top - display and update information about the top cpu processes
top [ -bCHIinqStuv ] [ -dcount ] [ -mio|cpu ] [ -ofield ] [ -stime ] [
-Uusername ] [ number ]
Top displays the top processes on the system and periodically updates
this information. If standard output is an intelligent terminal (see
below) then as many processes as will fit on the terminal screen are
displayed by default. Otherwise, a good number of them are shown
(around 20). Raw cpu percentage is used to rank the processes. If
number is given, then the top number processes will be displayed
instead of the default.
Top makes a distinction between terminals that support advanced capa-
bilities and those that do not. This distinction affects the choice of
defaults for certain options. In the remainder of this document, an
"intelligent" terminal is one that supports cursor addressing, clear
screen, and clear to end of line. Conversely, a "dumb" terminal is one
that does not support such features. If the output of top is redi-
rected to a file, it acts as if it were being run on a dumb terminal.
-C Toggle CPU display mode. By default top displays the weighted
CPU percentage in the WCPU column (this is the same value that
ps(1) displays as CPU). Each time -C flag is passed it toggles
between "raw cpu" mode and "weighted cpu" mode, showing the
"CPU" or the "WCPU" column respectively.
-S Show system processes in the display. Normally, system pro-
cesses such as the pager and the swapper are not shown. This
option makes them visible.
-b Use "batch" mode. In this mode, all input from the terminal is
ignored. Interrupt characters (such as ^C and ^\) still have an
effect. This is the default on a dumb terminal, or when the
output is not a terminal.
-i Use "interactive" mode. In this mode, any input is immediately
read for processing. See the section on "Interactive Mode" for
an explanation of which keys perform what functions. After the
command is processed, the screen will immediately be updated,
even if the command was not understood. This mode is the
default when standard output is an intelligent terminal.
-I Do not display idle processes. By default, top displays both
active and idle processes.
-t Do not display the top process.
Display either 'cpu' or 'io' statistics. Default is 'cpu'.
-n Use "non-interactive" mode. This is identical to "batch" mode.
-q Renice top to -20 so that it will run faster. This can be used
when the system is being very sluggish to improve the possibil-
ity of discovering the problem. This option can only be used by
-u Do not take the time to map uid numbers to usernames. Normally,
top will read as much of the file "/etc/passwd" as is necessary
to map all the user id numbers it encounters into login names.
This option disables all that, while possibly decreasing execu-
tion time. The uid numbers are displayed instead of the names.
-v Write version number information to stderr then exit immedi-
ately. No other processing takes place when this option is
used. To see current revision information while top is running,
use the help command "?".
Show only count displays, then exit. A display is considered to
be one update of the screen. This option allows the user to
select the number of displays he wants to see before top auto-
matically exits. For intelligent terminals, no upper limit is
set. The default is 1 for dumb terminals.
-stime Set the delay between screen updates to time seconds. The
default delay between updates is 2 seconds.
Sort the process display area on the specified field. The field
name is the name of the column as seen in the output, but in
lower case. Likely values are "cpu", "size", "res", and "time",
but may vary on different operating systems. Note that not all
operating systems support this option.
Show only those processes owned by username. This option cur-
rently only accepts usernames and will not understand uid num-
Both count and number fields can be specified as "infinite", indicating
that they can stretch as far as possible. This is accomplished by
using any proper prefix of the keywords "infinity", "maximum", or
"all". The default for count on an intelligent terminal is, in fact,
The environment variable TOP is examined for options before the command
line is scanned. This enables a user to set his or her own defaults.
The number of processes to display can also be specified in the envi-
ronment variable TOP. The options -I, -S, -u, and -t are actually tog-
gles. A second specification of any of these options will negate the
first. Thus a user who has the environment variable TOP set to "-I"
may use the command "top -I" to see idle processes.
When top is running in "interactive mode", it reads commands from the
terminal and acts upon them accordingly. In this mode, the terminal is
put in "CBREAK", so that a character will be processed as soon as it is
typed. Almost always, a key will be pressed when top is between dis-
plays; that is, while it is waiting for time seconds to elapse. If
this is the case, the command will be processed and the display will be
updated immediately thereafter (reflecting any changes that the command
may have specified). This happens even if the command was incorrect.
If a key is pressed while top is in the middle of updating the display,
it will finish the update and then process the command. Some commands
require additional information, and the user will be prompted accord-
ingly. While typing this information in, the user's erase and kill
keys (as set up by the command stty) are recognized, and a newline ter-
minates the input.
