This time, we monitor (and possibly control) a very slow system (a growing plant). So, using a simple Bash script is more than appropriate, while the web interface can be implemented by using two little HTML (with JavaScript) and PHP scripts. The real difficulty, apart from getting access to the peripherals, is using the Facebook API in order to get access to an account.

Apropos the monitoring loop and the web interface, there is a major issue, that is, the Inter Process Communication (IPC) system to use in order to exchange data between them. In Chapter 1, Dangerous Gas Sensors, we mainly used a MySQL server to store the system's data and configuration settings. But we also used it to exchange data between the different tasks composing the system! However, this time, we have very few data to store and using a database may be very expensive. So, I decided to use a simple way to solve the problem: I'm going to use a file! Yes, by using a normal file with a well-defined...