#!/usr/bin/perl
# tp-theft v0.1 ([url]http://thinkwiki.org/wiki/Script_for_theft_alarm_using_HDAPS[/url])
# This script uses the HDAPS accelerometer found on recent ThinkPad models
# to emit an audio alarm when the laptop is tilted. In sufficiently
# populated environments, it can be used as a laptop theft deterrent.
#
# This file is placed in the public domain and may be freely distributed.
use strict;
use warnings;
##############################
# Checks
# Here `lsmod` is in list context and returns the output of lsmod as a list of lines
# grep filters lists, returning only the line that matches the /hdaps/ regexp
unless ( grep { /hdaps/ } `lsmod` ) {
system 'modprobe', ( 'hdaps' ); sleep(1);
}
if ( `fuser /dev/dsp` ) {
system 'fuser', ( '-k' => '/dev/dsp' ) and die 'fuser -k /dev/dsp failed';
}
# system returns 0 on success which is the same as false in perl
# which is why we use 'and die ...' to report an error with the system call
# Audio volume (0..100)
my $volume = 100;
#Synthesize a siren for 1.0 seconds:
my $play_cmd = "sox -n -t ossdsp /dev/dsp -d synth 0.6 sine 800-1600 >/dev/null 2>&1";
#Play a file:
#my $play_cmd = ";
##############################
# Other tweakables
my $thresh = 0.20; # tilt threshold (increase value to decrease sensitivity)
my $interval = 0.5; # sampling interval in seconds
my $depth = 10; # number of recent samples to analyze
my $pos_file='/sys/devices/platform/hdaps/position';
my $verbose = 1;
##############################
# Code
sub get_pos {
open(POS,"<",$pos_file) or die "Can't open HDAPS file $pos_file: $!\n";
$_=<POS>;
m/^\((-?\d+),(-?\d+)\)$/ or die "Can't parse $pos_file content\n";
return ($1,$2);
}
sub stddev {
my $sum=0;
my $sumsq=0;
my $n=$#_+1;
for my $v (@_) {
$sum += $v;
$sumsq += $v*$v;
}
return sqrt($n*$sumsq - $sum*$sum)/($n*($n-1));
}
my (@XHIST, @YHIST);
my ($x,$y) = get_pos;
for (1..$depth) {
push(@XHIST,$x);
push(@YHIST,$y);
}
my $alarm_file; # flags ongoing alarm (and stores saved mixer settings)
while (1) {
my ($x,$y) = get_pos;
shift(@XHIST); push(@XHIST,$x);
shift(@YHIST); push(@YHIST,$y);
my $xdev = stddev(@XHIST);
my $ydev = stddev(@YHIST);
# Print variance and history
print "X: v=$xdev (".join(',',@XHIST).") Y: v=$ydev (".join(",",@YHIST).")\n" if $verbose>1;
my $tilted = $xdev>$thresh || $ydev>$thresh;
if ($tilted && !(defined($alarm_file) && -f $alarm_file)) {
print "ALARM\n" if $verbose>0;
$alarm_file = `mktemp /tmp/hdaps-tilt.XXXXXXXX` or die "mktemp: $?";
chomp($alarm_file);
system('/bin/bash', '-c', <<"EOF")==0 or die "Failed: $?";
( trap \"aumix -L -f $alarm_file > /dev/null; rm -f $alarm_file" EXIT HUP QUIT TERM
aumix -S -f $alarm_file &&
aumix -v $volume -w 100 &&
$play_cmd) &
EOF
}
select(undef, undef, undef, $interval); # sleep
}
