Perl code, so that once you have made your 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,
+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 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
Be aware of two important points:
+
=over 4
=item Not all Perl programs have to be portable
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 The vast majority of Perl 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
code. That way, you don't sacrifice much by way of the implementation
(E<lt>IMG SRC="yellow_sign.gif" ALT="Under Construction"E<gt>).
-
-
=head1 ISSUES
=head2 Newlines
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>.
+C<\015\012>. C<\015\012> is commonly referred to as CRLF.
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"
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, 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 C<Socket> module supplies the Right Thing for those who want it.
+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<$/> as
+When reading from a socket, remember that the default input record
+separator C<$/> is C<\n>, but code like this should recognize C<$/> as
C<\012> or C<\015\012>:
while (<SOCKET>) {
# ...
}
-Better:
+Since both CRLF and LF end in LF, the input record separator can
+be set to LF, and the CR can be stripped later, if present. Better:
use Socket qw(:DEFAULT :crlf);
local($/) = LF; # not needed if $/ is already \012
platforms, because now any C<\015>'s (C<\cM>'s) are stripped out
(and there was much rejoicing).
-An important thing to remember is that functions that return data
-should translate newlines when appropriate. Often one line of code
-will suffice:
+Similarly, functions that return text data--such as a function that
+fetches a web page--should, in some cases, translate newlines before
+returning the data, if they've not yet been trsnalted to the local
+newline. Often one line of code will 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
+
+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
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). This affects your programs if they attempt to transfer
-numbers in binary format from a CPU architecture to another over some
-channel: either 'live' via network connections or storing the numbers
-to secondary storage such as a disk file.
+numbers in binary format from one CPU architecture to another over some
+channel, usually either "live" via network connection, or by storing the
+numbers to secondary storage such as a disk file.
Conflicting storage orders make utter mess out of the numbers: if a
little-endian host (Intel, Alpha) stores 0x12345678 (305419896 in
decimal), a big-endian host (Motorola, MIPS, Sparc, PA) reads it as
0x78563412 (2018915346 in decimal). To avoid this problem in network
-(socket) connections use the C<pack()> and C<unpack()> formats C<"n">
-and C<"N">, the "network" orders, they are guaranteed to be portable.
+(socket) connections use the C<pack> and C<unpack> formats C<n>
+and C<N>, the "network" orders. They are guaranteed to be portable.
Different widths can cause truncation even between platforms of equal
endianness: the platform of shorter width loses the upper parts of the
One can circumnavigate both these problems in two ways: either
transfer and store numbers always in text format, instead of raw
-binary, or consider using modules like C<Data::Dumper> (included in
-the standard distribution as of Perl 5.005) and C<Storable>.
+binary, or consider using modules like Data::Dumper (included in
+the standard distribution as of Perl 5.005) and Storable.
+
=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.
+notion of a "path" to uniquely identify a file on the system. How
+that path is actually written differs.
While they are 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 idea of a single
root directory.
-VMS, Windows, and OS/2 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:).
+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 hard links (C<link>) nor
+symbolic links (C<symlink>, C<readlink>, C<lstat>).
-The filesystem may not support neither access timestamp nor change
+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).
native pathname characters greater-than, less-than, number-sign, and
percent-sign are always accepted.
-C<RISC OS> perl can emulate Unix filenames with C</> as path
+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 filing systems and disc names.
+signal filesystems and disk names.
-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
+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;
- chdir(File::Spec->updir()); # go up one directory
- $file = File::Spec->catfile(
- File::Spec->curdir(), 'temp', 'file.txt'
- );
+ use File::Spec::Functions;
+ chdir(updir()); # go up one directory
+ $file = catfile(curdir(), 'temp', 'file.txt');
# on Unix and Win32, './temp/file.txt'
# on Mac OS, ':temp:file.txt'
This is especially noticeable in scripts like Makefiles and test suites,
which often assume C</> as a path separator for subdirectories.
-Also of use is C<File::Basename>, from the standard distribution, which
+Also of use is File::Basename, from the standard distribution, which
splits a pathname into pieces (base filename, full path to directory,
and file suffix).
system-specific files or directories, like F</etc/passwd>,
F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For
example, F</etc/passwd> may exist but it may not contain the encrypted
-passwords because the system is using some form of enhanced security --
+passwords because the system is using some form of enhanced security,
or it may not contain all the accounts because the system is using NIS.
