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PERLPORT(1)
NAME
perlport - Writing portable Perl
DESCRIPTION
Perl runs on numerous operating systems. While most of them share much in
common, they also have their own unique features.
This document is meant to help you to find out what constitutes portable
Perl code. That way once you make a decision to write portably, you know
where the lines are drawn, and you can stay within them.
There is a tradeoff between taking full advantage of one particular type of
computer and taking advantage of a full range of them. Naturally, as you
broaden your range and become more diverse, the common factors drop, and
you are left with an increasingly smaller area of common ground in which
you can operate to accomplish a particular task. Thus, when you begin
attacking a problem, it is important to consider under which part of the
tradeoff curve you want to operate. Specifically, you must decide whether
it is important that the task that you are coding have the full generality
of being portable, or whether to just get the job done right now. This is
the hardest choice to be made. The rest is easy, because Perl provides
many choices, whichever way you want to approach your problem.
Looking at it another way, writing portable code is usually about willfully
limiting your available choices. Naturally, it takes discipline and
sacrifice to do that. The product of portability and convenience may be a
constant. You have been warned.
Be aware of two important points:
Not all Perl programs have to be portable
There is no reason you should not use Perl as a language to glue Unix
tools together, or to prototype a Macintosh application, or to manage
the Windows registry. If it makes no sense to aim for portability for
one reason or another in a given program, then don't bother.
Nearly all of Perl already is portable
Don't be fooled into thinking that it is hard to create portable Perl
code. It isn't. Perl tries its level-best to bridge the gaps between
what's available on different platforms, and all the means available to
use those features. Thus almost all Perl code runs on any machine
without modification. But there are some significant issues in writing
portable code, and this document is entirely about those issues.
Here's the general rule: When you approach a task commonly done using a
whole range of platforms, think about writing portable code. That way, you
don't sacrifice much by way of the implementation choices you can avail
yourself of, and at the same time you can give your users lots of platform
choices. On the other hand, when you have to take advantage of some unique
feature of a particular platform, as is often the case with systems
programming (whether for Unix, Windows, Mac OS, VMS, etc.), consider
writing platform-specific code.
When the code will run on only two or three operating systems, you may need
to consider only the differences of those particular systems. The
important thing is to decide where the code will run and to be deliberate
in your decision.
The material below is separated into three main sections: main issues of
portability ("ISSUES", platform-specific issues ("PLATFORMS", and built-in
perl functions that behave differently on various ports ("FUNCTION
IMPLEMENTATIONS".
This information should not be considered complete; it includes possibly
transient information about idiosyncrasies of some of the ports, almost all
of which are in a state of constant evolution. Thus, this material should
be considered a perpetual work in progress ("<IMG SRC="yellow_sign.gif"
ALT="Under Construction">").
ISSUES
Newlines
In most operating systems, lines in files are terminated by newlines. Just
what is used as a newline may vary from OS to OS. Unix traditionally uses
"\012", one type of DOSish I/O uses "\015\012", and Mac OS uses "\015".
Perl uses "\n" to represent the "logical" newline, where what is logical
may depend on the platform in use. In MacPerl, "\n" always means "\015".
In DOSish perls, "\n" usually means "\012", but when accessing a file in
"text" mode, STDIO translates it to (or from) "\015\012", depending on
whether you're reading or writing. Unix does the same thing on ttys in
canonical mode. "\015\012" is commonly referred to as CRLF.
A common cause of unportable programs is the misuse of chop() to trim
newlines:
# XXX UNPORTABLE!
while(<FILE>) {
chop;
@array = split(/:/);
#...
}
You can get away with this on Unix and Mac OS (they have a single character
end-of-line), but the same program will break under DOSish perls because
you're only chop()ing half the end-of-line. Instead, chomp() should be
used to trim newlines. The Dunce::Files module can help audit your code
for misuses of chop().
When dealing with binary files (or text files in binary mode) be sure to
explicitly set $/ to the appropriate value for your file format before
using chomp().
Because of the "text" mode translation, DOSish perls have limitations in
using "seek" and "tell" on a file accessed in "text" mode. Stick to
"seek"-ing to locations you got from "tell" (and no others), and you are
usually free to use "seek" and "tell" even in "text" mode. Using "seek" or
"tell" or other file operations may be non-portable. If you use "binmode"
on a file, however, you can usually "seek" and "tell" with arbitrary values
in safety.
A common misconception in socket programming is that "\n" eq "\012"
everywhere. When using protocols such as common Internet protocols, "\012"
and "\015" are called for specifically, and the values of the logical "\n"
and "\r" (carriage return) are not reliable.
print SOCKET "Hi there, client!\r\n"; # WRONG
print SOCKET "Hi there, client!\015\012"; # RIGHT
However, using "\015\012" (or "\cM\cJ", or "\x0D\x0A") can be tedious and
unsightly, as well as confusing to those maintaining the code. As such,
the Socket module supplies the Right Thing for those who want it.
use Socket qw(:DEFAULT :crlf);
print SOCKET "Hi there, client!$CRLF" # RIGHT
When reading from a socket, remember that the default input record
separator $/ is "\n", but robust socket code will recognize as either
"\012" or "\015\012" as end of line:
while (<SOCKET>) {
# ...
}
Because both CRLF and LF end in LF, the input record separator can be set
to LF and any CR stripped later. Better to write:
use Socket qw(:DEFAULT :crlf);
local($/) = LF; # not needed if $/ is already \012
while (<SOCKET>) {
s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK
# s/\015?\012/\n/; # same thing
}
This example is preferred over the previous one--even for Unix platforms--
because now any "\015"'s ("\cM"'s) are stripped out (and there was much
rejoicing).
Similarly, functions that return text data--such as a function that fetches
a web page--should sometimes translate newlines before returning the data,
if they've not yet been translated to the local newline representation. A
single line of code will often suffice:
$data =~ s/\015?\012/\n/g;
return $data;
Some of this may be confusing. Here's a handy reference to the ASCII CR
and LF characters. You can print it out and stick it in your wallet.
LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10
CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13
| Unix | DOS | Mac |
---------------------------
\n | LF | LF | CR |
\r | CR | CR | LF |
\n * | LF | CRLF | CR |
\r * | CR | CR | LF |
---------------------------
* text-mode STDIO
The Unix column assumes that you are not accessing a serial line (like a
tty) in canonical mode. If you are, then CR on input becomes "\n", and
"\n" on output becomes CRLF.
These are just the most common definitions of "\n" and "\r" in Perl. There
may well be others. For example, on an EBCDIC implementation such as z/OS
or OS/400 the above material is similar to "Unix" but the code numbers
change:
LF eq \025 eq \x15 eq chr(21) eq CP-1047 21
LF eq \045 eq \x25 eq \cU eq chr(37) eq CP-0037 37
CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
| z/OS | OS/400 |
----------------------
\n | LF | LF |
\r | CR | CR |
\n * | LF | LF |
\r * | CR | CR |
----------------------
* text-mode STDIO
Numbers endianness and Width
Different CPUs store integers and floating point numbers in different
orders (called endianness) and widths (32-bit and 64-bit being the most
common today). This affects your programs when they attempt to transfer
numbers in binary format from one CPU architecture to another, usually
either "live" via network connection, or by storing the numbers to
secondary storage such as a disk file or tape.
Conflicting storage orders make utter mess out of the numbers. If a
little-endian host (Intel, VAX) stores 0x12345678 (305419896 in decimal), a
big-endian host (Motorola, Sparc, PA) reads it as 0x78563412 (2018915346 in
decimal). Alpha and MIPS can be either: Digital/Compaq used/uses them in
little-endian mode; SGI/Cray uses them in big-endian mode. To avoid this
problem in network (socket) connections use the "pack" and "unpack" formats
"n" and "N", the "network" orders. These are guaranteed to be portable.
You can explore the endianness of your platform by unpacking a data
structure packed in native format such as:
print unpack("h*", pack("s2", 1, 2)), "\n";
# '10002000' on e.g. Intel x86 or Alpha 21064 in little-endian mode
# '00100020' on e.g. Motorola 68040
If you need to distinguish between endian architectures you could use
either of the variables set like so:
$is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
$is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
Differing widths can cause truncation even between platforms of equal
endianness. The platform of shorter width loses the upper parts of the
number. There is no good solution for this problem except to avoid
transferring or storing raw binary numbers.
One can circumnavigate both these problems in two ways. Either transfer
and store numbers always in text format, instead of raw binary, or else
consider using modules like Data::Dumper (included in the standard
distribution as of Perl 5.005) and Storable (included as of perl 5.8).
