perlport

perlport - Writing portable Perl

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 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 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 \s-1OS\s0, \s-1VMS\s0, 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 (“\s-1ISSUES\s0”), platform-specific issues (“\s-1PLATFORMS\s0”), and built-in perl functions that behave differently on various ports (“\s-1FUNCTION\s0 \s-1IMPLEMENTATIONS\s0”).

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 (CW<IMG SRC="yellow_sign.gif" ALT="Under Construction">).

In most operating systems, lines in files are terminated by newlines. Just what is used as a newline may vary from \s-1OS\s0 to \s-1OS\s0. Unix traditionally uses CW\012, one type of DOSish I/O uses CW\015\012, and Mac \s-1OS\s0 uses CW\015.

Perl uses CW\n to represent the “logical” newline, where what is logical may depend on the platform in use. In MacPerl, CW\n always means CW\015. In DOSish perls, CW\n usually means CW\012, but when accessing a file in “text” mode, \s-1STDIO\s0 translates it to (or from) CW\015\012, depending on whether you're reading or writing. Unix does the same thing on ttys in canonical mode. CW\015\012 is commonly referred to as \s-1CRLF\s0.

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 \s-1OS\s0 (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 CWseek and CWtell on a file accessed in “text” mode. Stick to CWseek-ing to locations you got from CWtell (and no others), and you are usually free to use CWseek and CWtell even in “text” mode. Using CWseek or CWtell or other file operations may be non-portable. If you use CWbinmode on a file, however, you can usually CWseek and CWtell with arbitrary values in safety.

A common misconception in socket programming is that CW\n eq CW\012 everywhere. When using protocols such as common Internet protocols, CW\012 and CW\015 are called for specifically, and the values of the logical CW\n and CW\r (carriage return) are not reliable.

print SOCKET "Hi there, client!\r\n"; # WRONG print SOCKET "Hi there, client!\015\012"; # RIGHT

However, using CW\015\012 (or CW\cM\cJ, or CW\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 CW$/ is CW\n, but robust socket code will recognize as either CW\012 or CW\015\012 as end of line:

while (<SOCKET>) { # ... }

Because both \s-1CRLF\s0 and \s-1LF\s0 end in \s-1LF\s0, the input record separator can be set to \s-1LF\s0 and any \s-1CR\s0 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 oneeven for Unix platformsbecause now any CW\015's (CW\cM's) are stripped out (and there was much rejoicing).

Similarly, functions that return text datasuch as a function that fetches a web pageshould 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 \s-1ASCII\s0 \s-1CR\s0 and \s-1LF\s0 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 \s-1CR\s0 on input becomes “\n”, and “\n” on output becomes \s-1CRLF\s0.

These are just the most common definitions of CW\n and CW\r in Perl. There may well be others. For example, on an \s-1EBCDIC\s0 implementation such as z/OS (\s-1OS/390\s0) or \s-1OS/400\s0 (using the \s-1ILE\s0, the \s-1PASE\s0 is ASCII-based) the above material is similar to “Unix” but the code numbers change:

LF eq \025 eq \x15 eq \cU eq chr(21) eq CP-1047 21 LF eq \045 eq \x25 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

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 \s-1CPU\s0 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, \s-1VAX\s0) stores 0x12345678 (305419896 in decimal), a big-endian host (Motorola, Sparc, \s-1PA\s0) reads it as 0x78563412 (2018915346 in decimal). Alpha and \s-1MIPS\s0 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 CWpack and CWunpack formats CWn and CWN, the “network” orders. These are guaranteed to be portable.

As of perl 5.8.5, you can also use the CW> and CW< modifiers to force big- or little-endian byte-order. This is useful if you want to store signed integers or 64-bit integers, for example.

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 \s-1EBCDIC\s0, or more precisely UTF-EBCDIC will go.

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 \s-1OS\s0, \s-1OS/2\s0, \s-1VMS\s0, \s-1VOS\s0, \s-1RISC\s0 \s-1OS\s0, and probably others. Unix, for example, is one of the few OSes that has the elegant idea of a single root directory.

\s-1DOS\s0, \s-1OS/2\s0, \s-1VMS\s0, \s-1VOS\s0, and Windows can work similarly to Unix with CW/ as path separator, or in their own idiosyncratic ways (such as having several root directories and various “unrooted” device files such \s-1NIL:\s0 and \s-1LPT:\s0).

Mac \s-1OS\s0 uses CW: as a path separator instead of CW/.

The filesystem may support neither hard links (CWlink) nor symbolic links (CWsymlink, CWreadlink, CWlstat).

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 \s-1FAT\s0 filesystem limits the time granularity to two seconds).

The “inode change timestamp” (the CW-C filetest) may really be the “creation timestamp” (which it is not in \s-1UNIX\s0).

\s-1VOS\s0 perl can emulate Unix filenames with CW/ as path separator. The native pathname characters greater-than, less-than, number-sign, and percent-sign are always accepted.

\s-1RISC\s0 \s-1OS\s0 perl can emulate Unix filenames with CW/ as path separator, or go native and use CW. for path separator and CW: to signal filesystems and disk names.

Don't assume \s-1UNIX\s0 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 \s-1UNIX\s0 ones. The various \s-1UNIX/POSIX\s0 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 CW/ 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 \s-1NIS\s0. 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 CW.) 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 (\s-1DOS\s0, \s-1VMS\s0) cannot have more than one CW. in their filenames.

Don't assume CW> won't be the first character of a filename. Always use CW< 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 CWsysopen instead of CWopen. CWopen is magic and can translate characters like CW>, CW<, and CW|, 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 CW: as a part of a filename since many systems use that for their own semantics (Mac \s-1OS\s0 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 CW@, CW; and CW|.

