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diff --git a/Master/tlpkg/tlperl/lib/pods/perlport.pod b/Master/tlpkg/tlperl/lib/pods/perlport.pod new file mode 100644 index 00000000000..9c81e73e445 --- /dev/null +++ b/Master/tlpkg/tlperl/lib/pods/perlport.pod @@ -0,0 +1,2345 @@ +=head1 NAME + +perlport - Writing portable Perl + +=head1 DESCRIPTION + +Perl runs on numerous operating systems. While most of them share +much in common, they also have their own unique features. + +This document is meant to help you to find out what constitutes portable +Perl code. That way once you make a decision to write portably, +you know where the lines are drawn, and you can stay within them. + +There is a tradeoff between taking full advantage of one particular +type of computer and taking advantage of a full range of them. +Naturally, as you broaden your range and become more diverse, the +common factors drop, and you are left with an increasingly smaller +area of common ground in which you can operate to accomplish a +particular task. Thus, when you begin attacking a problem, it is +important to consider under which part of the tradeoff curve you +want to operate. Specifically, you must decide whether it is +important that the task that you are coding have the full generality +of being portable, or whether to just get the job done right now. +This is the hardest choice to be made. The rest is easy, because +Perl provides many choices, whichever way you want to approach your +problem. + +Looking at it another way, writing portable code is usually about +willfully limiting your available choices. Naturally, it takes +discipline and sacrifice to do that. The product of portability +and convenience may be a constant. You have been warned. + +Be aware of two important points: + +=over 4 + +=item Not all Perl programs have to be portable + +There is no reason you should not use Perl as a language to glue Unix +tools together, or to prototype a Macintosh application, or to manage the +Windows registry. If it makes no sense to aim for portability for one +reason or another in a given program, then don't bother. + +=item Nearly all of Perl already I<is> portable + +Don't be fooled into thinking that it is hard to create portable Perl +code. It isn't. Perl tries its level-best to bridge the gaps between +what's available on different platforms, and all the means available to +use those features. Thus almost all Perl code runs on any machine +without modification. But there are some significant issues in +writing portable code, and this document is entirely about those issues. + +=back + +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, +VMS, etc.), consider writing platform-specific code. + +When the code will run on only two or three operating systems, you +may need to consider only the differences of those particular systems. +The important thing is to decide where the code will run and to be +deliberate in your decision. + +The material below is separated into three main sections: main issues of +portability (L<"ISSUES">), platform-specific issues (L<"PLATFORMS">), and +built-in perl functions that behave differently on various ports +(L<"FUNCTION IMPLEMENTATIONS">). + +This information should not be considered complete; it includes possibly +transient information about idiosyncrasies of some of the ports, almost +all of which are in a state of constant evolution. Thus, this material +should be considered a perpetual work in progress +(C<< <IMG SRC="yellow_sign.gif" ALT="Under Construction"> >>). + +=head1 ISSUES + +=head2 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 C<\012>, one type of DOSish I/O uses C<\015\012>, +and S<Mac OS> uses C<\015>. + +Perl uses C<\n> to represent the "logical" newline, where what is +logical may depend on the platform in use. In MacPerl, C<\n> always +means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but when +accessing a file in "text" mode, perl uses the C<:crlf> layer that +translates it to (or from) C<\015\012>, depending on whether you're +reading or writing. Unix does the same thing on ttys in canonical +mode. C<\015\012> is commonly referred to as CRLF. + +To trim trailing newlines from text lines use chomp(). With default +settings that function looks for a trailing C<\n> character and thus +trims in a portable way. + +When dealing with binary files (or text files in binary mode) be sure +to explicitly set $/ to the appropriate value for your file format +before using chomp(). + +Because of the "text" mode translation, DOSish perls have limitations +in using C<seek> and C<tell> on a file accessed in "text" mode. +Stick to C<seek>-ing to locations you got from C<tell> (and no +others), and you are usually free to use C<seek> and C<tell> even +in "text" mode. Using C<seek> or C<tell> or other file operations +may be non-portable. If you use C<binmode> on a file, however, you +can usually C<seek> and C<tell> with arbitrary values in safety. + +A common misconception in socket programming is that C<\n> eq C<\012> +everywhere. When using protocols such as common Internet protocols, +C<\012> and C<\015> are called for specifically, and the values of +the logical C<\n> and C<\r> (carriage return) are not reliable. + + print SOCKET "Hi there, client!\r\n"; # WRONG + print SOCKET "Hi there, client!\015\012"; # RIGHT + +However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious +and unsightly, as well as confusing to those maintaining the code. As +such, the Socket module supplies the Right Thing for those who want it. + + use Socket qw(:DEFAULT :crlf); + print SOCKET "Hi there, client!$CRLF" # RIGHT + +When reading from a socket, remember that the default input record +separator C<$/> is C<\n>, but robust socket code will recognize as +either C<\012> or C<\015\012> as end of line: + + while (<SOCKET>) { + # ... + } + +Because both CRLF and LF end in LF, the input record separator can +be set to LF and any CR stripped later. Better to write: + + use Socket qw(:DEFAULT :crlf); + local($/) = LF; # not needed if $/ is already \012 + + while (<SOCKET>) { + s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK + # s/\015?\012/\n/; # same thing + } + +This example is preferred over the previous one--even for Unix +platforms--because now any C<\015>'s (C<\cM>'s) are stripped out +(and there was much rejoicing). + +Similarly, functions that return text data--such as a function that +fetches a web page--should sometimes translate newlines before +returning the data, if they've not yet been translated to the local +newline representation. A single line of code will often suffice: + + $data =~ s/\015?\012/\n/g; + return $data; + +Some of this may be confusing. Here's a handy reference to the ASCII CR +and LF characters. You can print it out and stick it in your wallet. + + LF eq \012 eq \x0A eq \cJ eq chr(10) eq ASCII 10 + CR eq \015 eq \x0D eq \cM eq chr(13) eq ASCII 13 + + | Unix | DOS | Mac | + --------------------------- + \n | LF | LF | CR | + \r | CR | CR | LF | + \n * | LF | CRLF | CR | + \r * | CR | CR | LF | + --------------------------- + * text-mode STDIO + +The Unix column assumes that you are not accessing a serial line +(like a tty) in canonical mode. If you are, then CR on input becomes +"\n", and "\n" on output becomes CRLF. + +These are just the most common definitions of C<\n> and C<\r> in Perl. +There may well be others. For example, on an EBCDIC implementation +such as z/OS (OS/390) or OS/400 (using the ILE, the PASE 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 + +=head2 Numbers endianness and Width + +Different CPUs store integers and floating point numbers in different +orders (called I<endianness>) and widths (32-bit and 64-bit being the +most common today). This affects your programs when they attempt to transfer +numbers in binary format from one CPU architecture to another, +usually either "live" via network connection, or by storing the +numbers to secondary storage such as a disk file or tape. + +Conflicting storage orders make utter mess out of the numbers. If a +little-endian host (Intel, VAX) stores 0x12345678 (305419896 in +decimal), a big-endian host (Motorola, Sparc, PA) reads it as +0x78563412 (2018915346 in decimal). Alpha and MIPS can be either: +Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses +them in big-endian mode. To avoid this problem in network (socket) +connections use the C<pack> and C<unpack> formats C<n> and C<N>, the +"network" orders. These are guaranteed to be portable. + +As of perl 5.9.2, you can also