Keeping all data as text significantly simplifies matters.
The v-strings are portable only up to v2147483647 (0x7FFFFFFF), that's how
far EBCDIC, or more precisely UTF-EBCDIC will go.
Files and Filesystems
Most platforms these days structure files in a hierarchical fashion. So,
it is reasonably safe to assume that all platforms support the notion of a
"path" to uniquely identify a file on the system. How that path is really
written, though, differs considerably.
Although similar, file path specifications differ between Unix, Windows,
Mac OS, OS/2, VMS, VOS, RISC OS, and probably others. Unix, for example,
is one of the few OSes that has the elegant idea of a single root
directory.
DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with "/" as
path separator, or in their own idiosyncratic ways (such as having several
root directories and various "unrooted" device files such NIL: and LPT:).
Mac OS uses ":" as a path separator instead of "/".
The filesystem may support neither hard links ("link") nor symbolic links
("symlink", "readlink", "lstat").
The filesystem may support neither access timestamp nor change timestamp
(meaning that about the only portable timestamp is the modification
timestamp), or one second granularity of any timestamps (e.g. the FAT
filesystem limits the time granularity to two seconds).
The "inode change timestamp" (the "-C" filetest) may really be the
"creation timestamp" (which it is not in UNIX).
VOS perl can emulate Unix filenames with "/" as path separator. The native
pathname characters greater-than, less-than, number-sign, and percent-sign
are always accepted.
RISC OS perl can emulate Unix filenames with "/" as path separator, or go
native and use "." for path separator and ":" to signal filesystems and
disk names.
Don't assume UNIX filesystem access semantics: that read, write, and
execute are all the permissions there are, and even if they exist, that
their semantics (for example what do r, w, and x mean on a directory) are
the UNIX ones. The various UNIX/POSIX compatibility layers usually try to
make interfaces like chmod() work, but sometimes there simply is no good
mapping.
If all this is intimidating, have no (well, maybe only a little) fear.
There are modules that can help. The File::Spec modules provide methods to
do the Right Thing on whatever platform happens to be running the program.
use File::Spec::Functions;
chdir(updir()); # go up one directory
$file = catfile(curdir(), 'temp', 'file.txt');
# on Unix and Win32, './temp/file.txt'
# on Mac OS, ':temp:file.txt'
# on VMS, '[.temp]file.txt'
File::Spec is available in the standard distribution as of version
5.004_05. File::Spec::Functions is only in File::Spec 0.7 and later, and
some versions of perl come with version 0.6. If File::Spec is not updated
to 0.7 or later, you must use the object-oriented interface from File::Spec
(or upgrade File::Spec).
In general, production code should not have file paths hardcoded. Making
them user-supplied or read from a configuration file is better, keeping in
mind that file path syntax varies on different machines.
This is especially noticeable in scripts like Makefiles and test suites,
which often assume "/" as a path separator for subdirectories.
Also of use is File::Basename from the standard distribution, which splits
a pathname into pieces (base filename, full path to directory, and file
suffix).
Even when on a single platform (if you can call Unix a single platform),
remember not to count on the existence or the contents of particular
system-specific files or directories, like /etc/passwd, /etc/sendmail.conf,
/etc/resolv.conf, or even /tmp/. For example, /etc/passwd may exist but
not contain the encrypted passwords, because the system is using some form
of enhanced security. Or it may not contain all the accounts, because the
system is using NIS. If code does need to rely on such a file, include a
description of the file and its format in the code's documentation, then
make it easy for the user to override the default location of the file.
Don't assume a text file will end with a newline. They should, but people
forget.
Do not have two files or directories of the same name with different case,
like test.pl and Test.pl, as many platforms have case-insensitive (or at
least case-forgiving) filenames. Also, try not to have non-word characters
(except for ".") in the names, and keep them to the 8.3 convention, for
maximum portability, onerous a burden though this may appear.
Likewise, when using the AutoSplit module, try to keep your functions to
8.3 naming and case-insensitive conventions; or, at the least, make it so
the resulting files have a unique (case-insensitively) first 8 characters.
Whitespace in filenames is tolerated on most systems, but not all, and even
on systems where it might be tolerated, some utilities might become
confused by such whitespace.
Many systems (DOS, VMS) cannot have more than one "." in their filenames.
Don't assume ">" won't be the first character of a filename. Always use
"<" explicitly to open a file for reading, or even better, use the three-
arg version of open, unless you want the user to be able to specify a pipe
open.
open(FILE, '<', $existing_file) or die $!;
If filenames might use strange characters, it is safest to open it with
"sysopen" instead of "open". "open" is magic and can translate characters
like ">", "<", and "|", which may be the wrong thing to do. (Sometimes,
though, it's the right thing.) Three-arg open can also help protect against
this translation in cases where it is undesirable.
Don't use ":" as a part of a filename since many systems use that for their
own semantics (Mac OS Classic for separating pathname components, many
networking schemes and utilities for separating the nodename and the
pathname, and so on). For the same reasons, avoid "@", ";" and "|".
Don't assume that in pathnames you can collapse two leading slashes "//"
into one: some networking and clustering filesystems have special semantics
for that. Let the operating system to sort it out.
The portable filename characters as defined by ANSI C are
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
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
0 1 2 3 4 5 6 7 8 9
. _ -
and the "-" shouldn't be the first character. If you want to be
hypercorrect, stay case-insensitive and within the 8.3 naming convention
(all the files and directories have to be unique within one directory if
their names are lowercased and truncated to eight characters before the
".", if any, and to three characters after the ".", if any). (And do not
use "."s in directory names.)
System Interaction
Not all platforms provide a command line. These are usually platforms that
rely primarily on a Graphical User Interface (GUI) for user interaction. A
program requiring a command line interface might not work everywhere. This
is probably for the user of the program to deal with, so don't stay up late
worrying about it.
Some platforms can't delete or rename files held open by the system.
Remember to "close" files when you are done with them. Don't "unlink" or
"rename" an open file. Don't "tie" or "open" a file already tied or
opened; "untie" or "close" it first.
Don't open the same file more than once at a time for writing, as some
operating systems put mandatory locks on such files.
Don't assume that write/modify permission on a directory gives the right to
add or delete files/directories in that directory. That is filesystem
specific: in some filesystems you need write/modify permission also (or
even just) in the file/directory itself. In some filesystems (AFS, DFS)
the permission to add/delete directory entries is a completely separate
permission.
Don't assume that a single "unlink" completely gets rid of the file: some
filesystems (most notably the ones in VMS) have versioned filesystems, and
unlink() removes only the most recent one (it doesn't remove all the
versions because by default the native tools on those platforms remove just
the most recent version, too). The portable idiom to remove all the
versions of a file is
1 while unlink "file";
This will terminate if the file is undeleteable for some reason (protected,
not there, and so on).
Don't count on a specific environment variable existing in %ENV. Don't
count on %ENV entries being case-sensitive, or even case-preserving. Don't
try to clear %ENV by saying "%ENV = ();", or, if you really have to, make
it conditional on "$^O ne 'VMS'" since in VMS the %ENV table is much more
than a per-process key-value string table.
Don't count on signals or %SIG for anything.
Don't count on filename globbing. Use "opendir", "readdir", and "closedir"
instead.
Don't count on per-program environment variables, or per-program current
directories.
Don't count on specific values of $!.
Command names versus file pathnames
Don't assume that the name used to invoke a command or program with
"system" or "exec" can also be used to test for the existence of the file
that holds the executable code for that command or program. First, many
systems have "internal" commands that are built-in to the shell or OS and
while these commands can be invoked, there is no corresponding file.
Second, some operating systems (e.g., Cygwin, DJGPP, OS/2, and VOS) have
required suffixes for executable files; these suffixes are generally
permitted on the command name but are not required. Thus, a command like
"perl" might exist in a file named "perl", "perl.exe", or "perl.pm",
depending on the operating system. The variable "_exe" in the Config
module holds the executable suffix, if any. Third, the VMS port carefully
sets up $^X and $Config{perlpath} so that no further processing is
required. This is just as well, because the matching regular expression
used below would then have to deal with a possible trailing version number
in the VMS file name.
To convert $^X to a file pathname, taking account of the requirements of
the various operating system possibilities, say:
use Config;
$thisperl = $^X;
if ($^O ne 'VMS')
{$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
To convert $Config{perlpath} to a file pathname, say:
use Config;
$thisperl = $Config{perlpath};
if ($^O ne 'VMS')
{$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
Interprocess Communication (IPC)
In general, don't directly access the system in code meant to be portable.
