Using Perl to read Linux events

For a simple demo that played a movie on a BeagleBoard, I wanted to add a simple mechanism to start the movie over again if the USER button was pressed. To read a Linux input event, it is as simple as just performing a read. The only trick to this for me, however, is that I wanted the read to timeout. This was resolved by using the Perl alarm() function can catching the signal within an eval(). I've uploaded a gist of my example play_movie.pl script: #!/usr/bin/perl $ENV{'DISPLAY'} = ":0.0"; system("xhost +"); ("totem --quit"); ("nice -n -5 totem --fullscreen /home/root/playlist.xml &"); $cmdline_start = "nice -n -5 mplayer /home/root/*.mov &"; system($cmdline_start); open(FILE, "/dev/input/event0"); binmode(FILE); while(1) { eval { local $SIG{ALRM} = sub { die("Alarm!\n") }; alarm(60*28); # 28 minutes read(FILE, $buf, 16); alarm(0); }; if($@) { printf("Restarting due to timeout\n"); ("totem --next"); system("killall -15 mplayer"); sleep(1); system("killall -9 mplayer"); sleep(1); system($cmdline_start); } else { ($time1, $time2, $type, $code, $value) = unpack("iissi", $buf); printf("%f %05d %05d 0x%08x\n", $time1+$time2/1000000, $type, $code, $value); if($code == 276 && $value == 1) # USER button pressed { printf("Restarting due to USER button press\n"); ("totem --next"); system("killall -15 mplayer"); sleep(1); system("killall -9 mplayer"); sleep(1); system($cmdline_start); } } }

You can listen to Using Perl to read Linux events online on Radio and Podcast. Open the player on this page to stream the available audio.

Using Perl to read Linux events is an episode from BeagleBoard by Jason Kridner, Gerald Coley and Jeffery Osier-Mixon.

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This episode was published on Feb 28, 2011.

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