perlport - Writing portable Perl
-
=head1 DESCRIPTION
-Perl runs on a variety of operating systems. While most of them share
-a lot in common, they also have their own very particular and unique
-features.
+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, so that once you have made your decision to write portably,
+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 B<a> particular type
-of computer, and taking advantage of a full B<range> of them. Naturally,
-as you make your range bigger (and thus more diverse), the common denominators
-drop, and you are left with fewer areas 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 which part of the tradeoff
-curve you want to operate under. Specifically, whether it is important to
-you that the task that you are coding needs the full generality of being
-portable, or if it is sufficient to just get the job done. This is the
-hardest choice to be made. The rest is easy, because Perl provides lots
-of 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 to do that.
+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:
=item Not all Perl programs have to be portable
-There is no reason why you should not use Perl as a language to glue Unix
+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 The vast majority of Perl B<is> portable
+=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 I<are> some significant issues in
+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 that is commonly done
-using a whole range of platforms, think in terms of writing portable
+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
often the case with systems programming (whether for Unix, Windows,
S<Mac OS>, VMS, etc.), consider writing platform-specific code.
-When the code will run on only two or three operating systems, then you may
-only need to consider the differences of those particular systems. The
-important thing is to decide where the code will run, and to be deliberate
-in your decision.
+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 idiosyncracies of some of the ports, almost
-all of which are in a state of constant evolution. Thus this material
+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
-(E<lt>IMG SRC="yellow_sign.gif" ALT="Under Construction"E<gt>).
-
+(<IMG SRC="yellow_sign.gif" ALT="Under Construction">).
=head1 ISSUES
=head2 Newlines
-In most operating systems, lines in files are separated with 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 kind of Windows I/O uses C<\015\012>,
+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, STDIO translates it to (or from)
-C<\015\012>.
-
-Due to the "text" mode translation, DOSish perls have limitations
-of using C<seek> and C<tell> when a file is being accessed in "text"
-mode. Specifically, if you stick to C<seek>-ing to locations you got
-from C<tell> (and no others), you are usually free to use C<seek> and
-C<tell> even in "text" mode. In general, using C<seek> or C<tell> or
-other file operations that count bytes instead of characters, without
-considering the length of C<\n>, may be non-portable. If you use
-C<binmode> on a file, however, you can usually use C<seek> and C<tell>
-with arbitrary values quite safely.
+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, STDIO 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.
+
+A common cause of unportable programs is the misuse of chop() to trim
+newlines:
+
+ # XXX UNPORTABLE!
+ while(<FILE>) {
+ chop;
+ @array = split(/:/);
+ #...
+ }
+
+You can get away with this on Unix and MacOS (they have a single
+character end-of-line), but the same program will break under DOSish
+perls because you're only chop()ing half the end-of-line. Instead,
+chomp() should be used to trim newlines. The Dunce::Files module can
+help audit your code for misuses of chop().
+
+When dealing with binary files (or text files in binary mode) be sure
+to explicitly set $/ to the appropriate value for your file format
+before using chomp().
+
+Because of the "text" mode translation, DOSish perls have limitations
+in using C<seek> and C<tell> on a file accessed in "text" mode.
+Stick to C<seek>-ing to locations you got from C<tell> (and no
+others), and you are usually free to use C<seek> and C<tell> even
+in "text" mode. Using C<seek> or C<tell> or other file operations
+may be non-portable. If you use C<binmode> on a file, however, you
+can usually C<seek> and C<tell> with arbitrary values in safety.
A common misconception in socket programming is that C<\n> eq C<\012>
-everywhere. When using protocols, such as common Internet protocols,
+everywhere. When using protocols such as common Internet protocols,
C<\012> and C<\015> are called for specifically, and the values of
the logical C<\n> and C<\r> (carriage return) are not reliable.
print SOCKET "Hi there, client!\r\n"; # WRONG
print SOCKET "Hi there, client!\015\012"; # RIGHT
-[NOTE: this does not necessarily apply to communications that are
-filtered by another program or module before sending to the socket; the
-the most popular EBCDIC webserver, for instance, accepts C<\r\n>,
-which translates those characters, along with all other
-characters in text streams, from EBCDIC to ASCII.]
-
-However, C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious and
-unsightly, as well as confusing to those maintaining the code. As such,
-the C<Socket> module supplies the Right Thing for those who want it.
+However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious
+and unsightly, as well as confusing to those maintaining the code. As
+such, the Socket module supplies the Right Thing for those who want it.
use Socket qw(:DEFAULT :crlf);
print SOCKET "Hi there, client!$CRLF" # RIGHT
-When reading I<from> a socket, remember that the default input record
-separator (C<$/>) is C<\n>, but code like this should recognize C<$/> as
-C<\012> or C<\015\012>:
+When reading from a socket, remember that the default input record
+separator C<$/> is C<\n>, but robust socket code will recognize as
+either C<\012> or C<\015\012> as end of line:
while (<SOCKET>) {
# ...
}
-Better:
+Because both CRLF and LF end in LF, the input record separator can
+be set to LF and any CR stripped later. Better to write:
use Socket qw(:DEFAULT :crlf);
local($/) = LF; # not needed if $/ is already \012
# s/\015?\012/\n/; # same thing
}
-And this example is actually better than the previous one even for Unix
-platforms, because now any C<\015>'s (C<\cM>'s) are stripped out
+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 == \012 == \x0A == \cJ == ASCII 10
+ CR == \015 == \x0D == \cM == ASCII 13
+
+ | Unix | DOS | Mac |
+ ---------------------------
+ \n | LF | LF | CR |
+ \r | CR | CR | LF |
+ \n * | LF | CRLF | CR |
+ \r * | CR | CR | LF |
+ ---------------------------
+ * text-mode STDIO
+
+The Unix column assumes that you are not accessing a serial line
+(like a tty) in canonical mode. If you are, then CR on input becomes
+"\n", and "\n" on output becomes CRLF.
+
+These are just the most common definitions of C<\n> and C<\r> in Perl.
+There may well be others.
+
+=head2 Numbers endianness and Width
-=head2 File Paths
+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.
+
+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.
+
+=head2 Files and Filesystems
Most platforms these days structure files in a hierarchical fashion.
-So, it is reasonably safe to assume that any platform supports the
-notion of a "path" to uniquely identify a file on the system. Just
-how that path is actually written, differs.