That means, no "system", "exec", "fork", "pipe", ``, "qx//", "open" with a
"|", nor any of the other things that makes being a perl hacker worth
being.
Commands that launch external processes are generally supported on most
platforms (though many of them do not support any type of forking). The
problem with using them arises from what you invoke them on. External
tools are often named differently on different platforms, may not be
available in the same location, might accept different arguments, can
behave differently, and often present their results in a platform-dependent
way. Thus, you should seldom depend on them to produce consistent results.
(Then again, if you're calling netstat -a, you probably don't expect it to
run on both Unix and CP/M.)
One especially common bit of Perl code is opening a pipe to sendmail:
open(MAIL, '|/usr/lib/sendmail -t')
or die "cannot fork sendmail: $!";
This is fine for systems programming when sendmail is known to be
available. But it is not fine for many non-Unix systems, and even some
Unix systems that may not have sendmail installed. If a portable solution
is needed, see the various distributions on CPAN that deal with it.
Mail::Mailer and Mail::Send in the MailTools distribution are commonly
used, and provide several mailing methods, including mail, sendmail, and
direct SMTP (via Net::SMTP) if a mail transfer agent is not available.
Mail::Sendmail is a standalone module that provides simple, platform-
independent mailing.
The Unix System V IPC ("msg*(), sem*(), shm*()") is not available even on
all Unix platforms.
Do not use either the bare result of "pack("N", 10, 20, 30, 40)" or bare
v-strings (such as "v10.20.30.40") to represent IPv4 addresses: both forms
just pack the four bytes into network order. That this would be equal to
the C language "in_addr" struct (which is what the socket code internally
uses) is not guaranteed. To be portable use the routines of the Socket
extension, such as "inet_aton()", "inet_ntoa()", and "sockaddr_in()".
The rule of thumb for portable code is: Do it all in portable Perl, or use
a module (that may internally implement it with platform-specific code, but
expose a common interface).
External Subroutines (XS)
XS code can usually be made to work with any platform, but dependent
libraries, header files, etc., might not be readily available or portable,
or the XS code itself might be platform-specific, just as Perl code might
be. If the libraries and headers are portable, then it is normally
reasonable to make sure the XS code is portable, too.
A different type of portability issue arises when writing XS code:
availability of a C compiler on the end-user's system. C brings with it
its own portability issues, and writing XS code will expose you to some of
those. Writing purely in Perl is an easier way to achieve portability.
Standard Modules
In general, the standard modules work across platforms. Notable exceptions
are the CPAN module (which currently makes connections to external programs
that may not be available), platform-specific modules (like
ExtUtils::MM_VMS), and DBM modules.
There is no one DBM module available on all platforms. SDBM_File and the
others are generally available on all Unix and DOSish ports, but not in
MacPerl, where only NBDM_File and DB_File are available.
The good news is that at least some DBM module should be available, and
AnyDBM_File will use whichever module it can find. Of course, then the
code needs to be fairly strict, dropping to the greatest common factor
(e.g., not exceeding 1K for each record), so that it will work with any DBM
module. See AnyDBM_File for more details.
Time and Date
The system's notion of time of day and calendar date is controlled in
widely different ways. Don't assume the timezone is stored in $ENV{TZ},
and even if it is, don't assume that you can control the timezone through
that variable.
Don't assume that the epoch starts at 00:00:00, January 1, 1970, because
that is OS- and implementation-specific. It is better to store a date in
an unambiguous representation. The ISO-8601 standard defines "YYYY-MM-DD"
as the date format. A text representation (like "1987-12-18") can be
easily converted into an OS-specific value using a module like Date::Parse.
An array of values, such as those returned by "localtime", can be converted
to an OS-specific representation using Time::Local.
When calculating specific times, such as for tests in time or date modules,
it may be appropriate to calculate an offset for the epoch.
require Time::Local;
$offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
The value for $offset in Unix will be 0, but in Mac OS will be some large
number. $offset can then be added to a Unix time value to get what should
be the proper value on any system.
Character sets and character encoding
Assume very little about character sets.
Assume nothing about numerical values ("ord", "chr") of characters. Do not
use explicit code point ranges (like \xHH-\xHH); use for example symbolic
character classes like "[:print:]".
Do not assume that the alphabetic characters are encoded contiguously (in
the numeric sense). There may be gaps.
Do not assume anything about the ordering of the characters. The lowercase
letters may come before or after the uppercase letters; the lowercase and
uppercase may be interlaced so that both `a' and `A' come before `b'; the
accented and other international characters may be interlaced so that ae
comes before `b'.
Internationalisation
If you may assume POSIX (a rather large assumption), you may read more
about the POSIX locale system from perllocale. The locale system at least
attempts to make things a little bit more portable, or at least more
convenient and native-friendly for non-English users. The system affects
character sets and encoding, and date and time formatting--amongst other
things.
System Resources
If your code is destined for systems with severely constrained (or
missing!) virtual memory systems then you want to be especially mindful of
avoiding wasteful constructs such as:
# NOTE: this is no longer "bad" in perl5.005
for (0..10000000) {} # bad
for (my $x = 0; $x <= 10000000; ++$x) {} # good
@lines = <VERY_LARGE_FILE>; # bad
while (<FILE>) {$file .= $_} # sometimes bad
$file = join('', <FILE>); # better
The last two constructs may appear unintuitive to most people. The first
repeatedly grows a string, whereas the second allocates a large chunk of
memory in one go. On some systems, the second is more efficient that the
first.
Security
Most multi-user platforms provide basic levels of security, usually
implemented at the filesystem level. Some, however, do not--
unfortunately. Thus the notion of user id, or "home" directory, or even
the state of being logged-in, may be unrecognizable on many platforms. If
you write programs that are security-conscious, it is usually best to know
what type of system you will be running under so that you can write code
explicitly for that platform (or class of platforms).
Don't assume the UNIX filesystem access semantics: the operating system or
the filesystem may be using some ACL systems, which are richer languages
than the usual rwx. Even if the rwx exist, their semantics might be
different.
(From security viewpoint testing for permissions before attempting to do
something is silly anyway: if one tries this, there is potential for race
conditions-- someone or something might change the permissions between the
permissions check and the actual operation. Just try the operation.)
Don't assume the UNIX user and group semantics: especially, don't expect
the $< and $> (or the $( and $)) to work for switching identities (or
memberships).
Don't assume set-uid and set-gid semantics. (And even if you do, think
twice: set-uid and set-gid are a known can of security worms.)
Style
For those times when it is necessary to have platform-specific code,
consider keeping the platform-specific code in one place, making porting to
other platforms easier. Use the Config module and the special variable $^O
to differentiate platforms, as described in "PLATFORMS".
Be careful in the tests you supply with your module or programs. Module
code may be fully portable, but its tests might not be. This often happens
when tests spawn off other processes or call external programs to aid in
the testing, or when (as noted above) the tests assume certain things about
the filesystem and paths. Be careful not to depend on a specific output
style for errors, such as when checking $! after a system call. Some
platforms expect a certain output format, and perl on those platforms may
have been adjusted accordingly. Most specifically, don't anchor a regex
when testing an error value.
CPAN Testers
Modules uploaded to CPAN are tested by a variety of volunteers on different
platforms. These CPAN testers are notified by mail of each new upload, and
reply to the list with PASS, FAIL, NA (not applicable to this platform), or
UNKNOWN (unknown), along with any relevant notations.
The purpose of the testing is twofold: one, to help developers fix any
problems in their code that crop up because of lack of testing on other
platforms; two, to provide users with information about whether a given
module works on a given platform.
Mailing list: cpan-testers@perl.org
Testing results: http://testers.cpan.org/
PLATFORMS
As of version 5.002, Perl is built with a $^O variable that indicates the
operating system it was built on. This was implemented to help speed up
code that would otherwise have to "use Config" and use the value of
$Config{osname}. Of course, to get more detailed information about the
system, looking into %Config is certainly recommended.
%Config cannot always be trusted, however, because it was built at compile
time. If perl was built in one place, then transferred elsewhere, some
values may be wrong. The values may even have been edited after the fact.
