Scheduling tasks using Cron

Overview

• In this lesson we are going to learn how to automate routine tasks on the Raspberry Pi.
• This is helpful is ever you need to back up files, upload content to a web server or sample data from a sensor.
• Cron is a program that was designed to schedule routine tasks (commands, scripts or programs) on Linux systems, such as the Raspberry Pi.
• The command crontab is used to edit the list of scheduled tasks.
• Each user on the computer has their own cron table, so you can think of cron as your own personal assistant.
• In this lesson we will automate the running of the atm_sensor_get.py python program using cron.

Learning Objectives

• Running python programs from the Terminal
• Learn how to find the directory path to applications and programs on your computer
• Learn how to use the text editing software nano
• Learn how to create scheduled tasks in cron

Running python programs from the Terminal

• In this example we are going to run the atm_sensor_get.py program using the Terminal.
• Up to now, we have only run python programs from within the Python3 IDLE3 environment.
• To run our atm_sensor_get.py program we will use the command python3.

Open the Terminal and navigate to your project’s directory

• From the Raspberry Pi top bar menu click on the Terminal icon.
• Once in your default home directory (/home/pi) enter ls to list all contents.
• Find your project’s directory (e.g. botanica-park-lake) and use the change directory (cd) command to enter the directory (e.g. cd botanica-park-lake)
• Enter the command ls to list all directory contents.

• You should see the python file atm_sensor_get.py
• To run this file, enter the command python3 atm_sensor_get.py
  • python3 – name of application
  • atm_sensor_get.py – script or program to run
• The printouts we can see in the Terminal are the outputs from print() statements within our python code.

Finding the directory path to applications and python programs

• In this example we will find the path of the python3 application and scratch on the Raspberry Pi.
• A path shows the location where a software application can be found within the directory structure on your computer.
• To find the path for an application we use the Terminal command which followed by the name of the software application.

Open the Terminal and navigate to your project’s directory

• From the Raspberry Pi top bar menu click on the Terminal icon.
• Once in your default home directory (/home/pi) enter ls to list all contents.
• Find your project’s directory (e.g. botanica-park-lake) and use the change directory (cd) command to enter the directory (e.g. cd botanica-park-lake)
• Enter the command ls to list all directory contents.