-
-While they are similar, file path specifications differ between Unix,
-Windows, S<Mac OS>, OS/2, VMS and probably others. Unix, for example, is
-one of the few OSes that has the idea of a root directory. S<Mac OS>
-uses C<:> as a path separator instead of C</>. VMS, Windows, and OS/2
-can work similarly to Unix with C</> as path separator, or in their own
-idiosyncratic ways.
-
-As with the newline problem above, there are modules that can help. The
-C<File::Spec> modules provide methods to do the Right Thing on whatever
-platform happens to be running the program.
-
- use File::Spec;
- chdir(File::Spec->updir()); # go up one directory
- $file = File::Spec->catfile(
- File::Spec->curdir(), 'temp', 'file.txt'
- );
+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> uses 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).
+
+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.
+
+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 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 from a configuration file is better, keeping in mind
-that file path syntax varies on different machines.
+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 C<File::Basename>, from the standard distribution, which
+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).
-Remember not to count on the existence of system-specific files, like
-F</etc/resolv.conf>. If code does need to rely on such a file, include a
-description of the file and its format in the code's documentation, and
-make it easy for the user to override the default location of the file.
-
+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 of the same name with different case, like
+F<test.pl> and F<Test.pl>, as many platforms have case-insensitive
+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.
+Many systems (DOS, VMS) 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,
+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 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.)
=head2 System Interaction
-Not all platforms provide for the notion of a command line, necessarily.
-These are usually platforms that rely on a Graphical User Interface (GUI)
-for user interaction. So a program requiring command lines might not work
-everywhere. But this is probably for the user of the program to deal
-with.
+Not all platforms provide a command line. These are usually platforms
+that rely primarily on a Graphical User Interface (GUI) for user
+interaction. A program requiring a command line interface might
+not work everywhere. This is probably for the user of the program
+to deal with, so don't stay up late worrying about it.
+
+Some platforms can't delete or rename files held open by the system.
+Remember to 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.
-Some platforms can't delete or rename files that are being held open by
-the system. 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> to or C<open> a
-file that is already tied to or opened; C<untie> or C<close> first.
+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 even count on C<%ENV> entries being case-sensitive, or even
-case-preserving.
+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.
-Don't count on signals in portable programs.
+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<$!>.
=head2 Interprocess Communication (IPC)
-In general, don't directly access the system in code that is meant to be
-portable. That means, no: C<system>, C<exec>, C<fork>, C<pipe>, C<``>,
-C<qx//>, C<open> with a C<|>, or any of the other things that makes being
-a Unix perl hacker worth being.
+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),
-but the problem with using them arises from what you invoke with them.
-External tools are often named differently on different platforms, often
-not available in the same location, often accept different arguments,
-often behave differently, and often represent their results in a
-platform-dependent way. Thus you should seldom depend on them to produce
-consistent results.
+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 sendmail:
+One especially common bit of Perl code is opening a pipe to B<sendmail>:
- open(MAIL, '|/usr/lib/sendmail -t') or die $!;
+ 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 C<Mail::Send> and C<Mail::Mailer> modules
-in the C<MailTools> distribution. C<Mail::Mailer> provides several
-mailing methods, including mail, sendmail, and direct SMTP
-(via C<Net::SMTP>) if a mail transfer agent is not available.
+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>) or 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. By portable Perl, we mean code that
-avoids the constructs described in this document as being non-portable.
-
+use a module (that may internally implement it with platform-specific
+code, but expose a common interface).
=head2 External Subroutines (XS)
-XS code, in general, can be made to work with any platform; but dependent
+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.
-There is a different kind of portability issue with 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 a comparatively easier way to
+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 C<CPAN.pm> (which currently makes connections to external
+exceptions are the CPAN module (which currently makes connections to external
programs that may not be available), platform-specific modules (like
-C<ExtUtils::MM_VMS>), and DBM modules.
+ExtUtils::MM_VMS), and DBM modules.
-There is no one DBM module that is available on all platforms.
-C<SDBM_File> and the others are generally available on all Unix and DOSish
-ports, but not in MacPerl, where C<NBDM_File> and C<DB_File> are available.
+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
-C<AnyDBM_File> will use whichever module it can find. Of course, then
-the code needs to be fairly strict, dropping to the lowest common
-denominator (e.g., not exceeding 1K for each record).
-
+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 that the epoch starts at January 1, 1970, because that is
-OS-specific. Better to store a date in an unambiguous representation.
-A text representation (like C<1 Jan 1970>) can be easily converted into an
-OS-specific value using a module like C<Date::Parse>. An array of values,
-such as those returned by C<localtime>, can be converted to an OS-specific
-representation using C<Time::Local>.
-
+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 that the epoch starts at 00:00:00, January 1, 1970,
+because that is OS- and implementation-specific. It is better to store a date
+in an unambiguous representation. The ISO-8601 standard defines
+"YYYY-MM-DD" as the date format. A text representation (like "1987-12-18")
+can be easily converted into an OS-specific value using a module like
+Date::Parse. An array of values, such as those returned by
+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;
+ $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70);
+
+The value for C<$offset> in Unix will be C<0>, but in Mac OS will be
+some large number. C<$offset> can then be added to a Unix time value
+to get what should be the proper value on any system.
+
+=head2 Character sets and character encoding
+
+Assume little about character sets. Assume nothing about
+numerical values (C<ord>, C<chr>) of characters. Do not
+assume that the alphabetic characters are encoded contiguously (in
+the numeric sense). Do not assume anything about the ordering of the
+characters. The lowercase letters may come before or after the
+uppercase letters; the lowercase and uppercase may be interlaced so
+that both `a' and `A' come before `b'; the accented and other
+international characters may be interlaced so that E<auml> comes
+before `b'.
+
+=head2 Internationalisation
+
+If you may assume POSIX (a rather large assumption), you may read
+more about the POSIX locale system from L<perllocale>. The locale
+system at least attempts to make things a little bit more portable,
+or at least more convenient and native-friendly for non-English
+users. The system affects character sets and encoding, and date
+and time formatting--amongst other things.
=head2 System Resources
-If your code is destined for systems with severely constrained (or missing!)
-virtual memory systems then you want to be especially mindful of avoiding
-wasteful constructs such as:
+If your code is destined for systems with severely constrained (or
+missing!) virtual memory systems then you want to be I<especially> mindful
+of avoiding wasteful constructs such as:
# NOTE: this is no longer "bad" in perl5.005
for (0..10000000) {} # bad
@lines = <VERY_LARGE_FILE>; # bad
while (<FILE>) {$file .= $_} # sometimes bad
- $file = join '', <FILE>; # better
+ $file = join('', <FILE>); # better
-The last two may appear unintuitive to most people. The first of those
-two constructs repeatedly grows a string, while the second allocates a
-large chunk of memory in one go. On some systems, the latter is more
-efficient that the former.