If code does need to rely on such a file, include a description of the
file and its format in the code's documentation, and make it easy for
in the names, and keep them to the 8.3 convention, for maximum
portability.
-Likewise, if using C<AutoSplit>, try to keep the split functions to
+Likewise, if using the AutoSplit module, try to keep the split functions to
8.3 naming and case-insensitive conventions; or, at the very least,
make it so the resulting files have a unique (case-insensitively)
first 8 characters.
-There certainly can be whitespace in filenames. Many systems (DOS,
-VMS) cannot have more than one C<"."> in their filenames.
+There certainly can be whitespace in filenames on most systems, but
+some may not allow it. Many systems (DOS, VMS) cannot have more than
+one C<.> in their filenames.
Don't assume C<E<gt>> won't be the first character of a filename.
Always use C<E<lt>> explicitly to open a file for reading.
- open(FILE, "<$existing_file") or die $!;
+ open(FILE, "< $existing_file") or die $!;
-Actually, though, if filenames might use strange characters, it is
-safest to open it with C<sysopen> instead of C<open>, which is magic.
+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<E<gt>>, C<E<lt>>, and C<|>, which may
+be the wrong thing to do.
=head2 System Interaction
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.
+with, so don't stay up late worrying about it.
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 C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a
+file that is already tied or opened; C<untie> or C<close> first.
Don't open the same file more than once at a time for writing, as some
operating systems put mandatory locks on such files.
Don't count on C<%ENV> entries being case-sensitive, or even
case-preserving.
-Don't count on signals.
+Don't count on signals for anything.
Don't count on filename globbing. Use C<opendir>, C<readdir>, and
C<closedir> instead.
platform-dependent way. Thus you should seldom depend on them to produce
consistent results.
+The UNIX System V IPC (msg*(), sem*(), shm*()) is not available
+even in all UNIX platforms.
+
One especially common bit of Perl code is opening a pipe to sendmail:
- open(MAIL, '|/usr/lib/sendmail -t') or die $!;
+ open(MAIL, '| /usr/lib/sendmail -t') or die $!;
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 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).
-The UNIX System V IPC (C<msg*(), sem*(), shm*()>) is not available
-even in all UNIX platforms.
-
=head2 External Subroutines (XS)
=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 only C<NBDM_File> and C<DB_File> are
+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
+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).
+denominator (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
that variable.
Don't assume that the epoch starts at 00:00:00, January 1, 1970,
-because that is OS-specific. 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 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
+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
-C<Time::Local>.
+Time::Local.
=head2 Character sets and character encoding
Assume very little about character sets. Do not assume anything about
-the numerical values (C<ord()>, C<chr()>) of characters. Do not
+the numerical values (C<ord>, C<chr>) of characters. Do not
assume that the alphabetic characters are encoded contiguously (in
numerical sense). Do not assume anything about the ordering of the
characters. The lowercase letters may come before or after the
=head2 Internationalisation
If you may assume POSIX (a rather large assumption, that in practice
-means UNIX), you may read more about the POSIX locale system from
+means UNIX), you may read more about the POSIX locale system (see
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
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 many platforms. If
-you write programs that are security conscious, it is usually best to know
+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).
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
+to other platforms easier. Use the Config module and the special
variable C<$^O> to differentiate platforms, as described in
L<"PLATFORMS">.
+Be careful not to depend on a specific output style for errors,
+such as when checking C<$@> after an C<eval>. 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.
+
+ $@ =~ /^I got an error!/ # may fail
+ $@ =~ /I got an error!/ # probably better
+
=head1 CPAN Testers
=item Mailing list: cpan-testers@perl.org
-=item Testing results: C<http://www.connect.net/gbarr/cpan-test/>
+=item Testing results: C<http://www.perl.org/cpan-testers/>
=back
detailed information about the system, looking into C<%Config> is
certainly recommended.
+C<%Config> cannot always be trusted, however,
+because it is built at compile time, and if perl was built in once
+place and transferred elsewhere, some values may be off, or the
+values may have been edited after the fact.