Unix
Perl works on a bewildering variety of Unix and Unix-like platforms (see
e.g. most of the files in the hints/ directory in the source code kit). On
most of these systems, the value of $^O (hence $Config{'osname'}, too) is
determined either by lowercasing and stripping punctuation from the first
field of the string returned by typing "uname -a" (or a similar command) at
the shell prompt or by testing the file system for the presence of uniquely
named files such as a kernel or header file. Here, for example, are a few
of the more popular Unix flavors:
uname $^O $Config{'archname'}
--------------------------------------------
AIX aix aix
BSD/OS bsdos i386-bsdos
Darwin darwin darwin
dgux dgux AViiON-dgux
DYNIX/ptx dynixptx i386-dynixptx
FreeBSD freebsd freebsd-i386
Linux linux arm-linux
Linux linux i386-linux
Linux linux i586-linux
Linux linux ppc-linux
HP-UX hpux PA-RISC1.1
IRIX irix irix
Mac OS X darwin darwin
MachTen PPC machten powerpc-machten
NeXT 3 next next-fat
NeXT 4 next OPENSTEP-Mach
openbsd openbsd i386-openbsd
OSF1 dec_osf alpha-dec_osf
reliantunix-n svr4 RM400-svr4
SCO_SV sco_sv i386-sco_sv
SINIX-N svr4 RM400-svr4
sn4609 unicos CRAY_C90-unicos
sn6521 unicosmk t3e-unicosmk
sn9617 unicos CRAY_J90-unicos
SunOS solaris sun4-solaris
SunOS solaris i86pc-solaris
SunOS4 sunos sun4-sunos
Because the value of $Config{archname} may depend on the hardware
architecture, it can vary more than the value of $^O.
DOS and Derivatives
Perl has long been ported to Intel-style microcomputers running under
systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can bring
yourself to mention (except for Windows CE, if you count that). Users
familiar with COMMAND.COM or CMD.EXE style shells should be aware that each
of these file specifications may have subtle differences:
$filespec0 = "c:/foo/bar/file.txt";
$filespec1 = "c:\\foo\\bar\\file.txt";
$filespec2 = 'c:\foo\bar\file.txt';
$filespec3 = 'c:\\foo\\bar\\file.txt';
System calls accept either "/" or "\" as the path separator. However, many
command-line utilities of DOS vintage treat "/" as the option prefix, so
may get confused by filenames containing "/". Aside from calling any
external programs, "/" will work just fine, and probably better, as it is
more consistent with popular usage, and avoids the problem of remembering
what to backwhack and what not to.
The DOS FAT filesystem can accommodate only "8.3" style filenames. Under
the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT)
filesystems you may have to be careful about case returned with functions
like "readdir" or used with functions like "open" or "opendir".
DOS also treats several filenames as special, such as AUX, PRN, NUL, CON,
COM1, LPT1, LPT2, etc. Unfortunately, sometimes these filenames won't even
work if you include an explicit directory prefix. It is best to avoid such
filenames, if you want your code to be portable to DOS and its derivatives.
It's hard to know what these all are, unfortunately.
Users of these operating systems may also wish to make use of scripts such
as pl2bat.bat or pl2cmd to put wrappers around your scripts.
Newline ("\n") is translated as "\015\012" by STDIO when reading from and
writing to files (see "Newlines"). "binmode(FILEHANDLE)" will keep "\n"
translated as "\012" for that filehandle. Since it is a no-op on other
systems, "binmode" should be used for cross-platform code that deals with
binary data. That's assuming you realize in advance that your data is in
binary. General-purpose programs should often assume nothing about their
data.
The $^O variable and the $Config{archname} values for various DOSish perls
are as follows:
OS $^O $Config{archname} ID Version
--------------------------------------------------------
MS-DOS dos ?
PC-DOS dos ?
OS/2 os2 ?
Windows 3.1 ? ? 0 3 01
Windows 95 MSWin32 MSWin32-x86 1 4 00
Windows 98 MSWin32 MSWin32-x86 1 4 10
Windows ME MSWin32 MSWin32-x86 1 ?
Windows NT MSWin32 MSWin32-x86 2 4 xx
Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
Windows NT MSWin32 MSWin32-ppc 2 4 xx
Windows 2000 MSWin32 MSWin32-x86 2 5 xx
Windows XP MSWin32 MSWin32-x86 2 ?
Windows CE MSWin32 ? 3
Cygwin cygwin ?
The various MSWin32 Perl's can distinguish the OS they are running on via
the value of the fifth element of the list returned from
Win32::GetOSVersion(). For example:
if ($^O eq 'MSWin32') {
my @os_version_info = Win32::GetOSVersion();
print +('3.1','95','NT')[$os_version_info[4]],"\n";
}
There are also Win32::IsWinNT() and Win32::IsWin95(), try "perldoc Win32",
and as of libwin32 0.19 (not part of the core Perl distribution)
Win32::GetOSName(). The very portable POSIX::uname() will work too:
c:\> perl -MPOSIX -we "print join '|', uname"
Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86
Also see:
· The djgpp environment for DOS, http://www.delorie.com/djgpp/ and
perldos.
· The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also perlos2.
· Build instructions for Win32 in perlwin32, or under the Cygnus
environment in perlcygwin.
· The "Win32::*" modules in Win32.
· The ActiveState Pages, http://www.activestate.com/
· The Cygwin environment for Win32; README.cygwin (installed as
perlcygwin), http://www.cygwin.com/
· The U/WIN environment for Win32,
http://www.research.att.com/sw/tools/uwin/
· Build instructions for OS/2, perlos2
Mac OS
Any module requiring XS compilation is right out for most people, because
MacPerl is built using non-free (and non-cheap!) compilers. Some XS
modules that can work with MacPerl are built and distributed in binary form
on CPAN.
Directories are specified as:
volume:folder:file for absolute pathnames
volume:folder: for absolute pathnames
:folder:file for relative pathnames
:folder: for relative pathnames
:file for relative pathnames
file for relative pathnames
Files are stored in the directory in alphabetical order. Filenames are
limited to 31 characters, and may include any character except for null and
":", which is reserved as the path separator.
Instead of "flock", see "FSpSetFLock" and "FSpRstFLock" in the Mac::Files
module, or "chmod(0444, ...)" and "chmod(0666, ...)".
In the MacPerl application, you can't run a program from the command line;
programs that expect @ARGV to be populated can be edited with something
like the following, which brings up a dialog box asking for the command
line arguments.
if (!@ARGV) {
@ARGV = split /\s+/, MacPerl::Ask('Arguments?');
}
A MacPerl script saved as a "droplet" will populate @ARGV with the full
pathnames of the files dropped onto the script.
Mac users can run programs under a type of command line interface under MPW
(Macintosh Programmer's Workshop, a free development environment from
Apple). MacPerl was first introduced as an MPW tool, and MPW can be used
like a shell:
perl myscript.plx some arguments
ToolServer is another app from Apple that provides access to MPW tools from
MPW and the MacPerl app, which allows MacPerl programs to use "system",
backticks, and piped "open".
"Mac OS" is the proper name for the operating system, but the value in $^O
is "MacOS". To determine architecture, version, or whether the application
or MPW tool version is running, check:
$is_app = $MacPerl::Version =~ /App/;
$is_tool = $MacPerl::Version =~ /MPW/;
($version) = $MacPerl::Version =~ /^(\S+)/;
$is_ppc = $MacPerl::Architecture eq 'MacPPC';
$is_68k = $MacPerl::Architecture eq 'Mac68K';
Mac OS X, based on NeXT's OpenStep OS, runs MacPerl natively, under the
"Classic" environment. There is no "Carbon" version of MacPerl to run
under the primary Mac OS X environment. Mac OS X and its Open Source
version, Darwin, both run Unix perl natively.
Also see:
· MacPerl Development, http://dev.macperl.org/ .
· The MacPerl Pages, http://www.macperl.com/ .
· The MacPerl mailing lists, http://lists.perl.org/ .
VMS
Perl on VMS is discussed in perlvms in the perl distribution. Perl on VMS
can accept either VMS- or Unix-style file specifications as in either of
the following:
$ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
$ perl -ne "print if /perl_setup/i" /sys$login/login.com
but not a mixture of both as in:
$ perl -ne "print if /perl_setup/i" sys$login:/login.com
Can't open sys$login:/login.com: file specification syntax error
Interacting with Perl from the Digital Command Language (DCL) shell often
requires a different set of quotation marks than Unix shells do. For
example:
$ perl -e "print ""Hello, world.\n"""
Hello, world.
There are several ways to wrap your perl scripts in DCL .COM files, if you
are so inclined. For example:
$ write sys$output "Hello from DCL!"
$ if p1 .eqs. ""
$ then perl -x 'f$environment("PROCEDURE")
$ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8
$ deck/dollars="__END__"
#!/usr/bin/perl
print "Hello from Perl!\n";
__END__
$ endif
Do take care with "$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT" if your
perl-in-DCL script expects to do things like "$read = <STDIN>;".
