
2192 UTS
2193 VOS
811b48f2 2194 Win95/98/ME/2K/XP 2)
c40b5d1d 2195 WinCE
6f683aa2 2196 z/OS (formerly OS/390)
cec2c193 2197 VM/ESA
ba58ab26 2198
811b48f2
JH
2199 1) in DOS mode either the DOS or OS/2 ports can be used
2200 2) compilers: Borland, MinGW (GCC), VC6
cec2c193 2201
c40b5d1d 2202The following platforms worked with the previous releases (5.6 and
cec2c193
JH
22035.7), but we did not manage either to fix or to test these in time
2204for the 5.8.0 release. There is a very good chance that many of these
70de81db 2205will work fine with the 5.8.0.
cec2c193 2206
8da2b1be 2207 BSD/OS
cec2c193
JH
2208 DomainOS
2209 Hurd
2210 LynxOS
2211 MachTen
2212 PowerMAX
2213 SCO SV
cec2c193
JH
2214 SVR4
2215 Unixware
2216 Windows 3.1
ba58ab26 2217
70de81db
JH
2218Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used):
2219
2220 AmigaOS
2221
ba58ab26 2222The following platforms have been known to build Perl from source in
fd46a41b
JH
2223the past (5.005_03 and earlier), but we haven't been able to verify
2224their status for the current release, either because the
2225hardware/software platforms are rare or because we don't have an
2226active champion on these platforms--or both. They used to work,
2227though, so go ahead and try compiling them, and let perlbug@perl.org
2228of any trouble.
ba58ab26 2229
cec2c193
JH
2230 3b1
2231 A/UX
cec2c193
JH
2232 ConvexOS
2233 CX/UX
2234 DC/OSx
2235 DDE SMES
2236 DOS EMX
2237 Dynix
2238 EP/IX
2239 ESIX
2240 FPS
2241 GENIX
2242 Greenhills
2243 ISC
2244 MachTen 68k
2245 MiNT
2246 MPC
2247 NEWS-OS
2248 NextSTEP
2249 OpenSTEP
2250 Opus
2251 Plan 9
cec2c193 2252 RISC/os
8da2b1be 2253 SCO ODT/OSR
cec2c193
JH
2254 Stellar
2255 SVR2
2256 TI1500
2257 TitanOS
2258 Ultrix
2259 Unisys Dynix
ba58ab26
JH
2260
2261The following platforms have their own source code distributions and
1577cd80 2262binaries available via http://www.cpan.org/ports/
ba58ab26 2263
cec2c193 2264 Perl release
ba58ab26 2265
522b859a 2266 OS/400 (ILE) 5.005_02
cec2c193 2267 Tandem Guardian 5.004
ba58ab26
JH
2268
2269The following platforms have only binaries available via
a93751fa 2270http://www.cpan.org/ports/index.html :
ba58ab26 2271
cec2c193 2272 Perl release
ba58ab26 2273
cec2c193
JH
2274 Acorn RISCOS 5.005_02
2275 AOS 5.002
2276 LynxOS 5.004_02
ba58ab26
JH
2277
2278Although we do suggest that you always build your own Perl from
2279the source code, both for maximal configurability and for security,
2280in case you are in a hurry you can check
a93751fa 2281http://www.cpan.org/ports/index.html for binary distributions.
ba58ab26 2282
c997b287
GS
2283=head1 SEE ALSO
2284
cec2c193 2285L<perlaix>, L<perlamiga>, L<perlapollo>, L<perlbeos>, L<perlbs2000>,
18a271bd 2286L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>,
469e7be4 2287L<perlebcdic>, L<perlfreebsd>, L<perlhurd>, L<perlhpux>, L<perlirix>,
0d53b15f 2288L<perlmachten>, L<perlmacos>, L<perlmacosx>, L<perlmint>, L<perlmpeix>,
522b859a
JH
2289L<perlnetware>, L<perlos2>, L<perlos390>, L<perlos400>,
2290L<perlplan9>, L<perlqnx>, L<perlsolaris>, L<perltru64>,
2291L<perlunicode>, L<perlvmesa>, L<perlvms>, L<perlvos>,
2292L<perlwin32>, and L<Win32>.
c997b287 2293
e41182b5
GS
2294=head1 AUTHORS / CONTRIBUTORS
2295
06e9666b 2296Abigail <abigail@foad.org>,
c47ff5f1
GS
2297Charles Bailey <bailey@newman.upenn.edu>,
2298Graham Barr <gbarr@pobox.com>,
2299Tom Christiansen <tchrist@perl.com>,
06e9666b 2300Nicholas Clark <nick@ccl4.org>,
c47ff5f1 2301Thomas Dorner <Thomas.Dorner@start.de>,
06e9666b
A
2302Andy Dougherty <doughera@lafayette.edu>,
2303Dominic Dunlop <domo@computer.org>,
2304Neale Ferguson <neale@vma.tabnsw.com.au>,
c47ff5f1 2305David J. Fiander <davidf@mks.com>,
3fd80bd6 2306Paul Green <Paul.Green@stratus.com>,
06e9666b 2307M.J.T. Guy <mjtg@cam.ac.uk>,
61f30a5e 2308Jarkko Hietaniemi <jhi@iki.fi>,
c47ff5f1 2309Luther Huffman <lutherh@stratcom.com>,
06e9666b
A
2310Nick Ing-Simmons <nick@ing-simmons.net>,
2311Andreas J. KE<ouml>nig <a.koenig@mind.de>,
c47ff5f1
GS
2312Markus Laker <mlaker@contax.co.uk>,
2313Andrew M. Langmead <aml@world.std.com>,
2314Larry Moore <ljmoore@freespace.net>,
2315Paul Moore <Paul.Moore@uk.origin-it.com>,
2316Chris Nandor <pudge@pobox.com>,
1afc07ec 2317Matthias Neeracher <neeracher@mac.com>,
e71a7dc8 2318Philip Newton <pne@cpan.org>,
c47ff5f1
GS
2319Gary Ng <71564.1743@CompuServe.COM>,
2320Tom Phoenix <rootbeer@teleport.com>,
2321AndrE<eacute> Pirard <A.Pirard@ulg.ac.be>,
2322Peter Prymmer <pvhp@forte.com>,
2323Hugo van der Sanden <hv@crypt0.demon.co.uk>,
2324Gurusamy Sarathy <gsar@activestate.com>,
2325Paul J. Schinder <schinder@pobox.com>,
2326Michael G Schwern <schwern@pobox.com>,
06e9666b 2327Dan Sugalski <dan@sidhe.org>,
c47ff5f1 2328Nathan Torkington <gnat@frii.com>.
016930a6 2329John Malmberg <wb8tyw@qsl.net>