In most Unix and Unix-likeoperating systems, the ps program (short for "process status") displays the currently-running processes. A related Unix utility named top provides a real-time view of the running processes.
Implementations
KolibriOS includes an implementation of the pscommand.[1] The ps command has also been ported to the IBM i operating system.[2] In Windows PowerShell, ps is a predefined command alias for the Get-Process cmdlet, which essentially serves the same purpose.
Examples
# ps
PID TTY TIME CMD 7431 pts/0 00:00:00 su 7434 pts/0 00:00:00 bash18585 pts/0 00:00:00 ps
Users can pipelineps with other commands, such as less to view the process status output one page at a time:
$ ps-A|less
Users can also utilize the ps command in conjunction with the grep command (see the pgrep and pkill commands) to find information about a single process, such as its id:
$ # Trying to find the PID of `firefox-bin` which is 2701$ ps-A|grepfirefox-bin
2701 ? 22:16:04 firefox-bin
The use of pgrep simplifies the syntax and avoids potential race conditions:
$ pgrep-lfirefox-bin
2701 firefox-bin
To see every process running as root in user format:
# ps-Uroot-u
USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMANDroot 1 0.0 0.0 9436 128 - ILs Sun00AM 0:00.12 /sbin/init --
Memory address of the event the process is waiting for
* = Often abbreviated
Options
ps has many options. On operating systems that support the SUS and POSIX standards, ps 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.
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, ps 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.
