Process management

Use the CLI to manipulate the OSes processes.

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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:

bash


ps
top  # hit q or Control+C to quit the program.

Monitoring and Controlling Processes

ps - Report a snapshot of current processes
top - Display Linux 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.

On Ubuntu only: Run the command sudo apt install python3
- You will be prompted to type your password. The terminal will not show any characters while you are typing.
- You will see some text as python3 installs.
Open a second Terminal:
- On Mac or in VirtualBox Ubuntu: You can click the + button on the tab in the current Terminal. You should see a second “fresh” terminal pane.
- Ubuntu on WSL: Click the drop down next to your Ubuntu tab and make sure to pick Ubuntu again. You should see a second “fresh” Linux pane. If you see Powershell or Command Prompt, you’re in the wrong place.
Now run python3 and create the following infinite loop.
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.

bash


ps
top  # find the PID of the python process that is gobbling all the CPU
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.

Also, the commands above have equivalent commands on Windows machines (mostly). If you are a regular Windows user, you would do yourself a favor to learn the equivalent commands to things like ls, rmdir, and cd in the Windows CLI (PowerShell).

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?