+The last two constructs may appear unintuitive to most people. The
+first repeatedly grows a string, whereas the second allocates a
+large chunk of memory in one go. On some systems, the second is
+more efficient that the first.
=head2 Security
-Most Unix platforms provide basic levels of security that is usually felt
-at the file-system level. Other platforms usually don't (unfortunately).
-Thus the notion of User-ID, or "home" directory, or even the state of
-being logged-in may be unrecognizable on may platforms. If you write
-programs that are security conscious, it is usually best to know what
-type of system you will be operating under, and write code explicitly
-for that platform (or class of platforms).
+Most multi-user platforms provide basic levels of security, usually
+implemented at the filesystem level. Some, however, do
+not--unfortunately. Thus the notion of user id, or "home" directory,
+or even the state of being logged-in, may be unrecognizable on many
+platforms. If you write programs that are security-conscious, it
+is usually best to know what type of system you will be running
+under so that you can write code explicitly for that platform (or
+class of platforms).
=head2 Style
For those times when it is necessary to have platform-specific code,
consider keeping the platform-specific code in one place, making porting
-to other platforms easier. Use the C<Config> module and the special
-variable C<$^O> to differentiate platforms, as described in L<"PLATFORMS">.
-
-
-=head1 CPAN TESTERS
-
-Module uploaded to CPAN are tested by a variety of volunteers on
-different platforms. These CPAN testers are notified by e-mail of each
+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 an system call. Some platforms expect a certain
+output format, and perl on those platforms may have been adjusted
+accordingly. Most specifically, don't anchor a regex when testing
+an error value.
+
+=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), along with any relevant notations.
+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; two, to provide users with information about
-whether or not a given module works on a given platform.
+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.
=over 4
=item Mailing list: cpan-testers@perl.org
-=item Testing results: C<http://www.connect.net/gbarr/cpan-test/>
+=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
+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 by lowercasing and stripping punctuation from the first
-field of the string returned by typing
-
- % uname -a
-
-(or a similar command) at the shell prompt. Here, for example, are a few
-of the more popular Unix flavors:
-
- uname $^O
- --------------------
- AIX aix
- FreeBSD freebsd
- Linux linux
- HP-UX hpux
- OSF1 dec_osf
- SunOS solaris
- SunOS4 sunos
+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 $Config{'archname'}
+ --------------------------------------------
+ AIX aix aix
+ BSD/OS bsdos i386-bsdos
+ dgux dgux AViiON-dgux
+ DYNIX/ptx dynixptx i386-dynixptx
+ FreeBSD freebsd freebsd-i386
+ Linux linux arm-linux
+ Linux linux i386-linux
+ Linux linux i586-linux
+ Linux linux ppc-linux
+ HP-UX hpux PA-RISC1.1
+ IRIX irix irix
+ Mac OS X darwin darwin
+ MachTen PPC machten powerpc-machten
+ NeXT 3 next next-fat
+ NeXT 4 next OPENSTEP-Mach
+ openbsd openbsd i386-openbsd
+ OSF1 dec_osf alpha-dec_osf
+ reliantunix-n svr4 RM400-svr4
+ SCO_SV sco_sv i386-sco_sv
+ SINIX-N svr4 RM400-svr4
+ sn4609 unicos CRAY_C90-unicos
+ sn6521 unicosmk t3e-unicosmk
+ sn9617 unicos CRAY_J90-unicos
+ SunOS solaris sun4-solaris
+ SunOS solaris i86pc-solaris
+ SunOS4 sunos sun4-sunos
+
+Because the value of C<$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 PC style microcomputers running under
+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> and/or I<CMD.EXE> style shells should
+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:
$filespec2 = 'c:\foo\bar\file.txt';
$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 they 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 file system can only accomodate "8.3" style filenames. Under
-the "case insensitive, but case preserving" HPFS (OS/2) and NTFS (NT)
-file systems you may have to be careful about case returned with functions
+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 these filenames won't even work
-if you include an explicit directory prefix, in some cases. It is best
-to avoid such filenames, if you want your code to be portable to DOS
-and its derivatives.
+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> as appropriate to
+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. C<binmode(FILEHANDLE)> will keep C<\n> translated
-as C<\012> for that filehandle. Since it is a noop on other systems,
-C<binmode> should be used for cross-platform code that deals with binary
-data.
-
-The C<$^O> variable and the C<$Config{'archname'}> values for various
+and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
+will keep C<\n> translated as C<\012> for that filehandle. Since it is a
+no-op on other systems, C<binmode> should be used for cross-platform code
+that deals with binary data. That's assuming you realize in advance
+that your data is in binary. General-purpose programs should
+often assume nothing about their data.
+
+The C<$^O> variable and the C<$Config{archname}> values for various
DOSish perls are as follows:
- OS $^O $Config{'archname'}
- --------------------------------------------
- MS-DOS dos
- PC-DOS dos
- OS/2 os2
- Windows 95 MSWin32 MSWin32-x86
- Windows NT MSWin32 MSWin32-x86
- Windows NT MSWin32 MSWin32-alpha
- Windows NT MSWin32 MSWin32-ppc
+ OS $^O $Config{archname} ID Version
+ --------------------------------------------------------
+ MS-DOS dos ?
+ PC-DOS dos ?
+ OS/2 os2 ?
+ Windows 3.1 ? ? 0 3 01
+ Windows 95 MSWin32 MSWin32-x86 1 4 00
+ Windows 98 MSWin32 MSWin32-x86 1 4 10
+ Windows ME MSWin32 MSWin32-x86 1 ?
+ Windows NT MSWin32 MSWin32-x86 2 4 xx
+ Windows NT MSWin32 MSWin32-ALPHA 2 4 xx
+ Windows NT MSWin32 MSWin32-ppc 2 4 xx
+ Windows 2000 MSWin32 MSWin32-x86 2 5 xx
+ Windows XP MSWin32 MSWin32-x86 2 ?
+ Windows CE MSWin32 ? 3
+ Cygwin cygwin ?