use the C<E<gt>> and C<E<lt>> 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 EBCDIC, or more precisely UTF-EBCDIC will go. + +=head2 Files and Filesystems + +Most platforms these days structure files in a hierarchical fashion. +So, it is reasonably safe to assume that all platforms support the +notion of a "path" to uniquely identify a file on the system. How +that path is really written, though, differs considerably. + +Although similar, file path specifications differ between Unix, +Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others. +Unix, for example, is one of the few OSes that has the elegant idea +of a single root directory. + +DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</> +as path separator, or in their own idiosyncratic ways (such as having +several root directories and various "unrooted" device files such NIL: +and LPT:). + +S<Mac OS> 9 and earlier used C<:> as a path separator instead of C</>. + +The filesystem may support neither hard links (C<link>) nor +symbolic links (C<symlink>, C<readlink>, C<lstat>). + +The filesystem may support neither access timestamp nor change +timestamp (meaning that about the only portable timestamp is the +modification timestamp), or one second granularity of any timestamps +(e.g. the FAT filesystem limits the time granularity to two seconds). + +The "inode change timestamp" (the C<-C> filetest) may really be the +"creation timestamp" (which it is not in Unix). + +VOS perl can emulate Unix filenames with C</> as path separator. The +native pathname characters greater-than, less-than, number-sign, and +percent-sign are always accepted. + +S<RISC OS> perl can emulate Unix filenames with C</> as path +separator, or go native and use C<.> for path separator and C<:> to +signal filesystems and disk names. + +Don't assume Unix filesystem access semantics: that read, write, +and execute are all the permissions there are, and even if they exist, +that their semantics (for example what do r, w, and x mean on +a directory) are the Unix ones. The various Unix/POSIX compatibility +layers usually try to make interfaces like chmod() work, but sometimes +there simply is no good mapping. + +If all this is intimidating, have no (well, maybe only a little) +fear. There are modules that can help. The File::Spec modules +provide methods to do the Right Thing on whatever platform happens +to be running the program. + + use File::Spec::Functions; + chdir(updir()); # go up one directory + my $file = catfile(curdir(), 'temp', 'file.txt'); + # on Unix and Win32, './temp/file.txt' + # on Mac OS Classic, ':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 C</> 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 F</etc/passwd>, +F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For +example, F</etc/passwd> may exist but not contain the encrypted +passwords, because the system is using some form of enhanced security. +Or it may not contain all the accounts, because the system is using NIS. +If code does need to rely on such a file, include a description of the +file and its format in the code's documentation, then make it easy for +the user to override the default location of the file. + +Don't assume a text file will end with a newline. They should, +but people forget. + +Do not have two files or directories of the same name with different +case, like F<test.pl> and F<Test.pl>, as many platforms have +case-insensitive (or at least case-forgiving) filenames. Also, try +not to have non-word characters (except for C<.>) in the names, and +keep them to the 8.3 convention, for maximum portability, onerous a +burden though this may appear. + +Likewise, when using the AutoSplit module, try to keep your functions to +8.3 naming and case-insensitive conventions; or, at the least, +make it so the resulting files have a unique (case-insensitively) +first 8 characters. + +Whitespace in filenames is tolerated on most systems, but not all, +and even on systems where it might be tolerated, some utilities +might become confused by such whitespace. + +Many systems (DOS, VMS ODS-2) cannot have more than one C<.> in their +filenames. + +Don't assume C<< > >> won't be the first character of a filename. +Always use C<< < >> 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 my $fh, '<', $existing_file) or die $!; + +If filenames might use strange characters, it is safest to open it +with C<sysopen> instead of C<open>. C<open> is magic and can +translate characters like C<< > >>, C<< < >>, and C<|>, 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 C<:> as a part of a filename since many systems use that for +their own semantics (Mac OS Classic for separating pathname components, +many networking schemes and utilities for separating the nodename and +the pathname, and so on). For the same reasons, avoid C<@>, C<;> and +C<|>. + +Don't assume that in pathnames you can collapse two leading slashes +C<//> into one: some networking and clustering filesystems have special +semantics for that. Let the operating system to sort it out. + +The I<portable filename characters> as defined by ANSI C are + + a b c d e f g h i j k l m n o p q r t u v w x y z + A B C D E F G H I J K L M N O P Q R T U V W X Y Z + 0 1 2 3 4 5 6 7 8 9 + . _ - + +and the "-" shouldn't be the first character. If you want to be +hypercorrect, stay case-insensitive and within the 8.3 naming +convention (all the files and directories have to be unique within one +directory if their names are lowercased and truncated to eight +characters before the C<.>, if any, and to three characters after the +C<.>, if any). (And do not use C<.>s in directory names.) + +=head2 System Interaction + +Not all platforms provide a command line. These are usually platforms +that rely primarily on a Graphical User Interface (GUI) for user +interaction. A program requiring a command line interface might +not work everywhere. This is probably for the user of the program +to deal with, so don't stay up late worrying about it. + +Some platforms can't delete or rename files held open by the system, +this limitation may also apply to changing filesystem metainformation +like file permissions or owners. Remember to C<close> files when you +are done with them. Don't C<unlink> or C<rename> an open file. Don't +C<tie> or C<open> a file already tied or opened; C<untie> or C<close> +it first. + +Don't open the same file more than once at a time for writing, as some +operating systems put mandatory locks on such files. + +Don't assume that write/modify permission on a directory gives the +right to add or delete files/directories in that directory. That is +filesystem specific: in some filesystems you need write/modify +permission also (or even just) in the file/directory itself. In some +filesystems (AFS, DFS) the permission to add/delete directory entries +is a completely separate permission. + +Don't assume that a single C<unlink> completely gets rid of the file: +some filesystems (most notably the ones in VMS) have versioned +filesystems, and unlink() removes only the most recent one (it doesn't +remove all the versions because by default the native tools on those +platforms remove just the most recent version, too). The portable +idiom to remove all the versions of a file is + + 1 while unlink "file"; + +This will terminate if the file is undeleteable for some reason +(protected, not there, and so on). + +Don't count on a specific environment variable existing in C<%ENV>. +Don't count on C<%ENV> entries being case-sensitive, or even +case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or, +if you really have to, make it conditional on C<$^O ne 'VMS'> since in +VMS the C<%ENV> table is much more than a per-process key-value string +table. + +On VMS, some entries in the %ENV hash are dynamically created when +their key is used on a read if they did not previously exist. The +values for C<$ENV{HOME}>, C<$ENV{TERM}>, C<$ENV{HOME}>, and C<$ENV{USER}>, +are known to be dynamically generated. The specific names that are +dynamically generated may vary with the version of the C library on VMS, +and more may exist than is documented. + +On VMS by default, changes to the %ENV hash are persistent after the process +exits. This can cause unintended issues. + +Don't count on signals or C<%SIG> for anything. + +Don't count on filename globbing. Use C<opendir>, C<readdir>, and +C<closedir> instead. + +Don't count on per-program environment variables, or per-program current +directories. + +Don't count on specific values of C<$!