PERLPORT(1) Perl Programmers Reference Guide PERLPORT(1)NAMEperlport - 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 con
stitutes 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 usu
ally about willfully limiting your available choices.
Naturally, it takes discipline and sacrifice to do that.
The product of portability and convenience may be a con
stant. 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 lan
guage to glue Unix tools together, or to prototype a
Macintosh application, or to manage the Windows reg
istry. 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 cre
ate 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 plat
form 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 plat
form-specific code.
When the code will run on only two or three operating sys
tems, 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 (the section on "ISSUES", plat
form-specific issues (the section on "PLATFORMS", and
built-in perl functions that behave differently on various
ports (the section on "FUNCTION IMPLEMENTATIONS".
This information should not be considered complete; it
includes possibly transient information about idiosyn
crasies 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="yel
low_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", depend
ing on whether you're reading or writing. Unix does the
same thing on ttys in canonical mode. "\015\012" is com
monly 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 MacOS (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 "$/" is "\n", but robust socket
code will recognize as either "\012" or "\015\012" as end
of line:
while (<SOCKET>) {
# ...
}
Because both CRLF and LF end in LF, the input record sepa
rator can be set to LF and any CR stripped later. Better
to write:
use Socket qw(:DEFAULT :crlf);
local($/) = 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 trans
late 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 == \012 == \x0A == \cJ == ASCII 10
CR == \015 == \x0D == \cM == 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.
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, usu
ally 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 num
bers. 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 unpack
ing 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 plat
forms 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. Keeping all data as text sig
nificantly simplifies matters.
Files and Filesystems
Most platforms these days structure files in a hierarchi
cal fashion. So, it is reasonably safe to assume that all
platforms support the notion of a "path" to uniquely iden
tify a file on the system. How that path is really writ
ten, though, differs considerably.
Although similar, file path specifications differ between
Unix, Windows, Mac OS, OS/2, VMS, VOS, RISC OS, and proba
bly 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 idiosyn
cratic 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).
VOS perl can emulate Unix filenames with "/" as path sepa
rator. 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.
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 con
figuration 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 separa
tor for subdirectories.
Also of use is File::Basename from the standard distribu
tion, 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 of the same name with different
case, like test.pl and Test.pl, as many platforms have
case-insensitive 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, oner
ous a burden though this may appear.
Likewise, when using the AutoSplit module, try to keep
your functions to 8.3 naming and case-insensitive conven
tions; 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. Many systems (DOS, VMS) cannot have more than
one "." in their filenames.
Don't assume ">" won't be the first character of a file
name. Always use "<" explicitly to open a file for read
ing, unless you want the user to be able to specify a pipe
open.
open(FILE, "< $existing_file") or die $!;
If filenames might use strange characters, it is safest to
open it with "sysopen" instead of "open". "open" is magic
and can translate characters like ">", "<", and "|", which
may be the wrong thing to do. (Sometimes, though, it's
the right thing.)
System Interaction
Not all platforms provide a command line. These are usu
ally platforms that rely primarily on a Graphical User
Interface (GUI) for user interaction. A program requiring
a command line interface might not work everywhere. This
is probably for the user of the program to deal with, so
don't stay up late worrying about it.
Some platforms can't delete or rename files held open by
the system. Remember to "close" files when you are done
with them. Don't "unlink" or "rename" an open file.
Don't "tie" or "open" a file already tied or opened;
"untie" or "close" it first.
Don't open the same file more than once at a time for
writing, as some operating systems put mandatory locks on
such files.
Don't count on a specific environment variable existing in
"%ENV". Don't count on "%ENV" entries being case-sensi
tive, or even case-preserving. Don't try to clear %ENV by
saying "%ENV = ();", or, if you really have to, make it
conditional on "$^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", "read
dir", and "closedir" instead.
Don't count on per-program environment variables, or per-
program current directories.
Don't count on specific values of "$!".
