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TOP (1) | General commands | Unix Manual Pages | :man


top - display and update information about the top cpu processes


Display Of Threads
Description Of Memory


top [ -SbiInqutv ] [ -dcount ] [ -stime ] [ -ofield ] [ -Uusername ] [ -mio|cpu ] [ 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 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.


-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.
-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 possibility of discovering the problem. This option can only be used by root.
-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 execution time. The uid numbers are displayed instead of the names.
-v Write version number information to stderr then exit immediately. No other processing takes place when this option is used. To see current revision information while top is running, use the help command ‘‘?’’.
-dcount 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 automatically 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.
-ofield 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 currently only accepts usernames and will not understand uid numbers.
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, -u, and -t 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.


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) are recognized, and a newline terminates 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 information 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 number).
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 processes 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 fron 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 allocation.

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. 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 COMMAND is the name of the command that the process is currently running (if the process is swapped out, this column is marked ‘‘<swapped>’’).


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


TOPuser-configurable defaults for options.


/dev/kmemkernel memory
/dev/mem physical memory
/etc/passwd used to map uid numbers to user names
/boot/kernel/kernelsystem 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 reality.






Created by Blin Media, 2008-2013