+
+The various MSWin32 Perl's can distinguish the OS they are running on
+via the value of the fifth element of the list returned from
+Win32::GetOSVersion(). For example:
+
+ if ($^O eq 'MSWin32') {
+ my @os_version_info = Win32::GetOSVersion();
+ print +('3.1','95','NT')[$os_version_info[4]],"\n";
+ }
Also see:
=over 4
-=item The djgpp environment for DOS, C<http://www.delorie.com/djgpp/>
+=item *
-=item The EMX environment for DOS, OS/2, etc. C<emx@iaehv.nl>,
-C<http://www.juge.com/bbs/Hobb.19.html>
+The djgpp environment for DOS, http://www.delorie.com/djgpp/
+and L<perldos>.
-=item Build instructions for Win32, L<perlwin32>.
+=item *
-=item The ActiveState Pages, C<http://www.activestate.com/>
+The EMX environment for DOS, OS/2, etc. emx@iaehv.nl,
+http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or
+ftp://hobbes.nmsu.edu/pub/os2/dev/emx. Also L<perlos2>.
-=back
+=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>
-=head2 MacPerl
+=back
+
+=head2 S<Mac OS>
Any module requiring XS compilation is right out for most people, because
MacPerl is built using non-free (and non-cheap!) compilers. Some XS
modules that can work with MacPerl are built and distributed in binary
-form on CPAN. See I<MacPerl: Power and Ease> for more details.
+form on CPAN.
Directories are specified as:
:file for relative pathnames
file for relative pathnames
-Files in a directory are stored in alphabetical order. Filenames are
-limited to 31 characters, and may include any character except C<:>,
-which is reserved as a path separator.
+Files are stored in the directory in alphabetical order. Filenames are
+limited to 31 characters, and may include any character except for
+null and C<:>, which is reserved as the path separator.
-Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in
-C<Mac::Files>.
+Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
+Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
In the MacPerl application, you can't run a program from the command line;
programs that expect C<@ARGV> to be populated can be edited with something
@ARGV = split /\s+/, MacPerl::Ask('Arguments?');
}
-A MacPerl script saved as a droplet will populate C<@ARGV> with the full
+A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full
pathnames of the files dropped onto the script.
-Mac users can use programs on a kind of command line under MPW (Macintosh
-Programmer's Workshop, a free development environment from Apple).
-MacPerl was first introduced as an MPW tool, and MPW can be used like a
-shell:
+Mac users can run programs under a type of command line interface
+under MPW (Macintosh Programmer's Workshop, a free development
+environment from Apple). MacPerl was first introduced as an MPW
+tool, and MPW can be used like a shell:
perl myscript.plx some arguments
ToolServer is another app from Apple that provides access to MPW tools
-from MPW and the MacPerl app, which allows MacPerl program to use
+from MPW and the MacPerl app, which allows MacPerl programs to use
C<system>, backticks, and piped C<open>.
"S<Mac OS>" is the proper name for the operating system, but the value
$is_ppc = $MacPerl::Architecture eq 'MacPPC';
$is_68k = $MacPerl::Architecture eq 'Mac68K';
+S<Mac OS X>, based on NeXT's OpenStep OS, runs MacPerl natively, under the
+"Classic" environment. There is no "Carbon" version of MacPerl to run
+under the primary Mac OS X environment. S<Mac OS X> and its Open Source
+version, Darwin, both run Unix perl natively.
Also see:
=over 4
-=item The MacPerl Pages, C<http://www.ptf.com/macperl/>.
+=item *
-=item The MacPerl mailing list, C<mac-perl-request@iis.ee.ethz.ch>.
+MacPerl Development, http://dev.macperl.org/ .
-=back
+=item *
+
+The MacPerl Pages, http://www.macperl.com/ .
+=item *
+
+The MacPerl mailing lists, http://lists.perl.org/ .
+
+=back
=head2 VMS
-Perl on VMS is discussed in F<vms/perlvms.pod> in the perl distribution.
-Note that perl on VMS can accept either VMS or Unix style file
+Perl on VMS is discussed in L<perlvms> in the perl distribution.
+Perl on VMS can accept either VMS- or Unix-style file
specifications as in either of the following:
$ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM
$ perl -e "print ""Hello, world.\n"""
Hello, world.
-There are a number of ways to wrap your perl scripts in DCL .COM files if
+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!"
$ 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 = E<lt>STDINE<gt>;>.
+perl-in-DCL script expects to do things like C<< $read = <STDIN>; >>.
Filenames are in the format "name.extension;version". The maximum
length for filenames is 39 characters, and the maximum length for
extensions is also 39 characters. Version is a number from 1 to
32767. Valid characters are C</[A-Z0-9$_-]/>.
-VMS' RMS filesystem is case insensitive and does not preserve case.
+VMS's RMS filesystem is case-insensitive and does not preserve case.
C<readdir> returns lowercased filenames, but specifying a file for
-opening remains case insensitive. Files without extensions have a
+opening remains case-insensitive. Files without extensions have a
trailing period on them, so doing a C<readdir> with a file named F<A.;5>
-will return F<a.> (though that file could be opened with C<open(FH, 'A')>.
-
-RMS has an eight level limit on directory depths from any rooted logical
-(allowing 16 levels overall). 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/>.
-
-The C<VMS::Filespec> module, which gets installed as part
-of the build process on VMS, is a pure Perl module that can easily be
-installed on non-VMS platforms and can be helpful for conversions to
-and from RMS native formats.
-
-What C<\n> represents depends on the type of file that is open. It could
-be C<\015>, C<\012>, C<\015\012>, or nothing. Reading from a file
-translates newlines to C<\012>, unless C<binmode> was executed on that
-handle, just like DOSish perls.
+will return F<a.> (though that file could be opened with
+C<open(FH, 'A')>).
+
+RMS had an eight level limit on directory depths from any rooted logical
+(allowing 16 levels overall) prior to VMS 7.2. Hence
+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/>.
+
+The VMS::Filespec module, which gets installed as part of the build
+process on VMS, is a pure Perl module that can easily be installed on
+non-VMS platforms and can be helpful for conversions to and from RMS
+native formats.
+
+What 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 organiztion and
+record format. The VMS::Stdio module provides access to the
+special fopen() requirements of files with unusual attributes on VMS.
TCP/IP stacks are optional on VMS, so socket routines might not be
implemented. UDP sockets may not be supported.
if (grep(/VMS_AXP/, @INC)) {
print "I'm on Alpha!\n";
+
} elsif (grep(/VMS_VAX/, @INC)) {
print "I'm on VAX!\n";
+
} else {
print "I'm not so sure about where $^O is...\n";
}
+On VMS, perl determines the UTC offset from the C<SYS$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 L<perlvms.pod>
+=item *
+
+F<README.vms> (installed as L<README_vms>), L<perlvms>
+
+=item *
-=item vmsperl list, C<vmsperl-request@newman.upenn.edu>
+vmsperl list, majordomo@perl.org
-Put words C<SUBSCRIBE VMSPERL> in message body.