>, neither numeric nor +especially the strings values. Users may switch their locales causing +error messages to be translated into their languages. If you can +trust a POSIXish environment, you can portably use the symbols defined +by the Errno module, like ENOENT. And don't trust on the values of C<$!> +at all except immediately after a failed system call. + +=head2 Command names versus file pathnames + +Don't assume that the name used to invoke a command or program with +C<system> or C<exec> can also be used to test for the existence of the +file that holds the executable code for that command or program. +First, many systems have "internal" commands that are built-in to the +shell or OS and while these commands can be invoked, there is no +corresponding file. Second, some operating systems (e.g., Cygwin, +DJGPP, OS/2, and VOS) have required suffixes for executable files; +these suffixes are generally permitted on the command name but are not +required. Thus, a command like "perl" might exist in a file named +"perl", "perl.exe", or "perl.pm", depending on the operating system. +The variable "_exe" in the Config module holds the executable suffix, +if any. Third, the VMS port carefully sets up $^X and +$Config{perlpath} so that no further processing is required. This is +just as well, because the matching regular expression used below would +then have to deal with a possible trailing version number in the VMS +file name. + +To convert $^X to a file pathname, taking account of the requirements +of the various operating system possibilities, say: + + use Config; + my $thisperl = $^X; + if ($^O ne 'VMS') + {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;} + +To convert $Config{perlpath} to a file pathname, say: + + use Config; + my $thisperl = $Config{perlpath}; + if ($^O ne 'VMS') + {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;} + +=head2 Networking + +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 SMTP 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 IP 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 API 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 that for +things such as DHCP 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. + +=head2 Interprocess Communication (IPC) + +In general, don't directly access the system in code meant to be +portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>, +C<``>, C<qx//>, C<open> with a C<|>, 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 +I<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 B<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 (C<msg*(), sem*(), shm*()>) is not available +even on all Unix platforms. + +Do not use either the bare result of C<pack("N", 10, 20, 30, 40)> or +bare v-strings (such as C<v10.20.30.40>) to represent IPv4 addresses: +both forms just pack the four bytes into network order. That this +would be equal to the C language C<in_addr> struct (which is what the +socket code internally uses) is not guaranteed. To be portable use +the routines of the Socket extension, such as C<inet_aton()>, +C<inet_ntoa()>, and C<sockaddr_in()>. + +The rule of thumb for portable code is: Do it all in portable Perl, or +use a module (that may internally implement it with platform-specific +code, but expose a common interface). + +=head2 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. + +=head2 Standard Modules + +In general, the standard modules work across platforms. Notable +exceptions are the CPAN module (which currently makes connections to external +programs that may not be available), platform-specific modules (like +ExtUtils::MM_VMS), and DBM modules. + +There is no one DBM module available on all platforms. +SDBM_File and the others are generally available on all Unix and DOSish +ports, but not in MacPerl, where only NBDM_File and DB_File are +available. + +The good news is that at least some DBM module should be available, and +AnyDBM_File will use whichever module it can find. Of course, then +the code needs to be fairly strict, dropping to the greatest common +factor (e.g., not exceeding 1K for each record), so that it will +work with any DBM module. See L<AnyDBM_File> for more details. + +=head2 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 C<$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 MST 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 UTC, or the POSIX timezone +format. + +Don't assume that the epoch starts at 00:00:00, January 1, 1970, +because that is OS- and implementation-specific. It is better to +store a date in an unambiguous representation. The ISO 8601 standard +defines YYYY-MM-DD as the date format, or YYYY-MM-DDTHH-MM-SS +(that's a literal "T" separating the date from the time). +Please do use the ISO 8601 instead of making us to guess what +date 02/03/04 might be. ISO 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 C<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; + my $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70); + +The value for C<$offset> in Unix will be C<0>, but in Mac OS Classic +will be some large number. C<$offset> can then be added to a Unix time +value to get what should be the proper value on any system. + +=head2 Character sets and character encoding + +Assume very little about character sets. + +Assume nothing about numerical values (C<ord>, C<chr>) of characters. +Do not use explicit code point ranges (like \xHH-\xHH); use for +example symbolic character classes like C<[: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 E<auml> comes before "b". + +=head2 Internationalisation + +If you may assume POSIX (a rather large assumption), you may read +more about the POSIX locale system from L<perllocale>. The locale +system at least attempts to make things a little bit more portable, +or at least more convenient and native-friendly for non-English +users. The system affects character sets and encoding, and date +and time formatting--amongst other things. + +If you really want to be international, you should consider Unicode. +See L<perluniintro> and L<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 UTF-8 locale, in which case random native bytes might be +illegal ("Malformed UTF-8 ...") This means that for example embedding +ISO 8859-1 bytes beyond 0x7f into your strings might cause trouble +later. If the bytes are native 8-bit bytes, you can use the C<bytes> +pragma. If the bytes are in a string (regular expression being a +curious string), you can often also use the C<\xHH> notation instead +of embedding the bytes as-is. (If you want to write your code in UTF-8, +you can use the C<utf8>.) The C<bytes> and C<utf8> pragmata are +available since Perl 5.6.0. + +=head2 System Resources + +If your code is destined for systems with severely constrained (or +missing!) virtual memory systems then you want to be I<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 + + my @lines = <$very_large_file>; # bad + + while (<$fh>) {$file .= $_} # sometimes bad + my $file = join('', <$fh>); # 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. + +=head2 Security + +Most multi-user platforms provide basic levels of security, usually +implemented at the filesystem level. Some, however, unfortunately do +not. Thus the notion of user id, or "home" directory, +or even the state of being logged-in, may be unrecognizable on many +platforms. If you write programs that are security-conscious, it +is usually best to know what type of system you will be running +under so that you can write code explicitly for that platform (or +class of platforms). + +Don't assume the Unix filesystem access semantics: the operating +system or the filesystem may be using some ACL systems, which are +richer languages than the usual rwx. Even if the rwx exist, +their semantics might be different. + +(From security viewpoint testing for permissions before attempting to +do something is silly anyway: if one tries this, there is potential +for race conditions. Someone or something might change the +permissions between the permissions check and the actual operation. +Just try the operation.) + +Don't assume the Unix user and group semantics: especially, don't +expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work +for switching identities (or memberships). + +Don't assume set-uid and set-gid semantics. (And even if you do, +think twice: set-uid and set-gid are a known can of security worms.) + +=head2 Style + +For those times when it is necessary to have platform-specific code, +consider keeping the platform-specific code in one place, making porting +to other platforms easier. Use the Config module and the special +variable C<$^O> to differentiate platforms, as described in +L<"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 +C<$!