Linux and Unix ps command

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About ps
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About ps

Reports a snapshot of the status of currently running processes.

Syntax

ps [options]

Description

On every UNIX-like operating system, the process status command (ps) displays information about active processes. Every operating system's version of ps is slightly different, so consult your own documentation for specific options.

This documentation describes a version of ps common to many distributions of Linux. It 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 might cause conflicts. There are some synonymous options, which are functionally identical, due to the many standards and ps implementations that ps is compatible with.

Note that "ps -aux" is different than "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, ps may interpret the command as "ps aux" instead and print a warning. This behavior is intended to aid in the transitioning of legacy scripts, but it is 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 arguments (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.

Options: Simple Process Selection

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.
-A Select all processes. Identical to -e.
-a Select all processes except both session leaders and processes not associated with a terminal.
-d Select all processes except session leaders.
--deselect Select all processes except those that fulfill the specified conditions (negates the selection). Identical to -N.
-e Select all processes. Identical to -A.
g Really all processes, 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.
-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.
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.

Options: Process Selection By List

These options accept a single argument in the form of a blank-separated or comma-separated list, and they can be used multiple times. For example:

 ps -p "1 2" -p 3,4 

...is a valid command.

Options which select processes by list are as follows:

-123 Identical to "--pid 123".
123 Identical to "--pid 123".
-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.
-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.
--Group grplist Select by real group ID (RGID) or name. Identical to -G.
--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. The -g option is often an alternative to --group.
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.
--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.
-s sesslist Select by session ID. This selects the processes with a session ID specified in sesslist.
--sid sesslist Select by session ID. Identical to -s.
t ttylist Select by tty. Nearly identical to -t and --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.
--tty ttylist Select by terminal. Identical to -t and t.
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. 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.
-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. Identical to U and --user.
--User userlist Select by real user ID (RUID) or name. Identical to -U.
--user userlist Select by effective user ID (EUID) or name. Identical to -u and U.

Options: Output Format Control

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

-c Show different scheduler information for the -l option.
--context Display security context format (when using SE Linux).
-f Do 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.
-F Extra full format. See the -f option, which -F implies.
--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 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 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.
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.
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).

Options: Output Modifiers

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 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.
--cols n Set screen width.
--columns n Set screen width.
--cumulative Include some dead child process data (as a sum with the parent).
e Show the environment after the command.
f ASCII art process hierarchy (as many trees, also referred to as a "forest").
--forest ASCII art process tree.
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. Linux ps follows the standard 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.
-H Show process hierarchy (forest).
--headers Repeat header lines, one per page of output.
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
--lines n Set screen height.
-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).
N namelist Specify namelist file. Identical to -n; see -n, above.
--no-headers Print no header line at all. --no-heading is an alias for this option.
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.
--rows n Set screen height.
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.
--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"
w Wide output. Use this option twice for unlimited width.
-w Wide output. Use this option twice for unlimited width.
--width n Set screen width.

Options: Thread Display

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

Options: Displaying Other Information

--help section Print a help message. The section argument can be one of simple, list, output, threads, misc or all. The argument can be shortened to one of the underlined letters as in: s|l|o|t|m|a.
--info Print debugging info.
L List all format specifiers.
V Print the procps-ng version.
-V Print the procps-ng version.
--version Print the procps-ng version.

Notes

ps works by reading the virtual files in /proc. 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 if the parent process exits.

If the length of the username is greater than the length of the display column, the numeric user ID is displayed instead.

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 command if you want to sort the cooked values.

key long name 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 KiB
y priority kernel scheduling priority

AIX Format Descriptors

ps supports AIX format descriptors, which work somewhat like the formatting codes of printf. For example, the normal default output can be produced with this:

ps -eo "%p %y %x %c"

AIX Format Descriptors are as follows:

code normal header
%C pcpu %CPU
%G group GROUP
%P ppid PPID
%U user USER
%a args COMMAND
%c comm COMMAND
%g rgroup RGROUP
%n nice NI
%p pid PID
%r pgid PGID
%t etime ELAPSED
%u ruser RUSER
%x time TIME
%y tty TTY
%z vsz VSZ

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".

