With any system, it's useful to be able to log data when something happens. We can do this with our detectors too by writing to a log file every time a detector in a zone is triggered. This way, you can keep a log of every time someone enters a room, which you can review at a later date even if the system isn't armed. You can also keep a log of when the system is armed and disarmed.
Here's a simple script that shows you how to do this whenever an event happens on our zones connected to the GPIO inputs:
#!/bin/bash
#set up the I2C expansion port
sudo i2cset –y 1 0x20 0x00 0xFF
#reset status
CURR_STATE="0x00"
LAST_STATE="0x00"
#path to the log file
LOG_FILE="/etc/pi-alarm/zones.log"
# loop forever
while true
do
# read the gpio inputs
CURR_STATE=$(sudo i2cget –y 1 0x20 0x12)
#check if state has changed
if [ "$CURR_STATE" != "$LAST_STATE" ]
then
#write change to log file
TIMESTAMP=`date "+%Y-%m-%d %H:%M:%S"`
echo "$TIMESTAMP Zone Status...