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 sup
ported on most platforms (though many of them do not sup
port 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.
The rule of thumb for portable code is: Do it all in
portable Perl, or use a module (that may internally imple
ment 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 ExtU
tils::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 the AnyDBM_File manpage 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 representa
tion. 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 little about character sets. Assume nothing about
numerical values ("ord", "chr") of characters. Do not
assume that the alphabetic characters are encoded contigu
ously (in the numeric sense). Do not assume anything
about the ordering of the characters. The lowercase let
ters 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 interna
tional 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 the perl
locale manpage. 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 con
strained (or missing!) virtual memory systems then you
want to be especially mindful of avoiding wasteful con
structs 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
$file = join('', <FILE>); # better
The last two constructs may appear unintuitive to most
people. The first repeatedly grows a string, whereas the
second allocates a large chunk of memory in one go. On
some systems, the second is more efficient that the first.
Security
Most multi-user platforms provide basic levels of secu
rity, usually implemented at the filesystem level. Some,
however, do not--unfortunately. Thus the notion of user
id, or "home" directory, or even the state of being
logged-in, may be unrecognizable on many platforms. If
you write programs that are security-conscious, it is usu
ally best to know what type of system you will be running
under so that you can write code explicitly for that plat
form (or class of platforms).
Style
For those times when it is necessary to have platform-spe
cific code, consider keeping the platform-specific code in
one place, making porting to other platforms easier. Use
the Config module and the special variable "$^O" to dif
ferentiate platforms, as described in the section on
"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 "$!" after an system call. Some plat
forms expect a certain output format, and perl on those
platforms may have been adjusted accordingly. Most
specifically, don't anchor a regex when testing an error
value.
CPAN Testers
Modules uploaded to CPAN are tested by a variety of volun
teers on different platforms. These CPAN testers are
notified by mail of each new upload, and reply to the list
with PASS, FAIL, NA (not applicable to this platform), or
UNKNOWN (unknown), along with any relevant notations.
The purpose of the testing is twofold: one, to help devel
opers fix any problems in their code that crop up because
of lack of testing on other platforms; two, to provide
users with information about whether a given module works
on a given platform.
Mailing list: cpan-testers@perl.org
Testing results: http://testers.cpan.org/
PLATFORMS
As of version 5.002, Perl is built with a "$^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 "$Con
fig{osname}". Of course, to get more detailed information
about the system, looking into "%Config" is certainly rec
ommended.
"%Config" cannot always be trusted, however, because it
was built at compile time. If perl was built in one
place, then transferred elsewhere, some values may be
wrong. The values may even have been edited after the
fact.
Unix
Perl works on a bewildering variety of Unix and Unix-like
platforms (see e.g. most of the files in the hints/ direc
tory in the source code kit). On most of these systems,
the value of "$^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 $Config{'archname'}
--------------------------------------------
AIX aix aix
BSD/OS bsdos i386-bsdos
dgux dgux AViiON-dgux
DYNIX/ptx dynixptx i386-dynixptx
FreeBSD freebsd freebsd-i386
Linux linux arm-linux
Linux linux i386-linux
Linux linux i586-linux
Linux linux ppc-linux
HP-UX hpux PA-RISC1.1
IRIX irix irix
Mac OS X rhapsody rhapsody
MachTen PPC machten powerpc-machten
NeXT 3 next next-fat
NeXT 4 next OPENSTEP-Mach
openbsd openbsd i386-openbsd
OSF1 dec_osf alpha-dec_osf
reliantunix-n svr4 RM400-svr4
SCO_SV sco_sv i386-sco_sv
SINIX-N svr4 RM400-svr4
sn4609 unicos CRAY_C90-unicos
sn6521 unicosmk t3e-unicosmk
sn9617 unicos CRAY_J90-unicos
SunOS solaris sun4-solaris
SunOS solaris i86pc-solaris
SunOS4 sunos sun4-sunos
Because the value of "$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 famil
iar with COMMAND.COM or CMD.EXE style shells should be
aware that each of these file specifications may have sub
tle differences:
$filespec0 = "c:/foo/bar/file.txt";
$filespec1 = "c:\\foo\\bar\\file.txt";
$filespec2 = 'c:\foo\bar\file.txt';
$filespec3 = 'c:\\foo\\bar\\file.txt';
System calls accept either "/" or "\" as the path separa
tor. However, many command-line utilities of DOS vintage
treat "/" as the option prefix, so may get confused by
filenames containing "/". Aside from calling any external
programs, "/" will work just fine, and probably better, as
it is more consistent with popular usage, and avoids the
problem of remembering what to backwhack and what not to.
