Name

ps - report a snapshot of the current processes.

Synopsis

ps [options]

Description

ps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top(1) instead.

This version of ps accepts several kinds of options:

1  UNIX options, which may be grouped and must be preceded by a dash.
2  BSD options, which may be grouped and must not be used with a dash.
3  GNU long options, which are preceded by two dashes.

Options of different types may be freely mixed, but conflicts can appear. There are some synonymous options, which are functionally identical, due to the many standards and ps implementations that this ps is compatible with.

Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards require that "ps -aux" print all processes owned by a user named "x", as well as printing all processes that would be selected by the -a option. If the user named "x" does not exist, this ps may interpret the command as "ps aux" instead and print a warning. This
behavior is intended to aid in transitioning old scripts and habits. It is fragile, subject to change, and thus should not be relied upon.

By default, ps selects all processes with the same effective user ID (euid=EUID) as the current user and associated with the same terminal as the invoker. It displays the process ID (pid=PID), the terminal associated with the process (tname=TTY), the cumulated CPU time in [dd-]hh:mm:ss format (time=TIME), and the executable name (ucmd=CMD).

Output is unsorted by default.

The use of BSD-style options will add process state (stat=STAT) to the default display and show the command args (args=COMMAND) instead of the
executable name. You can override this with the PS_FORMAT environment variable. The use of BSD-style options will also change the process selection to include processes on other terminals (TTYs) that are owned by you; alternately, this may be described as setting the selection to be the set of all processes filtered to exclude processes owned by
other users or not on a terminal. These effects are not considered when options are described as being "identical" below, so -M will be considered identical to Z and so on.

Except as described below, process selection options are additive. The default selection is discarded, and then the selected processes are added to the set of processes to be displayed. A process will thus be shown if it meets any of the given selection criteria.

Examples

To see every process on the system using standard syntax:

ps -e
ps -ef
ps -eF
ps -ely

To see every process on the system using BSD syntax:

ps ax
ps axu

To print a process tree:

ps -ejH
ps axjf

To get info about threads:

ps -eLf
ps axms

To get security info:

ps -eo euser,ruser,suser,fuser,f,comm,label
ps axZ
ps -eM

To see every process running as root (real & effective ID) in user format:

ps -U root -u root u

To see every process with a user-defined format:

ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm
ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm
ps -eopid,tt,user,fname,tmout,f,wchan

Print only the process IDs of syslogd:

ps -C syslogd -o pid=

Print only the name of PID 42:

ps -p 42 -o comm=

Simple Process Selection

Process Selection by List

These options accept a single argument in the form of a blank-separated or comma-separated list. They can be used multiple times.

For example: ps -p "1 2" -p 3,4

-C cmdlist     Select by command name.

This selects the processes whose executable name is given in cmdlist.

-G grplist     Select by real group ID (RGID) or name.

This selects the processes whose real group name or ID is in the grplist list. The real group ID identifies the group of the user who created the process, see getgid(2).

U userlist     Select by effective user ID (EUID) or name.

This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the process (see geteuid(2)). Identical to -u and --user.

-U userlist    select by real user ID (RUID) or name.

It selects the processes whose real user name or ID is in the userlist list. The real user ID identifies the user who created the process, see getuid(2).

-g grplist     Select by session OR by effective group name.

Selection by session is specified by many standards, but selection by effective group is the logical behavior that several other operating systems use. This
ps will select by session when the list is completely numeric (as sessions are). Group ID numbers will work only when some group names are also specified. See the
-s and --group options.

p pidlist       Select by process ID. Identical to -p and --pid.

-p pidlist     Select by PID.

This selects the processes whose process ID numbers appear in pidlist. Identical to p and --pid.

-s sesslist     Select by session ID.

This selects the processes with a session ID specified in sesslist.

t ttylist     Select by tty.

Nearly identical to --tty, but can also be used with an empty ttylist to indicate the terminal associated with ps. Using the T option is considered cleaner than using  T with an empty ttylist.

-t ttylist     Select by tty.

This selects the processes associated with the terminals given in ttylist. Terminals (ttys, or screens for text output) can be specified in several forms:

/dev/ttyS1, ttyS1, S1. A plain "-" may be used to select processes not attached to any terminal.

