Have you ever encountered a situation where you are running a Python script and you want to interrupt it using the keyboard, but it doesn't seem to work as expected? Specifically, if you are calling the "stress-ng" command within your script, you may face difficulties in catching the interrupt signal properly. In this article, we will explore this issue and provide a solution to correctly catch the key interrupt in your Python script when calling "stress-ng".
Before we dive into the solution, let's first understand what exactly is happening. When you run a Python script, it runs in a single thread by default. This means that it executes the instructions in a sequential manner, one after the other. However, when you call an external command like "stress-ng" within your script, it creates a separate process that runs independently.
Now, when you press Ctrl+C on your keyboard to interrupt the script, it sends a signal called SIGINT to the process. By default, the Python script's main thread receives this signal and raises a KeyboardInterrupt exception, allowing you to gracefully handle the interruption. However, since the "stress-ng" command is running in a separate process, it doesn't receive the SIGINT signal directly, and therefore, the KeyboardInterrupt exception is not raised.
So, how can we solve this problem? The solution lies in using the "subprocess" module in Python, which allows us to create and manage additional processes from our script. By using the "subprocess" module, we can catch the SIGINT signal and handle it appropriately, even when calling external commands like "stress-ng". Here's an example:
import subprocess
import signal
def handle_interrupt(signum, frame):
print("Interrupt signal received. Stopping stress-ng...")
# Stop the stress-ng process gracefully
stress_ng_process.terminate()
# Register the signal handler
signal.signal(signal.SIGINT, handle_interrupt)
# Start the stress-ng process
stress_ng_process = subprocess.Popen(["stress-ng", "--cpu", "1"])
# Wait for the process to finish
stress_ng_process.wait()
In the above code, we first define a signal handler function called "handle_interrupt". This function will be called when the SIGINT signal is received. Inside the signal handler, we print a message indicating that the interrupt signal has been received and gracefully terminate the "stress-ng" process using the "terminate()" method.
Next, we register the signal handler using the "signal.signal()" function, passing the signal type (SIGINT) and the signal handler function as arguments. This tells the Python script to call our signal handler function when the SIGINT signal is received.
After registering the signal handler, we start the "stress-ng" process using the "subprocess.Popen()" function. This function creates a new process and returns a "Popen" object that represents the running process. We pass the command and its arguments as a list to the function.
Finally, we wait for the process to finish using the "wait()" method of the "Popen" object. This ensures that the Python script doesn't exit before the "stress-ng" process completes.
By using this approach, we can correctly catch the interrupt signal and gracefully stop the "stress-ng" process when running it within our Python script.
References:
| Number | Source |
|---|---|
| 1 | Python subprocess documentation |
| 2 | Python signal documentation |