🧠 Raspberry Pi – Programming & Scripting: Python, Shell, Cron Jobs & Services

🧲 Introduction – Bring Your Raspberry Pi to Life with Code

Raspberry Pi isn’t just a microcomputer—it’s a playground for programming. Whether you’re automating sensors, writing Linux services, or scheduling scripts, Python, Bash, and Java are powerful tools to drive your Pi projects.

🎯 In this guide, you’ll learn:

• How to control GPIO with Python
• How to run Java programs on the Pi
• How to write shell scripts for automation
• How to use cron to schedule tasks
• How to manage background services with systemd

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📘 Topics Covered

🔹 Topic	📖 Description
🐍 Raspberry Pi – Python with GPIO	Use Python to control GPIO pins and hardware
☕ Raspberry Pi – Java Programming	Install JDK and run Java applications
🖥️ Raspberry Pi – Shell Scripting Basics	Automate tasks with Bash scripts and system utilities
🧪 Raspberry Pi – Automation Scripts & Cron Jobs	Schedule Python, Bash, or cleanup jobs using cron
🔁 Raspberry Pi – Services & systemd Usage	Create and manage services to run scripts at boot or in the background

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🐍 Raspberry Pi – Python with GPIO

Python is the go-to language for Raspberry Pi. You can use the RPi.GPIO or gpiozero libraries to interact with the GPIO pins.

🔹 Basic LED Blink (using RPi.GPIO)

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)

while True:
    GPIO.output(17, GPIO.HIGH)
    time.sleep(1)
    GPIO.output(17, GPIO.LOW)
    time.sleep(1)

✅ Run with:

sudo python3 led.py

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☕ Raspberry Pi – Java Programming

Install Java and run full Java apps on your Pi:

🔹 Install OpenJDK:

sudo apt install default-jdk

🔹 Compile and Run:

Hello.java:

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello from Raspberry Pi!");
    }
}

javac Hello.java
java Hello

✅ Use Java for backend services, desktop GUIs, and cross-platform apps.

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🖥️ Raspberry Pi – Shell Scripting Basics

Shell scripts allow you to automate tasks, such as backups, updates, or GPIO toggles.

🔹 Example: toggle_led.sh

#!/bin/bash
echo "17" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio17/direction
echo "1" > /sys/class/gpio/gpio17/value
sleep 2
echo "0" > /sys/class/gpio/gpio17/value

Make it executable:

chmod +x toggle_led.sh

Run with:

sudo ./toggle_led.sh

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🧪 Raspberry Pi – Automation Scripts & Cron Jobs

Use cron to schedule scripts or commands to run at specific intervals.

🔹 Open crontab:

crontab -e

🔹 Schedule Script:

0 7 * * * /home/pi/scripts/temperature_log.py

This runs the script every day at 7 AM.

✅ Add logging to monitor task success:

0 0 * * * /path/script.sh >> /home/pi/logs/backup.log 2>&1

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🔁 Raspberry Pi – Services & systemd Usage

Use systemd to run scripts or applications as services at startup.

🔹 Create a Service:

/etc/systemd/system/myservice.service

[Unit]
Description=My Custom Python Service
After=network.target

[Service]
ExecStart=/usr/bin/python3 /home/pi/my_script.py
WorkingDirectory=/home/pi
StandardOutput=inherit
StandardError=inherit
Restart=always
User=pi

[Install]
WantedBy=multi-user.target

Enable & start it:

sudo systemctl enable myservice
sudo systemctl start myservice

✅ Check status:

sudo systemctl status myservice

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📌 Summary – Recap & Next Steps

From blinking LEDs in Python to full system services in Bash or Java, Raspberry Pi offers a rich programming environment that supports automated, scalable, and interactive projects.

🔍 Key Takeaways:

• Python is ideal for GPIO and project scripting
• Java can be used for more structured applications
• Bash scripts automate system tasks and GPIO control
• cron helps schedule recurring tasks
• systemd enables background services that start on boot

⚙️ Real-World Applications:

• Smart lighting or alert systems
• Scheduled sensor readings and data logging
• Running servers, APIs, or bots
• Automating boot-time checks or tasks

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❓ Frequently Asked Questions

❓ Can I run multiple Python scripts on Raspberry Pi?
✅ Yes, but monitor CPU/RAM usage and avoid GPIO pin conflicts.

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❓ How do I debug a script that runs at boot?
✅ Use logs:

journalctl -u myservice.service

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❓ How often can a cron job run?
✅ Every minute using:

* * * * * /path/to/script.sh

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❓ Which is better for GPIO – RPi.GPIO or gpiozero?
✅ gpiozero is easier for beginners; RPi.GPIO offers lower-level control.

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