Re: How to have OS specific code sections in Perl

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Re^2: How to have OS specific code sections in Perl by aitap (Curate) on Oct 31, 2012 at 18:54 UTC
Unfortunately, this is not going to work because $LINUX is undef at compile-time: $ perl if ($^O eq 'linux') { $LINUX=1; }; use if $LINUX, 'MIDI::ALSA' => ('SND_SEQ_EVENT_PORT_UNSUBSCRIBED', 'SND_SEQ_EVENT_SYSEX'); __END__ $ perl -MMIDI::ALSA Can't locate MIDI/ALSA.pm in @INC (@INC contains: /home/aitap/perl5/li +b/perl5/i486-linux-gnu-thread-multi-64int /home/aitap/perl5/lib/perl5 +/i486-linux-gnu-thread-multi-64int /home/aitap/perl5/lib/perl5 /etc/p +erl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/ +perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/l +ocal/lib/site_perl .). BEGIN failed--compilation aborted. [download] But if the test is done in the `BEGIN{}` section, everything works (well, not for me because of the absence of the module): $ perl BEGIN{ if ($^O eq 'linux') { $LINUX=1; }; } use if $LINUX, 'MIDI::ALSA' => ('SND_SEQ_EVENT_PORT_UNSUBSCRIBED', 'SND_SEQ_EVENT_SYSEX'); Can't locate MIDI/ALSA.pm in @INC (@INC contains: /home/aitap/perl5/li +b/perl5/i486-linux-gnu-thread-multi-64int /home/aitap/perl5/lib/perl5 +/i486-linux-gnu-thread-multi-64int /home/aitap/perl5/lib/perl5 /etc/p +erl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/ +perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/l +ocal/lib/site_perl .) at /usr/share/perl/5.14/if.pm line 13. BEGIN failed--compilation aborted at - line 3. [download] Sorry if my advice was wrong.	[reply] [d/l] [select]
Re^3: How to have OS specific code sections in Perl by perltux (Monk) on Oct 31, 2012 at 19:02 UTC
Thank you, that explains why I had to use: `use if ($^O eq 'linux'), 'MIDI::ALSA'` and why any other alternative with $LINUX I tried didn't work!	[reply] [d/l]
Re^2: How to have OS specific code sections in Perl by perltux (Monk) on Oct 31, 2012 at 17:36 UTC
Thanks, this works great (apart from the second 'use' after the comma in the 'use if' line which is incorrect) and does exactly what I wanted!	[reply]
Re^3: How to have OS specific code sections in Perl by toolic (Bishop) on Oct 31, 2012 at 17:43 UTC
You're welcome. Thanks for pointing out the copy'n'paste error; I updated the post to delete it.	[reply]
Re^2: How to have OS specific code sections in Perl by perltux (Monk) on Oct 31, 2012 at 18:43 UTC
The 'use if' line seems to work only if written as follows: `use if ($^O eq 'linux'), 'MIDI::ALSA' => ('SND_SEQ_EVENT_PORT_UNSUBSCR +IBED', 'SND_SEQ_EVENT_SYSEX');` [download] Any other way to write the 'use if' CONDITION doesn't seem to work. Weird...	[reply] [d/l]
Re^2: How to have OS specific code sections in Perl by perltux (Monk) on Oct 31, 2012 at 18:00 UTC
Actually unfortunately I spoke to soon, the code now works fine in Windows (no errors anymore) but now I get an error in Linux: Undefined subroutine &MIDI::ALSA::client called at ./test.pl line 15 It looks like the 'use if' line needs some more tweaking to work correctly, but how?	[reply]
Re^3: How to have OS specific code sections in Perl by tobyink (Canon) on Oct 31, 2012 at 18:44 UTC
The problem is that the conditional block is only evaluated at run time, by which time it's too late for `use if`. You want: `my $LINUX; BEGIN { $LINUX = ($^O eq 'linux') }; use if $LINUX, 'MIDI::ALSA' => ('SND_SEQ_EVENT_PORT_UNSUBSCRIBED', 'SN +D_SEQ_EVENT_SYSEX');` [download] Or better: `use if ($^O eq 'linux'), 'MIDI::ALSA' => ('SND_SEQ_EVENT_PORT_UNSUBSCR +IBED', 'SND_SEQ_EVENT_SYSEX');` [download] `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re^3: How to have OS specific code sections in Perl by Anonymous Monk on Nov 01, 2012 at 00:56 UTC
Re^3: code that runs (and works) on both Linux and Win32, Devel::AssertOS, Devel::CheckOS, Re: mention a non-installed module in script, Perl::OSType, Module::Loaded `use if eval { require MIDI::ALSA; MIDI::ALSA->VERSION > 0.01; 1 } , 'M +IDI::ALSA', ...; use if not exist $INC{'MIDI/ALSA.pm'}, 'something::else', ...;` [download]	[reply] [d/l]


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