Filenames are in the format "name.extension;version". The maximum length
for filenames is 39 characters, and the maximum length for extensions is
also 39 characters. Version is a number from 1 to 32767. Valid characters
are "/[A-Z0-9$_-]/".
VMS's RMS filesystem is case-insensitive and does not preserve case.
"readdir" returns lowercased filenames, but specifying a file for opening
remains case-insensitive. Files without extensions have a trailing period
on them, so doing a "readdir" with a file named A.;5 will return a. (though
that file could be opened with "open(FH, 'A')").
RMS had an eight level limit on directory depths from any rooted logical
(allowing 16 levels overall) prior to VMS 7.2. Hence
"PERL_ROOT:[LIB.2.3.4.5.6.7.8]" is a valid directory specification but
"PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]" is not. Makefile.PL authors might have
to take this into account, but at least they can refer to the former as
"/PERL_ROOT/lib/2/3/4/5/6/7/8/".
The VMS::Filespec module, which gets installed as part of the build process
on VMS, is a pure Perl module that can easily be installed on non-VMS
platforms and can be helpful for conversions to and from RMS native
formats.
What "\n" represents depends on the type of file opened. It usually
represents "\012" but it could also be "\015", "\012", "\015\012", "\000",
"\040", or nothing depending on the file organiztion and record format.
The VMS::Stdio module provides access to the special fopen() requirements
of files with unusual attributes on VMS.
TCP/IP stacks are optional on VMS, so socket routines might not be
implemented. UDP sockets may not be supported.
The value of $^O on OpenVMS is "VMS". To determine the architecture that
you are running on without resorting to loading all of %Config you can
examine the content of the @INC array like so:
if (grep(/VMS_AXP/, @INC)) {
print "I'm on Alpha!\n";
} elsif (grep(/VMS_VAX/, @INC)) {
print "I'm on VAX!\n";
} else {
print "I'm not so sure about where $^O is...\n";
}
On VMS, perl determines the UTC offset from the "SYS$TIMEZONE_DIFFERENTIAL"
logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00,
calls to "localtime" are adjusted to count offsets from 01-JAN-1970
00:00:00.00, just like Unix.
Also see:
· README.vms (installed as README_vms), perlvms
· vmsperl list, majordomo@perl.org
(Put the words "subscribe vmsperl" in message body.)
· vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
VOS
Perl on VOS is discussed in README.vos in the perl distribution (installed
as perlvos). Perl on VOS can accept either VOS- or Unix-style file
specifications as in either of the following:
C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
or even a mixture of both as in:
C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
Even though VOS allows the slash character to appear in object names,
because the VOS port of Perl interprets it as a pathname delimiting
character, VOS files, directories, or links whose names contain a slash
character cannot be processed. Such files must be renamed before they can
be processed by Perl. Note that VOS limits file names to 32 or fewer
characters.
Perl on VOS can be built using two different compilers and two different
versions of the POSIX runtime. The recommended method for building full
Perl is with the GNU C compiler and the generally-available version of VOS
POSIX support. See README.vos (installed as perlvos) for restrictions that
apply when Perl is built using the VOS Standard C compiler or the alpha
version of VOS POSIX support.
The value of $^O on VOS is "VOS". To determine the architecture that you
are running on without resorting to loading all of %Config you can examine
the content of the @INC array like so:
if ($^O =~ /VOS/) {
print "I'm on a Stratus box!\n";
} else {
print "I'm not on a Stratus box!\n";
die;
}
if (grep(/860/, @INC)) {
print "This box is a Stratus XA/R!\n";
} elsif (grep(/7100/, @INC)) {
print "This box is a Stratus HP 7100 or 8xxx!\n";
} elsif (grep(/8000/, @INC)) {
print "This box is a Stratus HP 8xxx!\n";
} else {
print "This box is a Stratus 68K!\n";
}
Also see:
· README.vos (installed as perlvos)
· The VOS mailing list.
There is no specific mailing list for Perl on VOS. You can post
comments to the comp.sys.stratus newsgroup, or subscribe to the general
Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
the message body to majordomo@list.stratagy.com.
· VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
EBCDIC Platforms
Recent versions of Perl have been ported to platforms such as OS/400 on
AS/400 minicomputers as well as OS/390, VM/ESA, and BS2000 for S/390
Mainframes. Such computers use EBCDIC character sets internally (usually
Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390
systems). On the mainframe perl currently works under the "Unix system
services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition,
or the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater).
See perlos390 for details.
As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix sub-
systems do not support the "#!" shebang trick for script invocation.
Hence, on OS/390 and VM/ESA perl scripts can be executed with a header
similar to the following simple script:
: # use perl
eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
if 0;
#!/usr/local/bin/perl # just a comment really
print "Hello from perl!\n";
OS/390 will support the "#!" shebang trick in release 2.8 and beyond.
Calls to "system" and backticks can use POSIX shell syntax on all S/390
systems.
On the AS/400, if PERL5 is in your library list, you may need to wrap your
perl scripts in a CL procedure to invoke them like so:
BEGIN
CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
ENDPGM
This will invoke the perl script hello.pl in the root of the QOpenSys file
system. On the AS/400 calls to "system" or backticks must use CL syntax.
On these platforms, bear in mind that the EBCDIC character set may have an
effect on what happens with some perl functions (such as "chr", "pack",
"print", "printf", "ord", "sort", "sprintf", "unpack"), as well as bit-
fiddling with ASCII constants using operators like "^", "&" and "|", not to
mention dealing with socket interfaces to ASCII computers (see "Newlines").
Fortunately, most web servers for the mainframe will correctly translate
the "\n" in the following statement to its ASCII equivalent ("\r" is the
same under both Unix and OS/390 & VM/ESA):
print "Content-type: text/html\r\n\r\n";
The values of $^O on some of these platforms includes:
uname $^O $Config{'archname'}
--------------------------------------------
OS/390 os390 os390
OS400 os400 os400
POSIX-BC posix-bc BS2000-posix-bc
VM/ESA vmesa vmesa
Some simple tricks for determining if you are running on an EBCDIC platform
could include any of the following (perhaps all):
if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
One thing you may not want to rely on is the EBCDIC encoding of punctuation
characters since these may differ from code page to code page (and once
your module or script is rumoured to work with EBCDIC, folks will want it
to work with all EBCDIC character sets).
Also see:
· *
perlos390, README.os390, perlbs2000, README.vmesa, perlebcdic.
· The perl-mvs@perl.org list is for discussion of porting issues as well
as general usage issues for all EBCDIC Perls. Send a message body of
"subscribe perl-mvs" to majordomo@perl.org.
· AS/400 Perl information at http://as400.rochester.ibm.com/ as well as
on CPAN in the ports/ directory.
Acorn RISC OS
Because Acorns use ASCII with newlines ("\n") in text files as "\012" like
Unix, and because Unix filename emulation is turned on by default, most
simple scripts will probably work "out of the box". The native filesystem
is modular, and individual filesystems are free to be case-sensitive or
insensitive, and are usually case-preserving. Some native filesystems have
name length limits, which file and directory names are silently truncated
to fit. Scripts should be aware that the standard filesystem currently has
a name length limit of 10 characters, with up to 77 items in a directory,
but other filesystems may not impose such limitations.
Native filenames are of the form
Filesystem#Special_Field::DiskName.$.Directory.Directory.File
where
Special_Field is not usually present, but may contain . and $ .
Filesystem =~ m|[A-Za-z0-9_]|
DsicName =~ m|[A-Za-z0-9_/]|
$ represents the root directory
. is the path separator
@ is the current directory (per filesystem but machine global)
^ is the parent directory
Directory and File =~ m|[^\0- "\.\$\%<!>:\@\\^\|\177]+|
The default filename translation is roughly "tr|/.|./|;"
Note that ""ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'" and that the
second stage of "$" interpolation in regular expressions will fall foul of
the $. if scripts are not careful.
Logical paths specified by system variables containing comma-separated
search lists are also allowed; hence "System:Modules" is a valid filename,
and the filesystem will prefix "Modules" with each section of "System$Path"
until a name is made that points to an object on disk. Writing to a new
file "System:Modules" would be allowed only if "System$Path" contains a
single item list. The filesystem will also expand system variables in
filenames if enclosed in angle brackets, so "<System$Dir>.Modules" would
look for the file "$ENV{'System$Dir'} . 'Modules'". The obvious
implication of this is that fully qualified filenames can start with "<>"
and should be protected when "open" is used for input.
