The ps command displays information about active processes. It lists all running processes by default but additional switches provide more details. Common switches include -A for a complete list, -f for full details, and -l for a long listing. The ps command is often used to find the process ID (PID) of a frozen process so it can be killed using the kill command. Piping ps output to grep can filter results to quickly find a specific process.

1. The ps command
Kevin O'Brien
Washtenaw Linux Users Group
http://www.lugwash.org

2. What is ps?
● ps stands for Process Status
● Gives a list of all processes
2

3. Usage
● Type “ps” at the prompt, and you get very
little
● Switches are key, as always
● To get a complete list, for instance, type “ps
-A” (Note: Linux is case-sensitive)
● Also, “ps -e” will give a complete list
3

4. Other switches you might want
● -f give a full listing, i.e. more information
about each process listed
● -u username will list all processes running by
a specific user
● -l gives a long listing. This is even more data
than in a full listing
4

5. Combining switches
● You can use more than one switch at a time
● Example: “ps -el” would give you a long
listing of all of your processes
● Example: “ps -el -u username” would give
you a long listing of all processes owned by
a certain username
5

6. Common use
● The most common reason to use ps is the
get the process ID for a process that is out of
control
● With the process ID you can use the kill
command (e.g. “kill 6985” would kill
whichever process had that process ID)
6

7. Piping
● Sometimes, the list of processes can be long
● If you only need to get a process ID, try
piping to grep
● Example: Firefox is frozen and I need to kill it
● “ps -e | grep firefox” would return one line
with the process for Firefox
● I can then easily enter the kill command
7