Scheduled data collection with cron in Raspberry Pi

Introduction

Scheduling data collection helps you automatically gather information at set times without doing it manually.

You want to record temperature every hour from a sensor.

You need to save system performance data daily.

You want to back up your database every night.

You want to collect data from a website every 10 minutes.

You want to run a script to clean old data weekly.

Syntax

Raspberry Pi

crontab -e

# Each line in crontab has this format:
# * * * * * command_to_run
# | | | | |
# | | | | +---- Day of week (0-7, Sunday=0 or 7)
# | | | +------ Month (1-12)
# | | +-------- Day of month (1-31)
# | +---------- Hour (0-23)
# +------------ Minute (0-59)

Use 'crontab -e' to edit your scheduled tasks.

The five stars (*) mean 'every' unit of time (every minute, hour, etc.).

Examples

Runs the script 'collect_data.sh' every hour at minute 0.

Raspberry Pi

0 * * * * /home/pi/collect_data.sh

Runs the script every 10 minutes.

Raspberry Pi

*/10 * * * * /home/pi/collect_data.sh

Runs the backup script every Sunday at midnight.

Raspberry Pi

0 0 * * 0 /home/pi/backup_db.sh

Sample Program

This example sets up a script that records the Raspberry Pi's CPU temperature every 15 minutes into a text file.

Raspberry Pi

# Step 1: Create a script to collect data
# File: /home/pi/collect_data.sh
#!/bin/bash
DATE=$(date '+%Y-%m-%d %H:%M:%S')
TEMP=$(vcgencmd measure_temp | egrep -o '[0-9]*\.[0-9]*')
echo "$DATE Temperature: $TEMP C" >> /home/pi/temperature_log.txt

# Step 2: Make the script executable
# Run in terminal:
chmod +x /home/pi/collect_data.sh

# Step 3: Schedule the script to run every 15 minutes
# Run in terminal:
crontab -e
# Add this line:
*/15 * * * * /home/pi/collect_data.sh

Important Notes

Make sure your script has execute permission (chmod +x).

Cron runs commands with limited environment; use full paths in scripts.

Check cron logs if your scheduled task does not run as expected.

Summary

Cron helps automate tasks by running scripts at set times.

Use 'crontab -e' to add or edit scheduled jobs.

Scripts must be executable and use full paths for reliability.