+(Put the words C<subscribe vmsperl> in message body.)
-=item vmsperl on the web, C<http://www.sidhe.org/vmsperl/index.html>
+=item *
+
+vmsperl on the web, http://www.sidhe.org/vmsperl/index.html
=back
+=head2 VOS
+
+Perl on VOS 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. Note that VOS limits
+file names to 32 or fewer characters.
+
+See F<README.vos> for restrictions that apply when Perl is built
+with the alpha version of VOS POSIX.1 support.
+
+Perl on VOS is built without any extensions and does not support
+dynamic loading.
+
+The value of 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;
+ }
+
+ 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:
+
+=over 4
+
+=item *
+
+F<README.vos>
+
+=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 subscribe to the general
+Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
+the message body to majordomo@list.stratagy.com.
+
+=item *
+
+VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.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 for IBM Mainframes. Such computers
-use EBCDIC character sets internally (usually Character Code Set ID 00819
-for OS/400 and IBM-1047 for OS/390). Note that on the mainframe perl
-currently works under the "Unix system services for OS/390" (formerly
-known as OpenEdition).
-
-As of R2.5 of USS for OS/390 that Unix sub-system did not support the
-C<#!> shebang trick for script invocation. Hence, on OS/390 perl scripts
-can executed with a header similar to the following simple script:
+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.
+
+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 ${1+"$@"}'
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 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">).
+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 (note that
-C<\r> is the same under both ASCII and EBCDIC):
+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 value of C<$^O> on OS/390 is "os390".
+The values of C<$^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 (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; }
-Note that 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).
+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 perl-mvs list
+=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 C<http://as400.rochester.ibm.com>
+=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 a variety of platforms that do not fit into
-any of the above categories. Some, such as AmigaOS, BeOS, MPE/iX,
-OS/390 (MVS), QNX, and Plan 9, 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: acorn, aos, atari, lynxos, riscos, Tandem Guardian, vos,
-I<etc.> (yes we know that some of these OSes may fall under the Unix
-category but we are not a standards body.)
+Perl has been ported to many platforms that do not fit into any of
+the categories listed above. Some, such as AmigaOS, Atari MiNT,
+BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated
+into the standard Perl source code kit. You may need to see the
+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 $Config{'archname'}
+ ------------------------------------------
+ Amiga DOS amigaos m68k-amigos
+ MPE/iX mpeix PA-RISC1.1
See also:
=over 4
-=item Atari, Guido Flohr's page C<http://stud.uni-sb.de/~gufl0000/>
+=item *
-=item HP 300 MPE/iX C<http://www.cccd.edu/~markb/perlix.html>
+Amiga, F<README.amiga> (installed as L<perlamiga>).
-=item Novell Netware
+=item *
-A free Perl 5 based PERL.NLM for Novell Netware is available from
-C<http://www.novell.com/>
+Atari, F<README.mint> and Guido Flohr's web page
+http://stud.uni-sb.de/~gufl0000/
-=back
+=item *
+Be OS, F<README.beos>
-=head1 FUNCTION IMPLEMENTATIONS
+=item *
-Listed below are functions unimplemented or implemented differently on
-various platforms. Following each description will be, in parentheses, a
-list of platforms that the description applies to.
+HP 300 MPE/iX, F<README.mpeix> and Mark Bixby's web page
+http://www.bixby.org/mark/perlix.html
-The list may very well be incomplete, or wrong in some places. When in
-doubt, consult the platform-specific README files in the Perl source
-distribution, and other documentation resources for a given port.
+=item *
-Be aware, moreover, that even among Unix-ish systems there are variations,
-and not all functions listed here are necessarily available, though
-most usually are.
+A free perl5-based PERL.NLM for Novell Netware is available in
+precompiled binary and source code form from http://www.novell.com/
+as well as from CPAN.
-For many functions, you can also query C<%Config>, exported by default
-from C<Config.pm>. For example, to check if the platform has the C<lstat>
-call, check C<$Config{'d_lstat'}>. See L<Config> for a full description
-of available variables.
+=item *
+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
=item -X
-C<-r>, C<-w>, and C<-x> have only a very limited meaning; directories
+C<-r>, C<-w>, and C<-x> have a limited meaning only; directories
and applications are executable, and there are no uid/gid
-considerations. C<-o> is not supported. (S<Mac OS>)
+considerations. C<-o> is not supported. (S<Mac OS>)
+
+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<-r>, C<-w>, C<-x>, and C<-o> tell whether or not file is accessible,
-which may not reflect UIC-based file protections. (VMS)
+C<-s> returns the size of the data fork, not the total size of data fork
+plus resource fork. (S<Mac OS>).
+
+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>. (S<Mac OS>, Win32, VMS)
+C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>)
C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented.
(S<Mac OS>)
C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful.
-(Win32, VMS)
+(Win32, VMS, S<RISC OS>)
C<-d> is true if passed a device spec without an explicit directory.
(VMS)
C<-T> and C<-B> are implemented, but might misclassify Mac text files
-with foreign characters; this is the case will all platforms, but
-affects S<Mac OS> a lot. (S<Mac OS>)
+with foreign characters; this is the case will all platforms, but may
+affect S<Mac OS> often. (S<Mac OS>)
C<-x> (or C<-X>) determine if a file ends in one of the executable
-suffixes. C<-S> is meaningless. (Win32)
+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 SECONDS
+
+=item alarm
+
+Not implemented. (Win32)
=item binmode FILEHANDLE
-Meaningless. (S<Mac OS>)
+Meaningless. (S<Mac OS>, S<RISC OS>)
Reopens file and restores pointer; if function fails, underlying
filehandle may be closed, or pointer may be in a different position.
