ps - report process status
ps gives a snapshot of the current processes. If you want a repetitive update of this status, use top. This man page documents the /proc-based version of ps, or tries to.
This version of ps accepts several kinds of options.
Unix options may be grouped and must be preceeded by a dash. BSD options may be grouped and must not be used with a dash. GNU long options are preceeded by two dashes.
Options of different types may be freely mixed.
Set the I_WANT_A_BROKEN_PS environment variable to force BSD syntax even when options are preceeded by a dash. The PS_PERSONALITY environment variable (described below) provides more detailed control of ps behavior.
SIMPLE PROCESS SELECTION -A select all processes
-N negate selection
-a select all with a tty except session leaders
-d select all, but omit session leaders
-e select all processes
T select all processes on this terminal
a select all processes on a terminal, including those of other users
g really all, even group leaders (does nothing w/o SunOS settings)
r restrict output to running processes
x select processes without controlling ttys
--deselect negate selection
PROCESS SELECTION BY LIST -C select by command name
-G select by RGID (supports names)
-U select by RUID (supports names)
-g select by session leader OR by group name
-p select by PID
-s select processes belonging to the sessions given
-t select by tty
-u select by effective user ID (supports names)
U select processes for specified users
p select by process ID
t select by tty
--Group select by real group name or ID
--User select by real user name or ID
--group select by effective group name or ID
--pid select by process ID
--sid select by session ID
--tty select by terminal
--user select by effective user name or ID
-123 implied --sid
123 implied --pid
OUTPUT FORMAT CONTROL -O is preloaded "-o"
-c different scheduler info for -l option
-f does full listing
-j jobs format
-l long format
-o user-defined format
-y do not show flags; show rss in place of addr
O is preloaded "o" (overloaded)
X old Linux i386 register format
j job control format
l Display long format
o specify user-defined format
s display signal format
u display user-oriented format
v display virtual memory format
--format user-defined format
OUTPUT MODIFIERS -H show process hierarchy (forest)
-m shows threads
-n sets namelist file
-w wide output
C use raw CPU time for %CPU instead of decaying average
N specify namelist file
O sorting order (overloaded)
--cumulative include some dead child process data (as a sum with the parent)
c true command name
e show environment after the command
f, --forest ASCII-art process hierarchy (forest)
h no header (or, one header per screen in the BSD personality)
m all threads
n numeric output for WCHAN and USER
--width set screen width
--headers repeat header lines, one per page of output
--no-headers print no header line at all
--rows set screen height
--sort specify sorting order
INFORMATION -V, V,
--version print version
L list all format specifiers
--help print help message
--info print debugging info
OBSOLETE A increases the argument space (DecUnix)
M use alternate core (try -n or N instead)
W get swap info from ... not /dev/drum (try -n or N instead)
k use /vmcore as c-dumpfile (try -n or N instead)
The -g option can select by session leader OR by group name. Selection by session leader is specified by many standards, but selection by group is the logical behavior that several other operating systems use. This ps will select by session leader when the list is completely numeric (as sessions are). Group ID numbers will work only when some group names are also specified.
The m option should not be used. Use -m or -o with a list. (m displays memory info, shows threads, or sorts by memory use)
The h option is problematic. Standard BSD ps uses the option to print a header on each page of output, but older Linux ps uses the 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 and disable headers entirely, respectively.
Terminals (ttys, or screens for text output) can be specified in several forms: /dev/ttyS1, ttyS1, S1. Obsolete ps t (your own terminal) and ps t? (processes without a terminal) syntax is supported, but modern options (T, -t with list, x, t with list) should be used instead.
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, specify the other option (sorting or formatting) in some other way.
For sorting, BSD O option syntax is O[+|-]k1[,[+|-]k2[,...]] Order the process listing according to the multilevel sort specified by the sequence of short keys from SORT KEYS, k1, k2, ... The `+' is quite optional, merely re-iterating the default direction on a key. `-' reverses direction only on the key it precedes. The O option must be the last option in a single command argument, but specifications in successive arguments are catenated.
GNU sorting syntax is --sortX[+|-]key[,[+|-]key[,...]] Choose a multi-letter key from the SORT KEYS section. X may be any convenient separator character. To be GNU-ish use `='. The `+' is really optional since default direction is increasing numerical or lexicographic order. For example, ps jax --sort=uid,-ppid,+pid
This ps works by reading the virtual files in /proc. This ps does not need to be suid kmem or have any privileges to run. Do not give this ps any special permissions.
This ps needs access to a namelist file for proper WCHAN display. The namelist file must match the current Linux kernel exactly for correct output.
To produce the WCHAN field, ps needs to read the System.map file created when the kernel is compiled. The search path is:
The member used_math of task_struct is not shown, since crt0.s checks to see if math is present. This causes the math flag to be set for all processes, and so it is worthless. (Somebody fix libc or the kernel please)
Programs swapped out to disk will be shown without command line arguments, and unless the c option is given, in brackets.
%CPU shows the cputime/realtime percentage. It will not add up to 100% unless you are lucky. It is time used divided by the time the process has been running.
The SIZE and RSS fields don't count the page tables and the task_struct of a proc; this is at least 12k of memory that is always resident. SIZE is the virtual size of the proc (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 ALIGNWARN 001 print alignment warning msgs
STARTING 002 being created
EXITING 004 getting shut down
PTRACED 010 set if ptrace (0) has been called
TRACESYS 020 tracing system calls
FORKNOEXEC 040 forked but didn't exec
SUPERPRIV 100 used super-user privileges
DUMPCORE 200 dumped core
SIGNALED 400 killed by a signal
PROCESS STATE CODES D uninterruptible sleep (usually IO)
R runnable (on run queue)
T traced or stopped
Z a defunct ("zombie") process
For BSD formats and when the "stat" keyword is used, additional letters may be displayed: W has no resident pages
< high-priority process
N low-priority task
L has pages locked into memory (for real-time and custom IO)
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. 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 cmdline full command line
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
K stime system 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 minor device number of 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"
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
These may be used to control both output format and sorting. For example: ps -eo pid,user,args --sort user
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...
CMD_ENV Set to one of posix,old,linux,bsd,sun,digital...
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.
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".
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 Digital Unix 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)
sco like SCO ps
sgi like Irix ps
sun like SunOS 4 ps (totally non-standard)
sunos like SunOS 4 ps (totally non-standard)
To see every process on the system using standard syntax:
To see every process on the system using BSD syntax:
To see every process except those running as root (real & effective ID)
ps -U root -u root -N
To see every process with a user-defined format:
ps -eo pid,tt,user,fname,tmout,f,wchan
Odd display with AIX field descriptors:
ps -o "%u : %U : %p : %a"
Print only the process IDs of syslogd:
ps -C syslogd -o pid=
This ps conforms to version 2 of the Single Unix Specification.