transient information about idiosyncrasies of some of the ports, almost
all of which are in a state of constant evolution. Thus, this material
should be considered a perpetual work in progress
-(<IMG SRC="yellow_sign.gif" ALT="Under Construction">).
+(C<< <IMG SRC="yellow_sign.gif" ALT="Under Construction"> >>).
=head1 ISSUES
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
+ 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", 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.
+There may well be others. For example, on an EBCDIC implementation such
+as z/OS or OS/400 the above material is similar to "Unix" but the code
+numbers change:
+
+ LF eq \025 eq \x15 eq chr(21) eq CP-1047 21
+ LF eq \045 eq \x25 eq \cU eq chr(37) eq CP-0037 37
+ CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-1047 13
+ CR eq \015 eq \x0D eq \cM eq chr(13) eq CP-0037 13
+
+ | z/OS | OS/400 |
+ ----------------------
+ \n | LF | LF |
+ \r | CR | CR |
+ \n * | LF | LF |
+ \r * | CR | CR |
+ ----------------------
+ * text-mode STDIO
=head2 Numbers endianness and Width
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.
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.
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
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.
+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.
+Whitespace in filenames is tolerated on most systems, but not all,
+and even on systems where it might be tolerated, some utilities
+might become confused by such whitespace.
+
Many systems (DOS, VMS) cannot have more than one 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.
+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(FILE, "< $existing_file") or die $!;
+ 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.)
+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 (MacOS 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
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 the 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()>.
+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
=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'.
+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
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,
+not-- unfortunately. Thus the notion of user id, or "home" directory,
or even the state of being logged-in, may be unrecognizable on many
platforms. If you write programs that are security-conscious, it
is usually best to know what type of system you will be running
under so that you can write code explicitly for that platform (or
class of platforms).
+Don't assume the UNIX filesystem access semantics: the operating
+system or the filesystem may be using some ACL systems, which are
+richer languages than the usual rwx. Even if the rwx exist,
+their semantics might be different.
+
+(From security viewpoint testing for permissions before attempting to
+do something is silly anyway: if one tries this, there is potential
+for race conditions-- someone or something might change the
+permissions between the permissions check and the actual operation.
+Just try the operation.)
+
+Don't assume the UNIX user and group semantics: especially, don't
+expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work
+for switching identities (or memberships).
+
+Don't assume set-uid and set-gid semantics. (And even if you do,
+think twice: set-uid and set-gid are a known can of security worms.)
+
=head2 Style
For those times when it is necessary to have platform-specific code,
programs to aid in the testing, or when (as noted above) the tests
assume certain things about the filesystem and paths. Be careful
not to depend on a specific output style for errors, such as when
-checking C<$!> after an system call. Some platforms expect a certain
+checking C<$!> after a system call. Some platforms expect a certain
output format, and perl on those platforms may have been adjusted
accordingly. Most specifically, don't anchor a regex when testing
an error value.
--------------------------------------------
AIX aix aix
BSD/OS bsdos i386-bsdos
+ Darwin darwin darwin
dgux dgux AViiON-dgux
DYNIX/ptx dynixptx i386-dynixptx
FreeBSD freebsd freebsd-i386
The C<$^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 98 MSWin32 MSWin32-x86
- Windows NT MSWin32 MSWin32-x86
- Windows NT MSWin32 MSWin32-ALPHA
- Windows NT MSWin32 MSWin32-ppc
- Cygwin cygwin
+ 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
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>.
+ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L<perlos2>.
=item *
(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
+ C<< $ perl -ne "print if /perl_setup/i" >system>notices >>
+ C<< $ perl -ne "print if /perl_setup/i" /system/notices >>
or even a mixture of both as in:
- $ perl -ne "print if /perl_setup/i" >system/notices
+ C<< $ perl -ne "print if /perl_setup/i" >system/notices >>
Even though VOS allows the slash character to appear in object
names, because the VOS port of Perl interprets it as a pathname
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.
+Perl on VOS can be built using two different compilers and two different
+versions of the POSIX runtime. The recommended method for building full
+Perl is with the GNU C compiler and the generally-available version of
+VOS POSIX support. See F<README.vos> (installed as L<perlvos>) for
+restrictions that apply when Perl is built using the VOS Standard C
+compiler or the alpha version of VOS POSIX support.
The value of C<$^O> on VOS is "VOS". To determine the architecture that
you are running on without resorting to loading all of C<%Config> you
=item *
-F<README.vos>
+F<README.vos> (installed as L<perlvos>)
=item *
There is no specific mailing list for Perl on VOS. You can post
comments to the comp.sys.stratus newsgroup, or subscribe to the general
-Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in
+Stratus mailing list. Send a letter with "subscribe Info-Stratus" in
the message body to majordomo@list.stratagy.com.