Because "." was in use as a directory separator and filenames could not be
assumed to be unique after 10 characters, Acorn implemented the C compiler
to strip the trailing ".c" ".h" ".s" and ".o" suffix from filenames
specified in source code and store the respective files in subdirectories
named after the suffix. Hence files are translated:
foo.h h.foo
C:foo.h C:h.foo (logical path variable)
sys/os.h sys.h.os (C compiler groks Unix-speak)
10charname.c c.10charname
10charname.o o.10charname
11charname_.c c.11charname (assuming filesystem truncates at 10)
The Unix emulation library's translation of filenames to native assumes
that this sort of translation is required, and it allows a user-defined
list of known suffixes that it will transpose in this fashion. This may
seem transparent, but consider that with these rules "foo/bar/baz.h" and
"foo/bar/h/baz" both map to "foo.bar.h.baz", and that "readdir" and "glob"
cannot and do not attempt to emulate the reverse mapping. Other "."'s in
filenames are translated to "/".
As implied above, the environment accessed through %ENV is global, and the
convention is that program specific environment variables are of the form
"Program$Name". Each filesystem maintains a current directory, and the
current filesystem's current directory is the global current directory.
Consequently, sociable programs don't change the current directory but rely
on full pathnames, and programs (and Makefiles) cannot assume that they can
spawn a child process which can change the current directory without
affecting its parent (and everyone else for that matter).
Because native operating system filehandles are global and are currently
allocated down from 255, with 0 being a reserved value, the Unix emulation
library emulates Unix filehandles. Consequently, you can't rely on passing
"STDIN", "STDOUT", or "STDERR" to your children.
The desire of users to express filenames of the form "<Foo$Dir>.Bar" on the
command line unquoted causes problems, too: `` command output capture has
to perform a guessing game. It assumes that a string "<[^<>]+\$[^<>]>" is
a reference to an environment variable, whereas anything else involving "<"
or ">" is redirection, and generally manages to be 99% right. Of course,
the problem remains that scripts cannot rely on any Unix tools being
available, or that any tools found have Unix-like command line arguments.
Extensions and XS are, in theory, buildable by anyone using free tools. In
practice, many don't, as users of the Acorn platform are used to binary
distributions. MakeMaker does run, but no available make currently copes
with MakeMaker's makefiles; even if and when this should be fixed, the lack
of a Unix-like shell will cause problems with makefile rules, especially
lines of the form "cd sdbm && make all", and anything using quoting.
"RISC OS" is the proper name for the operating system, but the value in $^O
is "riscos" (because we don't like shouting).
Other perls
Perl has been ported to many platforms that do not fit into any of the
categories listed above. Some, such as AmigaOS, Atari MiNT, BeOS, HP
MPE/iX, QNX, Plan 9, and VOS, have been well-integrated into the standard
Perl source code kit. You may need to see the ports/ directory on CPAN for
information, and possibly binaries, for the likes of: aos, Atari ST,
lynxos, riscos, Novell Netware, Tandem Guardian, etc. (Yes, we know that
some of these OSes may fall under the Unix category, but we are not a
standards body.)
Some approximate operating system names and their $^O values in the "OTHER"
category include:
OS $^O $Config{'archname'}
------------------------------------------
Amiga DOS amigaos m68k-amigos
BeOS beos
MPE/iX mpeix PA-RISC1.1
See also:
· Amiga, README.amiga (installed as perlamiga).
· Atari, README.mint and Guido Flohr's web page
http://stud.uni-sb.de/~gufl0000/
· Be OS, README.beos
· HP 300 MPE/iX, README.mpeix and Mark Bixby's web page
http://www.bixby.org/mark/perlix.html
· A free perl5-based PERL.NLM for Novell Netware is available in
precompiled binary and source code form from http://www.novell.com/ as
well as from CPAN.
· Plan 9, README.plan9
FUNCTION IMPLEMENTATIONS
Listed below are functions that are either completely unimplemented or else
have been implemented differently on various platforms. Following each
description will be, in parentheses, a list of platforms that the
description applies to.
The list may well be incomplete, or even wrong in some places. When in
doubt, consult the platform-specific README files in the Perl source
distribution, and any other documentation resources accompanying a given
port.
Be aware, moreover, that even among Unix-ish systems there are variations.
For many functions, you can also query %Config, exported by default from
the Config module. For example, to check whether the platform has the
"lstat" call, check $Config{d_lstat}. See Config for a full description of
available variables.
Alphabetical Listing of Perl Functions
-X FILEHANDLE
-X EXPR
-X "-r", "-w", and "-x" have a limited meaning only; directories and
applications are executable, and there are no uid/gid
considerations. "-o" is not supported. (Mac OS)
"-r", "-w", "-x", and "-o" tell whether the file is accessible,
which may not reflect UIC-based file protections. (VMS)
"-s" returns the size of the data fork, not the total size of data
fork plus resource fork. (Mac OS).
"-s" by name on an open file will return the space reserved on
disk, rather than the current extent. "-s" on an open filehandle
returns the current size. (RISC OS)
"-R", "-W", "-X", "-O" are indistinguishable from "-r", "-w", "-x",
"-o". (Mac OS, Win32, VMS, RISC OS)
"-b", "-c", "-k", "-g", "-p", "-u", "-A" are not implemented.
(Mac OS)
"-g", "-k", "-l", "-p", "-u", "-A" are not particularly meaningful.
(Win32, VMS, RISC OS)
"-d" is true if passed a device spec without an explicit directory.
(VMS)
"-T" and "-B" are implemented, but might misclassify Mac text files
with foreign characters; this is the case will all platforms, but
may affect Mac OS often. (Mac OS)
"-x" (or "-X") determine if a file ends in one of the executable
suffixes. "-S" is meaningless. (Win32)
"-x" (or "-X") determine if a file has an executable file type.
(RISC OS)
alarm SECONDS
alarm Not implemented. (Win32)
binmode FILEHANDLE
Meaningless. (Mac OS, RISC OS)
Reopens file and restores pointer; if function fails, underlying
filehandle may be closed, or pointer may be in a different
position. (VMS)
The value returned by "tell" may be affected after the call, and
the filehandle may be flushed. (Win32)
chmod LIST
Only limited meaning. Disabling/enabling write permission is
mapped to locking/unlocking the file. (Mac OS)
Only good for changing "owner" read-write access, "group", and
"other" bits are meaningless. (Win32)
Only good for changing "owner" and "other" read-write access.
(RISC OS)
Access permissions are mapped onto VOS access-control list changes.
(VOS)
The actual permissions set depend on the value of the "CYGWIN" in
the SYSTEM environment settings. (Cygwin)
chown LIST
Not implemented. (Mac OS, Win32, Plan 9, RISC OS, VOS)
Does nothing, but won't fail. (Win32)
chroot FILENAME
chroot Not implemented. (Mac OS, Win32, VMS, Plan 9, RISC OS, VOS, VM/ESA)
crypt PLAINTEXT,SALT
May not be available if library or source was not provided when
building perl. (Win32)
Not implemented. (VOS)
dbmclose HASH
Not implemented. (VMS, Plan 9, VOS)
dbmopen HASH,DBNAME,MODE
Not implemented. (VMS, Plan 9, VOS)
dump LABEL
Not useful. (Mac OS, RISC OS)
Not implemented. (Win32)
Invokes VMS debugger. (VMS)
exec LIST
Not implemented. (Mac OS)
Implemented via Spawn. (VM/ESA)
Does not automatically flush output handles on some platforms.
(SunOS, Solaris, HP-UX)
exit EXPR
exit Emulates UNIX exit() (which considers "exit 1" to indicate an
error) by mapping the 1 to SS$_ABORT (44). This behavior may be
overridden with the pragma "use vmsish 'exit'". As with the CRTL's
exit() function, "exit 0" is also mapped to an exit status of
SS$_NORMAL (1); this mapping cannot be overridden. Any other
argument to exit() is used directly as Perl's exit status. (VMS)
fcntl FILEHANDLE,FUNCTION,SCALAR
Not implemented. (Win32, VMS)
flock FILEHANDLE,OPERATION
Not implemented (Mac OS, VMS, RISC OS, VOS).
Available only on Windows NT (not on Windows 95). (Win32)
fork Not implemented. (Mac OS, AmigaOS, RISC OS, VOS, VM/ESA, VMS)
Emulated using multiple interpreters. See perlfork. (Win32)
Does not automatically flush output handles on some platforms.