Don't assume that in pathnames you can collapse two leading slashes CW// 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 \s-1ANSI\s0 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 CW., if any, and to three characters after the CW., if any). (And do not use CW.s in directory names.)

Not all platforms provide a command line. These are usually platforms that rely primarily on a Graphical User Interface (\s-1GUI\s0) 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, this limitation may also apply to changing filesystem metainformation like file permissions or owners. Remember to CWclose files when you are done with them. Don't CWunlink or CWrename an open file. Don't CWtie or CWopen a file already tied or opened; CWuntie or CWclose 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 (\s-1AFS\s0, \s-1DFS\s0) the permission to add/delete directory entries is a completely separate permission.

Don't assume that a single CWunlink completely gets rid of the file: some filesystems (most notably the ones in \s-1VMS\s0) 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 CW%ENV. Don't count on CW%ENV entries being case-sensitive, or even case-preserving. Don't try to clear CW%ENV by saying CW%ENV = ();, or, if you really have to, make it conditional on CW$^O ne 'VMS' since in \s-1VMS\s0 the CW%ENV table is much more than a per-process key-value string table.

Don't count on signals or CW%SIG for anything.

Don't count on filename globbing. Use CWopendir, CWreaddir, and CWclosedir instead.

Don't count on per-program environment variables, or per-program current directories.

Don't count on specific values of CW$!, neither numeric nor especially the strings values users may switch their locales causing error messages to be translated into their languages. If you can trust a POSIXish environment, you can portably use the symbols defined by the Errno module, like \s-1ENOENT\s0. And don't trust on the values of CW$! at all except immediately after a failed system call.

Don't assume that the name used to invoke a command or program with CWsystem or CWexec 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 \s-1OS\s0 and while these commands can be invoked, there is no corresponding file. Second, some operating systems (e.g., Cygwin, \s-1DJGPP\s0, \s-1OS/2\s0, and \s-1VOS\s0) 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 \s-1VMS\s0 port carefully sets up $^X and CW$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 \s-1VMS\s0 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 CW$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;}

Don't assume that you can reach the public Internet.

Don't assume that there is only one way to get through firewalls to the public Internet.

Don't assume that you can reach outside world through any other port than 80, or some web proxy. ftp is blocked by many firewalls.

Don't assume that you can send email by connecting to the local \s-1SMTP\s0 port.

Don't assume that you can reach yourself or any node by the name 'localhost'. The same goes for '127.0.0.1'. You will have to try both.

Don't assume that the host has only one network card, or that it can't bind to many virtual \s-1IP\s0 addresses.

Don't assume a particular network device name.

Don't assume a particular set of ioctl()s will work.

Don't assume that you can ping hosts and get replies.

Don't assume that any particular port (service) will respond.

Don't assume that Sys::Hostname (or any other \s-1API\s0 or command) returns either a fully qualified hostname or a non-qualified hostname: it all depends on how the system had been configured. Also remember things like \s-1DHCP\s0 and NAT the hostname you get back might not be very useful.

All the above “don't”:s may look daunting, and they are but the key is to degrade gracefully if one cannot reach the particular network service one wants. Croaking or hanging do not look very professional.

In general, don't directly access the system in code meant to be portable. That means, no CWsystem, CWexec, CWfork, CWpipe, CW``, CWqx//, CWopen with a CW|, 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 \s-1CP/M\s0.)

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 \s-1CPAN\s0 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 \s-1SMTP\s0 (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 \s-1IPC\s0 (CWmsg*(), sem*(), shm*()) is not available even on all Unix platforms.

Do not use either the bare result of CWpack("N", 10, 20, 30, 40) or bare v-strings (such as CWv10.20.30.40) to represent IPv4 addresses: both forms just pack the four bytes into network order. That this would be equal to the C language CWin_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 CWinet_aton(), CWinet_ntoa(), and CWsockaddr_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).

\s-1XS\s0 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 \s-1XS\s0 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 \s-1XS\s0 code is portable, too.

A different type of portability issue arises when writing \s-1XS\s0 code: availability of a C compiler on the end-user's system. C brings with it its own portability issues, and writing \s-1XS\s0 code will expose you to some of those. Writing purely in Perl is an easier way to achieve portability.

In general, the standard modules work across platforms. Notable exceptions are the \s-1CPAN\s0 module (which currently makes connections to external programs that may not be available), platform-specific modules (like ExtUtils::MM_VMS), and \s-1DBM\s0 modules.

There is no one \s-1DBM\s0 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 \s-1DBM\s0 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 \s-1DBM\s0 module. See AnyDBM_File for more details.

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 CW$ENV{TZ}, and even if it is, don't assume that you can control the timezone through that variable. Don't assume anything about the three-letter timezone abbreviations (for example that \s-1MST\s0 would be the Mountain Standard Time, it's been known to stand for Moscow Standard Time). If you need to use timezones, express them in some unambiguous format like the exact number of minutes offset from \s-1UTC\s0, or the \s-1POSIX\s0 timezone format.

Don't assume that the epoch starts at 00:00:00, January 1, 1970, because that is \s-1OS-\s0 and implementation-specific. It is better to store a date in an unambiguous representation. The \s-1ISO\s0 8601 standard defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH-MM-SS (that's a literal “T” separating the date from the time). Please do use the \s-1ISO\s0 8601 instead of making us to guess what date 02/03/04 might be. \s-1ISO\s0 8601 even sorts nicely as-is. 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 CWlocaltime, 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 CW$offset in Unix will be CW0, but in Mac \s-1OS\s0 will be some large number. CW$offset can then be added to a Unix time value to get what should be the proper value on any system.