+
+
=head2 Unix
Perl works on a bewildering variety of Unix and Unix-like platforms (see
at the shell prompt. Here, for example, are a few of the more popular
Unix flavors:
- uname $^O $Config{'archname'}
- -------------------------------------------
- AIX aix aix
- FreeBSD freebsd freebsd-i386
- Linux linux i386-linux
- HP-UX hpux PA-RISC1.1
- IRIX irix irix
- OSF1 dec_osf alpha-dec_osf
- SunOS solaris sun4-solaris
- SunOS solaris i86pc-solaris
- SunOS4 sunos sun4-sunos
+ uname $^O $Config{'archname'}
+ --------------------------------------------
+ AIX aix aix
+ BSD/OS bsdos i386-bsdos
+ dgux dgux AViiON-dgux
+ DYNIX/ptx dynixptx i386-dynixptx
+ FreeBSD freebsd freebsd-i386
+ Linux linux i386-linux
+ Linux linux i586-linux
+ Linux linux ppc-linux
+ HP-UX hpux PA-RISC1.1
+ IRIX irix irix
+ openbsd openbsd i386-openbsd
+ OSF1 dec_osf alpha-dec_osf
+ reliantunix-n svr4 RM400-svr4
+ SCO_SV sco_sv i386-sco_sv
+ SINIX-N svr4 RM400-svr4
+ sn4609 unicos CRAY_C90-unicos
+ sn6521 unicosmk t3e-unicosmk
+ sn9617 unicos CRAY_J90-unicos
+ sn9716 unicos CRAY_J90-unicos
+ SunOS solaris sun4-solaris
+ SunOS solaris i86pc-solaris
+ SunOS4 sunos sun4-sunos
Note that because the C<$Config{'archname'}> may depend on the hardware
architecture it may vary quite a lot, much more than the C<$^O>.
+
=head2 DOS and Derivatives
Perl has long been ported to PC style microcomputers running under
and its derivatives.
Users of these operating systems may also wish to make use of
-scripts such as I<pl2bat.bat> or I<pl2cmd> as appropriate to
+scripts such as F<pl2bat.bat> or F<pl2cmd> as appropriate to
put wrappers around your scripts.
Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from
-and writing to files. C<binmode(FILEHANDLE)> will keep C<\n> translated
-as C<\012> for that filehandle. Since it is a noop on other systems,
-C<binmode> should be used for cross-platform code that deals with binary
-data.
+and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)>
+will keep C<\n> translated as C<\012> for that filehandle. Since it is a
+no-op on other systems, C<binmode> should be used for cross-platform code
+that deals with binary data.
The C<$^O> variable and the C<$Config{'archname'}> values for various
DOSish perls are as follows:
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-ALPHA
Windows NT MSWin32 MSWin32-ppc
Also see:
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> and L<"CPAN Testers">
-for more details.
+form on CPAN.
Directories are specified as:
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.
+limited to 31 characters, and may include any character except for
+null and C<:>, which is reserved as path separator.
Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the
-C<Mac::Files> module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>.
+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
$is_ppc = $MacPerl::Architecture eq 'MacPPC';
$is_68k = $MacPerl::Architecture eq 'Mac68K';
-S<Mac OS X>, to be based on NeXT's OpenStep OS, will (in theory) be able
-to run MacPerl natively, but Unix perl will also run natively under the
-built-in Unix environment.
+S<Mac OS X> and S<Mac OS X Server>, based on NeXT's OpenStep OS, will
+(in theory) be able to run MacPerl natively, under the "Classic"
+environment. The new "Cocoa" environment (formerly called the "Yellow Box")
+may run a slightly modified version of MacPerl, using the Carbon interfaces.
+
+S<Mac OS X Server> and its Open Source version, Darwin, both run Unix
+perl natively (with a small number of patches). Full support for these
+is slated for perl5.006.
+
Also see:
=over 4
-=item The MacPerl Pages, C<http://www.ptf.com/macperl/>.
+=item The MacPerl Pages, C<http://www.macperl.com/>.
-=item The MacPerl mailing list, C<mac-perl-request@iis.ee.ethz.ch>.
+=item The MacPerl mailing lists, C<http://www.macperl.org/>.
+
+=item MacPerl Module Porters, C<http://pudge.net/mmp/>.
=back
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
+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.