=item chmod LIST
-Only limited meaning. Disabling/enabling write permission is mapped to
+Only limited meaning. Disabling/enabling write permission is mapped to
locking/unlocking the file. (S<Mac OS>)
Only good for changing "owner" read-write access, "group", and "other"
bits are meaningless. (Win32)
+Only good for changing "owner" and "other" read-write access. (S<RISC OS>)
+
+Access permissions are mapped onto VOS access-control list changes. (VOS)
+
=item chown LIST
-Not implemented. (S<Mac OS>, Win32, Plan9)
+Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
Does nothing, but won't fail. (Win32)
=item chroot
-Not implemented. (S<Mac OS>, Win32, VMS, Plan9)
+Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA)
=item crypt PLAINTEXT,SALT
May not be available if library or source was not provided when building
-perl. (Win32)
+perl. (Win32)
+
+Not implemented. (VOS)
=item dbmclose HASH
-Not implemented. (VMS, Plan9)
+Not implemented. (VMS, Plan9, VOS)
=item dbmopen HASH,DBNAME,MODE
-Not implemented. (VMS, Plan9)
+Not implemented. (VMS, Plan9, VOS)
=item dump LABEL
-Not useful. (S<Mac OS>)
+Not useful. (S<Mac OS>, S<RISC OS>)
Not implemented. (Win32)
-Invokes VMS debugger. (VMS)
+Invokes VMS debugger. (VMS)
=item exec LIST
Not implemented. (S<Mac OS>)
+Implemented via Spawn. (VM/ESA)
+
+Does not automatically flush output handles on some platforms.
+(SunOS, Solaris, HP-UX)
+
=item fcntl FILEHANDLE,FUNCTION,SCALAR
Not implemented. (Win32, VMS)
=item flock FILEHANDLE,OPERATION
-Not implemented (S<Mac OS>, VMS).
+Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS).
Available only on Windows NT (not on Windows 95). (Win32)
=item fork
-Not implemented. (S<Mac OS>, Win32, AmigaOS)
+Not implemented. (S<Mac OS>, AmigaOS, S<RISC OS>, VOS, VM/ESA)
+
+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<Mac OS>)
+Not implemented. (S<Mac OS>, S<RISC OS>)
=item getpgrp PID
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
=item getppid
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
=item getpriority WHICH,WHO
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
=item getpwnam NAME
Not implemented. (S<Mac OS>, Win32)
+Not useful. (S<RISC OS>)
+
=item getgrnam NAME
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
=item getnetbyname NAME
Not implemented. (S<Mac OS>, Win32)
+Not useful. (S<RISC OS>)
+
=item getgrgid GID
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
=item getnetbyaddr ADDR,ADDRTYPE
=item getpwent
-Not implemented. (S<Mac OS>, Win32)
+Not implemented. (S<Mac OS>, Win32, VM/ESA)
=item getgrent
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA)
=item gethostent
=item setpwent
-Not implemented. (S<Mac OS>, Win32)
+Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
=item setgrent
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
=item sethostent STAYOPEN
-Not implemented. (S<Mac OS>, Win32, Plan9)
+Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
=item setnetent STAYOPEN
-Not implemented. (S<Mac OS>, Win32, Plan9)
+Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
=item setprotoent STAYOPEN
-Not implemented. (S<Mac OS>, Win32, Plan9)
+Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
=item setservent STAYOPEN
-Not implemented. (Plan9, Win32)
+Not implemented. (Plan9, Win32, S<RISC OS>)
=item endpwent
-Not implemented. (S<Mac OS>, Win32)
+Not implemented. (S<Mac OS>, MPE/iX, VM/ESA, Win32)
=item endgrent
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, MPE/iX, S<RISC OS>, VM/ESA, VMS, Win32)
=item endhostent
Not implemented. (Plan9, Win32)
+=item exit EXPR
+
+=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$_NORMAL
+(C<1>); this mapping cannot be overridden. Any other argument to exit()
+is used directly as Perl's exit status. (VMS)
+
=item getsockopt SOCKET,LEVEL,OPTNAME
-Not implemented. (S<Mac OS>, Plan9)
+Not implemented. (Plan9)
=item glob EXPR
=item glob
-Globbing built-in, but only C<*> and C<?> metacharacters are supported.
-(S<Mac OS>)
-
-Features depend on external perlglob.exe or perlglob.bat. May be overridden
-with something like File::DosGlob, which is recommended. (Win32)
+This operator is implemented via the File::Glob extension on most
+platforms. See L<File::Glob> for portability information.
=item ioctl FILEHANDLE,FUNCTION,SCALAR
Available only for socket handles, and it does what the ioctlsocket() call
in the Winsock API does. (Win32)
-=item kill LIST
+Available only for socket handles. (S<RISC OS>)
-Not implemented. (S<Mac OS>)
+=item kill SIGNAL, LIST
-Available only for process handles returned by the C<system(1, ...)> method of
-spawning a process. (Win32)
+C<kill(0, LIST)> is implemented for the sake of taint checking;
+use with other signals is unimplemented. (S<Mac OS>)
+
+Not implemented, hence not useful for taint checking. (S<RISC OS>)
+
+C<kill()> doesn't have the semantics of C<raise()>, i.e. it doesn't send
+a signal to the identified process like it does on Unix platforms.
+Instead C<kill($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)
=item link OLDFILE,NEWFILE
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, MPE/iX, VMS, S<RISC OS>)
+
+Link count not updated because hard links are not quite that hard
+(They are sort of half-way between hard and soft links). (AmigaOS)
+
+Hard links are implemented on Win32 (Windows NT and Windows 2000)
+under NTFS only.
=item lstat FILEHANDLE
=item lstat
-Not implemented. (VMS)
+Not implemented. (VMS, S<RISC OS>)
-Return values may be bogus. (Win32)
+Return values (especially for device and inode) may be bogus. (Win32)
=item msgctl ID,CMD,ARG
=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
-Not implemented. (S<Mac OS>, Win32, VMS, Plan9)
+Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS)
=item open FILEHANDLE,EXPR
=item open FILEHANDLE
-The C<|> variants are only supported if ToolServer is installed.
+The C<|> variants are supported only if ToolServer is installed.
(S<Mac OS>)
-open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32)
+open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>)
+
+Opening a process does not automatically flush output handles on some
+platforms. (SunOS, Solaris, HP-UX)
=item pipe READHANDLE,WRITEHANDLE
-Not implemented. (S<Mac OS>)
+Very limited functionality. (MiNT)
=item readlink EXPR
=item readlink
-Not implemented. (Win32, VMS)
+Not implemented. (Win32, VMS, S<RISC OS>)
=item select RBITS,WBITS,EBITS,TIMEOUT
Only implemented on sockets. (Win32)
+Only reliable on sockets. (S<RISC OS>)
+
+Note that the C<socket FILEHANDLE> form is generally portable.