> after a failed system call. Using C<$!> 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. + +=head1 CPAN Testers + +Modules uploaded to CPAN are tested by a variety of volunteers on +different platforms. These CPAN testers are notified by mail of each +new upload, and reply to the list with PASS, FAIL, NA (not applicable to +this platform), or UNKNOWN (unknown), along with any relevant notations. + +The purpose of the testing is twofold: one, to help developers fix any +problems in their code that crop up because of lack of testing on other +platforms; two, to provide users with information about whether +a given module works on a given platform. + +Also see: + +=over 4 + +=item * + +Mailing list: cpan-testers@perl.org + +=item * + +Testing results: http://testers.cpan.org/ + +=back + +=head1 PLATFORMS + +As of version 5.002, Perl is built with a C<$^O> variable that +indicates the operating system it was built on. This was implemented +to help speed up code that would otherwise have to C<use Config> +and use the value of C<$Config{osname}>. Of course, to get more +detailed information about the system, looking into C<%Config> is +certainly recommended. + +C<%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. + +=head2 Unix + +Perl works on a bewildering variety of Unix and Unix-like platforms (see +e.g. most of the files in the F<hints/> directory in the source code kit). +On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>, +too) is determined either by lowercasing and stripping punctuation from the +first field of the string returned by typing C<uname -a> (or a similar command) +at the shell prompt or by testing the file system for the presence of +uniquely named files such as a kernel or header file. Here, for example, +are a few of the more popular Unix flavors: + + uname $^O $Config{'archname'} + -------------------------------------------- + AIX aix aix + BSD/OS bsdos i386-bsdos + Darwin darwin darwin + dgux dgux AViiON-dgux + DYNIX/ptx dynixptx i386-dynixptx + FreeBSD freebsd freebsd-i386 + Haiku haiku BePC-haiku + Linux linux arm-linux + Linux linux i386-linux + Linux linux i586-linux + Linux linux ppc-linux + HP-UX hpux PA-RISC1.1 + IRIX irix irix + Mac OS X darwin darwin + NeXT 3 next next-fat + NeXT 4 next OPENSTEP-Mach + openbsd openbsd i386-openbsd + OSF1 dec_osf alpha-dec_osf + reliantunix-n svr4 RM400-svr4 + SCO_SV sco_sv i386-sco_sv + SINIX-N svr4 RM400-svr4 + sn4609 unicos CRAY_C90-unicos + sn6521 unicosmk t3e-unicosmk + sn9617 unicos CRAY_J90-unicos + SunOS solaris sun4-solaris + SunOS solaris i86pc-solaris + SunOS4 sunos sun4-sunos + +Because the value of C<$Config{archname}> may depend on the +hardware architecture, it can vary more than the value of C<$^O>. + +=head2 DOS and Derivatives + +Perl has long been ported to Intel-style microcomputers running under +systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can +bring yourself to mention (except for Windows CE, if you count that). +Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should +be aware that each of these file specifications may have subtle +differences: + + my $filespec0 = "c:/foo/bar/file.txt"; + my $filespec1 = "c:\\foo\\bar\\file.txt"; + my $filespec2 = 'c:\foo\bar\file.txt'; + my $filespec3 = 'c:\\foo\\bar\\file.txt'; + +System calls accept either C</> or C<\> as the path separator. +However, many command-line utilities of DOS vintage treat C</> as +the option prefix, so may get confused by filenames containing C</>. +Aside from calling any external programs, C</> will work just fine, +and probably better, as it is more consistent with popular usage, +and avoids the problem of remembering what to backwhack and what +not to. + +The DOS FAT filesystem can accommodate only "8.3" style filenames. Under +the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT) +filesystems you may have to be careful about case returned with functions +like C<readdir> or used with functions like C<open> or C<opendir>. + +DOS also treats several filenames as special, such as AUX, PRN, +NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these +filenames won't even work if you include an explicit directory +prefix. It is best to avoid such filenames, if you want your code +to be portable to DOS and its derivatives. It's hard to know what +these all are, unfortunately. + +Users of these operating systems may also wish to make use of +scripts such as I<pl2bat.bat> or I<pl2cmd> to +put wrappers around your scripts. + +Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from +and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)> +will keep C<\n> translated as C<\012> for that filehandle. Since it is a +no-op on other systems, C<binmode> should be used for cross-platform code +that deals with binary data. That's assuming you realize in advance +that your data is in binary. General-purpose programs should +often assume nothing about their data. + +The C<$^O> variable and the C<$Config{archname}> values for various +DOSish perls are as follows: + + OS $^O $Config{archname} ID Version + -------------------------------------------------------- + MS-DOS dos ? + PC-DOS dos ? + OS/2 os2 ? + Windows 3.1 ? ? 0 3 01 + Windows 95 MSWin32 MSWin32-x86 1 4 00 + Windows 98 MSWin32 MSWin32-x86 1 4 10 + Windows ME MSWin32 MSWin32-x86 1 ? + Windows NT MSWin32 MSWin32-x86 2 4 xx + Windows NT MSWin32 MSWin32-ALPHA 2 4 xx + Windows NT MSWin32 MSWin32-ppc 2 4 xx + Windows 2000 MSWin32 MSWin32-x86 2 5 00 + Windows XP MSWin32 MSWin32-x86 2 5 01 + Windows 2003 MSWin32 MSWin32-x86 2 5 02 + Windows Vista MSWin32 MSWin32-x86 2 6 00 + Windows 7 MSWin32 MSWin32-x86 2 6 01 + Windows 7 MSWin32 MSWin32-x64 2 6 01 + Windows CE MSWin32 ? 3 + Cygwin cygwin cygwin + +The various MSWin32 Perl's can distinguish the OS they are running on +via the value of the fifth element of the list returned from +Win32::GetOSVersion(). For example: + + if ($^O eq 'MSWin32') { + my @os_version_info = Win32::GetOSVersion(); + print +('3.1','95','NT')[$os_version_info[4]],"\n"; + } + +There are also Win32::IsWinNT() and Win32::IsWin95(), try C<perldoc Win32>, +and as of libwin32 0.19 (not part of the core Perl distribution) +Win32::GetOSName(). The very portable POSIX::uname() will work too: + + c:\> perl -MPOSIX -we "print join '|', uname" + Windows NT|moonru|5.0|Build 2195 (Service Pack 2)|x86 + +Also see: + +=over 4 + +=item * + +The djgpp environment for DOS, http://www.delorie.com/djgpp/ +and L<perldos>. + +=item * + +The EMX environment for DOS, OS/2, etc. emx@iaehv.nl, +ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>. + +=item * + +Build instructions for Win32 in L<perlwin32>, or under the Cygnus environment +in L<perlcygwin>. + +=item * + +The C<Win32::*> modules in L<Win32>. + +=item * + +The ActiveState Pages, http://www.activestate.com/ + +=item * + +The Cygwin environment for Win32; F<README.cygwin> (installed +as L<perlcygwin>), http://www.cygwin.com/ + +=item * + +The U/WIN environment for Win32, +http://www.research.att.com/sw/tools/uwin/ + +=item * + +Build instructions for OS/2, L<perlos2> + +=back + +=head2 VMS + +Perl on VMS is discussed in L<perlvms> in the perl distribution. + +The official name of VMS as of this writing is OpenVMS. + +Perl on VMS can accept either VMS- or Unix-style file +specifications as in either of the following: + + $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM + $ perl -ne "print if /perl_setup/i" /sys$login/login.com + +but not a mixture of both as in: + + $ perl -ne "print if /perl_setup/i" sys$login:/login.com + Can't open sys$login:/login.com: file specification syntax error + +Interacting with Perl from the Digital Command Language (DCL) shell +often requires a different set of quotation marks than Unix shells do. +For example: + + $ perl -e "print ""Hello, world.\n""" + Hello, world. + +There are several ways to wrap your perl scripts in DCL F<.