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. Though 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 vmsperl list, C<vmsperl-request@newman.upenn.edu>
+=item vmsperl list, C<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>
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 8000!\n";
+
} elsif (grep(/8000/, @INC)) {
print "This box is a Stratus HP 8000!\n";
+
} else {
print "This box is a Stratus 68K...\n";
}
print "Hello from perl!\n";
+On the AS/400, assuming that PERL5 is in your library list, you may need
+to wrap your perl scripts in a CL procedure to invoke them like so:
+
+ BEGIN
+ CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl')
+ ENDPGM
+
+This will invoke the perl script F<hello.pl> in the root of the
+QOpenSys file system. On the AS/400 calls to C<system> or backticks
+must use CL syntax.
+
On these platforms, bear in mind that the EBCDIC character set may have
an effect on what happens with some perl functions (such as C<chr>,
C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as
well as bit-fiddling with ASCII constants using operators like C<^>, C<&>
and C<|>, not to mention dealing with socket interfaces to ASCII computers
-(see L<Newlines>).
+(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
As Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like
Unix and Unix filename emulation is turned on by default, it is quite
likely that most simple scripts will work "out of the box". The native
-filing system is modular, and individual filing systems are free to be
+filesystem is modular, and individual filesystems are free to be
case-sensitive or insensitive, and are usually case-preserving. Some
-native filing systems have name length limits which file and directory
-names are silently truncated to fit - scripts should be aware that the
-standard disc filing system currently has a name length limit of B<10>
-characters, with up to 77 items in a directory, but other filing systems
+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::DiscName.$.Directory.Directory.File
+ Filesystem#Special_Field::DiskName.$.Directory.Directory.File
where
The default filename translation is roughly C<tr|/.|./|;>
-Note that C<"ADFS::HardDisc.$.File" ne 'ADFS::HardDisc.$.File'> and that
+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$Path> until a name is made that points to an object on disc.
+C<System$Path> until a name is made that points to an object on disk.
Writing to a new file C<System:Modules> would only be allowed if
C<System$Path> contains a single item list. The filesystem will also
expand system variables in filenames if enclosed in angle brackets, so
appear transparent, but consider that with these rules C<foo/bar/baz.h>
and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and
C<glob> cannot and do not attempt to emulate the reverse mapping. Other
-C<.>s in filenames are translated to C</>.
+C<.>'s in filenames are translated to C</>.
As implied above the environment accessed through C<%ENV> is global, and
the convention is that program specific environment variables are of the
-form C<Program$Name>. Each filing system maintains a current directory,
-and the current filing system's current directory is the B<global> current
+form C<Program$Name>. Each filesystem maintains a current directory,
+and the current filesystem's current directory is the B<global> current
directory. Consequently, sociable scripts don't change the current
directory but rely on full pathnames, and scripts (and Makefiles) cannot
assume that they can spawn a child process which can change the current
"S<RISC OS>" is the proper name for the operating system, but the value
in C<$^O> is "riscos" (because we don't like shouting).
-Also see:
-
-=over 4
-
-=item perl list
-
-=back
-
=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, 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: 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.)
+the above categories. 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.)
See also:
=item Novell Netware
-A free perl5-based PERL.NLM for Novell Netware is available from
-C<http://www.novell.com/>
+A free perl5-based PERL.NLM for Novell Netware is available in
+precompiled binary and source code form from C<http://www.novell.com/>
+as well as from CPAN.
=back
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 C<Config.pm>. For example, to check if the platform has the C<lstat>
-call, check C<$Config{'d_lstat'}>. See L<Config.pm> for a full
+from the Config module. For example, to check if the platform has the C<lstat>
+call, check C<$Config{'d_lstat'}>. See L<Config> for a full
description of available variables.
=over 4
-=item v1.39, 11 February, 1999
+=item v1.41, 19 May 1999
+
+Lots more little changes to formatting and content.
+
+Added a bunch of <$^O> and related values
+for various platforms; fixed mail and web addresses, and added
+and changed miscellaneous notes. (Peter Prymmer)
+
+=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.
=head1 VERSION
-Version 1.39, last modified 11 February 1999
+Version 1.41, last modified 19 May 1999
projects / p5sagit/p5-mst-13.2.git / commitdiff