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ps

The ps (process status) command is one of the most commonly used utilities in Linux to view a snapshot of currently running processes. Unlike top, which provides a dynamic view, ps gives a static list of processes at the exact moment the command is executed.

Basic Syntax​

ps [OPTIONS]

Common Flags/Options​

The ps command supports several syntax styles (UNIX, BSD, and GNU). The most common combinations are UNIX/BSD style.

OptionDescription
-e or ASelect all processes (every process on the system).
-fDo a full-format listing (shows UID, PID, PPID, C, STIME, TTY, TIME, CMD).
aLift the BSD-style "only yourself" restriction (show processes for all users).
uDisplay user-oriented format (shows USER, PID, %CPU, %MEM, VSZ, RSS, TTY, STAT, START, TIME, COMMAND).
xShow processes without a controlling terminal (daemons).
-p PIDShow process information for a specific Process ID (PID).

Real-world Examples​

1. View all running processes (System V style)​

This is a very common command combination used to see absolutely everything running on the system in a detailed format.

ps -ef

2. View all running processes (BSD style)​

This combination is extremely popular for getting a comprehensive, user-oriented list of all processes.

ps aux

3. Find a specific process​

You will frequently pipe the output of ps to grep to find a specific application.

ps aux | grep nginx

4. View processes for a specific user​

If you want to see what processes the user alice is running:

ps -u alice

5. Display a process tree​

You can visualize the parent-child relationships between processes using the --forest flag (or by using the pstree command separately).

ps -ejH --forest