Process management

Part 4: Process Management

Key terms

We discussed what a process is when we introduced Operating Systems concepts. Below you will see a reference to PID - Process ID. This is an integer that uniquely identifies the process to the OS. As a user, you use the PID to specify which process you are talking about.

Run the following:

ps
top  # (Mac/Linux only) hit q or Control+C to quit the program.

Monitoring and Controlling Processes

• ps - Report a snapshot of current processes
• top - (Mac/Linux only) Display processes and how much memory or CPU they are using. Similar to the Activity Monitor on Mac and the Task Manager on Windows. Hit q to exit.
• Use the keyboard combo Control+C to kill/quit the current process.
• kill - Send a signal to a process

Exercise

We are going to install Python and create a wild task.

1. Open a second Termina by clicking the + button next to the tab in the menu of the current Terminal. You should see a second “fresh” terminal pane.

2. Now run python3 or python and create the following infinite loop. You can also do this in IDLE or other editor if having trouble running python from the command line.

   python

   
   while True:
       print("hello there")
       

We should now have an out of control Python process gobbling up CPU cycles.

Switch back to the other Terminal tab and run the following commands.

ps
top  # (Mac/Linux only) find the PID of the python process that is gobbling all the CPU
     # If using Windows, open the Task Manager program
kill <PID>  # Replace <PID> with the actual process ID

The terminal will not say anything, but run top again. The runaway Python process should be gone. Switch back to the Terminal tab where you had that Python process and it should say terminated or something similar.

Knowledge Check

• Question: How can you view real-time process activity?

Conclusion

Anything you can do with your OS’s GUI, you can do on the command line. It just looks different. Become comfortable with the CLI – you will find that it can be MUCH faster for certain tasks, and will be indispensable to you as a software engineer.

Final Knowledge Check

• Question: Summarize the steps to create a new directory, navigate into it, create a text file, and view it using less.
• Question: From the CLI, how would you find the runaway process with a memory leak (probably using the most memory) and terminate it?

Programming PRactice

• Once finished, work on the Warm-up Programming Practice problems.