Android adb shell – ash or ksh?
When you connect to an Android device using adb shell, you’re entering a shell environment. But which shell are you using? This depends on the device and Android version.
Understanding the Shells
Two common shells found on Android devices are:
- ash: A lightweight and basic shell developed specifically for Android.
- ksh: The Korn shell, a powerful and feature-rich shell widely used on Unix-like systems.
Determining the Shell in Use
To find out which shell you’re currently using, run the following command in your adb shell session:
echo $SHELL
If the output is /system/bin/sh, then you’re using ash. If it’s /system/bin/ksh, you’re using ksh.
Key Differences
| Feature | ash | ksh |
|---|---|---|
| Features | Basic shell commands, limited scripting capabilities. | Extensive set of built-in commands, advanced scripting features, job control, history management. |
| Performance | Faster and lighter on resource-constrained devices. | Potentially slower due to its richer feature set. |
| Availability | Standard shell on most Android devices. | May be present on newer or customized Android devices. |
Using ksh on Android
If your device doesn’t have ksh installed, you can try installing it through package managers like apt or dpkg if supported by your device. Alternatively, you can download a ksh binary and place it in a location accessible to your device. However, this is usually not recommended for security reasons.
When to Choose Which Shell
In most scenarios, ash is sufficient for basic commands and simple scripts. Use ksh when you need:
- Advanced scripting features like functions, arrays, and conditional statements.
- More robust shell environment with comprehensive command-line editing capabilities.
- Better support for background processes and job control.
Conclusion
While ash is the default shell on most Android devices, ksh offers a more powerful and feature-rich alternative. Choose the shell that best suits your needs and understanding the capabilities of each can help you make informed decisions when working within the Android shell environment.