The DOS FAT filesystem can accommodate only "8.3" style
filenames. Under the "case-insensitive, but case-preserv
ing" HPFS (OS/2) and NTFS (NT) filesystems you may have to
be careful about case returned with functions like "read
dir" or used with functions like "open" or "opendir".
DOS also treats several filenames as special, such as AUX,
PRN, NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately,
sometimes these filenames won't even work if you include
an explicit directory prefix. It is best to avoid such
filenames, if you want your code to be portable to DOS and
its derivatives. It's hard to know what these all are,
unfortunately.
Users of these operating systems may also wish to make use
of scripts such as pl2bat.bat or pl2cmd to put wrappers
around your scripts.
Newline ("\n") is translated as "\015\012" by STDIO when
reading from and writing to files (see the section on
"Newlines"). "binmode(FILEHANDLE)" will keep "\n" trans
lated as "\012" for that filehandle. Since it is a no-op
on other systems, "binmode" should be used for cross-plat
form code that deals with binary data. That's assuming
you realize in advance that your data is in binary. Gen
eral-purpose programs should often assume nothing about
their data.
The "$^O" variable and the "$Config{archname}" values for
various DOSish perls are as follows:
OS $^O $Config{'archname'}
--------------------------------------------
MS-DOS dos
PC-DOS dos
OS/2 os2
Windows 95 MSWin32 MSWin32-x86
Windows 98 MSWin32 MSWin32-x86
Windows NT MSWin32 MSWin32-x86
Windows NT MSWin32 MSWin32-ALPHA
Windows NT MSWin32 MSWin32-ppc
Cygwin cygwin
The various MSWin32 Perl's can distinguish the OS they are
running on via the value of the fifth element of the list
returned from Win32::GetOSVersion(). For example:
if ($^O eq 'MSWin32') {
my @os_version_info = Win32::GetOSVersion();
print +('3.1','95','NT')[$os_version_info[4]],"\n";
}
Also see:
The djgpp environment for DOS, http://www.delo
rie.com/djgpp/ and the perldos manpage.
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 the
perlos2 manpage.
Build instructions for Win32 in the perlwin32 manpage,
or under the Cygnus environment in the perlcygwin man
page.
The "Win32::*" modules in the Win32 manpage.
The ActiveState Pages, http://www.activestate.com/
The Cygwin environment for Win32; README.cygwin
(installed as the perlcygwin manpage), http://www.cyg
win.com/
The U/WIN environment for Win32,
http://www.research.att.com/sw/tools/uwin/
Build instructions for OS/2, the perlos2 manpage
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 popu
lated 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 and Mac OS X Server, based on NeXT's OpenStep OS,
will (in theory) be able to run MacPerl natively, under
the "Classic" environment. The new "Cocoa" environment
(formerly called the "Yellow Box") may run a slightly mod
ified version of MacPerl, using the Carbon interfaces.
Mac OS X Server and its Open Source version, Darwin, both
run Unix perl natively (with a few patches). Full support
for these is slated for perl 5.6.
Also see:
The MacPerl Pages, http://www.macperl.com/ .
The MacPerl mailing lists, http://www.macperl.org/ .
