TOP(1)

NAME
top - display and update information about the top CPU processes

SYNOPSIS
top [-1bCHIinqSu] [-d count] [-g string] [-o field] [-p pid] [-s time] [-U [-]user] [number]

DESCRIPTION
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 capabilities 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 redirected to a file, it acts as if it were being run on a dumb terminal.

The options are as follows:

-1  Display combined CPU statistics for all processors on a single line instead of one line per CPU. If there are more than 8 CPUs detected in the system this option is automatically enabled.

-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.

-C  Show command line arguments as well as the process itself.

-d count
    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 to be shown before top automatically exits. For intelligent terminals, no upper limit is set. The default is 1 for dumb terminals.

-g string
    Display only processes that contain string in their command name. If displaying of arguments is enabled, the arguments are searched too.

-H  Show process threads in the display. Normally, only the main process is shown. This option makes all threads visible.

-I  Do not display idle processes. By default, top displays both active and idle processes.

-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.

-n  Use non-interactive mode. This is identical to batch mode.

-o field
    Sort the process display area using the specified field as the primary key. The field name is the name of the column as seen in the output, but in lower case. The OpenBSD version of top supports cpu, size, res, time, pri, pid, and command.

-p pid
    Show only the process pid.

-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 possibility of discovering the problem. This option can only be used by root.

-S  Show system processes in the display. Normally, system processes such as the pager and the swapper are not shown. This option makes them visible.

-s time
    Set the delay between screen updates to time seconds. The value may be fractional, to permit delays of less than 1 second. The default delay between updates is 5 seconds.

-U [-]user
    Show only those processes owned by user. The prefix ‘-’ hides processes owned by that user. This option currently only accepts usernames and does not understand UID numbers.

-u  Do not take the time to map UID numbers to usernames. Normally, top will read as much of the password database as is necessary to map all the user ID numbers it encounters into login names. This option disables all that, while possibly decreasing execution time. The UID numbers are displayed instead of the names.

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, infinity.

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 environment variable TOP.

The options -I, -S, and -u are actually toggles. 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.

INTERACTIVE MODE
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 displays; 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 accordingly. While typing this information in, the user's erase and kill keys (as set up by the command stty(1)) are recognized, and a newline terminates the input.

These commands are currently recognized (^L refers to control-L):

h |?
    Display a summary of the commands (help screen).

^L  Redraw the screen.

<space>
    Update the screen.

q   Quit top.

+   Reset any filters put in place by the ‘g’, ‘p’, and ‘u’ interactive commands, or their command line equivalents, or any process highlighting put in place by the ‘P’ interactive command.

1   Toggle the display of per CPU or combined CPU statistics.

C   Toggle the display of process command line arguments.

d count
    Show only count displays, then exit.

e   Display a list of system errors (if any) generated by the last kill or renice command.

g string
    Display only processes that contain string in their command name. If displaying of arguments is enabled, the arguments are searched too. ‘g+’ shows all processes.

H   Toggle the display of process threads.

I | i
    Toggle the display of idle processes.

k   [-sig] pid Send signal -sig (TERM by default) to process pid. This acts similarly to the command kill(1).

n# count
    Show count processes.

o field
    Sort the process display area using the specified field as the primary key. Values are the same as for the -o flag, as detailed above.

P pid
    Highlight a specific process, selected by pid. ‘P+’ removes process highlighting.

p pid
    Show only the process pid. ‘p+’ shows all processes.

r count pid
    Change the priority (the nice) of a list of processes to count for process pid. This acts similarly to the command renice(8).

S   Toggle the display of system processes.

s time
    Set the delay between screen updates to time seconds.

u [-]user
    Show only those processes owned by user. ‘u+’ shows processes belonging to all users. The ‘-’ prefix hides processes belonging to a single user.

THE DISPLAY
The top few lines of the display show general information about the state of the system, including the three load average numbers, the hostname, the current time, the number of existing processes, the number of processes in each state (starting, running, idle, stopped, zombie, dead, and on processor), and a percentage of time spent in each of the processor states (user, nice, system, interrupt, and idle). It also includes information about physical and virtual memory allocation. The load average numbers give the number of jobs in the run queue averaged over 1, 5, and 15 minutes.

The remainder of the screen displays information about individual processes. This display is similar in spirit to ps(1) but it is not exactly the same. The following fields are displayed:

PID The process ID.

USERNAME
    The name of the process's owner.

TID The thread ID, used instead of USERNAME if -H is specified.

UID Used instead of USERNAME if -u is specified.

PRI The current priority of the process.

NICE
    The nice amount (in the range -20 to 20).

SIZE
    The total size of the process (the text, data, and stack segments).

RES The current amount of resident memory.

STATE
    The current state (one of start, run, sleep, stop, idle, zomb, dead, or onproc). On multiprocessor systems, this is followed by a slash and the CPU number on which the process is bound.

WAIT
    A description of the wait channel the process is sleeping on if it's asleep.

TIME
    The number of system and user CPU seconds that the process has used.

CPU The raw percentage of CPU usage and the default field on which the display is sorted.

COMMAND
    The name of the command that the process is currently running. (If the process is swapped out, this column is enclosed by angle brackets.)

ENVIRONMENT

TOP User-configurable defaults for options.

FILES
/dev/kmem
    kernel memory
/dev/mem
    physical memory
/etc/passwd
    used to map user ID to user
/bsd
    kernel image

SEE ALSO
fstat(1), kill(1), netstat(1), ps(1), stty(1), systat(1), mem(4), iostat(8), pstat(8), renice(8), vmstat(8)

AUTHORS
William LeFebvre, EECS Department, Northwestern University

CAVEATS
As with ps(1), top only provides snapshots of a constantly changing system.