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.

code header description
%cpu %CPU CPU utilization of the process in "##.#" format. Currently, it is the CPU time used divided by the time the process has been running (cputime/realtime ratio), expressed as a percentage. It will not add up to 100% unless you are lucky. (alias: pcpu).
%mem %MEM ratio of the process's resident set size to the physical memory on the machine, expressed as a percentage. (alias: pmem).
args COMMAND command with all its arguments as a string. Modifications to the arguments may be shown. The output in this column may contain spaces. A process marked <defunct> is partly dead, waiting to be fully destroyed by its parent. Sometimes the process arguments will be unavailable; when this happens, ps will instead print the executable name in brackets. (alias: cmd, command). See also the comm format keyword, the -f option, and the c option. When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width.
blocked BLOCKED mask of the blocked signals, see signals. According to the width of the field, a 32 or 64-bit mask in hexadecimal format is displayed. (alias: sig_block, sigmask).
bsdstart START time the command started. If the process was started less than 24 hours ago, the output format is " HH:MM", else it is " Mmm:SS" (where Mmm is the three letters of the month). See also lstart, start, start_time, and stime.
bsdtime TIME accumulated CPU time, user + system. The display format is usually "MMM:SS", but can be shifted to the right if the process used more than 999 minutes of CPU time.
c C processor utilization. Currently, this is the integer value of the percent usage over the lifetime of the process. (see %cpu).
caught CAUGHT mask of the caught signals, see signals. According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed. (alias: sig_catch, sigcatch).
cgroup CGROUP display control groups to which the process belongs.
class CLS scheduling class of the process. (alias: policy, cls). Field's possible values are:
- not reported
TS SCHED_OTHER
FF SCHED_FIFO
RR SCHED_RR
B SCHED_BATCH
ISO SCHED_ISO
IDL SCHED_IDLE
? unknown value
cls CLS scheduling class of the process. (alias: policy, class). Field's possible values are the same as for class, listed above.
cmd CMD see args. (alias: args, command).
comm COMMAND command name (only the executable name). Modifications to the command name will not be shown. A process marked <defunct> is partly dead, waiting to be fully destroyed by its parent. The output in this column may contain spaces. (alias: ucmd, ucomm). See also the args format keyword, the -f option, and the c option.

When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width.
command COMMAND See args. (alias: args, command).
cp CP per-mill (tenths of a percent) CPU usage. (see %cpu).
cputime TIME cumulative CPU time, "[DD-]hh:mm:ss" format. (alias: time).
egid EGID effective group ID number of the process as a decimal integer. (alias: <bgid>).
egroup EGROUP effective group ID of the process. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias: group).
eip EIP instruction pointer.
esp ESP stack pointer.
etime ELAPSED elapsed time since the process was started, in the form "[[DD-]hh:]mm:ss".
etimes ELAPSED elapsed time since the process was started, in seconds.
euid EUID effective user ID (alias: uid).
euser EUSER effective user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. The n option can be used to force the decimal representation. (alias: uname, user).
f F flags associated with the process, see the PROCESS FLAGS section. (alias: flag, flags).
fgid FGID filesystem access group ID. (alias: fsgid).
fgroup FGROUP filesystem access group ID. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias: fsgroup).
flag F see f. (alias: f, flags).
flags F see f. (alias: f, flag).
fname COMMAND first 8 bytes of the base name of the process's executable file. The output in this column may contain spaces.
fuid FUID filesystem access user ID. (alias: fsuid).
fuser FUSER filesystem access user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise.
gid GID see egid. (alias: egid).
group GROUP see egroup. (alias: egroup).
ignored IGNORED mask of the ignored signals, see signals. According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed. (alias: sig_ignore, sigignore).
label LABEL security label, most commonly used for SE Linux context data. This is for the Mandatory Access Control ("MAC") found on high-security systems.
lstart STARTED time the command started. See also bsdstart, start, start_time, and stime.
lwp LWP light weight process (thread) ID of the dispatchable entity (alias: spid, tid). See tid for additional information.
maj_flt MAJFLT The number of major page faults that have occurred with this process.
min_flt MINFLT The number of minor page faults that have occurred with this process.
ni NI nice value. This ranges from 19 (nicest) to -20 (not nice to others). (alias: nice).
nice NI see ni. (alias: ni).
nlwp NLWP number of lwps (threads) in the process. (alias: thcount).
nwchan WCHAN address of the kernel function where the process is sleeping (use wchan if you want the kernel function name). Running tasks will display a dash ('-') in this column.
pcpu %CPU see %cpu. (alias: %cpu).
pending PENDING mask of the pending signals. See signals. Signals pending on the process are distinct from signals pending on individual threads. Use the m option or the -m option to see both. According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed. (alias: sig).
pgid PGID process group ID or, equivalently, the process ID of the process group leader. (alias: pgrp).
pgrp PGRP see pgid. (alias: pgid).
pid PID a number representing the process ID (alias: tgid).
pmem %MEM see %mem. (alias: %mem).
policy POL scheduling class of the process. (alias: class, cls). Possible values are:

- not reported
TS SCHED_OTHER
FF SCHED_FIFO
RR SCHED_RR
B SCHED_BATCH
ISO SCHED_ISO
IDL SCHED_IDLE
? unknown value
ppid PPID parent process ID.
pri PRI priority of the process. Higher number means lower priority.
psr PSR processor that process is currently assigned to.
rgid RGID real group ID.
rgroup RGROUP real group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise.
rss RSS resident set size, the non-swapped physical memory that a task has used (in kilobytes). (alias: rssize, rsz).
rssize RSS see rss. (alias: rss, rsz).
rsz RSZ see rss. (alias: rss, rssize).
rtprio RTPRIO realtime priority.
ruid RUID real user ID.
ruser RUSER real user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise.
s S minimal state display (one character). See section PROCESS STATE CODES for the different values. See also stat if you want additional information displayed. (alias: state).
sched SCH scheduling policy of the process. The policies SCHED_OTHER (SCHED_NORMAL), SCHED_FIFO, SCHED_RR, SCHED_BATCH, SCHED_ISO, and SCHED_IDLE are respectively displayed as 0, 1, 2, 3, 4, and 5.
sess SESS session ID or, equivalently, the process ID of the session leader. (alias: session, sid).
sgi_p P processor that the process is currently executing on. Displays "*" if the process is not currently running or runnable.
sgid SGID saved group ID. (alias: svgid).
sgroup SGROUP saved group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise.
sid SID see sess. (alias: sess, session).
sig PENDING see pending. (alias: pending, sig_pend).
sigcatch CAUGHT see caught. (alias: caught, sig_catch).
sigignore IGNORED see ignored. (alias: ignored, sig_ignore).
sigmask BLOCKED see blocked. (alias: blocked, sig_block).
size SIZE approximate amount of swap space that would be required if the process were to dirty all writable pages and then be swapped out. This approximation is very rough.
spid SPID see lwp. (alias: lwp, tid).
stackp STACKP address of the bottom (start) of stack for the process.
start STARTED time the command started. If the process was started less than 24 hours ago, the output format is "HH:MM:SS", else it is " Mmm dd" (where Mmm is a three-letter month name). See also lstart, bsdstart, start_time, and stime.
start_time START starting time or date of the process. Only the year will be displayed if the process was not started the same year ps was invoked, or "MmmDD" if it was not started the same day, or "HH:MM" otherwise. See also bsdstart, start, lstart, and stime.
stat STAT multi-character process state. See section PROCESS STATE CODES for the different values meaning. See also s and state if you just want the first character displayed.
state S see s. (alias: s).
suid SUID saved user ID. (alias: svuid).
supgid SUPGID group ids of supplementary groups, if any.
supgrp SUPGRP group names of supplementary groups, if any.
suser SUSER saved user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias: svuser).
svgid SVGID see sgid. (alias: sgid).
svuid SVUID see suid. (alias: suid).
sz SZ size in physical pages of the core image of the process. This includes text, data, and stack space. Device mappings are currently excluded; this is subject to change. See vsz and rss.
tgid TGID a number representing the thread group to which a task belongs (alias: pid). It is the process ID of the thread group leader.
thcount THCNT see nlwp. (alias: nlwp). number of kernel threads owned by the process.
tid TID the unique number representing a dispatacable entity (alias: lwp, spid). This value may also appear as: a process ID (pid); a process group ID (pgrp); a session ID for the session leader (sid); a thread group ID for the thread group leader (tgid); and a tty process group ID for the process group leader (tpgid).
time TIME cumulative CPU time, "[DD-]HH:MM:SS" format. (alias: cputime).
tname TTY controlling tty (terminal). (alias: tt, tty).
tpgid TPGID ID of the foreground process group on the tty (terminal) that the process is connected to, or -1 if the process is not connected to a tty.
tt TT controlling tty (terminal). (alias: tname, tty).
tty TT controlling tty (terminal). (alias: tname, tt).
ucmd CMD see comm. (alias: comm, ucomm).
ucomm COMMAND see comm. (alias: comm, ucmd).
uid UID see euid. (alias: euid).
uname USER see euser. (alias: euser, user).
user USER see euser. (alias: euser, uname).
vsize VSZ see vsz. (alias: vsz).
vsz VSZ virtual memory size of the process in KiB (1024-byte units). Device mappings are currently excluded; this is subject to change. (alias: vsize).
wchan WCHAN name of the kernel function in which the process is sleeping, a "-" if the process is running, or a "*" if the process is multi-threaded and ps is not displaying threads.

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

The following "personalities" affect the output of ps:

390 like the OS/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 This is the recommended personality for ps.
old like the original Linux ps (totally non-standard)
os390 like OS/390 Open Edition ps
posix The personality which conforms to the 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.

Examples

To see every process running on the system, using the 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 display 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 and 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 -Ao pid,tt,user,fname,tmout,f,wchan

Print only the process IDs of syslogd, the syslog daemon:

ps -C syslogd -o pid=

Print only the name of process ID 15:

ps -p 15 -o comm=

Related commands

bg
free
fuser
kill
killall
nice
pagesize
pgrep
priocntrl
pstree
top
tty
uptime
who