On Windows (at least), you shouldn't pass a negative value to CWgmtime or CWlocaltime.

Assume very little about character sets.

Assume nothing about numerical values (CWord, CWchr) of characters. Do not use explicit code point ranges (like \xHH-\xHH); use for example symbolic character classes like CW[: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 a\*: comes before “b”.

If you may assume \s-1POSIX\s0 (a rather large assumption), you may read more about the \s-1POSIX\s0 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 formattingamongst other things.

If you really want to be international, you should consider Unicode. See perluniintro and perlunicode for more information.

If you want to use non-ASCII bytes (outside the bytes 0x00..0x7f) in the “source code” of your code, to be portable you have to be explicit about what bytes they are. Someone might for example be using your code under a \s-1UTF-8\s0 locale, in which case random native bytes might be illegal (“Malformed \s-1UTF-8\s0 ...”) This means that for example embedding \s-1ISO\s0 8859-1 bytes beyond 0x7f into your strings might cause trouble later. If the bytes are native 8-bit bytes, you can use the CWbytes pragma. If the bytes are in a string (regular expression being a curious string), you can often also use the CW\xHH notation instead of embedding the bytes as-is. If they are in some particular legacy encoding (ether single-byte or something more complicated), you can use the CWencoding pragma. (If you want to write your code in \s-1UTF-8\s0, you can use either the CWutf8 pragma, or the CWencoding pragma.) The CWbytes and CWutf8 pragmata are available since Perl 5.6.0, and the CWencoding pragma since Perl 5.8.0.

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.

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 \s-1UNIX\s0 filesystem access semantics: the operating system or the filesystem may be using some \s-1ACL\s0 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 \s-1UNIX\s0 user and group semantics: especially, don't expect the CW$< and CW$> (or the CW$( and CW$)) 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.)

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 CW$^O to differentiate platforms, as described in “\s-1PLATFORMS\s0”.

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 CW$! after a failed system call. Using CW$! for anything else than displaying it as output is doubtful (though see the Errno module for testing reasonably portably for error value). 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.

Modules uploaded to \s-1CPAN\s0 are tested by a variety of volunteers on different platforms. These \s-1CPAN\s0 testers are notified by mail of each new upload, and reply to the list with \s-1PASS\s0, \s-1FAIL\s0, \s-1NA\s0 (not applicable to this platform), or \s-1UNKNOWN\s0 (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.

Also see:

"" Mailing list: cpan-testers@perl.org

"" Testing results: http://testers.cpan.org/

As of version 5.002, Perl is built with a CW$^O variable that indicates the operating system it was built on. This was implemented to help speed up code that would otherwise have to CWuse Config and use the value of CW$Config{osname}. Of course, to get more detailed information about the system, looking into CW%Config is certainly recommended.

CW%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.

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 CW$^O (hence CW$Config{'osname'}, too) is determined either by lowercasing and stripping punctuation from the first field of the string returned by typing CWuname -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 CW$Config{archname} may depend on the hardware architecture, it can vary more than the value of CW$^O.

Perl has long been ported to Intel-style microcomputers running under systems like \s-1PC-DOS\s0, \s-1MS-DOS\s0, \s-1OS/2\s0, and most Windows platforms you can bring yourself to mention (except for Windows \s-1CE\s0, if you count that). Users familiar with \s-1COMMAND\s0.COM or \s-1CMD\s0.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 CW/ or CW\ as the path separator. However, many command-line utilities of \s-1DOS\s0 vintage treat CW/ as the option prefix, so may get confused by filenames containing CW/. Aside from calling any external programs, CW/ 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 \s-1DOS\s0 \s-1FAT\s0 filesystem can accommodate only “8.3” style filenames. Under the “case-insensitive, but case-preserving” \s-1HPFS\s0 (\s-1OS/2\s0) and \s-1NTFS\s0 (\s-1NT\s0) filesystems you may have to be careful about case returned with functions like CWreaddir or used with functions like CWopen or CWopendir.

\s-1DOS\s0 also treats several filenames as special, such as \s-1AUX\s0, \s-1PRN\s0, \s-1NUL\s0, \s-1CON\s0, \s-1COM1\s0, \s-1LPT1\s0, \s-1LPT2\s0, 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 \s-1DOS\s0 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 (CW\n) is translated as CW\015\012 by \s-1STDIO\s0 when reading from and writing to files (see “Newlines”). CWbinmode(FILEHANDLE) will keep CW\n translated as CW\012 for that filehandle. Since it is a no-op on other systems, CWbinmode 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 CW$^O variable and the CW$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 00 Windows XP MSWin32 MSWin32-x86 2 5 01 Windows 2003 MSWin32 MSWin32-x86 2 5 02 Windows CE MSWin32 ? 3 Cygwin cygwin cygwin

The various MSWin32 Perl's can distinguish the \s-1OS\s0 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 CWperldoc 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 \s-1DOS\s0, http://www.delorie.com/djgpp/ and perldos.

"" The \s-1EMX\s0 environment for \s-1DOS\s0, \s-1OS/2\s0, 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 CWWin32::* modules in Win32.

"" The ActiveState Pages, http://www.activestate.com/

"" The Cygwin environment for Win32; \s-1README\s0.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 \s-1OS/2\s0, perlos2

Any module requiring \s-1XS\s0 compilation is right out for most people, because MacPerl is built using non-free (and non-cheap!) compilers. Some \s-1XS\s0 modules that can work with MacPerl are built and distributed in binary form on \s-1CPAN\s0.

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 CW:, which is reserved as the path separator.

