Shell Script to Check if Android Device is Connected Over USB: A Step-by-Step Guide

For developers working with Android devices, connecting your device over USB is often an essential step in the debugging and testing process. But how do you quickly check if an Android device is connected over USB? Writing a shell script to check if an Android device is connected can save time and make your development workflow smoother. This detailed guide will help you create a script to automate the device detection process, ensuring you know exactly when your device is ready.

By the end of this post, you’ll understand how to detect Android devices over USB, how the adb (Android Debug Bridge) works in this context, and how to automate this check using a simple shell script.

What is ADB and How Does it Work?

ADB (Android Debug Bridge) is a command-line tool that allows you to communicate with an Android device. It is used extensively by developers to run commands, install or debug apps, and interact with devices from a computer. ADB plays a crucial role in determining whether a device is connected over USB.

• Why Use ADB?
• Quick Device Detection: Easily detect if the Android device is connected to the computer.
• Automation: Incorporate ADB commands into a shell script to automate testing processes.
• Multi-purpose: Besides checking connectivity, ADB can be used for many other development tasks.

To check if an Android device is connected, you need ADB installed and configured on your machine. Let’s dive into the script that helps you automate this.

Setting Up ADB to Detect Android Devices

Before you can use a shell script, you need to have ADB installed. ADB is a part of the Android SDK. You can install ADB using the following command on Ubuntu:

sudo apt-get install android-tools-adb

After installing ADB, make sure your device has USB Debugging enabled. You can enable it in Developer Options on your Android device.

Shell Script to Check if Android Device is Connected

Here is a simple shell script to check if an Android device is connected over USB:

#!/bin/bash

# Check if ADB is installed
if ! command -v adb &> /dev/null; then
    echo "Error: ADB is not installed. Please install ADB and try again."
    exit 1
fi

# List connected devices
DEVICE_COUNT=$(adb devices | grep -w "device" | wc -l)

if [ $DEVICE_COUNT -gt 0 ]; then
    echo "Android device is connected over USB."
else
    echo "No Android device connected over USB."
fi

• Explanation:
• command -v adb &> /dev/null: Checks if ADB is installed on the system. If not, it prompts the user to install ADB.
• adb devices: Lists all connected devices.
• grep -w "device": Filters the output to find only connected devices.
• wc -l: Counts the number of connected devices.
• The script then prints a message indicating whether an Android device is connected.

Running the Script

To run this script, save it as check_android_device.sh and make it executable:

chmod +x check_android_device.sh

Then execute the script using the following command:

./check_android_device.sh

Output:

• If a device is connected:

Android device is connected over USB.

• If no device is connected:

No Android device connected over USB.

Troubleshooting Common Issues

1. Device Not Detected

Problem: Your Android device is not detected when running the script.

Solution:

• Ensure USB Debugging is enabled on your Android device.
• Check if the USB cable is functional and properly connected.
• Verify that ADB drivers are installed and working correctly on your machine.

2. Multiple Devices Connected

Problem: If multiple devices are connected, the script may provide inaccurate results.

Solution: Modify the script to display information about all connected devices. You can use adb devices without filtering to see the list of all connected devices and their states.

adb devices

This will print the list of all connected devices, allowing you to manually verify the status.

Enhancing the Script for Multiple Devices

If you need to handle multiple devices, you can adjust the script to display details of each connected device:

#!/bin/bash

# Check if ADB is installed
if ! command -v adb &> /dev/null; then
    echo "Error: ADB is not installed. Please install ADB and try again."
    exit 1
fi

# List all connected devices
adb devices | while read -r line; do
    if [[ $line == *"device"* ]]; then
        echo "Device detected: $line"
    fi
done

Advanced Usage: Automate Actions on Device Detection

With minor modifications, you can automate actions when a device is detected. For example, you can use this script to install an APK or run automated tests when a device is connected:

if [ $DEVICE_COUNT -gt 0 ]; then
    echo "Device detected, installing APK..."
    adb install path/to/your/app.apk
else
    echo "No Android device connected."
fi

Best Practices for Using ADB and Shell Scripts

• Always Validate ADB Installation: Ensure that ADB is installed and accessible from the terminal.
• Check USB Debugging: Make sure that USB debugging is enabled on your Android device for a successful connection.
• Test the Script with Multiple Devices: If you regularly use multiple devices, enhance your script to manage and report all connected devices.
• Provide User Instructions: When arguments are missing or ADB is not found, provide helpful instructions to the user.

Conclusion

Writing a shell script to check if an Android device is connected over USB can streamline your workflow as an Android developer. This guide covered everything from setting up ADB to creating a shell script that checks for connected devices. By using this script, you can save time and automate repetitive tasks, making your development process more efficient.

The script provided is a simple yet effective way to determine if your device is properly connected and ready for testing. Feel free to expand upon this script to suit your specific development needs, such as installing apps or running tests automatically.