ps

The ps (process status) command is one of the most frequently used commands in Linux. Usually it is used to get the more and detailed information about a specific process or all processes. For example it is used to know whether a particular process is running or not, who is running what process in system, which process is using higher memory or CPU, how long a process is running, etc.

ps aux command and ps command explained

Document

ps(1) - Linux manual page

Example

ps aux | grep nginx