Instead of CWflock, see CWFSpSetFLock and CWFSpRstFLock in the Mac::Files module, or CWchmod(0444, ...) and CWchmod(0666, ...).

In the MacPerl application, you can't run a program from the command line; programs that expect CW@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 CW@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 \s-1MPW\s0 (Macintosh Programmer's Workshop, a free development environment from Apple). MacPerl was first introduced as an \s-1MPW\s0 tool, and \s-1MPW\s0 can be used like a shell:

perl myscript.plx some arguments

ToolServer is another app from Apple that provides access to \s-1MPW\s0 tools from \s-1MPW\s0 and the MacPerl app, which allows MacPerl programs to use CWsystem, backticks, and piped CWopen.

"Mac \s-1OS\s0" is the proper name for the operating system, but the value in CW$^O is “MacOS”. To determine architecture, version, or whether the application or \s-1MPW\s0 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 \s-1OS\s0 X, based on NeXT's OpenStep \s-1OS\s0, runs MacPerl natively, under the “Classic” environment. There is no “Carbon” version of MacPerl to run under the primary Mac \s-1OS\s0 X environment. Mac \s-1OS\s0 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/ .

"" \s-1MPW\s0, ftp://ftp.apple.com/developer/Tool_Chest/Core_Mac_OS_Tools/

Perl on \s-1VMS\s0 is discussed in perlvms in the perl distribution. Perl on \s-1VMS\s0 can accept either \s-1VMS-\s0 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 (\s-1DCL\s0) 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 \s-1DCL\s0 .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 CW$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT if your perl-in-DCL script expects to do things like CW$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 CW/[A-Z0-9$_-]/.

\s-1VMS\s0's \s-1RMS\s0 filesystem is case-insensitive and does not preserve case. CWreaddir returns lowercased filenames, but specifying a file for opening remains case-insensitive. Files without extensions have a trailing period on them, so doing a CWreaddir with a file named A.;5 will return a. (though that file could be opened with CWopen(FH, 'A')).

\s-1RMS\s0 had an eight level limit on directory depths from any rooted logical (allowing 16 levels overall) prior to \s-1VMS\s0 7.2. Hence CWPERL_ROOT:[LIB.2.3.4.5.6.7.8] is a valid directory specification but CWPERL_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 CW/PERL_ROOT/lib/2/3/4/5/6/7/8/.

The VMS::Filespec module, which gets installed as part of the build process on \s-1VMS\s0, is a pure Perl module that can easily be installed on non-VMS platforms and can be helpful for conversions to and from \s-1RMS\s0 native formats.

What CW\n represents depends on the type of file opened. It usually represents CW\012 but it could also be CW\015, CW\012, CW\015\012, CW\000, CW\040, or nothing depending on the file organization and record format. The VMS::Stdio module provides access to the special fopen() requirements of files with unusual attributes on \s-1VMS\s0.

\s-1TCP/IP\s0 stacks are optional on \s-1VMS\s0, so socket routines might not be implemented. \s-1UDP\s0 sockets may not be supported.

The value of CW$^O on OpenVMS is “\s-1VMS\s0”. To determine the architecture that you are running on without resorting to loading all of CW%Config you can examine the content of the CW@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 \s-1VMS\s0, perl determines the \s-1UTC\s0 offset from the CWSYS$TIMEZONE_DIFFERENTIAL logical name. Although the \s-1VMS\s0 epoch began at 17-NOV-1858 00:00:00.00, calls to CWlocaltime are adjusted to count offsets from 01-JAN-1970 00:00:00.00, just like Unix.

Also see:

"" \s-1README\s0.vms (installed as README_vms), perlvms

"" vmsperl list, majordomo@perl.org (Put the words CWsubscribe vmsperl in message body.)

"" vmsperl on the web, http://www.sidhe.org/vmsperl/index.html

Perl on \s-1VOS\s0 is discussed in \s-1README\s0.vos in the perl distribution (installed as perlvos). Perl on \s-1VOS\s0 can accept either \s-1VOS-\s0 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 \s-1VOS\s0 allows the slash character to appear in object names, because the \s-1VOS\s0 port of Perl interprets it as a pathname delimiting character, \s-1VOS\s0 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 \s-1VOS\s0 limits file names to 32 or fewer characters.

Perl on \s-1VOS\s0 can be built using two different compilers and two different versions of the \s-1POSIX\s0 runtime. The recommended method for building full Perl is with the \s-1GNU\s0 C compiler and the generally-available version of \s-1VOS\s0 \s-1POSIX\s0 support. See \s-1README\s0.vos (installed as perlvos) for restrictions that apply when Perl is built using the \s-1VOS\s0 Standard C compiler or the alpha version of \s-1VOS\s0 \s-1POSIX\s0 support.

The value of CW$^O on \s-1VOS\s0 is “\s-1VOS\s0”. To determine the architecture that you are running on without resorting to loading all of CW%Config you can examine the content of the CW@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:

"" \s-1README\s0.vos (installed as perlvos)

"" The \s-1VOS\s0 mailing list. There is no specific mailing list for Perl on \s-1VOS\s0. 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.

