diff options
Diffstat (limited to 'pod/perlport.pod')
| -rw-r--r-- | pod/perlport.pod | 62 |
1 files changed, 38 insertions, 24 deletions
diff --git a/pod/perlport.pod b/pod/perlport.pod index a2c798f8cc..4234fcd797 100644 --- a/pod/perlport.pod +++ b/pod/perlport.pod @@ -196,6 +196,8 @@ transfer and store numbers always in text format, instead of raw binary, or consider using modules like Data::Dumper (included in the standard distribution as of Perl 5.005) and Storable. +Also, don't depend on specific values returned from C<printf> and +C<sprintf>. These in some cases may differ from platform to platform. =head2 Files and Filesystems @@ -257,7 +259,7 @@ Also of use is File::Basename, from the standard distribution, which splits a pathname into pieces (base filename, full path to directory, and file suffix). -Even when on a single platform (if you can call UNIX a single platform), +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 system-specific files or directories, like F</etc/passwd>, F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For @@ -343,27 +345,25 @@ often behave differently, and often represent their results in a 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 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. +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. 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) @@ -415,6 +415,13 @@ 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<$offset> can then be added to a Unix time value +to get what should be the proper value on any system. =head2 Character sets and character encoding @@ -432,7 +439,7 @@ before the 'b'. =head2 Internationalisation If you may assume POSIX (a rather large assumption, that in practice -means UNIX), you may read more about the POSIX locale system (see +means Unix), you may read more about the POSIX locale system from L<perllocale>. The locale system at least attempts to make things a little bit more portable, or at least more convenient and native-friendly for non-English users. The system affects character @@ -479,6 +486,11 @@ to other platforms easier. Use the Config module and the special variable C<$^O> to differentiate platforms, as described in L<"PLATFORMS">. +Be careful in the tests you supply with your module or programs. Often +module code is fully portable, but the tests are not. This occurs +often 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 C<eval>. Some platforms expect a certain output format, and perl on those platforms may @@ -535,30 +547,29 @@ field of the string returned by typing C<uname -a> (or a similar command) at the shell prompt. Here, for example, are a few of the more popular Unix flavors: - uname $^O $Config{'archname'} + uname $^O $Config{'archname'} -------------------------------------------- - AIX aix aix + AIX aix aix BSD/OS bsdos i386-bsdos dgux dgux AViiON-dgux DYNIX/ptx dynixptx i386-dynixptx - FreeBSD freebsd freebsd-i386 - Linux linux i386-linux + FreeBSD freebsd freebsd-i386 + Linux linux i386-linux Linux linux i586-linux Linux linux ppc-linux - HP-UX hpux PA-RISC1.1 - IRIX irix irix + HP-UX hpux PA-RISC1.1 + IRIX irix irix openbsd openbsd i386-openbsd - OSF1 dec_osf alpha-dec_osf + OSF1 dec_osf alpha-dec_osf reliantunix-n svr4 RM400-svr4 SCO_SV sco_sv i386-sco_sv SINIX-N svr4 RM400-svr4 sn4609 unicos CRAY_C90-unicos sn6521 unicosmk t3e-unicosmk sn9617 unicos CRAY_J90-unicos - sn9716 unicos CRAY_J90-unicos - SunOS solaris sun4-solaris - SunOS solaris i86pc-solaris - SunOS4 sunos sun4-sunos + SunOS solaris sun4-solaris + SunOS solaris i86pc-solaris + SunOS4 sunos sun4-sunos Note that because the C<$Config{'archname'}> may depend on the hardware architecture it may vary quite a lot, much more than the C<$^O>. @@ -1603,6 +1614,8 @@ Not useful. (S<RISC OS>) =over 4 +=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. @@ -1675,6 +1688,7 @@ Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>, Andreas J. KE<ouml>nig E<lt>koenig@kulturbox.deE<gt>, Markus Laker E<lt>mlaker@contax.co.ukE<gt>, Andrew M. Langmead E<lt>aml@world.std.comE<gt>, +Larry Moore E<lt>ljmoore@freespace.netE<gt>, Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>, Chris Nandor E<lt>pudge@pobox.comE<gt>, Matthias Neeracher E<lt>neeri@iis.ee.ethz.chE<gt>, @@ -1693,4 +1707,4 @@ E<lt>pudge@pobox.comE<gt>. =head1 VERSION -Version 1.41, last modified 19 May 1999 +Version 1.42, last modified 22 May 1999 |