+
=item semctl ID,SEMNUM,CMD,ARG
=item semget KEY,NSEMS,FLAGS
=item semop KEY,OPSTRING
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
+
+=item setgrent
+
+Not implemented. (MPE/iX, Win32)
=item setpgrp PID,PGRP
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
=item setpriority WHICH,WHO,PRIORITY
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
+
+=item setpwent
+
+Not implemented. (MPE/iX, Win32)
=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
-Not implemented. (S<Mac OS>, Plan9)
+Not implemented. (Plan9)
=item shmctl ID,CMD,ARG
=item shmwrite ID,STRING,POS,SIZE
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS)
+
+=item sockatmark SOCKET
+
+A relatively recent addition to socket functions, may not
+be implemented even in UNIX platforms.
=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (Win32, VMS, S<RISC OS>, VOS, VM/ESA)
=item stat FILEHANDLE
=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.
+
mtime and atime are the same thing, and ctime is creation time instead of
inode change time. (S<Mac OS>)
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)
+
=item symlink OLDFILE,NEWFILE
-Not implemented. (Win32, VMS)
+Not implemented. (Win32, VMS, S<RISC OS>)
=item syscall LIST
-Not implemented. (S<Mac OS>, Win32, VMS)
+Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA)
+
+=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
+
+The traditional "0", "1", and "2" MODEs are implemented with different
+numeric values on some systems. The flags exported by C<Fcntl>
+(O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac
+OS>, OS/390, VM/ESA)
=item system LIST
Only implemented if ToolServer is installed. (S<Mac OS>)
As an optimization, may not call the command shell specified in
-C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external
+C<$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>. (Win32)
+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 "$? >> 8",
+as described in the documentation). (Win32)
+
+There is no shell to process metacharacters, and the native standard is
+to pass a command line terminated by "\n" "\r" or "\0" to the spawned
+program. Redirection such as C<< > foo >> is performed (if at all) by
+the run time library of the spawned program. C<system> I<list> will call
+the Unix emulation library's C<exec> emulation, which attempts to provide
+emulation of the stdin, stdout, stderr in force in the parent, providing
+the child program uses a compatible version of the emulation library.
+I<scalar> will call the native command line direct and no such emulation
+of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>)
+
+Far from being POSIX compliant. Because there may be no underlying
+/bin/sh tries to work around the problem by forking and execing the
+first token in its argument string. Handles basic redirection
+("<" or ">") on its own behalf. (MiNT)
+
+Does not automatically flush output handles on some platforms.
+(SunOS, Solaris, HP-UX)
+
+The return value is POSIX-like (shifted up by 8 bits), which only allows
+room for a made-up value derived from the severity bits of the native
+32-bit condition code (unless overridden by C<use vmsish 'status'>).
+For more details see L<perlvms/$?>. (VMS)
=item times
Only the first entry returned is nonzero. (S<Mac OS>)
-"cumulative" times will be bogus. On anything other than Windows NT,
-"system" time will be bogus, and "user" time is actually the time
-returned by the clock() function in the C runtime library. (Win32)
+"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 FILEHANDLE,LENGTH
=item truncate EXPR,LENGTH
-Not implemented. (VMS)
+Not implemented. (Older versions of VMS)
+
+Truncation to zero-length only. (VOS)
+
+If a FILEHANDLE is supplied, it must be writable and opened in append
+mode (i.e., use 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 EXPR
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 LIST
-Only the modification time is updated. (S<Mac OS>, VMS)
+Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
-May not behave as expected. (Win32)
+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 PID,FLAGS
-Not implemented. (S<Mac OS>)
+Not implemented. (S<Mac OS>, VOS)
Can only be applied to process handles returned for processes spawned
-using C<system(1, ...)>. (Win32)
+using C<system(1, ...)> or pseudo processes created with C<fork()>. (Win32)
+
+Not useful. (S<RISC OS>)
+
+=back
+
+=head1 CHANGES
+
+=over 4
+
+=item v1.48, 02 February 2001
+
+Various updates from perl5-porters over the past year, supported
+platforms update from Jarkko Hietaniemi.
+
+=item v1.47, 22 March 2000
+
+Various cleanups from Tom Christiansen, including migration of
+long platform listings from L<perl>.
+
+=item v1.46, 12 February 2000
+
+Updates for VOS and MPE/iX. (Peter Prymmer) Other small changes.
+
+=item v1.45, 20 December 1999
+
+Small changes from 5.005_63 distribution, more changes to EBCDIC info.
+
+=item v1.44, 19 July 1999
+
+A bunch of updates from Peter Prymmer for C<$^O> values,
+endianness, File::Spec, VMS, BS2000, OS/400.
+
+=item v1.43, 24 May 1999
+
+Added a lot of cleaning up from Tom Christiansen.
+
+=item v1.42, 22 May 1999
+
+Added notes about tests, sprintf/printf, and epoch offsets.
+
+=item v1.41, 19 May 1999
+
+Lots more little changes to formatting and content.
+
+Added a bunch of C<$^O> and related values
+for various platforms; fixed mail and web addresses, and added
+and changed miscellaneous notes. (Peter Prymmer)
+
+=item v1.40, 11 April 1999
+
+Miscellaneous changes.
+
+=item v1.39, 11 February 1999
+
+Changes from Jarkko and EMX URL fixes Michael Schwern. Additional
+note about newlines added.
+
+=item v1.38, 31 December 1998
+
+More changes from Jarkko.
+
+=item v1.37, 19 December 1998
+
+More minor changes. Merge two separate version 1.35 documents.
+
+=item v1.36, 9 September 1998
+
+Updated for Stratus VOS. Also known as version 1.35.
+
+=item v1.35, 13 August 1998
+
+Integrate more minor changes, plus addition of new sections under
+L<"ISSUES">: L<"Numbers endianness and Width">,
+L<"Character sets and character encoding">,
+L<"Internationalisation">.
+
+=item v1.33, 06 August 1998
+
+Integrate more minor changes.
+
+=item v1.32, 05 August 1998
+
+Integrate more minor changes.
+
+=item v1.30, 03 August 1998
+
+Major update for RISC OS, other minor changes.
+
+=item v1.23, 10 July 1998
+
+First public release with perl5.005.