"" \s-1VOS\s0 Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html

Recent versions of Perl have been ported to platforms such as \s-1OS/400\s0 on \s-1AS/400\s0 minicomputers as well as \s-1OS/390\s0, \s-1VM/ESA\s0, and \s-1BS2000\s0 for S/390 Mainframes. Such computers use \s-1EBCDIC\s0 character sets internally (usually Character Code Set \s-1ID\s0 0037 for \s-1OS/400\s0 and either 1047 or POSIX-BC for S/390 systems). On the mainframe perl currently works under the “Unix system services for \s-1OS/390\s0” (formerly known as OpenEdition), \s-1VM/ESA\s0 OpenEdition, or the \s-1BS200\s0 POSIX-BC system (\s-1BS2000\s0 is supported in perl 5.6 and greater). See perlos390 for details. Note that for \s-1OS/400\s0 there is also a port of Perl 5.8.1/5.9.0 or later to the \s-1PASE\s0 which is ASCII-based (as opposed to \s-1ILE\s0 which is EBCDIC-based), see perlos400.

As of R2.5 of \s-1USS\s0 for \s-1OS/390\s0 and Version 2.3 of \s-1VM/ESA\s0 these Unix sub-systems do not support the CW#! shebang trick for script invocation. Hence, on \s-1OS/390\s0 and \s-1VM/ESA\s0 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";

\s-1OS/390\s0 will support the CW#! shebang trick in release 2.8 and beyond. Calls to CWsystem and backticks can use \s-1POSIX\s0 shell syntax on all S/390 systems.

On the \s-1AS/400\s0, if \s-1PERL5\s0 is in your library list, you may need to wrap your perl scripts in a \s-1CL\s0 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 \s-1AS/400\s0 calls to CWsystem or backticks must use \s-1CL\s0 syntax.

On these platforms, bear in mind that the \s-1EBCDIC\s0 character set may have an effect on what happens with some perl functions (such as CWchr, CWpack, CWprint, CWprintf, CWord, CWsort, CWsprintf, CWunpack), as well as bit-fiddling with \s-1ASCII\s0 constants using operators like CW^, CW& and CW|, not to mention dealing with socket interfaces to \s-1ASCII\s0 computers (see “Newlines”).

Fortunately, most web servers for the mainframe will correctly translate the CW\n in the following statement to its \s-1ASCII\s0 equivalent (CW\r is the same under both Unix and \s-1OS/390\s0 & \s-1VM/ESA\s0):

print "Content-type: text/html\r\n\r\n";

The values of CW$^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 \s-1EBCDIC\s0 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 \s-1EBCDIC\s0 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 \s-1EBCDIC\s0, folks will want it to work with all \s-1EBCDIC\s0 character sets).

Also see:

"" perlos390, \s-1README\s0.os390, perlbs2000, \s-1README\s0.vmesa, perlebcdic.

"" The perl-mvs@perl.org list is for discussion of porting issues as well as general usage issues for all \s-1EBCDIC\s0 Perls. Send a message body of “subscribe perl-mvs” to majordomo@perl.org.

"" \s-1AS/400\s0 Perl information at http://as400.rochester.ibm.com/ as well as on \s-1CPAN\s0 in the ports/ directory.

Because Acorns use \s-1ASCII\s0 with newlines (CW\n) in text files as CW\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 CWtr|/.|./|;

Note that CW"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File' and that the second stage of CW$ interpolation in regular expressions will fall foul of the CW$. if scripts are not careful.

Logical paths specified by system variables containing comma-separated search lists are also allowed; hence CWSystem:Modules is a valid filename, and the filesystem will prefix CWModules with each section of CWSystem$Path until a name is made that points to an object on disk. Writing to a new file CWSystem:Modules would be allowed only if CWSystem$Path contains a single item list. The filesystem will also expand system variables in filenames if enclosed in angle brackets, so CW<System$Dir>.Modules would look for the file CW$ENV{'System$Dir'} . 'Modules'. The obvious implication of this is that fully qualified filenames can start with CB<> and should be protected when CWopen is used for input.

Because CW. 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 CW.c CW.h CW.s and CW.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 CWfoo/bar/baz.h and CWfoo/bar/h/baz both map to CWfoo.bar.h.baz, and that CWreaddir and CWglob cannot and do not attempt to emulate the reverse mapping. Other CW.'s in filenames are translated to CW/.

As implied above, the environment accessed through CW%ENV is global, and the convention is that program specific environment variables are of the form CWProgram$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 CWSTDIN, CWSTDOUT, or CWSTDERR to your children.

The desire of users to express filenames of the form CW<Foo$Dir>.Bar on the command line unquoted causes problems, too: CW`` command output capture has to perform a guessing game. It assumes that a string CW<[^<>]+\$[^<>]> is a reference to an environment variable, whereas anything else involving CW< or CW> 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 \s-1XS\s0 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 CWcd sdbm && make all, and anything using quoting.

"\s-1RISC\s0 \s-1OS\s0" is the proper name for the operating system, but the value in CW$^O is “riscos” (because we don't like shouting).

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, \s-1HP\s0 MPE/iX, \s-1QNX\s0, Plan 9, and \s-1VOS\s0, have been well-integrated into the standard Perl source code kit. You may need to see the ports/ directory on \s-1CPAN\s0 for information, and possibly binaries, for the likes of: aos, Atari \s-1ST\s0, 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 CW$^O values in the “\s-1OTHER\s0” category include:

OS $^O $Config{'archname'} ------------------------------------------ Amiga DOS amigaos m68k-amigos BeOS beos MPE/iX mpeix PA-RISC1.1

See also:

"" Amiga, \s-1README\s0.amiga (installed as perlamiga).

"" Atari, \s-1README\s0.mint and Guido Flohr's web page http://stud.uni-sb.de/~gufl0000/

"" Be \s-1OS\s0, \s-1README\s0.beos

"" \s-1HP\s0 300 MPE/iX, \s-1README\s0.mpeix and Mark Bixby's web page http://www.bixby.org/mark/perlix.html

"" A free perl5-based \s-1PERL\s0.NLM for Novell Netware is available in precompiled binary and source code form from http://www.novell.com/ as well as from \s-1CPAN\s0.

