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 +");
	#system("totem --quit");
	#system("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");
	#system("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 && $value == 1) # USER button pressed
	{
	printf("Restarting due to USER button press\n");
	#system("totem --next");
	system("killall -15 mplayer");
	sleep(1);
	system("killall -9 mplayer");
	sleep(1);
	system($cmdline_start);
	}
	}
	}

view raw play_movie.pl hosted with ❤ by GitHub