-u userlist     Select by effective user ID (EUID) or name.

This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the
process (see geteuid(2)). Identical to U and --user.

--Group grplist     Select by real group ID (RGID) or name. Identical to -G.

--User userlist       Select by real user ID (RUID) or name. Identical to -U.

--group grplist       Select by effective group ID (EGID) or name.

This selects the processes whose effective group name or ID is in grouplist. The effective group ID describes the group whose file access permissions are used by the
process (see geteuid(2)). The -g option is often an alternative to --group.

--pid pidlist     Select by process ID. Identical to -p and p.

--ppid pidlist    Select by parent process ID. 

This selects the processes with a parent process ID in pidlist. That is, it selects processes that are children of those listed in pidlist.

--sid sesslist     Select by session ID. Identical to -s.

--tty ttylist      Select by terminal. Identical to t.

--user userlist    Select by effective user ID (EUID) or name. Identical to -u and U.

-123 Identical to --sid 123.

123 Identical to --pid 123.

Out Put Format Control

These options are used to choose the information displayed by ps. The output may differ by personality.

-c     Show different scheduler information for the -l option.

--context     Display security context format. (for SE Linux)

-F     extra full format. See the -f option, which -F implies.

-f     does full-format listing. This option can be combined with many other UNIX-style options to add additional columns. It also causes the command arguments to be printed. When        used with -L, the NLWP (number of threads) and LWP (thread ID) columns will be added. See the c option, the format keyword args, and the format keyword comm.

--format  format user-defined format. Identical to -o and o.

j     BSD job control format.
-j      jobs format
l         display BSD long format.
-l     long format. The -y option is often useful with this.

-M       Add a column of security data. Identical to Z. (for SE Linux)

o          format specify user-defined format. Identical to -o and --format.
-o       format user-defined format.  format is a single argument in the form of a blank-separated or comma-separated list, which offers a way to specify individual output columns.     The recognized keywords are described in the Standard Format Specifiers section below. Headers may be renamed  (ps -o pid,ruser=RealUser -o comm=Command) as desired.  If all column headers are empty (ps -o pid= -o comm=) then the header line will not be output. Column width will increase as needed for wide headers; this may be used to widen up columns such as WCHAN (ps -o pid,wchan=WIDE-WCHAN-COLUMN -o comm). Explicit width control (ps opid,wchan:42,cmd) is offered too. 

The behavior of ps -o pid=X,comm=Y varies with personality; output may be one column named "X,comm=Y" or two columns named "X" and "Y". Use multiple - o options when in doubt. Use the PS_FORMAT environment variable to specify a default as desired; DefSysV and DefBSD are macros that may be used to choose the default UNIX or BSD columns.

O       format is preloaded o (overloaded).  The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or  formatting), specify the option in some other way (e.g. with -O or --sort). When used as a formatting option, it is identical to -O, with the BSD personality.

-O      format is like -o, but preloaded with some default columns. Identical to -o pid,format,state,tname,time,command or-o pid,format,tname,time,cmd, see -o below.

s       display signal format

u       display user-oriented format

v       display virtual memory format

X     Register format.

-y      Do not show flags; show rss in place of addr. This option can only be used with -l.

Z       Add a column of security data. Identical to -M. (for SE Linux)

-Z      display security context format (SELinux, etc.) 

Output Modifiers

-H        show process hierarchy (forest)
N namelist      Specify namelist file. Identical to -n, see -n above.
O order               Sorting order. (overloaded)

The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or formatting), specify the option in some other way (e.g. with -O or --sort).

For sorting, obsolete BSD O option syntax is O[+|-]k1[,[+|-]k2[,...]]. It orders the processes listing according to the multilevel sort specified by the sequence of one-letter short keys k1, k2, ... described in the Obsolete Sort Keys section below.
The "+" is currently optional, merely re-iterating the default direction on a key, but may help to distinguish an O sort from an O format. The "-" reverses direction only on the key it precedes.