"" Plan 9, \s-1README\s0.plan9

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 \s-1README\s0 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 CW%Config, exported by default from the Config module. For example, to check whether the platform has the CWlstat call, check CW$Config{d_lstat}. See Config for a full description of available variables.

"-X" CW-r, CW-w, and CW-x have a limited meaning only; directories and applications are executable, and there are no uid/gid considerations. CW-o is not supported. (Mac \s-1OS\s0) CW-r, CW-w, CW-x, and CW-o tell whether the file is accessible, which may not reflect UIC-based file protections. (\s-1VMS\s0) CW-s returns the size of the data fork, not the total size of data fork plus resource fork. (Mac \s-1OS\s0). CW-s by name on an open file will return the space reserved on disk, rather than the current extent. CW-s on an open filehandle returns the current size. (\s-1RISC\s0 \s-1OS\s0) CW-R, CW-W, CW-X, CW-O are indistinguishable from CW-r, CW-w, CW-x, CW-o. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0) CW-b, CW-c, CW-k, CW-g, CW-p, CW-u, CW-A are not implemented. (Mac \s-1OS\s0) CW-g, CW-k, CW-l, CW-p, CW-u, CW-A are not particularly meaningful. (Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0) CW-d is true if passed a device spec without an explicit directory. (\s-1VMS\s0) CW-T and CW-B are implemented, but might misclassify Mac text files with foreign characters; this is the case will all platforms, but may affect Mac \s-1OS\s0 often. (Mac \s-1OS\s0) CW-x (or CW-X) determine if a file ends in one of the executable suffixes. CW-S is meaningless. (Win32) CW-x (or CW-X) determine if a file has an executable file type. (\s-1RISC\s0 \s-1OS\s0)

"atan2 Due to issues with various CPUs, math libraries, compilers, and standards, results for CWatan2() may vary depending on any combination of the above. Perl attempts to conform to the Open Group/IEEE standards for the results returned from CWatan2(), but cannot force the issue if the system Perl is run on does not allow it. (Tru64, HP-UX 10.20) The current version of the standards for CWatan2() is available at <http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.

"atan2" Due to issues with various CPUs, math libraries, compilers, and standards, results for CWatan2() may vary depending on any combination of the above. Perl attempts to conform to the Open Group/IEEE standards for the results returned from CWatan2(), but cannot force the issue if the system Perl is run on does not allow it. (Tru64, HP-UX 10.20) The current version of the standards for CWatan2() is available at <http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.

"binmode" Meaningless. (Mac \s-1OS\s0, \s-1RISC\s0 \s-1OS\s0) Reopens file and restores pointer; if function fails, underlying filehandle may be closed, or pointer may be in a different position. (\s-1VMS\s0) The value returned by CWtell may be affected after the call, and the filehandle may be flushed. (Win32)

"chmod" Only limited meaning. Disabling/enabling write permission is mapped to locking/unlocking the file. (Mac \s-1OS\s0) 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. (\s-1RISC\s0 \s-1OS\s0) Access permissions are mapped onto \s-1VOS\s0 access-control list changes. (\s-1VOS\s0) The actual permissions set depend on the value of the CWCYGWIN in the \s-1SYSTEM\s0 environment settings. (Cygwin)

"chown" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0) Does nothing, but won't fail. (Win32)

"chroot" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, Plan 9, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0, \s-1VM/ESA\s0)

"crypt" May not be available if library or source was not provided when building perl. (Win32) Not implemented. (\s-1VOS\s0)

"dbmclose" Not implemented. (\s-1VMS\s0, Plan 9, \s-1VOS\s0)

"dbmopen" Not implemented. (\s-1VMS\s0, Plan 9, \s-1VOS\s0)

"dump" Not useful. (Mac \s-1OS\s0, \s-1RISC\s0 \s-1OS\s0) Not implemented. (Win32) Invokes \s-1VMS\s0 debugger. (\s-1VMS\s0)

"exec" Not implemented. (Mac \s-1OS\s0) Implemented via Spawn. (\s-1VM/ESA\s0) Does not automatically flush output handles on some platforms. (SunOS, Solaris, \s-1HP-UX\s0)

"exit" Emulates \s-1UNIX\s0 exit() (which considers CWexit 1 to indicate an error) by mapping the CW1 to \s-1SS$_ABORT\s0 (CW44). This behavior may be overridden with the pragma CWuse vmsish 'exit'. As with the \s-1CRTL\s0's exit() function, CWexit 0 is also mapped to an exit status of \s-1SS$_NORMAL\s0 (CW1); this mapping cannot be overridden. Any other argument to exit() is used directly as Perl's exit status. (\s-1VMS\s0)

"fcntl" Not implemented. (Win32, \s-1VMS\s0)

"flock" Not implemented (Mac \s-1OS\s0, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0). Available only on Windows \s-1NT\s0 (not on Windows 95). (Win32)

"fork" Not implemented. (Mac \s-1OS\s0, AmigaOS, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0, \s-1VM/ESA\s0, \s-1VMS\s0) Emulated using multiple interpreters. See perlfork. (Win32) Does not automatically flush output handles on some platforms. (SunOS, Solaris, \s-1HP-UX\s0)

"getlogin" Not implemented. (Mac \s-1OS\s0, \s-1RISC\s0 \s-1OS\s0)

"getpgrp" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"getppid" Not implemented. (Mac \s-1OS\s0, Win32, \s-1RISC\s0 \s-1OS\s0)

"getpriority" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0, \s-1VM/ESA\s0)