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 C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your +perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>. + +The VMS operating system has two filesystems, known as ODS-2 and ODS-5. + +For ODS-2, filenames are in the format "name.extension;version". The +maximum length for filenames is 39 characters, and the maximum length for +extensions is also 39 characters. Version is a number from 1 to +32767. Valid characters are C</[A-Z0-9$_-]/>. + +The ODS-2 filesystem is case-insensitive and does not preserve case. +Perl simulates this by converting all filenames to lowercase internally. + +For ODS-5, filenames may have almost any character in them and can include +Unicode characters. Characters that could be misinterpreted by the DCL +shell or file parsing utilities need to be prefixed with the C<^> +character, or replaced with hexadecimal characters prefixed with the +C<^> character. Such prefixing is only needed with the pathnames are +in VMS format in applications. Programs that can accept the Unix format +of pathnames do not need the escape characters. The maximum length for +filenames is 255 characters. The ODS-5 file system can handle both +a case preserved and a case sensitive mode. + +ODS-5 is only available on the OpenVMS for 64 bit platforms. + +Support for the extended file specifications is being done as optional +settings to preserve backward compatibility with Perl scripts that +assume the previous VMS limitations. + +In general routines on VMS that get a Unix format file specification +should return it in a Unix format, and when they get a VMS format +specification they should return a VMS format unless they are documented +to do a conversion. + +For routines that generate return a file specification, VMS allows setting +if the C library which Perl is built on if it will be returned in VMS +format or in Unix format. + +With the ODS-2 file system, there is not much difference in syntax of +filenames without paths for VMS or Unix. With the extended character +set available with ODS-5 there can be a significant difference. + +Because of this, existing Perl scripts written for VMS were sometimes +treating VMS and Unix filenames interchangeably. Without the extended +character set enabled, this behavior will mostly be maintained for +backwards compatibility. + +When extended characters are enabled with ODS-5, the handling of +Unix formatted file specifications is to that of a Unix system. + +VMS file specifications without extensions have a trailing dot. An +equivalent Unix file specification should not show the trailing dot. + +The result of all of this, is that for VMS, for portable scripts, you +can not depend on Perl to present the filenames in lowercase, to be +case sensitive, and that the filenames could be returned in either +Unix or VMS format. + +And if a routine returns a file specification, unless it is intended to +convert it, it should return it in the same format as it found it. + +C<readdir> by default has traditionally returned lowercased filenames. +When the ODS-5 support is enabled, it will return the exact case of the +filename on the disk. + +Files without extensions have a trailing period on them, so doing a +C<readdir> in the default mode with a file named F<A.;5> will +return F<a.> when VMS is (though that file could be opened with +C<open(FH, 'A')>). + +With support for extended file specifications and if C<opendir> was +given a Unix format directory, a file named F<A.;5> will return F<a> +and optionally in the exact case on the disk. When C<opendir> is given +a VMS format directory, then C<readdir> should return F<a.>, and +again with the optionally the exact case. + +RMS had an eight level limit on directory depths from any rooted logical +(allowing 16 levels overall) prior to VMS 7.2, and even with versions of +VMS on VAX up through 7.3. Hence C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a +valid directory specification but C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is +not. F<Makefile.PL> authors might have to take this into account, but at +least they can refer to the former as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>. + +Pumpkings and module integrators can easily see whether files with too many +directory levels have snuck into the core by running the following in the +top-level source directory: + + $ perl -ne "$_=~s/\s+.*//; print if scalar(split /\//) > 8;" < MANIFEST + + +The VMS::Filespec module, which gets installed as part of the build +process on VMS, is a pure Perl module that can easily be installed on +non-VMS platforms and can be helpful for conversions to and from RMS +native formats. It is also now the only way that you should check to +see if VMS is in a case sensitive mode. + +What C<\n> represents depends on the type of file opened. It usually +represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>, +C<\000>, C<\040>, or nothing depending on the file organization and +record format. The VMS::Stdio module provides access to the +special fopen() requirements of files with unusual attributes on VMS. + +TCP/IP stacks are optional on VMS, so socket routines might not be +implemented. UDP sockets may not be supported. + +The TCP/IP library support for all current versions of VMS is dynamically +loaded if present, so even if the routines are configured, they may +return a status indicating that they are not implemented. + +The value of C<$^O> on OpenVMS is "VMS". To determine the architecture +that you are running on without resorting to loading all of C<%Config> +you can examine the content of the C<@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"; + + } elsif (grep(/VMS_IA64/, @INC)) { + print "I'm on IA64!\n"; + + } else { + print "I'm not so sure about where $^O is...\n"; + } + +In general, the significant differences should only be if Perl is running +on VMS_VAX or one of the 64 bit OpenVMS platforms. + +On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL> +logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00, +calls to C<localtime> are adjusted to count offsets from +01-JAN-1970 00:00:00.00, just like Unix. + +Also see: + +=over 4 + +=item * + +F<README.vms> (installed as L<README_vms>), L<perlvms> + +=item * + +vmsperl list, vmsperl-subscribe@perl.org + +=item * + +vmsperl on the web, http://www.sidhe.org/vmsperl/index.html + +=back + +=head2 VOS + +Perl on VOS (also known as OpenVOS) is discussed in F<README.vos> +in the perl distribution (installed as L<perlvos>). 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, directories, or links whose +names contain a slash character cannot be processed. Such files +must be renamed before they can be processed by Perl. + +Older releases of VOS (prior to OpenVOS Release 17.0) limit file +names to 32 or fewer characters, prohibit file names from +starting with a C<-> character, and prohibit file names from +containing any character matching C<< tr/ !#%&'()*;<=>?// >>. + +Newer releases of VOS (OpenVOS Release 17.0 or later) support a +feature known as extended names. On these releases, file names +can contain up to 255 characters, are prohibited from starting +with a C<-> character, and the set of prohibited characters is +reduced to any character matching C<< tr/#%*<>?// >>. There are +restrictions involving spaces and apostrophies: these characters +must not begin or end a name, nor can they immediately precede or +follow a period. Additionally, a space must not immediately +precede another space or hyphen. Specifically, the following +character combinations are prohibited: space-space, +space-hyphen, period-space, space-period, period-apostrophe, +apostrophe-period, leading or trailing space, and leading or +trailing apostrophe. Although an extended file name is limited +to 255 characters, a path name is still limited to 256 +characters. + +The value of C<$^O> on VOS is "VOS". To determine the +architecture that you are running on without resorting to loading +all of C<%Config> you can examine the content of the @INC array +like so: + + if ($^O =~ /VOS/) { + print "I'm on a Stratus box!\n"; + } else { + print "I'm not on a Stratus box!\n"; + die; + } + +Also see: + +=over 4 + +=item * + +F<README.vos> (installed as L<perlvos>) + +=item * + +The VOS mailing list. + +There is no specific mailing list for Perl on VOS. You can post +comments to the comp.sys.stratus newsgroup, or use the contact +information located in the distribution files on the Stratus +Anonymous FTP site. + +=item * + +VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html + +=back + +=head2 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 L<perlos390> for details. Note that for OS/400 there is also a port of +Perl 5.8.1/5.9.0 or later to the PASE which is ASCII-based (as opposed to +ILE which is EBCDIC-based), see L<perlos400>. + +As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix +sub-systems do not support the C<#!> 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 C<#!