(SunOS, Solaris, HP-UX)
getlogin
Not implemented. (Mac OS, RISC OS)
getpgrp PID
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS)
getppid Not implemented. (Mac OS, Win32, RISC OS)
getpriority WHICH,WHO
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS, VM/ESA)
getpwnam NAME
Not implemented. (Mac OS, Win32)
Not useful. (RISC OS)
getgrnam NAME
Not implemented. (Mac OS, Win32, VMS, RISC OS)
getnetbyname NAME
Not implemented. (Mac OS, Win32, Plan 9)
getpwuid UID
Not implemented. (Mac OS, Win32)
Not useful. (RISC OS)
getgrgid GID
Not implemented. (Mac OS, Win32, VMS, RISC OS)
getnetbyaddr ADDR,ADDRTYPE
Not implemented. (Mac OS, Win32, Plan 9)
getprotobynumber NUMBER
Not implemented. (Mac OS)
getservbyport PORT,PROTO
Not implemented. (Mac OS)
getpwent
Not implemented. (Mac OS, Win32, VM/ESA)
getgrent
Not implemented. (Mac OS, Win32, VMS, VM/ESA)
gethostent
Not implemented. (Mac OS, Win32)
getnetent
Not implemented. (Mac OS, Win32, Plan 9)
getprotoent
Not implemented. (Mac OS, Win32, Plan 9)
getservent
Not implemented. (Win32, Plan 9)
sethostent STAYOPEN
Not implemented. (Mac OS, Win32, Plan 9, RISC OS)
setnetent STAYOPEN
Not implemented. (Mac OS, Win32, Plan 9, RISC OS)
setprotoent STAYOPEN
Not implemented. (Mac OS, Win32, Plan 9, RISC OS)
setservent STAYOPEN
Not implemented. (Plan 9, Win32, RISC OS)
endpwent
Not implemented. (Mac OS, MPE/iX, VM/ESA, Win32)
endgrent
Not implemented. (Mac OS, MPE/iX, RISC OS, VM/ESA, VMS, Win32)
endhostent
Not implemented. (Mac OS, Win32)
endnetent
Not implemented. (Mac OS, Win32, Plan 9)
endprotoent
Not implemented. (Mac OS, Win32, Plan 9)
endservent
Not implemented. (Plan 9, Win32)
getsockopt SOCKET,LEVEL,OPTNAME
Not implemented. (Plan 9)
glob EXPR
glob This operator is implemented via the File::Glob extension on most
platforms. See File::Glob for portability information.
ioctl FILEHANDLE,FUNCTION,SCALAR
Not implemented. (VMS)
Available only for socket handles, and it does what the
ioctlsocket() call in the Winsock API does. (Win32)
Available only for socket handles. (RISC OS)
kill SIGNAL, LIST
"kill(0, LIST)" is implemented for the sake of taint checking; use
with other signals is unimplemented. (Mac OS)
Not implemented, hence not useful for taint checking. (RISC OS)
"kill()" doesn't have the semantics of "raise()", i.e. it doesn't
send a signal to the identified process like it does on Unix
platforms. Instead "kill($sig, $pid)" terminates the process
identified by $pid, and makes it exit immediately with exit status
$sig. As in Unix, if $sig is 0 and the specified process exists,
it returns true without actually terminating it. (Win32)
link OLDFILE,NEWFILE
Not implemented. (Mac OS, MPE/iX, VMS, RISC OS)
Link count not updated because hard links are not quite that hard
(They are sort of half-way between hard and soft links). (AmigaOS)
Hard links are implemented on Win32 (Windows NT and Windows 2000)
under NTFS only.
lstat FILEHANDLE
lstat EXPR
lstat Not implemented. (VMS, RISC OS)
Return values (especially for device and inode) may be bogus.
(Win32)
msgctl ID,CMD,ARG
msgget KEY,FLAGS
msgsnd ID,MSG,FLAGS
msgrcv ID,VAR,SIZE,TYPE,FLAGS
Not implemented. (Mac OS, Win32, VMS, Plan 9, RISC OS, VOS)
open FILEHANDLE,EXPR
open FILEHANDLE
The "|" variants are supported only if ToolServer is installed.
(Mac OS)
open to "|-" and "-|" are unsupported. (Mac OS, Win32, RISC OS)
Opening a process does not automatically flush output handles on
some platforms. (SunOS, Solaris, HP-UX)
pipe READHANDLE,WRITEHANDLE
Very limited functionality. (MiNT)
readlink EXPR
readlink
Not implemented. (Win32, VMS, RISC OS)
select RBITS,WBITS,EBITS,TIMEOUT
Only implemented on sockets. (Win32, VMS)
Only reliable on sockets. (RISC OS)
Note that the "select FILEHANDLE" form is generally portable.
semctl ID,SEMNUM,CMD,ARG
semget KEY,NSEMS,FLAGS
semop KEY,OPSTRING
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS)
setgrent
Not implemented. (Mac OS, MPE/iX, VMS, Win32, RISC OS)
setpgrp PID,PGRP
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS)
setpriority WHICH,WHO,PRIORITY
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS)
setpwent
Not implemented. (Mac OS, MPE/iX, Win32, RISC OS)
setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
Not implemented. (Plan 9)
shmctl ID,CMD,ARG
shmget KEY,SIZE,FLAGS
shmread ID,VAR,POS,SIZE
shmwrite ID,STRING,POS,SIZE
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS)
sockatmark SOCKET
A relatively recent addition to socket functions, may not be
implemented even in UNIX platforms.
socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
Not implemented. (Win32, VMS, RISC OS, VOS, VM/ESA)
stat FILEHANDLE
stat EXPR
stat Platforms that do not have rdev, blksize, or blocks will return
these as '', so numeric comparison or manipulation of these fields
may cause 'not numeric' warnings.
mtime and atime are the same thing, and ctime is creation time
instead of inode change time. (Mac OS).
ctime not supported on UFS (Mac OS X).
ctime is creation time instead of inode change time (Win32).
device and inode are not meaningful. (Win32)
device and inode are not necessarily reliable. (VMS)
mtime, atime and ctime all return the last modification time.
Device and inode are not necessarily reliable. (RISC OS)
dev, rdev, blksize, and blocks are not available. inode is not
meaningful and will differ between stat calls on the same file.
(os2)
some versions of cygwin when doing a stat("foo") and if not finding
it may then attempt to stat("foo.exe") (Cygwin)
symlink OLDFILE,NEWFILE
Not implemented. (Win32, VMS, RISC OS)
syscall LIST
Not implemented. (Mac OS, Win32, VMS, RISC OS, VOS, VM/ESA)
sysopen FILEHANDLE,FILENAME,MODE,PERMS
The traditional "0", "1", and "2" MODEs are implemented with
different numeric values on some systems. The flags exported by
"Fcntl" (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though.
(Mac OS, OS/390, VM/ESA)
system LIST
In general, do not assume the UNIX/POSIX semantics that you can
shift $? right by eight to get the exit value, or that "$? & 127"
would give you the number of the signal that terminated the
program, or that "$? & 128" would test true if the program was
terminated by a coredump. Instead, use the POSIX W*() interfaces:
for example, use WIFEXITED($?) and WEXITVALUE($?) to test for a
normal exit and the exit value, WIFSIGNALED($?) and WTERMSIG($?)
for a signal exit and the signal. Core dumping is not a portable
concept, so there's no portable way to test for that.
Only implemented if ToolServer is installed. (Mac OS)
As an optimization, may not call the command shell specified in
$ENV{PERL5SHELL}. "system(1, @args)" spawns an external process
and immediately returns its process designator, without waiting for
it to terminate. Return value may be used subsequently in "wait"
or "waitpid". Failure to spawn() a subprocess is indicated by
setting $? to "255 << 8". $? is set in a way compatible with Unix
(i.e. the exitstatus of the subprocess is obtained by "$? >> 8", as
described in the documentation). (Win32)
There is no shell to process metacharacters, and the native
standard is to pass a command line terminated by "\n" "\r" or "\0"
to the spawned program. Redirection such as "> foo" is performed
(if at all) by the run time library of the spawned program.
"system" list will call the Unix emulation library's "exec"
emulation, which attempts to provide emulation of the stdin,
stdout, stderr in force in the parent, providing the child program
uses a compatible version of the emulation library. scalar will
call the native command line direct and no such emulation of a
child Unix program will exists. Mileage will vary. (RISC OS)
Far from being POSIX compliant. Because there may be no underlying
/bin/sh tries to work around the problem by forking and execing the
first token in its argument string. Handles basic redirection ("<"
or ">") on its own behalf. (MiNT)
Does not automatically flush output handles on some platforms.
