In most Unix-like operating systems, the ps command line program gives a snapshot of the currently running processes, including ps itself.

ps has many options. On operating systems that support the UNIX and POSIX standards, ps is commonly run with the options -ef, where "-e" selects every process and "-f" chooses the "full" output format. Another common option on these systems is -l, which specifies the "long" output format.

Most systems derived from BSD fail to accept the POSIX and UNIX standard options because of historical conflicts (for example, the "e" or "-e" option will cause environment variables to be displayed). On such systems, ps is commonly used with the non-standard options aux, where "a" lists all processes on a terminal, including those of other users, "x" lists all processes without controlling terminals and "u" adds the controlling user for each process. Note that, for maximum compatibility when using this syntax, there is no "-" in front of the "aux".

Another Unix utility named top provides a real-time view of the running processes.