> shebang trick in release 2.8 and beyond. +Calls to C<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 F<hello.pl> in the root of the +QOpenSys file system. On the AS/400 calls to C<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 C<chr>, +C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as +well as bit-fiddling with ASCII constants using operators like C<^>, C<&> +and C<|>, not to mention dealing with socket interfaces to ASCII computers +(see L<"Newlines">). + +Fortunately, most web servers for the mainframe will correctly +translate the C<\n> in the following statement to its ASCII equivalent +(C<\r> is the same under both Unix and OS/390 & VM/ESA): + + print "Content-type: text/html\r\n\r\n"; + +The values of C<$^O> on some of these platforms includes: + + uname $^O $Config{'archname'} + -------------------------------------------- + OS/390 os390 os390 + OS400 os400 os400 + POSIX-BC posix-bc BS2000-posix-bc + VM/ESA vmesa vmesa + +Some simple tricks for determining if you are running on an EBCDIC +platform could include any of the following (perhaps all): + + if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; } + + if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; } + + if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; } + +One thing you may not want to rely on is the EBCDIC encoding +of punctuation characters since these may differ from code page to code +page (and once your module or script is rumoured to work with EBCDIC, +folks will want it to work with all EBCDIC character sets). + +Also see: + +=over 4 + +=item * + +L<perlos390>, F<README.os390>, F<perlbs2000>, F<README.vmesa>, +L<perlebcdic>. + +=item * + +The perl-mvs@perl.org list is for discussion of porting issues as well as +general usage issues for all EBCDIC Perls. Send a message body of +"subscribe perl-mvs" to majordomo@perl.org. + +=item * + +AS/400 Perl information at +http://as400.rochester.ibm.com/ +as well as on CPAN in the F<ports/> directory. + +=back + +=head2 Acorn RISC OS + +Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like +Unix, and because Unix filename emulation is turned on by default, +most simple scripts will probably work "out of the box". The native +filesystem is modular, and individual filesystems are free to be +case-sensitive or insensitive, and are usually case-preserving. Some +native filesystems have name length limits, which file and directory +names are silently truncated to fit. Scripts should be aware that the +standard filesystem currently has a name length limit of B<10> +characters, with up to 77 items in a directory, but other filesystems +may not impose such limitations. + +Native filenames are of the form + + Filesystem#Special_Field::DiskName.$.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 C<tr|/.|./|;> + +Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that +the second stage of C<$> interpolation in regular expressions will fall +foul of the C<$.> if scripts are not careful. + +Logical paths specified by system variables containing comma-separated +search lists are also allowed; hence C<System:Modules> is a valid +filename, and the filesystem will prefix C<Modules> with each section of +C<System$Path> until a name is made that points to an object on disk. +Writing to a new file C<System:Modules> would be allowed only if +C<System$Path> contains a single item list. The filesystem will also +expand system variables in filenames if enclosed in angle brackets, so +C<< <System$Dir>.Modules >> would look for the file +S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is +that B<fully qualified filenames can start with C<< <> >>> and should +be protected when C<open> is used for input. + +Because C<.> was in use as a directory separator and filenames could not +be assumed to be unique after 10 characters, Acorn implemented the C +compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from +filenames specified in source code and store the respective files in +subdirectories named after the suffix. Hence files are translated: + + foo.h h.foo + C:foo.h C:h.foo (logical path variable) + sys/os.h sys.h.os (C compiler groks Unix-speak) + 10charname.c c.10charname + 10charname.o o.10charname + 11charname_.c c.11charname (assuming filesystem truncates at 10) + +The Unix emulation library's translation of filenames to native assumes +that this sort of translation is required, and it allows a user-defined list +of known suffixes that it will transpose in this fashion. This may +seem transparent, but consider that with these rules C<foo/bar/baz.h> +and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and +C<glob> cannot and do not attempt to emulate the reverse mapping. Other +C<.>'s in filenames are translated to C</>. + +As implied above, the environment accessed through C<%ENV> is global, and +the convention is that program specific environment variables are of the +form C<Program$Name>. Each filesystem maintains a current directory, +and the current filesystem's current directory is the B<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 C<STDIN>, C<STDOUT>, or C<STDERR> to your children. + +The desire of users to express filenames of the form +C<< <Foo$Dir>.Bar >> on the command line unquoted causes problems, +too: C<``> command output capture has to perform a guessing game. It +assumes that a string C<< <[^<>]+\$[^<>]> >> is a +reference to an environment variable, whereas anything else involving +C<< < >> or C<< > >> is redirection, and generally manages to be 99% +right. Of course, the problem remains that scripts cannot rely on any +Unix tools being available, or that any tools found have Unix-like command +line arguments. + +Extensions and XS are, in theory, buildable by anyone using free +tools. In practice, many don't, as users of the Acorn platform are +used to binary distributions. MakeMaker does run, but no available +make currently copes with MakeMaker's makefiles; even if and when +this should be fixed, the lack of a Unix-like shell will cause +problems with makefile rules, especially lines of the form C<cd +sdbm && make all>, and anything using quoting. + +"S<RISC OS>" is the proper name for the operating system, but the value +in C<$^O> is "riscos" (because we don't like shouting). + +=head2 Other perls + +Perl has been ported to many platforms that do not fit into any of +the categories listed above. Some, such as AmigaOS, 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 F<ports/> directory +on CPAN for information, and possibly binaries, for the likes of: +aos, Atari ST, lynxos, riscos, Novell Netware, Tandem Guardian, +I<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 C<$^O> values +in the "OTHER" category include: + + OS $^O $Config{'archname'} + ------------------------------------------ + Amiga DOS amigaos m68k-amigos + BeOS beos + MPE/iX mpeix PA-RISC1.1 + +See also: + +=over 4 + +=item * + +Amiga, F<README.amiga> (installed as L<perlamiga>). + +=item * + +Be OS, F<README.beos> + +=item * + +HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page +http://www.bixby.org/mark/porting.html + +=item * + +A free perl5-based PERL.NLM for Novell Netware is available in +precompiled binary and source code form from http://www.novell.com/ +as well as from CPAN. + +=item * + +S<Plan 9>, F<README.plan9> + +=back + +=head1 FUNCTION IMPLEMENTATIONS + +Listed below are functions that are either completely unimplemented +or else have been implemented differently on various platforms. +Following each description will be, in parentheses, a list of +platforms that the description applies to. + +The list may well be incomplete, or even wrong in some places. When +in doubt, consult the platform-specific README files in the Perl +source distribution, and any other documentation resources accompanying +a given port. + +Be aware, moreover, that even among Unix-ish systems there are variations. + +For many functions, you can also query C<%Config>, exported by +default from the Config module. For example, to check whether the +platform has the C<lstat> call, check C<$Config{d_lstat}>. See +L<Config> for a full description of available variables. + +=head2 Alphabetical Listing of Perl Functions + +=over 8 + +=item -X + +C<-w> only inspects the read-only file attribute (FILE_ATTRIBUTE_READONLY), +which determines whether the directory can be deleted, not whether it can +be written to. Directories always have read and write access unless denied +by discretionary access control lists (DACLs). (S<Win32>) + +C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible, +which may not reflect UIC-based file protections. (VMS) + +C<-s> by name on an open file will return the space reserved on disk, +rather than the current extent. C<-s> on an open filehandle returns the +current size. (S<RISC OS>) + +C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>, +C<-x>, C<-o>. (Win32, VMS, S<RISC OS>) + +C<-g>, C<-k>, C<-l>, C<-u>, C<-A> are not particularly meaningful. +(Win32, VMS, S<RISC OS>) + +C<-p> is not particularly meaningful. (VMS, S<RISC OS>) + +C<-d> is true if passed a device spec without an explicit directory. +(VMS) + +C<-x> (or C<-X>) determine if a file ends in one of the executable +suffixes. C<-S> is meaningless. (Win32) + +C<-x> (or C<-X>) determine if a file has an executable file type. +(S<RISC OS>) + +=item alarm + +Emulated using timers that must be explicitly polled whenever Perl +wants to dispatch "safe signals" and therefore cannot interrupt +blocking system calls. (Win32) + +=item atan2 + +Due to issues with various CPUs, math libraries, compilers, and standards, +results for C<atan2()> may vary depending on any combination of the above. +Perl attempts to conform to the Open Group/IEEE standards for the results +returned from C<atan2()>, 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 C<atan2()> is available at +L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>. + +=item binmode + +Meaningless. (S<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 C<tell> may be affected after the call, and +the filehandle may be flushed. (Win32) + +=item chmod + +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<RISC OS>) + +Access permissions are mapped onto VOS access-control list changes. (VOS) + +The actual permissions set depend on the value of the C<CYGWIN> +in the SYSTEM environment settings. (Cygwin) + +=item chown + +Not implemented. (Win32, S<Plan 9>, S<RISC OS>) + +Does nothing, but won't fail. (Win32) + +A little funky, because VOS's notion of ownership is a little funky (VOS). + +=item chroot + +Not implemented. (Win32, VMS, S<Plan 9>, S<RISC OS>, VOS, VM/ESA) + +=item crypt + +May not be available if library or source was not provided when building +perl. (Win32) + +=item dbmclose + +Not implemented. (VMS, S<Plan 9>, VOS) + +=item dbmopen + +Not implemented. (VMS, S<Plan 9>, VOS) + +=item dump + +Not useful. (S<RISC OS>) + +Not supported. (Cygwin, Win32) + +Invokes VMS debugger. (VMS) + +=item exec + +Implemented via Spawn. (VM/ESA) + +Does not automatically flush output handles on some platforms. +(SunOS, Solaris, HP-UX) + +=item exit + +Emulates Unix exit() (which considers C<exit 1> to indicate an error) by +mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden +with the pragma C<use vmsish 'exit'>. As with the CRTL's exit() +function, C<exit 0> is also mapped to an exit status of SS$_NORMAL +(C<1>); this mapping cannot be overridden. Any other argument to exit() +is used directly as Perl's exit status. On VMS, unless the future +POSIX_EXIT mode is enabled, the exit code should always be a valid +VMS exit code and not a generic number. When the POSIX_EXIT mode is +enabled, a generic number will be encoded in a method compatible with +the C library _POSIX_EXIT macro so that it can be decoded by other +programs, particularly ones written in C, like the GNV package. (VMS) + +=item fcntl + +Not implemented. (Win32) +Some functions available based on the version of VMS. (VMS) + +=item flock + +Not implemented (VMS, S<RISC OS>, VOS). + +Available only on Windows NT (not on Windows 95). (Win32) + +=item fork + +Not implemented. (AmigaOS, S<RISC OS>, VM/ESA, VMS) + +Emulated using multiple interpreters. See L<perlfork>. (Win32) + +Does not automatically flush output handles on some platforms. +(SunOS, Solaris, HP-UX) + +=item getlogin + +Not implemented. (S<RISC OS>) + +=item getpgrp + +Not implemented. (Win32, VMS, S<RISC OS>) + +=item getppid + +Not implemented. (Win32, S<RISC OS>) + +=item getpriority + +Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA) + +=item getpwnam + +Not implemented. (Win32) + +Not useful. (S<RISC OS>) + +=item getgrnam + +Not implemented. (Win32, VMS, S<RISC OS>) + +=item getnetbyname + +Not implemented. (Win32, S<Plan 9>) + +=item getpwuid + +Not implemented. (Win32) + +Not useful. (S<RISC OS>) + +=item getgrgid + +Not implemented. (Win32, VMS, S<RISC OS>) + +=item getnetbyaddr + +Not implemented. (Win32, S<Plan 9>) + +=item getprotobynumber + +=item getservbyport + +=item getpwent + +Not implemented. (Win32, VM/ESA) + +=item getgrent + +Not implemented. (Win32, VMS, VM/ESA) + +=item gethostbyname + +C<gethostbyname('localhost')> does not work everywhere: you may have +to use C<gethostbyname('127.0.0.1')>. (S<Irix 5>) + +=item gethostent + +Not implemented. (Win32) + +=item getnetent + +Not implemented. (Win32, S<Plan 9>) + +=item getprotoent + +Not implemented. (Win32, S<Plan 9>) + +=item getservent + +Not implemented. (Win32, S<Plan 9>) + +=item sethostent + +Not implemented. (Win32, S<Plan 9>, S<RISC OS>) + +=item setnetent + +Not implemented. (Win32, S<Plan 9>, S<RISC OS>) + +=item setprotoent + +Not implemented. (Win32, S<Plan 9>, S<RISC OS>) + +=item setservent + +Not implemented. (S<Plan 9>, Win32, S<RISC OS>) + +=item endpwent + +Not implemented. (MPE/iX, VM/ESA, Win32) + +=item endgrent + +Not implemented. (MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32) + +=item endhostent + +Not implemented. (Win32) + +=item endnetent + +Not implemented. (Win32, S<Plan 9>) + +=item endprotoent + +Not implemented. (Win32, S<Plan 9>) + +=item endservent + +Not implemented. (S<Plan 9>, Win32) + +=item getsockopt SOCKET,LEVEL,OPTNAME + +Not implemented. (S<Plan 9>) + +=item glob + +This operator is implemented via the File::Glob extension on most +platforms. See L<File::Glob> for portability information. + +=item gmtime + +In theory, gmtime() is reliable from -2**63 to 2**63-1. However, +because work arounds in the implementation use floating point numbers, +it will become inaccurate as the time gets larger. This is a bug and +will be fixed in the future. + +On VOS, time values are 32-bit quantities. + +=item 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. (S<RISC OS>) + +=item kill + +Not implemented, hence not useful for taint checking. (S<RISC OS>) + +C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send +a signal to the identified process like it does on Unix platforms. +Instead C<kill($sig, $pid)> terminates the process identified by $pid, +and makes it exit immediately with exit status $sig. As in Unix, if +$sig is 0 and the specified process exists, it returns true without +actually terminating it. (Win32) + +C<kill(-9, $pid)> will terminate the process specified by $pid and +recursively all child processes owned by it. This is different from +the Unix semantics, where the signal will be delivered to all +processes in the same process group as the process specified by +$pid. (Win32) + +Is not supported for process identification number of 0 or negative +numbers. (VMS) + +=item link + +Not implemented. (MPE/iX, S<RISC OS>, VOS) + +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 under NTFS only. They are +natively supported on Windows 2000 and later. On Windows NT they +are implemented using the Windows POSIX subsystem support and the +Perl process will need Administrator or Backup Operator privileges +to create hard links. + +Available on 64 bit OpenVMS 8.2 and later. (VMS) + +=item localtime + +localtime() has the same range as L<gmtime>, but because time zone +rules change its accuracy for historical and future times may degrade +but usually by no more than an hour. + +=item lstat + +Not implemented. (S<RISC OS>) + +Return values (especially for device and inode) may be bogus. (Win32) + +=item msgctl + +=item msgget + +=item msgsnd + +=item msgrcv + +Not implemented. (Win32, VMS, S<Plan 9>, S<RISC OS>, VOS) + +=item open + +open to C<|-> and C<-|> are unsupported. (Win32, S<RISC OS>) + +Opening a process does not automatically flush output handles on some +platforms. (SunOS, Solaris, HP-UX) + +=item readlink + +Not implemented. (Win32, VMS, S<RISC OS>) + +=item rename + +Can't move directories between directories on different logical volumes. (Win32) + +=item select + +Only implemented on sockets. (Win32, VMS) + +Only reliable on sockets. (S<RISC OS>) + +Note that the C<select FILEHANDLE> form is generally portable. + +=item semctl + +=item semget + +=item semop + +Not implemented. (Win32, VMS, S<RISC OS>) + +=item setgrent + +Not