S    Sum up some information, such as CPU usage, from dead child processes into their parent. This is useful for examining a system where a parent process repeatedly forks off short-lived children to do work.

c     Show the true command name. This is derived from the name of the executable file, rather than from the argv value. Command arguments and any modifications to them (see setproctitle(3)) are thus not shown. This option effectively turns the args format keyword into the comm format keyword; it is useful with the -f format option
and with the various BSD-style format options, which all normally display the command arguments. See the -f option, the format keyword args, and the format keyword  comm.

e       Show the environment after the command.

f         ASCII-art process hierarchy (forest)

h         No header. (or, one header per screen in the BSD personality) The h option is problematic. Standard BSD ps uses this option to print a header on each page of output, but older Linux ps uses this option to totally disable the header. This version of ps follows the Linux usage of not printing the header unless the BSD personality has been selected, in which case it prints a header on each page of output. Regardless of the current personality, you can use the long options --headers and --no-headers to enable printing headers each page or disable headers entirely, respectively.
k     spec specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]] Choose a multi-letter key from the Standard Format Specifiers section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to --sort.          

Examples:

ps jaxkuid,-ppid,+pid
ps axk comm o comm,args
ps kstart_time -ef

-n namelist     set namelist file. Identical to N. The namelist file is needed for a proper WCHAN display, and must match the current Linux kernel exactly for correct output. Without this option, the default search path for the namelist is:
            $PS_SYSMAP
          $PS_SYSTEM_MAP
          /proc/*/wchan
          /boot/System.map-`uname -r`
          /boot/System.map
          /lib/modules/`uname -r`/System.map
          /usr/src/linux/System.map
          /System.map

n Numeric        output for WCHAN and USER. (including all types of UID and GID)
-w                     Wide output. Use this option twice for unlimited width.
w                           Wide output. Use this option twice for unlimited width.
--cols n           set screen width
--columns n   set screen width
--cumulative    include some dead child process data (as a sum with the parent)
--forest           ASCII art process tree
--headers         repeat header lines, one per page of output
--no-headers   print no header line at all
--lines n        set screen height
--rows n           set screen height
--sort spec     specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]] Choose a multi-letter key from the Standard Format Specifiers section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to k.

For example: ps jax --sort=uid,-ppid,+pid

--width n       set screen width

Thread Display

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

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.

Notes

This ps works by reading the virtual files in /proc. This ps does not need to be setuid kmem or have any privileges to run. Do not give this ps any special permissions. 

This ps needs access to namelist data for proper WCHAN display. For kernels prior to 2.6, the System.map file must be installed. 

CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%.

The SIZE and RSS fields don’t count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack). 

Processes marked <defunct> are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits.

Process Flags

The sum of these values is displayed in the "F" column, which is provided by the flags output specifier.

1   forked but didn’t exec

4   used super-user privileges

Process State Codes

Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process.

D       Uninterruptible sleep (usually IO)

R       Running or runnable (on run queue)

S       Interruptible sleep (waiting for an event to complete)

T       Stopped, either by a job control signal or because it is being traced.

W      paging (not valid since the 2.6.xx kernel)

X       dead (should never be seen)

Z      Defunct ("zombie") process, terminated but not reaped by its parent. 

For BSD formats and when the stat keyword is used, additional characters may be displayed:

<     high-priority (not nice to other users)

N     low-priority (nice to other users)

L      has pages locked into memory (for real-time and custom IO)

s      is a session leader

l       is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)

+     is in the foreground process group

Obsolete Sort Keys

These keys are used by the BSD O option (when it is used for sorting). The GNU --sort option doesn’t use these keys, but the specifiers described below in the Standard Format Specifiers section. Note that the values used in sorting are the internal values ps uses and not the "cooked" values used in some of the output format fields (e.g. sorting on tty will sort into device number, not according to the terminal name displayed). Pipe ps output into the sort(1) command if you want to sort the cooked values.

KEY   LONG       DESCRIPTION

c         cmd                simple name of executable

C        pcpu               cpu utilization

f         flags                flags as in long format F field

g        pgrp                process group ID

G        tpgid              controlling tty process group ID

j         cutime            cumulative user time

J         cstime            cumulative system time

k        utime             user time

m      min_flt            number of minor page faults

M      maj_flt             number of major page faults

n       cmin_flt            cumulative minor page faults

N      cmaj_flt            cumulative major page faults

o      session             session ID

p      pid                    process ID

P      ppid                  parent process ID

r      rss                      resident set size

R      resident             resident pages

s      size                     memory size in kilobytes

S      share                  amount of shared pages

t      tty                       the device number of the controlling tty

T      start_time           time process was started

U      uid                      user ID number

u      user                     user name

v      vsize                    total VM size in kB

y      priority                kernel scheduling priority


AIX Format Descriptors

This ps supports AIX format descriptors, which work somewhat like the formatting codes of printf(1) and printf(3). For example, the normal default output can be produced with this: ps -eo "%p %y %x %c". The NORMAL codes are described in the next section.

