Processes

Note

This page is for computer processes. I don’t know why you’d ever make one about the English term, but hey, in case you do, you’ve now got a clear distinction.

What

It’s an instance of a program that’s currently executing. It has states. About:

• They must be loaded into Virtual Memory and uniquely identified (pid).
• pid’s have CPU times, memory usage, user ID that spawned it - uid, etc.
• Processes might control other processes (fork).
• Child process inherits context from parent process.

What can it do?

• By default, the process only has the privileges that it’s parent uid has.

Permissions! (Lowkey quite cool)

Every process has 3 user IDs:

• Real User ID (uid): The user ID that actually started the process
• Effective User ID (euid): The user ID that determines the process’ privileges. For example, you may want to temporarily run sudo, at which point the terminal’s command changes its euid to 0 (root’s).
• Saved UserID (suid): We save the user ID before changing the euid so we can go back to it.