implemented. (MPE/iX, VMS, Win32, S<RISC OS>) + +=item setpgrp + +Not implemented. (Win32, VMS, S<RISC OS>, VOS) + +=item setpriority + +Not implemented. (Win32, VMS, S<RISC OS>, VOS) + +=item setpwent + +Not implemented. (MPE/iX, Win32, S<RISC OS>) + +=item setsockopt + +Not implemented. (S<Plan 9>) + +=item shmctl + +=item shmget + +=item shmread + +=item shmwrite + +Not implemented. (Win32, VMS, S<RISC OS>, VOS) + +=item sockatmark + +A relatively recent addition to socket functions, may not +be implemented even in Unix platforms. + +=item socketpair + +Not implemented. (S<RISC OS>, VM/ESA) + +Available on OpenVOS Release 17.0 or later. (VOS) + +Available on 64 bit OpenVMS 8.2 and later. (VMS) + +=item 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. + +ctime not supported on UFS (S<Mac OS X>). + +ctime is creation time instead of inode change time (Win32). + +device and inode are not meaningful. (Win32) + +device and inode are not necessarily reliable. (VMS) + +mtime, atime and ctime all return the last modification time. Device and +inode are not necessarily reliable. (S<RISC OS>) + +dev, rdev, blksize, and blocks are not available. inode is not +meaningful and will differ between stat calls on the same file. (os2) + +some versions of cygwin when doing a stat("foo") and if not finding it +may then attempt to stat("foo.exe") (Cygwin) + +On Win32 stat() needs to open the file to determine the link count +and update attributes that may have been changed through hard links. +Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up stat() by +not performing this operation. (Win32) + +=item symlink + +Not implemented. (Win32, S<RISC OS>) + +Implemented on 64 bit VMS 8.3. VMS requires the symbolic link to be in Unix +syntax if it is intended to resolve to a valid path. + +=item syscall + +Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA) + +=item sysopen + +The traditional "0", "1", and "2" MODEs are implemented with different +numeric values on some systems. The flags exported by C<Fcntl> +(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac +OS>, OS/390, VM/ESA) + +=item system + +As an optimization, may not call the command shell specified in +C<$ENV{PERL5SHELL}>. C<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 C<wait> or C<waitpid>. Failure to spawn() a subprocess is indicated +by setting $? to "255 << 8". C<$?> is set in a way compatible with +Unix (i.e. the exitstatus of the subprocess is obtained by "$? >> 8", +as described in the documentation). (Win32) + +There is no shell to process metacharacters, and the native standard is +to pass a command line terminated by "\n" "\r" or "\0" to the spawned +program. Redirection such as C<< > foo >> is performed (if at all) by +the run time library of the spawned program. C<system> I<list> will call +the Unix emulation library's C<exec> emulation, which attempts to provide +emulation of the stdin, stdout, stderr in force in the parent, providing +the child program uses a compatible version of the emulation library. +I<scalar> will call the native command line direct and no such emulation +of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>) + +Does not automatically flush output handles on some platforms. +(SunOS, Solaris, HP-UX) + +The return value is POSIX-like (shifted up by 8 bits), which only allows +room for a made-up value derived from the severity bits of the native +32-bit condition code (unless overridden by C<use vmsish 'status'>). +If the native condition code is one that has a POSIX value encoded, the +POSIX value will be decoded to extract the expected exit value. +For more details see L<perlvms/$?>. (VMS) + +=item times + +"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. (S<RISC OS>) + +=item truncate + +Not implemented. (Older versions of VMS) + +Truncation to same-or-shorter lengths only. (VOS) + +If a FILEHANDLE is supplied, it must be writable and opened in append +mode (i.e., use C<<< open(FH, '>>filename') >>> +or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it +should not be held open elsewhere. (Win32) + +=item umask + +Returns undef where unavailable, as of version 5.005. + +C<umask> works but the correct permissions are set only when the file +is finally closed. (AmigaOS) + +=item utime + +Only the modification time is updated. (S<BeOS>, VMS, S<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) + +=item wait + +=item waitpid + +Can only be applied to process handles returned for processes spawned +using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32) + +Not useful. (S<RISC OS>) + +=back + + +=head1 Supported Platforms + +The following platforms are known to build Perl 5.12 (as of April 2010, +its release date) from the standard source code distribution available +at http://www.cpan.org/src + +=over + +=item Linux (x86, ARM, IA64) + +=item HP-UX + +=item AIX + +=item Win32 + +=over + +=item Windows 2000 + +=item Windows XP + +=item Windows Server 2003 + +=item Windows Vista + +=item Windows Server 2008 + +=item Windows 7 + +=back + +=item Cygwin + +=item Solaris (x86, SPARC) + +=item OpenVMS + +=over + +=item Alpha (7.2 and later) + +=item I64 (8.2 and later) + +=back + +=item Symbian + +=item NetBSD + +=item FreeBSD + +=item Haiku + +=item Irix (6.5. What else?) + +=item OpenBSD + +=item Dragonfly BSD + +=item MirOS BSD + +Caveats: + +=over + +=item time_t issues that may or may not be fixed + +=back + + +=item Symbian (Series 60 v3, 3.2 and 5 - what else?) + +=item Stratus VOS / OpenVOS + +=item AIX + +=back + +=head1 EOL Platforms (Perl 5.12) + +The following platforms were supported by a previous version of +Perl but have been officially removed from Perl's source code +as of 5.12: + +=over + +=item Atari MiNT + +=item Apollo Domain/OS + +=item Apple Mac OS 8/9 + +=item Tenon Machten + +=back + +The following platforms may still work as of Perl 5.12, but Perl's +developers have made an explicit decision to discontinue support for +them: + +=over + +=item Windows 95 + +=item Windows 98 + +=item Windows ME + +=item Windows NT4 + +=back + +=head1 Supported Platforms (Perl 5.8) + +As of July 2002 (the Perl release 5.8.0), the following platforms were +able to build Perl from the standard source code distribution +available at http://www.cpan.org/src/ + + 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 + 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) + 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 5.8.0 release. There is a very good chance that many of these +will work fine with the 5.8.0. + + BSD/OS + DomainOS + Hurd + LynxOS + MachTen + PowerMAX + SCO SV + SVR4 + Unixware + Windows 3.1 + +Known to be broken for 5.8.0 (but 5.6.1 and 5.7.2 can be used): + + AmigaOS + +The following platforms have been known to build Perl from source in +the past (5.005_03 and earlier), but we haven't been able to verify +their status for the current release, either because the +hardware/software platforms are rare or because we don't have an +active champion on these platforms--or both. They used to work, +though, so go ahead and try compiling them, and let perlbug@perl.org +of any trouble. + + 3b1 + A/UX + ConvexOS + CX/UX + DC/OSx + DDE SMES + DOS EMX + Dynix + EP/IX + ESIX + FPS + GENIX + Greenhills + ISC + MachTen 68k + 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. + +=head1 SEE ALSO + +L<perlaix>, L<perlamiga>, L<perlapollo>, L<perlbeos>, L<perlbs2000>, +L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, +L<perlebcdic>, L<perlfreebsd>, L<perlhurd>, L<perlhpux>, L<perlirix>, +L<perlmacos>, L<perlmacosx>, L<perlmpeix>, +L<perlnetware>, L<perlos2>, L<perlos390>, L<perlos400>, +L<perlplan9>, L<perlqnx>, L<perlsolaris>, L<perltru64>, +L<perlunicode>, L<perlvmesa>, L<perlvms>, L<perlvos>, +L<perlwin32>, and L<Win32>. + +=head1 AUTHORS / CONTRIBUTORS + +Abigail <abigail@foad.org>, +Charles Bailey <bailey@newman.upenn.edu>, +Graham Barr <gbarr@pobox.com>, +Tom Christiansen <tchrist@perl.com>, +Nicholas Clark <nick@ccl4.org>, +Thomas Dorner <Thomas.Dorner@start.de>, +Andy Dougherty <doughera@lafayette.edu>, +Dominic Dunlop <domo@computer.org>, +Neale Ferguson <neale@vma.tabnsw.com.au>, +David J. Fiander <davidf@mks.com>, +Paul Green <Paul.Green@stratus.com>, +M.J.T. Guy <mjtg@cam.ac.uk>, +Jarkko Hietaniemi <jhi@iki.fi>, +Luther Huffman <lutherh@stratcom.com>, +Nick Ing-Simmons <nick@ing-simmons.net>, +Andreas J. KE<ouml>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<eacute> 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>. +John Malmberg <wb8tyw@qsl.net> |