MacPerl Module Porters, http://pudge.net/mmp/ .
VMS
Perl on VMS is discussed in the perlvms manpage in the
perl distribution. Perl on VMS can accept either VMS- or
Unix-style file specifications as in either of the follow
ing:
$ 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 "$read = <STDIN>;".
Filenames are in the format "name.extension;version". The
maximum length for filenames is 39 characters, and the
maximum length for extensions is also 39 characters. Ver
sion is a number from 1 to 32767. Valid characters are
"/[A-Z0-9$_-]/".
VMS's RMS filesystem is case-insensitive and does not
preserve case. "readdir" returns lowercased filenames,
but specifying a file for opening remains case-insensi
tive. 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 help
ful for conversions to and from RMS native formats.
What "\n" represents depends on the type of file opened.
It could be "\015", "\012", "\015\012", or nothing. 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 sup
ported.
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 $^O is...\n";
}
On VMS, perl determines the UTC offset from the "SYS$TIME
ZONE_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 the README_vms manpage), the
perlvms manpage
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 distri
bution (installed as the perlvos manpage). Perl on VOS
can accept either VOS- or Unix-style file specifications
as in either of the following:
$ perl -ne "print if /perl_setup/i" >system>notices
$ perl -ne "print if /perl_setup/i" /system/notices
or even a mixture of both as in:
$ 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, directo
ries, or links whose names contain a slash character can
not 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.
See README.vos for restrictions that apply when Perl is
built with the alpha version of VOS POSIX.1 support.
Perl on VOS is built without any extensions and does not
support dynamic loading.
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
The VOS mailing list.
There is no specific mailing list for Perl on VOS.
You can post comments to the comp.sys.stratus news
group, 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.stra
tus.com/pub/vos/vos.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 the perlos390 manpage 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-fid
dling with ASCII constants using operators like "^", "&"
and "|", not to mention dealing with socket interfaces to
ASCII computers (see the section on "Newlines").
Fortunately, most web servers for the mainframe will cor
rectly 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 $Config{'archname'}
--------------------------------------------
OS/390 os390 os390
OS400 os400 os400
POSIX-BC posix-bc BS2000-posix-bc
VM/ESA vmesa vmesa
Some simple tricks for determining if you are running on
an EBCDIC platform could include any of the following
(perhaps all):
if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; }
if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; }
if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
One thing you may not want to rely on is the EBCDIC encod
ing of punctuation characters since these may differ from
code page to code page (and once your module or script is
rumoured to work with EBCDIC, folks will want it to work
with all EBCDIC character sets).
Also see:
*
the perlos390 manpage, README.os390, perlbs2000,
README.vmesa, the perlebcdic manpage.
The perl-mvs@perl.org list is for discussion of port
ing issues as well as general usage issues for all
EBCDIC Perls. Send a message body of "subscribe perl-
mvs" to majordomo@perl.org.
AS/400 Perl information at
http://as400.rochester.ibm.com/ as well as on CPAN in
the ports/ directory.
Acorn RISC OS
Because Acorns use ASCII with newlines ("\n") in text
files as "\012" like Unix, and because Unix filename emu
lation is turned on by default, most simple scripts will
probably work "out of the box". The native filesystem is
modular, and individual filesystems are free to be case-
sensitive or insensitive, and are usually case-preserving.
Some native filesystems have name length limits, which
file and directory names are silently truncated to fit.
Scripts should be aware that the standard filesystem cur
rently has a name length limit of 10 characters, with up
to 77 items in a directory, but other filesystems may not
impose such limitations.
Native filenames are of the form
Filesystem#Special_Field::DiskName.$.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.$.File" ne 'ADFS::Hard
Disk.$.File'" and that the second stage of "$" interpola
tion in regular expressions will fall foul of the "$." if
scripts are not careful.
