In most Unix and Unix-like operating systems, the <code>ps</code> (process status) program displays the currently-running processes. The related Unix utility <code>top</code> provides a real-time view of the running processes.
KolibriOS includes an implementation of the command. The command has also been ported to the IBM i operating system. In Windows PowerShell, <code>ps</code> is a predefined command alias for the <code>Get-Process</code> cmdlet, which essentially serves the same purpose.
Users can pipeline <code>ps</code> with other commands, such as less to view the process status output one page at a time:
Users can also utilize the <code>ps</code> command in conjunction with the <code>grep</code> command (see the <code>pgrep</code> and <code>pkill</code> commands) to find information about a single process, such as its id:
The use of <code>pgrep</code> simplifies the syntax and avoids potential race conditions:
To see every process running as root in user format:
<nowiki>* = Often abbreviated</nowiki>
<code>ps</code> has many options. On operating systems that support the SUS and POSIX standards, <code>ps</code> commonly runs 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 from X/Open System Interfaces (XSI), an optional extension to POSIX.
Most systems derived from BSD fail to accept the SUS and POSIX standard options because of historical conflicts. (For example, the "e" or "-e" option will display environment variables.) On such systems, <code>ps</code> commonly runs 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 a column for the controlling user for each process. For maximum compatibility, there is no "-" in front of the "aux". "ps auxww" provides complete information about the process, including all parameters.