Standard Format Specifiers

Here are the different keywords that may be used to control the output format (e.g. with option -o) or to sort the selected processes with the GNU-style --sort option.

For example: ps -eo pid,user,args --sort user

This version of ps tries to recognize most of the keywords used in other implementations of ps.

The following user-defined format specifiers may contain spaces: args,cmd, comm, command, fname, ucmd, ucomm, lstart, bsdstart, start.

Some keywords may not be available for sorting.

Environment Variables

The following environment variables could affect ps:

COLUMNS

Override default display width.

LINES

Override default display height.

PS_PERSONALITY

Set to one of posix, old, linux, bsd, sun, digital...(see section PERSONALITY below).

CMD_ENV

Set to one of posix, old, linux, bsd, sun, digital...(see section PERSONALITY below).

I_WANT_A_BROKEN_PS

Force obsolete command line interpretation.

LC_TIME

Date format.

PS_COLORS

Not currently supported.

PS_FORMAT

Default output format override. You may set this to a format string of the type used for the -o option. The DefSysV and DefBSD values are particularly useful.

PS_SYSMAP

Default namelist (System.map) location.

PS_SYSTEM_MAP

Default namelist (System.map) location.

POSIXLY_CORRECT

Don’t find excuses to ignore bad "features".

POSIX2

When set to "on", acts as POSIXLY_CORRECT.

UNIX95

Don’t find excuses to ignore bad "features".

_XPG

Cancel CMD_ENV=irix non-standard behavior.

In general, it is a bad idea to set these variables. The one exception is CMD_ENV or PS_PERSONALITY, which could be set to Linux for normal 
systems. Without that setting, ps follows the useless and bad parts of the Unix98 standard.

Personality

390 like the S/390 OpenEdition ps

aix like AIX ps

bsd like FreeBSD ps (totally non-standard)

compaq like Digital Unix ps

debian like the old Debian ps

digital like Tru64 (was Digital Unix, was OSF/1) ps

gnu like the old Debian ps

hp like HP-UX ps

hpux like HP-UX ps

irix like Irix ps

linux ***** RECOMMENDED *****

old like the original Linux ps (totally non-standard)

os390 like OS/390 Open Edition ps

posix standard

s390 like OS/390 Open Edition ps

sco like SCO ps

sgi like Irix ps

solaris2 like Solaris 2+ (SunOS 5) ps

sunos4 like SunOS 4 (Solaris 1) ps (totally non-standard)

svr4 standard

sysv standard

tru64 like Tru64 (was Digital Unix, was OSF/1) ps

unix standard

unix95 standard

unix98 standard

See Also

top(1), pgrep(1), pstree(1), proc(5).

Standards

This ps conforms to:

1  Version 2 of the Single Unix Specification

2  The Open Group Technical Standard Base Specifications, Issue 6

3  IEEE Std 1003.1, 2004 Edition

4  X/Open System Interfaces Extension [UP XSI]

5  ISO/IEC 9945:2003

Author

ps was originally written by Branko Lankester <lankeste@fwi.uva.nl>. Michael K. Johnson <johnsonm@redhat.com> re-wrote it significantly to use the proc filesystem, changing a few things in the process. Michael Shields <mjshield@nyx.cs.du.edu> added the pid-list feature. Charles Blake <cblake@bbn.com> added multi-level sorting, the dirent-style library, the device name-to-number mmaped database, the approximate binary search directly on System.map, and many code and documentation cleanups. David Mossberger-Tang wrote the generic BFD support for psupdate. Albert Cahalan <albert@users.sf.net> rewrote ps for full Unix98 and BSD support, along with some ugly hacks for obsolete and foreign syntax. 

Please send bug reports to <procps-feedback@lists.sf.net>. No subscription is required or suggested.