Logical paths specified by system variables containing
comma-separated search lists are also allowed; hence "Sys
tem: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$Dir'} . 'Modules'". The obvi
ous implication of this is that fully qualified filenames
can start with "<>" and should be protected when "open" is
used for input.
Because "." was in use as a directory separator and file
names could not be assumed to be unique after 10 charac
ters, Acorn implemented the C compiler to strip the trail
ing ".c" ".h" ".s" and ".o" suffix from filenames speci
fied in source code and store the respective files in sub
directories named after the suffix. Hence files are
translated:
foo.h h.foo
C:foo.h C:h.foo (logical path variable)
sys/os.h sys.h.os (C compiler groks Unix-speak)
10charname.c c.10charname
10charname.o o.10charname
11charname_.c c.11charname (assuming filesystem truncates at 10)
The Unix emulation library's translation of filenames to
native assumes that this sort of translation is required,
and it allows a user-defined list of known suffixes that
it will transpose in this fashion. This may seem trans
parent, but consider that with these rules "foo/bar/baz.h"
and "foo/bar/h/baz" both map to "foo.bar.h.baz", and that
"readdir" and "glob" cannot and do not attempt to emulate
the reverse mapping. Other "."'s in filenames are trans
lated to "/".
As implied above, the environment accessed through "%ENV"
is global, and the convention is that program specific
environment variables are of the form "Program$Name".
Each filesystem maintains a current directory, and the
current filesystem's current directory is the global cur
rent 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 direc
tory 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$Dir>.Bar" on the command line unquoted causes prob
lems, too: "``" command output capture has to perform a
guessing game. It assumes that a string "<[^<>]+\$[^<>]>"
is a reference to an environment variable, whereas any
thing else involving "<" or ">" is redirection, and gener
ally manages to be 99% right. Of course, the problem
remains that scripts cannot rely on any Unix tools being
available, or that any tools found have Unix-like command
line arguments.
Extensions and XS are, in theory, buildable by anyone
using free tools. In practice, many don't, as users of
the Acorn platform are used to binary distributions.
MakeMaker does run, but no available make currently copes
with MakeMaker's makefiles; even if and when this should
be fixed, the lack of a Unix-like shell will cause prob
lems with makefile rules, especially lines of the form "cd
sdbm && make all", and anything using quoting.
"RISC OS" is the proper name for the operating system, but
the value in "$^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 $Config{'archname'}
------------------------------------------
Amiga DOS amigaos m68k-amigos
MPE/iX mpeix PA-RISC1.1
See also:
Amiga, README.amiga (installed as the perlamiga man
page).
Atari, README.mint and Guido Flohr's web page
http://stud.uni-sb.de/~gufl0000/
Be OS, README.beos
HP 300 MPE/iX, README.mpeix and Mark Bixby's web page
http://www.bixby.org/mark/perlix.html
A free perl5-based PERL.NLM for Novell Netware is
available in precompiled binary and source code form
from http://www.novell.com/ as well as from CPAN.
Plan 9, README.plan9
FUNCTION IMPLEMENTATIONS
Listed below are functions that are either completely
unimplemented or else have been implemented differently on
various platforms. Following each description will be, in
parentheses, a list of platforms that the description
applies to.
The list may well be incomplete, or even wrong in some
places. When in doubt, consult the platform-specific
README files in the Perl source distribution, and any
other documentation resources accompanying a given port.
Be aware, moreover, that even among Unix-ish systems there
are variations.