These commands are currently recognized (^L refers to control-L):
^L Redraw the screen.
h or ? Display a summary of the commands (help screen). Version infor-
mation is included in this display.
q Quit top.
d Change the number of displays to show (prompt for new number).
Remember that the next display counts as one, so typing d1 will
make top show one final display and then immediately exit.
m Toggle the display between 'cpu' and 'io' modes.
n or # Change the number of processes to display (prompt for new num-
s Change the number of seconds to delay between displays (prompt
for new number).
S Toggle the display of system processes.
k Send a signal ("kill" by default) to a list of processes. This
acts similarly to the command kill(1)).
r Change the priority (the "nice") of a list of processes. This
acts similarly to the command renice(8)).
u Display only processes owned by a specific username (prompt for
username). If the username specified is simply "+", then pro-
cesses belonging to all users will be displayed.
o Change the order in which the display is sorted. This command
is not available on all systems. The sort key names vary from
system to system but usually include: "cpu", "res", "size",
"time". The default is cpu.
e Display a list of system errors (if any) generated by the last
kill or renice command.
i (or I) Toggle the display of idle processes.
t Toggle the display of the top process.
The actual display varies depending on the specific variant of Unix
that the machine is running. This description may not exactly match
what is seen by top running on this particular machine. Differences
are listed at the end of this manual entry.
The top few lines of the display show general information about the
state of the system, including the last process id assigned to a
process (on most systems), the three load averages, the current time,
the number of existing processes, the number of processes in each state
(sleeping, running, starting, zombies, and stopped), and a percentage
of time spent in each of the processor states (user, nice, system, and
idle). It also includes information about physical and virtual memory
The remainder of the screen displays information about individual pro-
cesses. This display is similar in spirit to ps(1) but it is not
exactly the same. PID is the process id, USERNAME is the name of the
process's owner (if -u is specified, a UID column will be substituted
for USERNAME), PRI is the current priority of the process, NICE is the
nice amount (in the range -20 to 20), SIZE is the total size of the
process (text, data, and stack), RES is the current amount of resident
memory (both SIZE and RES are given in kilobytes), STATE is the current
state (one of "sleep", "WAIT", "run", "idl", "zomb", or "stop"), TIME
is the number of system and user cpu seconds that the process has used,
WCPU, when displayed, is the weighted cpu percentage (this is the same
value that ps(1) displays as CPU), CPU is the raw percentage and is the
field that is sorted to determine the order of the processes, and COM-
MAND is the name of the command that the process is currently running
(if the process is swapped out, this column is marked "").
The "ABANDONED" state (known in the kernel as "SWAIT") was abandoned,
thus the name. A process should never end up in this state.
William LeFebvre, EECS Department, Northwestern University
TOP user-configurable defaults for options.
/dev/kmem kernel memory
/dev/mem physical memory
/etc/passwd used to map uid numbers to user names
/boot/kernel/kernel system image
Don't shoot me, but the default for -I has changed once again. So many
people were confused by the fact that top wasn't showing them all the
processes that I have decided to make the default behavior show idle
processes, just like it did in version 2. But to appease folks who
can't stand that behavior, I have added the ability to set "default"
options in the environment variable TOP (see the OPTIONS section).
Those who want the behavior that version 3.0 had need only set the
environment variable TOP to "-I".
The command name for swapped processes should be tracked down, but this
would make the program run slower.
As with ps(1), things can change while top is collecting information
for an update. The picture it gives is only a close approximation to
kill(1), ps(1), stty(1), mem(4), renice(8)
DISPLAY OF THREADS
The '-H' option will toggle the display of kernel visible thread con-
texts. At runtime the 'H' key will toggle this mode. The default is
DESCRIPTION OF MEMORY
Mem: 9220K Active, 1032K Inact, 3284K Wired, 1MB Cache, 2M Buf, 1320K
Free Swap: 91M Total, 79M Free, 13% Inuse, 80K In, 104 K Out
number of pages active
Inact: number of pages inactive
Wired: number of pages wired down, including cached file data pages
Cache: number of pages used for VM-level disk caching
Buf: number of pages used for BIO-level disk caching
Free: number of pages free
Total: total available swap usage
Free: total free swap usage
Inuse: swap usage
In: pages paged in from swap devices (last interval)
Out: pages paged out to swap devices (last interval)
4th Berkeley Distribution Local TOP(1)