(SunOS, Solaris, HP-UX)
The return value is POSIX-like (shifted up by 8 bits), which only
allows room for a made-up value derived from the severity bits of
the native 32-bit condition code (unless overridden by "use vmsish
'status'"). For more details see "$?" in perlvms. (VMS)
times Only the first entry returned is nonzero. (Mac OS)
"cumulative" times will be bogus. On anything other than Windows
NT or Windows 2000, "system" time will be bogus, and "user" time is
actually the time returned by the clock() function in the C runtime
library. (Win32)
Not useful. (RISC OS)
truncate FILEHANDLE,LENGTH
truncate EXPR,LENGTH
Not implemented. (Older versions of VMS)
Truncation to zero-length only. (VOS)
If a FILEHANDLE is supplied, it must be writable and opened in
append mode (i.e., use "open(FH, '>>filename')" or
"sysopen(FH,...,O_APPEND|O_RDWR)". If a filename is supplied, it
should not be held open elsewhere. (Win32)
umask EXPR
umask Returns undef where unavailable, as of version 5.005.
"umask" works but the correct permissions are set only when the
file is finally closed. (AmigaOS)
utime LIST
Only the modification time is updated. (BeOS, Mac OS, VMS, RISC OS)
May not behave as expected. Behavior depends on the C runtime
library's implementation of utime(), and the filesystem being used.
The FAT filesystem typically does not support an "access time"
field, and it may limit timestamps to a granularity of two seconds.
(Win32)
wait
waitpid PID,FLAGS
Not implemented. (Mac OS, VOS)
Can only be applied to process handles returned for processes
spawned using "system(1, ...)" or pseudo processes created with
"fork()". (Win32)
Not useful. (RISC OS)
CHANGES
v1.48, 02 February 2001
Various updates from perl5-porters over the past year, supported
platforms update from Jarkko Hietaniemi.
v1.47, 22 March 2000
Various cleanups from Tom Christiansen, including migration of long
platform listings from perl.
v1.46, 12 February 2000
Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
v1.45, 20 December 1999
Small changes from 5.005_63 distribution, more changes to EBCDIC info.
v1.44, 19 July 1999
A bunch of updates from Peter Prymmer for $^O values, endianness,
File::Spec, VMS, BS2000, OS/400.
v1.43, 24 May 1999
Added a lot of cleaning up from Tom Christiansen.
v1.42, 22 May 1999
Added notes about tests, sprintf/printf, and epoch offsets.
v1.41, 19 May 1999
Lots more little changes to formatting and content.
Added a bunch of $^O and related values for various platforms; fixed
mail and web addresses, and added and changed miscellaneous notes.
(Peter Prymmer)
v1.40, 11 April 1999
Miscellaneous changes.
v1.39, 11 February 1999
Changes from Jarkko and EMX URL fixes Michael Schwern. Additional note
about newlines added.
v1.38, 31 December 1998
More changes from Jarkko.
v1.37, 19 December 1998
More minor changes. Merge two separate version 1.35 documents.
v1.36, 9 September 1998
Updated for Stratus VOS. Also known as version 1.35.
v1.35, 13 August 1998
Integrate more minor changes, plus addition of new sections under
"ISSUES": "Numbers endianness and Width", "Character sets and character
encoding", "Internationalisation".
v1.33, 06 August 1998
Integrate more minor changes.
v1.32, 05 August 1998
Integrate more minor changes.
v1.30, 03 August 1998
Major update for RISC OS, other minor changes.
v1.23, 10 July 1998
First public release with perl5.005.
Supported Platforms
As of June 2002 (the Perl release 5.8.0), the following platforms are able
to build Perl from the standard source code distribution available at
http://www.cpan.org/src/index.html
AIX
BeOS
Cygwin
DG/UX
DOS DJGPP 1)
DYNIX/ptx
EPOC R5
FreeBSD
HP-UX
IRIX
Linux
Mac OS Classic
Mac OS X (Darwin)
MPE/iX
NetBSD
NetWare
NonStop-UX
ReliantUNIX (SINIX)
OpenBSD
OpenVMS (VMS)
OS/2
PowerUX
POSIX-BC (BS2000)
QNX
Solaris
SunOS 4
SUPER-UX
Tru64 UNIX (DEC OSF/1, Digital UNIX)
UNICOS
UNICOS/mk
UTS
VOS
Win95/98/ME/2K/XP 2)
WinCE
z/OS (OS/390)
VM/ESA
1) in DOS mode either the DOS or OS/2 ports can be used
2) compilers: Borland, MinGW (GCC), VC6
The following platforms worked with the previous releases (5.6 and 5.7),
but we did not manage either to fix or to test these in time for the 5.8.0
release. There is a very good chance that many of these will work fine
with the 5.8.0.
BSD/OS
DomainOS
Hurd
LynxOS
MachTen
PowerMAX
SCO SV
SVR4
Unixware
Windows 3.1
Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used):
AmigaOS
The following platforms have been known to build Perl from source in the
past (5.005_03 and earlier), but we haven't been able to verify their
status for the current release, either because the hardware/software
platforms are rare or because we don't have an active champion on these
platforms--or both. They used to work, though, so go ahead and try
compiling them, and let perlbug@perl.org of any trouble.
3b1
A/UX
ConvexOS
CX/UX
DC/OSx
DDE SMES
DOS EMX
Dynix
EP/IX
ESIX
FPS
GENIX
Greenhills
ISC
MachTen 68k
MiNT
MPC
NEWS-OS
NextSTEP
OpenSTEP
Opus
Plan 9
RISC/os
SCO ODT/OSR
Stellar
SVR2
TI1500
TitanOS
Ultrix
Unisys Dynix
The following platforms have their own source code distributions and
binaries available via http://www.cpan.org/ports/
Perl release
OS/400 5.005_02
Tandem Guardian 5.004
The following platforms have only binaries available via
http://www.cpan.org/ports/index.html :
Perl release
Acorn RISCOS 5.005_02
AOS 5.002
LynxOS 5.004_02
Although we do suggest that you always build your own Perl from the source
code, both for maximal configurability and for security, in case you are in
a hurry you can check http://www.cpan.org/ports/index.html for binary
distributions.
SEE ALSO
perlaix, perlamiga, perlapollo, perlbeos, perlbs2000, perlce, perlcygwin,
perldgux, perldos, perlepoc, perlebcdic, perlfreebsd, perlhurd, perlhpux,
perlirix, perlmachten, perlmacos, perlmint, perlmpeix, perlnetware,
perlos2, perlos390, perlplan9, perlqnx, perlsolaris, perltru64,
perlunicode, perlvmesa, perlvms, perlvos, perlwin32, and Win32.
AUTHORS / CONTRIBUTORS
Abigail <abigail@foad.org>, Charles Bailey <bailey@newman.upenn.edu>,
Graham Barr <gbarr@pobox.com>, Tom Christiansen <tchrist@perl.com>,
Nicholas Clark <nick@ccl4.org>, Thomas Dorner <Thomas.Dorner@start.de>,
Andy Dougherty <doughera@lafayette.edu>, Dominic Dunlop
<domo@computer.org>, Neale Ferguson <neale@vma.tabnsw.com.au>, David J.
Fiander <davidf@mks.com>, Paul Green <Paul_Green@stratus.com>, M.J.T. Guy
<mjtg@cam.ac.uk>, Jarkko Hietaniemi <jhi@iki.fi>, Luther Huffman
<lutherh@stratcom.com>, Nick Ing-Simmons <nick@ing-simmons.net>, Andreas J.
Koenig <a.koenig@mind.de>, Markus Laker <mlaker@contax.co.uk>, Andrew M.
Langmead <aml@world.std.com>, Larry Moore <ljmoore@freespace.net>, Paul
Moore <Paul.Moore@uk.origin-it.com>, Chris Nandor <pudge@pobox.com>,
Matthias Neeracher <neeracher@mac.com>, Philip Newton <pne@cpan.org>, Gary
Ng <71564.1743@CompuServe.COM>, Tom Phoenix <rootbeer@teleport.com>, Andre
Pirard <A.Pirard@ulg.ac.be>, Peter Prymmer <pvhp@forte.com>, Hugo van der
Sanden <hv@crypt0.demon.co.uk>, Gurusamy Sarathy <gsar@activestate.com>,
Paul J. Schinder <schinder@pobox.com>, Michael G Schwern
<schwern@pobox.com>, Dan Sugalski <dan@sidhe.org>, Nathan Torkington
<gnat@frii.com>.
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