Devel::AssertOS::ExtenUser(Contributed Perl DocumDevel::AssertOS::Extending(3)NAMEDevel::AssertOS::Extending - how to write Devel::AssertOS::* modules
that check what platform they're running on
DESCRIPTION
Devel::AssertOS::* modules are used by Devel::CheckOS to figure out
what OS it is running on. A set of modules are provided which should
correctly detect all platforms that perl *currently* runs on, as well
as detecting OS 'families' like 'Unix' and 'Windows'.
You can also use Devel::AssertOS::* modules on their own to quickly
check whether you're running on the right platform.
If you try to "use" a Devel::AssertOS module on the wrong platform, it
will "die" by calling "Devel::CheckOS::die_unsupported()". This
conveniently spits out the text that CPAN-testers look for to see if
your code failed simply because they're doing something as silly as
testing your Solaris-only code on HPUX.
HOW TO WRITE YOUR OWN MODULES
If you want to add support for new platforms, you need to write a
module called Devel::AssertOS::PlatformName which looks like:
package Devel::AssertOS::Linux;
use Devel::CheckOS;
$VERSION = '1.0';
sub os_is { $^O eq 'linux' ? 1 : 0; }
Devel::CheckOS::die_unsupported() unless(os_is());
1;
And that's it. The subroutine must be called "os_is" and loading the
module must die in precisely that manner if your code is running on the
wrong platform. Note that it is an error to say:
sub os_is { 1; }
and assume "well, on the wrong platform that'll never get reached
because the module can't load". Because the module *can* load, and
indeed *does get loaded* - some functions in Devel::CheckOS do things
like:
eval "use Devel::AssertOS::$os";
to suppress the error.
If you want to support a 'family' of OSes, then instead of matching
against $^O, instead use "Devel::CheckOS::os_is" to check that we're
running on any of the OSes in your family, like this:
match any of several values of $^O like this:
package Devel::AssertOS::FreeSoftware;
use Devel::CheckOS;
$VERSION = '1.0';
sub matches { return qw(Linux FreeBSD NetBSD OpenBSD DragonflyBSD); }
sub os_is { Devel::CheckOS::os_is(matches()); }
sub expn { "The operating system is some version of Microsoft Windows" }
Devel::CheckOS::die_unsupported() unless(os_is());
You may also add a subroutine called "expn" which should return a small
snipper of explanatory text. Again, see Devel::AssertOS::Unix for an
example. This is particularly useful for 'family' modules.
Note the "matches" subroutine - this is so that people can query your
module and see what OSes are in your family.
VERSIONS OF AN OS
Two levels of name are supported. So "Devel::AssertOS::Linux::v2_6" is
legal. More than two levels are not supported. Be careful to pick
names that are both legal perl package names and legal filenames on all
platforms. In general, this means anything that matches
"/[_a-z]\w*/i".
OS FEATURES
I would like to reserve the namespace "Devel::AssertOS::OSFeatures::*".
If you want to release a module that tells the user whether a
particular feature is available (eg, whether POSIX shell redirection
can be expected to work) then please discuss it with me first.
BUGS and FEEDBACK
I welcome feedback about my code, including constructive criticism.
Bug reports should be made using <http://rt.cpan.org/> or by email.
If you are feeling particularly generous you can encourage me in my
open source endeavours by buying me something from my wishlist:
<http://www.cantrell.org.uk/david/wishlist/>
SEE ALSO
Devel::CheckOS
$^O in perlvar
perlport
AUTHOR
David Cantrell <david@cantrell.org.uk>
Thanks to David Golden for the name and ideas about the interface, and
for the cpan-testers-discuss mailing list for prompting me to write it
in the first place.
COPYRIGHT and LICENCE
Copyright 2007 - 2008 David Cantrell
This documentation is free-as-in-speech. It may be used, distributed
and modified under the terms of the Creative Commons Attribution-Share
Alike 2.0 UK: England & Wales License, whose text you may read at
http://creativecommons.org/licenses/by-sa/2.0/uk/
<http://creativecommons.org/licenses/by-sa/2.0/uk/>.
CONSPIRACY
This documentation is also free-as-in-mason.
perl v5.14.1 2009-04-14 Devel::AssertOS::Extending(3)
