Managing Processes and Jobs

Small, Sharp Software Tools — by Brian P. Hogan (74 / 107)

👈 Reusing Previous Commands and Arguments | TOC | Terminating Processes 👉

The ps command, short for Process Status, shows you the running processes on your computer, as well as information about who’s running them. It’s good for finding out what’s currently running and for identifying a process ID with a program so you can stop it.

The ps command takes different options based on which OS you’re using. In this book, we’ll cover the Linux options, which also work on macOS.

When you execute the ps command without any arguments, you see the processes running in your current session:

The output shows the PID, or Process ID, the terminal session that’s running the command, how long it’s been running, and the command itself. In this case, the only results you see are the Bash shell itself and the ps command you just ran, since it’s only showing you what’s running in this particular session.

Use the -f flag to get a more detailed output:

The UID column shows the user that started the process. The PPID is the ID of the parent process. Some processes spawn child processes, so it’s often helpful to know what process is responsible for creating the process you’re looking at. The C column shows the CPU usage of the process, and STIME shows the time the process was started.

To see all of the processes running on the system, use ps -e. This generates a very long list, as your OS has a lot of background processes running.

Pipe the output to the less command to make it easier to read:

Some of the processes aren’t attached to a terminal session, so you see a question mark (?) in the TTY column.

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