"getpwnam" Not implemented. (Mac \s-1OS\s0, Win32) Not useful. (\s-1RISC\s0 \s-1OS\s0)

"getgrnam" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0)

"getnetbyname" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"getpwuid" Not implemented. (Mac \s-1OS\s0, Win32) Not useful. (\s-1RISC\s0 \s-1OS\s0)

"getgrgid" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0)

"getnetbyaddr" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"getprotobynumber" Not implemented. (Mac \s-1OS\s0)

"getservbyport" Not implemented. (Mac \s-1OS\s0)

"getpwent" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VM/ESA\s0)

"getgrent" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1VM/ESA\s0)

"gethostbyname" CWgethostbyname('localhost') does not work everywhere: you may have to use CWgethostbyname('127.0.0.1'). (Mac \s-1OS\s0, Irix 5)

"gethostent" Not implemented. (Mac \s-1OS\s0, Win32)

"getnetent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"getprotoent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"getservent" Not implemented. (Win32, Plan 9)

"sethostent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9, \s-1RISC\s0 \s-1OS\s0)

"setnetent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9, \s-1RISC\s0 \s-1OS\s0)

"setprotoent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9, \s-1RISC\s0 \s-1OS\s0)

"setservent" Not implemented. (Plan 9, Win32, \s-1RISC\s0 \s-1OS\s0)

"endpwent" Not implemented. (Mac \s-1OS\s0, MPE/iX, \s-1VM/ESA\s0, Win32)

"endgrent" Not implemented. (Mac \s-1OS\s0, MPE/iX, \s-1RISC\s0 \s-1OS\s0, \s-1VM/ESA\s0, \s-1VMS\s0, Win32)

"endhostent" Not implemented. (Mac \s-1OS\s0, Win32)

"endnetent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"endprotoent" Not implemented. (Mac \s-1OS\s0, Win32, Plan 9)

"endservent" Not implemented. (Plan 9, Win32)

"getsockopt Not implemented. (Plan 9)

"glob" This operator is implemented via the File::Glob extension on most platforms. See File::Glob for portability information.

"gmtime" Same portability caveats as localtime.

"ioctl Not implemented. (\s-1VMS\s0) Available only for socket handles, and it does what the ioctlsocket() call in the Winsock \s-1API\s0 does. (Win32) Available only for socket handles. (\s-1RISC\s0 \s-1OS\s0)

"kill" CWkill(0, LIST) is implemented for the sake of taint checking; use with other signals is unimplemented. (Mac \s-1OS\s0) Not implemented, hence not useful for taint checking. (\s-1RISC\s0 \s-1OS\s0) CWkill() doesn't have the semantics of CWraise(), i.e. it doesn't send a signal to the identified process like it does on Unix platforms. Instead CWkill($sig, $pid) terminates the process identified by CW$pid, and makes it exit immediately with exit status CW$sig. As in Unix, if CW$sig is 0 and the specified process exists, it returns true without actually terminating it. (Win32)

"link" Not implemented. (Mac \s-1OS\s0, MPE/iX, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0) 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 \s-1NT\s0 and Windows 2000) under \s-1NTFS\s0 only.

"localtime" Because Perl currently relies on the native standard C localtime() function, it is only safe to use times between 0 and (2**31)-1. Times outside this range may result in unexpected behavior depending on your operating system's implementation of localtime().

"lstat" Not implemented. (\s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0) Return values (especially for device and inode) may be bogus. (Win32)

"msgctl"

"msgget"

"msgsnd"

"msgrcv"

Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, Plan 9, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"open" The CW| variants are supported only if ToolServer is installed. (Mac \s-1OS\s0) open to CW|- and CW-| are unsupported. (Mac \s-1OS\s0, Win32, \s-1RISC\s0 \s-1OS\s0) Opening a process does not automatically flush output handles on some platforms. (SunOS, Solaris, \s-1HP-UX\s0)

"pipe" Very limited functionality. (MiNT)

"readlink" Not implemented. (Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0)

"rename" Can't move directories between directories on different logical volumes. (Win32)

"select" Only implemented on sockets. (Win32, \s-1VMS\s0) Only reliable on sockets. (\s-1RISC\s0 \s-1OS\s0) Note that the CWselect FILEHANDLE form is generally portable.

"semctl"

"semget"

"semop"

Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"setgrent" Not implemented. (Mac \s-1OS\s0, MPE/iX, \s-1VMS\s0, Win32, \s-1RISC\s0 \s-1OS\s0)

"setpgrp" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"setpriority" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"setpwent" Not implemented. (Mac \s-1OS\s0, MPE/iX, Win32, \s-1RISC\s0 \s-1OS\s0)

"setsockopt" Not implemented. (Plan 9)

"shmctl"

"shmget"

"shmread"

"shmwrite"

Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0)

"sockatmark" A relatively recent addition to socket functions, may not be implemented even in \s-1UNIX\s0 platforms.