For many functions, you can also query "%Config", exported
by default from the Config module. For example, to check
whether the platform has the "lstat" call, check "$Con
fig{d_lstat}". See the Config manpage for a full descrip
tion 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 partic
ularly 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 misclas
sify 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 exe
cutable 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-con
trol list changes. (VOS)
chown LIST
Not implemented. (Mac OS, Win32, Plan9, RISC OS,
VOS)
Does nothing, but won't fail. (Win32)
chroot FILENAME
chroot Not implemented. (Mac OS, Win32, VMS, Plan9,
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, Plan9, VOS)
dbmopen HASH,DBNAME,MODE
Not implemented. (VMS, Plan9, 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)
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)
Emulated using multiple interpreters. See the
perlfork manpage. (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, VMS, 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, Plan9)
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, Plan9)
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, Plan9)
getprotoent
Not implemented. (Mac OS, Win32, Plan9)
getservent
Not implemented. (Win32, Plan9)
setpwent
Not implemented. (Mac OS, Win32, RISC OS)
setgrent
Not implemented. (Mac OS, Win32, VMS, RISC OS)
sethostent STAYOPEN
Not implemented. (Mac OS, Win32, Plan9, RISC OS)
setnetent STAYOPEN
Not implemented. (Mac OS, Win32, Plan9, RISC OS)
setprotoent STAYOPEN
Not implemented. (Mac OS, Win32, Plan9, RISC OS)
setservent STAYOPEN
Not implemented. (Plan9, 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, Plan9)
endprotoent
Not implemented. (Mac OS, Win32, Plan9)
endservent
Not implemented. (Plan9, Win32)
getsockopt SOCKET,LEVEL,OPTNAME
Not implemented. (Mac OS, Plan9)
glob EXPR
glob Globbing built-in, but only "*" and "?" metachar
acters are supported. (Mac OS)
This operator is implemented via the File::Glob
extension on most platforms. See the File::Glob
manpage 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
Not implemented, hence not useful for taint check
ing. (Mac OS, 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 identi
fied 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, Plan9,
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
Not implemented. (Mac OS)
Very limited functionality. (MiNT)
readlink EXPR
readlink
Not implemented. (Win32, VMS, RISC OS)
select RBITS,WBITS,EBITS,TIMEOUT
Only implemented on sockets. (Win32)
Only reliable on sockets. (RISC OS)
Note that the "socket FILEHANDLE" form is gener
ally 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. (MPE/iX, Win32)
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. (MPE/iX, Win32)
setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
Not implemented. (Mac OS, Plan9)
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)
socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
Not implemented. (Mac OS, 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 compar
ison 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)
device and inode are not meaningful. (Win32)
device and inode are not necessarily reliable.
(VMS)
mtime, atime and ctime all return the last modifi
cation 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)
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 imple
mented with different numeric values on some sys
tems. The flags exported by "Fcntl" (O_RDONLY,
O_WRONLY, O_RDWR) should work everywhere though.
(Mac OS, OS/390, VM/ESA)
system LIST
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 docu
mentation). (Win32)
There is no shell to process metacharacters, and
the native standard is to pass a command line ter
minated by "\n" "\r" or "\0" to the spawned pro
gram. Redirection such as "> foo" is performed
(if at all) by the run time library of the spawned
program. "system" list will call the Unix emula
tion 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 pro
gram 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)
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. (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. (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 the perl man
page.
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" val
ues, 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 the section on "ISSUES": the section on
"Numbers endianness and Width", the section on "Char
acter sets and character encoding", the section on
"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 early 2001 (the Perl release 5.6.1), the following
platforms are able to build Perl from the standard source
code distribution available at
http://www.perl.com/CPAN/src/index.html
AIX
AmigaOS
Darwin (Rhapsody)
DG/UX
DOS DJGPP 1)
DYNIX/ptx
EPOC
FreeBSD
HP-UX
IRIX
Linux
MachTen
MacOS Classic 2)
NonStop-UX
ReliantUNIX (SINIX)
OpenBSD
OpenVMS (VMS)
OS/2
OS X
QNX
Solaris
Tru64 UNIX (DEC OSF/1, Digital UNIX)
UNICOS
UNICOS/mk
VOS
Win32/NT/2K 3)
1) in DOS mode either the DOS or OS/2 ports can be used
2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
the source does work with 5.6.1, but additional MacOS specific
source code is needed for a complete build. Contact the mailing
list macperl-porters@macperl.org for more information.
