ps (Unix)
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.
The following is an abridged list of valid options to run with the ps command:
SIMPLE PROCESS SELECTION
-A Select all processes. Identical to -e.
-N Select all processes except those that fulfill the specified
conditions. (negates the selection) Identical to --deselect.
T Select all processes associated with this terminal. Identical
to the t option without any argument.
-a Select all processes except session leaders (see getsid(2))
and processes not associated with a terminal.
a Lift the BSD-style "only yourself" restriction, which is
imposed upon the set of all processes when some BSD-style
(without "-") options are used or when the ps personality
setting is BSD-like. The set of processes selected in this
manner is in addition to the set of processes selected by
other means. An alternate description is that this option
causes ps to list all processes with a terminal (tty), or to
list all processes when used together with the x option.
-d Select all processes except session leaders.
-e Select all processes. Identical to -A.
g Really all, even session leaders. This flag is obsolete and
may be discontinued in a future release. It is normally
implied by the a flag, and is only useful when operating in
the sunos4 personality.
r Restrict the selection to only running processes.
x Lift the BSD-style "must have a tty" restriction, which is
imposed upon the set of all processes when some BSD-style
(without "-") options are used or when the ps personality
setting is BSD-like. The set of processes selected in this
manner is in addition to the set of processes selected by
other means. An alternate description is that this option
causes ps to list all processes owned by you (same EUID as
ps), or to list all processes when used together with the
"a" option.
--deselect Select all processes except those that fulfill the specified
conditions. (negates the selection) Identical to -N.
OTHER INFORMATION
L List all format specifiers.
-V Print the procps version.
V Print the procps version.
--help Print a help message.
--info Print debugging info.
--version Print the procps version.
An example of the ps command is:
tux ~ # ps PID TTY TIME CMD 7431 pts/0 00:00:00 su 7434 pts/0 00:00:00 bash 18585 pts/0 00:00:00 ps
The ps command can also be used in conjunction with the grep command to find information about one process, such as its process id. An example of this is:
tux ~ # ps -A | grep firefox-bin 11778 ? 02:40:08 firefox-bin 11779 ? 00:00:00 firefox-bin 11780 ? 00:00:18 firefox-bin 11782 ? 00:00:12 firefox-bin 12855 ? 00:00:00 firefox-bin 17438 ? 00:00:00 firefox-bin 17439 ? 00:00:00 firefox-bin
See also
External links
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