In scripting and automation, it is usually crucial to know if a command that you have run has been successful. This is especially true when the execution of other commands depends on the output or result of a previous command.

Python, being a versatile language, offers ways to help you check if a command is executed successfully. This guide will carry you through the steps to accomplish this.

Step One: Import Required Libraries

Firstly, we need to import the libraries necessary to check if a command ran successfully. We would be needing the subprocess library, which is a Python Standard Library designed to spawn new processes, connect to their input/output pipes, and obtain their return codes.

If you haven’t got it installed on your local machine, you can navigate to the official Python documentation to see how to install and use subprocess.

import subprocess

Step Two: Use the subprocess.run() Function

Next, we use the subprocess.run() function to help us run the command. It will run the command described by the command, wait for the command to complete, then return a CompletedProcess instance.

# Command to execute
if platform.system() == 'Windows':
    command = 'dir'
else:
    command = 'ls'

result = subprocess.run([command], stdout=subprocess.PIPE, shell=True, text=True)

Step Three: Check the Return Code

In this step, we simply check if the return code of the executed command is 0 (which signifies success), or not.

if result.returncode == 0:
    print("Command executed successfully")
else:
    print("Command execution failed")

Put the Codes Together

Now that we’ve gone through the steps individually, let’s put the codes together.

import subprocess
import platform

# Command to execute
if platform.system() == 'Windows':
    command = 'dir'
else:
    command = 'ls'

result = subprocess.run([command], stdout=subprocess.PIPE, shell=True, text=True)

# Check if command executed successfully
if result.returncode == 0:
    print("Command executed successfully")
else:
    print("Command execution failed")

Conclusion

Using the subprocess module in Python is a straightforward and efficient way to check if a command is executed successfully.

This is a fundamental aspect of error detection in scripting and automation that improves the robustness of your codes. It is worth noting that the subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function.

See the Python documentation for more information.