3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
The following platforms worked for the previous release
(5.6.0), but we did not manage to test these in time for
the 5.6.1 release. There is a very good chance that these
will work fine with 5.6.1.
DomainOS
Hurd
LynxOS
MinGW
MPE/iX
NetBSD
PowerMAX
SCO SV
SunOS
SVR4
Unixware
Windows 3.1
Windows 95
Windows 98
Windows Me
The following platform worked for the 5.005_03 major
release but not 5.6.0. Standardization on UTF-8 as the
internal string representation in 5.6.0 and 5.6.1 has
introduced incompatibilities in this EBCDIC platform.
While Perl 5.6.1 will build on this platform some regres
sion tests may fail and the "use utf8;" pragma typically
introduces text handling errors. UTF-8 support for this
platform may be enabled in a future release:
OS/390 1)
1) previously known as MVS, about to become z/OS.
Strongly related to the OS/390 platform by also being
EBCDIC-based mainframe platforms are the following plat
forms:
POSIX-BC (BS2000)
VM/ESA
These are also expected to work, albeit with no UTF-8 sup
port, under 5.6.1 for the same reasons as OS/390. Contact
the mailing list perl-mvs@perl.org for more details.
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 plat
forms--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
BeOS
BSD/OS
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
PowerUX
RISC/os
SCO ODT/OSR
Stellar
SVR2
TI1500
TitanOS
Ultrix
Unisys Dynix
Unixware
UTS
Support for the following platform is planned for a future
Perl release:
Netware
The following platforms have their own source code distri
butions and binaries available via
http://www.perl.com/CPAN/ports/index.html:
Perl release
Netware 5.003_07
OS/400 5.005_02
Tandem Guardian 5.004
The following platforms have only binaries available via
http://www.perl.com/CPAN/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.perl.com/CPAN/ports/index.html for binary dis
tributions.
SEE ALSO
the perlaix manpage, the perlamiga manpage, the perlcygwin
manpage, the perldos manpage, the perlepoc manpage, the
perlebcdic manpage, the perlhpux manpage, the perlos2 man
page, the perlos390 manpage, the perlbs2000 manpage, the
perlwin32 manpage, the perlvms manpage, the perlvos man
page, and the Win32 manpage.
AUTHORS / CONTRIBUTORS
Abigail <abigail@fnx.com>, Charles Bailey <bailey@new
man.upenn.edu>, Graham Barr <gbarr@pobox.com>, Tom Chris
tiansen <tchrist@perl.com>, Nicholas Clark
<Nicholas.Clark@liverpool.ac.uk>, Thomas Dorner
<Thomas.Dorner@start.de>, Andy Dougherty <doughera@laf
col.lafayette.edu>, Dominic Dunlop <domo@vo.lu>, Neale
Ferguson <neale@mailbox.tabnsw.com.au>, David J. Fiander
<davidf@mks.com>, Paul Green <Paul_Green@stratus.com>,
M.J.T. Guy <mjtg@cus.cam.ac.uk>, Jarkko Hietaniemi
<jhi@iki.fi>, Luther Huffman <lutherh@stratcom.com>, Nick
Ing-Simmons <nick@ni-s.u-net.com>, Andreas J. Koenig
<koenig@kulturbox.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 Neer
acher <neeri@iis.ee.ethz.ch>, Gary Ng <71564.1743@Com
puServe.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@actives
tate.com>, Paul J. Schinder <schinder@pobox.com>, Michael
G Schwern <schwern@pobox.com>, Dan Sugalski <sugal
skd@ous.edu>, Nathan Torkington <gnat@frii.com>.
This document is maintained by Chris Nandor
<pudge@pobox.com>.
VERSION
Version 1.47, last modified 22 March 2000
2001-03-18 perl v5.6.1 PERLPORT(1)
