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ps (short for process status) is a tool for reporting on a system's active processes. It has a long history on Unix-like operating systems such as BSD and Linux. Consequently, it accepts a very wide variety of input flags in one of three forms: Unix-style options preceded by a single dash, BSD-style options which do not have a dash, and GNU long options which are preceded by two dashes.


USE flags

USE flags for sys-process/procps Standard informational utilities and process-handling tools

elogind Use sys-auth/elogind for session tracking.
kill Build the kill program
modern-top Enables new startup defaults of top. Keeps old defaults if disabled
ncurses Build programs that use ncurses: top, slabtop, watch
nls Add Native Language Support (using gettext - GNU locale utilities)
selinux !!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
split-usr Enable behavior to support maintaining /bin, /lib*, /sbin and /usr/sbin separately from /usr/bin and /usr/lib*
static-libs Build static versions of dynamic libraries as well
systemd Enable use of systemd-specific libraries and features like socket activation or session tracking
test Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
unicode Add support for Unicode


sys-process/procps is part of the @system set, so it should be installed by default.

In case it is ever needed, reinstall sys-process/procps:

root #emerge --ask --oneshot sys-process/procps


Environment variables

  • $PS_FORMAT — override the default output format.


  • /proc — the virtual file system ps reads to obtain the information required for its reports.



To see options available to the ps command:

user $ps --help all
 ps [options]

Basic options:
 -A, -e               all processes
 -a                   all with tty, except session leaders
  a                   all with tty, including other users
 -d                   all except session leaders
 -N, --deselect       negate selection
  r                   only running processes
  T                   all processes on this terminal
  x                   processes without controlling ttys

Selection by list:
 -C <command>         command name
 -G, --Group <GID>    real group id or name
 -g, --group <group>  session or effective group name
 -p, p, --pid <PID>   process id
        --ppid <PID>  parent process id
 -q, q, --quick-pid <PID>
                      process id (quick mode)
 -s, --sid <session>  session id
 -t, t, --tty <tty>   terminal
 -u, U, --user <UID>  effective user id or name
 -U, --User <UID>     real user id or name

  The selection options take as their argument either:
    a comma-separated list e.g. '-u root,nobody' or
    a blank-separated list e.g. '-p 123 4567'

Output formats:
 -F                   extra full
 -f                   full-format, including command lines
  f, --forest         ascii art process tree
 -H                   show process hierarchy
 -j                   jobs format
  j                   BSD job control format
 -l                   long format
  l                   BSD long format
 -M, Z                add security data (for SELinux)
 -O <format>          preloaded with default columns
  O <format>          as -O, with BSD personality
 -o, o, --format <format>
                      user-defined format
  s                   signal format
  u                   user-oriented format
  v                   virtual memory format
  X                   register format
 -y                   do not show flags, show rss vs. addr (used with -l)
     --context        display security context (for SELinux)
     --headers        repeat header lines, one per page
     --no-headers     do not print header at all
     --cols, --columns, --width <num>
                      set screen width
     --rows, --lines <num>
                      set screen height

Show threads:
  H                   as if they were processes
 -L                   possibly with LWP and NLWP columns
 -m, m                after processes
 -T                   possibly with SPID column

Miscellaneous options:
 -c                   show scheduling class with -l option
  c                   show true command name
  e                   show the environment after command
  k,    --sort        specify sort order as: [+|-]key[,[+|-]key[,...]]
  L                   show format specifiers
  n                   display numeric uid and wchan
  S,    --cumulative  include some dead child process data
 -y                   do not show flags, show rss (only with -l)
 -V, V, --version     display version information and exit
 -w, w                unlimited output width

        --help <simple|list|output|threads|misc|all>
                      display help and exit

For more details see ps(1).

Show all running processes

ps may be used to show all running processes by using the a, u, and x, options (see invocation section on what these options do):

user $ps aux


Find a specific process

To find details of a specific process by name, the ps command output may be piped to grep:

user $ps aux | grep <process name>

See also

  • htop — a cross-platform interactive process viewer. It is a text-mode application (for console or X terminals) and requires ncurses.