=item *
-VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html
+VOS Perl on the web at http://ftp.stratus.com/pub/vos/posix/posix.html
=back
Access permissions are mapped onto VOS access-control list changes. (VOS)
+The actual permissions set depend on the value of the C<CYGWIN>
+in the SYSTEM environment settings. (Cygwin)
+
=item chown LIST
Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS)
Does not automatically flush output handles on some platforms.
(SunOS, Solaris, HP-UX)
+=item exit EXPR
+
+=item exit
+
+Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
+mapping the C<1> to SS$_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$_NORMAL
+(C<1>); this mapping cannot be overridden. Any other argument to exit()
+is used directly as Perl's exit status. (VMS)
+
=item fcntl FILEHANDLE,FUNCTION,SCALAR
Not implemented. (Win32, VMS)
Not implemented. (Win32, Plan9)
-=item setpwent
-
-Not implemented. (S<Mac OS>, Win32, S<RISC OS>)
-
-=item setgrent
-
-Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>)
-
=item sethostent STAYOPEN
Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>)
Not implemented. (Plan9, Win32)
-=item exit EXPR
-
-=item exit
-
-Emulates UNIX exit() (which considers C<exit 1> to indicate an error) by
-mapping the C<1> to SS$_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$_NORMAL
-(C<1>); this mapping cannot be overridden. Any other argument to exit()
-is used directly as Perl's exit status. (VMS)
-
=item getsockopt SOCKET,LEVEL,OPTNAME
-Not implemented. (S<Mac OS>, Plan9)
+Not implemented. (Plan9)
=item glob EXPR
=item select RBITS,WBITS,EBITS,TIMEOUT
-Only implemented on sockets. (Win32)
+Only implemented on sockets. (Win32, VMS)
Only reliable on sockets. (S<RISC OS>)
-Note that the C<socket FILEHANDLE> form is generally portable.
+Note that the C<select FILEHANDLE> form is generally portable.
=item semctl ID,SEMNUM,CMD,ARG
=item setgrent
-Not implemented. (MPE/iX, Win32)
+Not implemented. (S<Mac OS>, MPE/iX, VMS, Win32, VMS, S<RISC OS>)
=item setpgrp PID,PGRP
=item setpwent
-Not implemented. (MPE/iX, Win32)
+Not implemented. (S<Mac OS>, MPE/iX, Win32, S<RISC OS>)
=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
-Not implemented. (S<Mac OS>, Plan9)
+Not implemented. (Plan9)
=item shmctl ID,CMD,ARG
'not numeric' warnings.
mtime and atime are the same thing, and ctime is creation time instead of
-inode change time. (S<Mac OS>)
+inode change time. (S<Mac OS>).
+
+ctime not supported on UFS (S<Mac OS X>).
+
+ctime is creation time instead of inode change time (Win32).
device and inode are not meaningful. (Win32)
=item system LIST
+In general, do not assume the UNIX/POSIX semantics that you can shift
+C<$?> right by eight to get the exit value, or that C<$? & 127>
+would give you the number of the signal that terminated the program,
+or that C<$? & 128> would test true if the program was terminated by a
+coredump. Instead, use the POSIX W*() interfaces: for example, use
+WIFEXITED($?) and WEXITVALUE($?) to test for a normal exit and the exit
+value, WIFSIGNALED($?) and WTERMSIG($?) for a signal exit and the
+signal. Core dumping is not a portable concept, so there's no portable
+way to test for that.
+
Only implemented if ToolServer is installed. (S<Mac OS>)
As an optimization, may not call the command shell specified in
=item utime LIST
-Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>)
+Only the modification time is updated. (S<BeOS>, S<Mac OS>, VMS, S<RISC OS>)
May not behave as expected. Behavior depends on the C runtime
library's implementation of utime(), and the filesystem being
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
+distribution available at http://www.cpan.org/src/index.html
AIX
AmigaOS
DG/UX
DOS DJGPP 1)
DYNIX/ptx
- EPOC
+ EPOC R5
FreeBSD
HP-UX
IRIX
Netware
The following platforms have their own source code distributions and
-binaries available via http://www.perl.com/CPAN/ports/index.html:
+binaries available via http://www.cpan.org/ports/
Perl release
Tandem Guardian 5.004
The following platforms have only binaries available via
-http://www.perl.com/CPAN/ports/index.html :
+http://www.cpan.org/ports/index.html :
Perl release
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.
+http://www.cpan.org/ports/index.html for binary distributions.
=head1 SEE ALSO
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>,
+Matthias Neeracher <neeracher@mac.com>,
Philip Newton <pne@cpan.org>,
Gary Ng <71564.1743@CompuServe.COM>,
Tom Phoenix <rootbeer@teleport.com>,
Dan Sugalski <dan@sidhe.org>,
Nathan Torkington <gnat@frii.com>.
-=head1 VERSION
-
-Version 1.50, last modified 10 Jul 2001