"socketpair" Not implemented. (Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0, \s-1VM/ESA\s0)

"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 \s-1OS\s0). ctime not supported on \s-1UFS\s0 (Mac \s-1OS\s0 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. (\s-1VMS\s0) mtime, atime and ctime all return the last modification time. Device and inode are not necessarily reliable. (\s-1RISC\s0 \s-1OS\s0) 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" Not implemented. (Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0)

"syscall" Not implemented. (Mac \s-1OS\s0, Win32, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0, \s-1VOS\s0, \s-1VM/ESA\s0)

"sysopen" The traditional “0”, “1”, and “2” MODEs are implemented with different numeric values on some systems. The flags exported by CWFcntl (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (Mac \s-1OS\s0, \s-1OS/390\s0, \s-1VM/ESA\s0)

"system" In general, do not assume the \s-1UNIX/POSIX\s0 semantics that you can shift CW$? right by eight to get the exit value, or that CW$? & 127 would give you the number of the signal that terminated the program, or that CW$? & 128 would test true if the program was terminated by a coredump. Instead, use the \s-1POSIX\s0 W*() interfaces: for example, use \s-1WIFEXITED\s0($?) and \s-1WEXITVALUE\s0($?) to test for a normal exit and the exit value, \s-1WIFSIGNALED\s0($?) and \s-1WTERMSIG\s0($?) for a signal exit and the signal. Core dumping is not a portable concept, so there's no portable way to test for that. Only implemented if ToolServer is installed. (Mac \s-1OS\s0) As an optimization, may not call the command shell specified in CW$ENV{PERL5SHELL}. CWsystem(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 CWwait or CWwaitpid. Failure to spawn() a subprocess is indicated by setting $? to “255 << 8”. CW$? is set in a way compatible with Unix (i.e. the exitstatus of the subprocess is obtained by “$? >> 8”, as described in the documentation). (Win32) There is no shell to process metacharacters, and the native standard is to pass a command line terminated by “\n” “\r” or “\0” to the spawned program. Redirection such as CW> foo is performed (if at all) by the run time library of the spawned program. CWsystem list will call the Unix emulation library's CWexec emulation, which attempts to provide emulation of the stdin, stdout, stderr in force in the parent, providing the child program uses a compatible version of the emulation library. scalar will call the native command line direct and no such emulation of a child Unix program will exists. Mileage will vary. (\s-1RISC\s0 \s-1OS\s0) Far from being \s-1POSIX\s0 compliant. Because there may be no underlying /bin/sh tries to work around the problem by forking and execing the first token in its argument string. Handles basic redirection (“<” or “>”) on its own behalf. (MiNT) Does not automatically flush output handles on some platforms. (SunOS, Solaris, \s-1HP-UX\s0) The return value is POSIX-like (shifted up by 8 bits), which only allows room for a made-up value derived from the severity bits of the native 32-bit condition code (unless overridden by CWuse vmsish 'status'). For more details see “$?” in perlvms. (\s-1VMS\s0)

"times" Only the first entry returned is nonzero. (Mac \s-1OS\s0) “cumulative” times will be bogus. On anything other than Windows \s-1NT\s0 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. (\s-1RISC\s0 \s-1OS\s0)

"truncate" Not implemented. (Older versions of \s-1VMS\s0) Truncation to zero-length only. (\s-1VOS\s0) If a \s-1FILEHANDLE\s0 is supplied, it must be writable and opened in append mode (i.e., use CWopen(FH, '>>filename') or CWsysopen(FH,...,O_APPEND|O_RDWR). If a filename is supplied, it should not be held open elsewhere. (Win32)

"umask" Returns undef where unavailable, as of version 5.005. CWumask works but the correct permissions are set only when the file is finally closed. (AmigaOS)

"utime" Only the modification time is updated. (BeOS, Mac \s-1OS\s0, \s-1VMS\s0, \s-1RISC\s0 \s-1OS\s0) May not behave as expected. Behavior depends on the C runtime library's implementation of utime(), and the filesystem being used. The \s-1FAT\s0 filesystem typically does not support an “access time” field, and it may limit timestamps to a granularity of two seconds. (Win32)

"wait"

"waitpid"

Not implemented. (Mac \s-1OS\s0, \s-1VOS\s0) Can only be applied to process handles returned for processes spawned using CWsystem(1, ...) or pseudo processes created with CWfork(). (Win32) Not useful. (\s-1RISC\s0 \s-1OS\s0)

As of September 2003 (the Perl release 5.8.1), 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 BSD/OS (BSDi) Cygwin DG/UX DOS DJGPP 1) DYNIX/ptx EPOC R5 FreeBSD HI-UXMPP (Hitachi) (5.8.0 worked but we didn't know it) HP-UX IRIX Linux LynxOS Mac OS Classic Mac OS X (Darwin) MPE/iX NetBSD NetWare NonStop-UX ReliantUNIX (formerly SINIX) OpenBSD OpenVMS (formerly VMS) Open UNIX (Unixware) (since Perl 5.8.1/5.9.0) OS/2 OS/400 (using the PASE) (since Perl 5.8.1/5.9.0) PowerUX POSIX-BC (formerly BS2000) QNX Solaris SunOS 4 SUPER-UX (NEC) SVR4 Tru64 UNIX (formerly DEC OSF/1, Digital UNIX) UNICOS UNICOS/mk UTS VOS Win95/98/ME/2K/XP 2) WinCE z/OS (formerly 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 5.8.1 release. There is a very good chance that many of these will work fine with the 5.8.1.

DomainOS Hurd MachTen PowerMAX SCO SV Unixware Windows 3.1

Known to be broken for 5.8.0 and 5.8.1 (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 platformsor 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 (ILE) 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.

perlaix, perlamiga, perlapollo, perlbeos, perlbs2000, perlce, perlcygwin, perldgux, perldos, perlepoc, perlebcdic, perlfreebsd, perlhurd, perlhpux, perlirix, perlmachten, perlmacos, perlmacosx, perlmint, perlmpeix, perlnetware, perlos2, perlos390, perlos400, perlplan9, perlqnx, perlsolaris, perltru64, perlunicode, perlvmesa, perlvms, perlvos, perlwin32, and Win32.

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>, Luther Huffman <lutherh@stratcom.com>, Nick Ing-Simmons <nick@ing-simmons.net>, Andreas J. Ko\*:nig <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>.