=back
+=head1 Supported Platforms
+
+As of early 2001 (the Perl releases 5.6.1 and 5.7.1), the following
+platforms are able to build Perl from the standard source code
+distribution available at http://www.perl.com/CPAN/src/index.html
+
+ AIX
+ AmigaOS
+ Darwin (Mac OS X)
+ DG/UX
+ DOS DJGPP 1)
+ DYNIX/ptx
+ EPOC
+ FreeBSD
+ HP-UX
+ IRIX
+ Linux
+ MachTen
+ MacOS Classic 2)
+ NonStop-UX
+ ReliantUNIX (SINIX)
+ OpenBSD
+ OpenVMS (VMS)
+ OS/2
+ OS X
+ QNX
+ Solaris
+ Tru64 UNIX (DEC OSF/1, Digital UNIX)
+ UNICOS
+ UNICOS/mk
+ VOS
+ Win32/NT/2K 3)
+
+ 1) in DOS mode either the DOS or OS/2 ports can be used
+ 2) Mac OS Classic (pre-X) is almost 5.6.1-ready; building from
+ the source does work with 5.6.1, but additional MacOS specific
+ source code is needed for a complete build. See the web
+ site http://dev.macperl.org/ for more information.
+ 3) compilers: Borland, Cygwin, Mingw32 EGCS/GCC, VC++
+
+The following platforms worked for the previous releases (5.6.0 and 5.7.0),
+but we did not manage to test these in time for the 5.7.1 release.
+There is a very good chance that these will work fine with the 5.7.1.
+
+ DomainOS
+ Hurd
+ LynxOS
+ MinGW
+ MPE/iX
+ NetBSD
+ PowerMAX
+ SCO SV
+ SunOS
+ SVR4
+ Unixware
+ Windows 3.1
+ Windows 95
+ Windows 98
+ Windows Me
+
+The following platform worked for the 5.005_03 major release but not
+for 5.6.0. Standardization on UTF-8 as the internal string
+representation in 5.6.0 and 5.6.1 introduced incompatibilities in this
+EBCDIC platform. While Perl 5.7.1 will build on this platform some
+regression tests may fail and the C<use utf8;> pragma typically
+introduces text handling errors.
+
+ OS/390 1)
+
+ 1) previously known as MVS, about to become z/OS.
+
+Strongly related to the OS/390 platform by also being EBCDIC-based
+mainframe platforms are the following platforms:
+
+ POSIX-BC (BS2000)
+ VM/ESA
+
+These are also expected to work, albeit with no UTF-8 support, under 5.6.1
+for the same reasons as OS/390. Contact the mailing list perl-mvs@perl.org
+for more details.
+
+The following platforms have been known to build Perl from source in
+the past (5.005_03 and earlier), but we haven't been able to verify
+their status for the current release, either because the
+hardware/software platforms are rare or because we don't have an
+active champion on these 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
+ BeOS
+ BSD/OS
+ ConvexOS
+ CX/UX
+ DC/OSx
+ DDE SMES
+ DOS EMX
+ Dynix
+ EP/IX
+ ESIX
+ FPS
+ GENIX
+ Greenhills
+ ISC
+ MachTen 68k
+ MiNT
+ MPC
+ NEWS-OS
+ NextSTEP
+ OpenSTEP
+ Opus
+ Plan 9
+ PowerUX
+ RISC/os
+ SCO ODT/OSR
+ Stellar
+ SVR2
+ TI1500
+ TitanOS
+ Ultrix
+ Unisys Dynix
+ Unixware
+ UTS
+
+Support for the following platform is planned for a future Perl release:
+
+ Netware
+
+The following platforms have their own source code distributions and
+binaries available via http://www.perl.com/CPAN/ports/index.html:
+
+ Perl release
+
+ Netware 5.003_07
+ OS/400 5.005_02
+ Tandem Guardian 5.004
+
+The following platforms have only binaries available via
+http://www.perl.com/CPAN/ports/index.html :
+
+ Perl release
+
+ Acorn RISCOS 5.005_02
+ AOS 5.002
+ LynxOS 5.004_02
+
+Although we do suggest that you always build your own Perl from
+the source code, both for maximal configurability and for security,
+in case you are in a hurry you can check
+http://www.perl.com/CPAN/ports/index.html for binary distributions.
+
+=head1 SEE ALSO
+
+L<perlaix>, L<perlapollo>, L<perlamiga>, L<perlbeos>, L<perlbs200>,
+L<perlce>, L<perlcygwin>, L<perldgux>, L<perldos>, L<perlepoc>, L<perlebcdic>,
+L<perlhurd>, L<perlhpux>, L<perlmachten>, L<perlmacos>, L<perlmint>,
+L<perlmpeix>, L<perlnetware>, L<perlos2>, L<perlos390>, L<perlplan9>,
+L<perlqnx>, L<perlsolaris>, L<perltru64>, L<perlunicode>,
+L<perlvmesa>, L<perlvms>, L<perlvos>, L<perlwin32>, and L<Win32>.
=head1 AUTHORS / CONTRIBUTORS
-Chris Nandor E<lt>pudge@pobox.comE<gt>,
-Gurusamy Sarathy E<lt>gsar@umich.eduE<gt>,
-Peter Prymmer E<lt>pvhp@forte.comE<gt>,
-Tom Christiansen E<lt>tchrist@perl.comE<gt>,
-Nathan Torkington E<lt>gnat@frii.comE<gt>,
-Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>,
-Matthias Neercher E<lt>neeri@iis.ee.ethz.chE<gt>,
-Charles Bailey E<lt>bailey@genetics.upenn.eduE<gt>,
-Luther Huffman E<lt>lutherh@stratcom.comE<gt>,
-Gary Ng E<lt>71564.1743@CompuServe.COME<gt>,
-Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>,
-Paul J. Schinder E<lt>schinder@pobox.comE<gt>,
-Tom Phoenix E<lt>rootbeer@teleport.comE<gt>,
-Hugo van der Sanden E<lt>h.sanden@elsevier.nlE<gt>,
-Dominic Dunlop E<lt>domo@vo.luE<gt>,
-Dan Sugalski E<lt>sugalskd@ous.eduE<gt>,
-Andreas J. Koenig E<lt>koenig@kulturbox.deE<gt>,
-Andrew M. Langmead E<lt>aml@world.std.comE<gt>,
-Andy Dougherty E<lt>doughera@lafcol.lafayette.eduE<gt>,
-Abigail E<lt>abigail@fnx.comE<gt>.
-
-This document is maintained by Chris Nandor.
+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 <neeri@iis.ee.ethz.ch>,
+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>.
=head1 VERSION
-Version 1.23, last modified 10 July 1998.
-
+Version 1.50, last modified 10 Jul 2001
https://perl5.git.perl.org / perl5.git / blobdiff