Scheduled data collection with cron in Raspberry Pi - Mini Project: Build & Apply

Scheduled Data Collection with cron on Raspberry Pi

📖 Scenario: You have a Raspberry Pi that collects temperature data from a sensor. You want to save this data into a simple text database file every minute automatically.This project will guide you to set up a cron job that runs a script to append the current temperature and timestamp to a data file.

🎯 Goal: Create a cron job on your Raspberry Pi that runs a script every minute to collect temperature data and save it to a file called temperature_data.txt.

📋 What You'll Learn

Create a bash script called collect_temp.sh that appends the current timestamp and a simulated temperature value to temperature_data.txt.

Make the script executable.

Create a cron job that runs the script every minute.

Verify the cron job is scheduled correctly.

💡 Why This Matters

🌍 Real World

Automating data collection on devices like Raspberry Pi is common in home automation, weather stations, and IoT projects.

💼 Career

Understanding cron jobs and scripting is essential for system administrators, DevOps engineers, and IoT developers to automate tasks and manage data collection.

1

Create the data collection script

Create a bash script called collect_temp.sh that appends the current date and time plus a simulated temperature value (use $((RANDOM % 30 + 10)) to generate a temperature between 10 and 39) to a file named temperature_data.txt. Use the format: YYYY-MM-DD HH:MM:SS Temperature.

Raspberry Pi

# Create the collect_temp.sh script
# Your code here

Need a hint?

Use date '+%Y-%m-%d %H:%M:%S' to get the current timestamp. Use $((RANDOM % 30 + 10)) to simulate temperature.

2

Make the script executable

Make the collect_temp.sh script executable by adding the correct permission using the chmod command.

Raspberry Pi

#!/bin/bash

echo "$(date '+%Y-%m-%d %H:%M:%S') $((RANDOM % 30 + 10))" >> temperature_data.txt

# Make the script executable
# Your code here

Need a hint?

Use chmod +x collect_temp.sh to make the script executable.

3

Schedule the cron job

Add a cron job that runs the collect_temp.sh script every minute. Use crontab -e to edit the cron jobs and add the line: * * * * * /path/to/collect_temp.sh. Replace /path/to/collect_temp.sh with the full path to your script.

Raspberry Pi

# Add cron job line below
# Your code here

Need a hint?

Use * * * * * /full/path/collect_temp.sh to run the script every minute.

4

Verify the cron job setup

Verify that the cron job is scheduled by running crontab -l and ensure the line * * * * * /home/pi/collect_temp.sh appears. Also, check that the temperature_data.txt file is being updated every minute.

Raspberry Pi

# Verify cron job with crontab -l
# Your code here

Need a hint?

Run crontab -l to list scheduled cron jobs and confirm your job is listed.