The Top Command

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NAMEtop - display top CPU processes
SYNOPSIStop [-] [d
delay] [p pid] [q] [c] [C] [S] [s] [i] [n iter] [b]
DESCRIPTIONtop provides an ongoing look at processor activity
in real time. It displays a listing of the most CPU-intensive tasks on the
system, and can provide an interactive interface for manipulating processes. It
can sort the tasks by CPU usage, memory usage and runtime. can be better
configured than the standard top from the procps suite. Most features can either
be selected by an interactive command or by specifying the feature in the
personal or system-wide configuration file. See below for more information.

COMMAND-LINE OPTIONSd Specifies the delay between
screen updates. You can change this with the s interactive command. p Monitor
only processes with given process id. This flag can be given up to twenty times.
This option is neither available interactively nor can it be put into the
configuration file. q This causes top to refresh without any delay. If the
caller has superuser privileges, top runs with the highest possible priority. S
Specifies cumulative mode, where each process is listed with the CPU time that
it as well as its dead children has spent. This is like the -S flag to ps(1). See the
discussion below of the S interactive command. s Tells top to run in secure
mode. This disables the potentially dangerous of the interactive commands (see
below). A secure top is a nifty thing to leave running on a spare terminal. i
Start top ignoring any idle or zombie processes. See the interactive command i
below. C display total CPU states instead of individual CPUs. This option only
affects SMP systems. c display command line instead of the command name only.
The default behavior has been changed as this seems to be more useful. H Show
all threads. n Number of iterations. Update the display this number of times and
then exit. b Batch mode. Useful for sending output from top to other programs or
to a file. In this mode, top will not accept command line input. It runs until
it produces the number of iterations requested with the n option or until
killed. Output is plain text suitable for display on a dumb terminal.
FIELD DESCRIPTIONStop displays a variety of information about
the processor state. The display is updated every 5 seconds by default, but you
can change that with the d command-line option or the s interactive command.
"uptime" This line displays the time the system has been up, and the three load
averages for the system. The load averages are the average number of process
ready to run during the last 1, 5 and 15 minutes. This line is just like the
output of uptime(1). The
uptime display may be toggled by the interactive l command. processes The total
number of processes running at the time of the last update. This is also broken
down into the number of tasks which are running, sleeping, stopped, or undead.
The processes and states display may be toggled by the t interactive command.
"CPU states" Shows the percentage of CPU time in user mode, system mode, niced
tasks, iowait and idle. (Niced tasks are only those whose nice value is
positive.) Time spent in niced tasks will also be counted in system and user
time, so the total will be more than 100%. The processes and states display may
be toggled by the t interactive command. Mem Statistics on memory usage,
including total available memory, free memory, used memory, shared memory, and
memory used for buffers. The display of memory information may be toggled by the
m interactive command. Swap Statistics on swap space, including total swap
space, available swap space, and used swap space. This and Mem are just like the
output of free(1). PID The
process ID of each task. PPID The parent process ID each task. UID The user ID
of the task's owner. USER The user name of the task's owner. PRI The priority of
the task. NI The nice value of the task. Negative nice values are higher
priority. SIZE The size of the task's code plus data plus stack space, in
kilobytes, is shown here. TSIZE The code size of the task. This gives strange
values for kernel processes and is broken for ELF processes. DSIZE Data + Stack
size. This is broken for ELF processes. TRS Text resident size. SWAP Size of the
swapped out part of the task. D Size of pages marked dirty. LC Last used
processor. (That this changes from time to time is not a bug; Linux
intentionally uses weak affinity. Also notice that the very act of running top
may break weak affinity and cause more processes to change current CPU more
often because of the extra demand for CPU time.) RSS The total amount of
physical memory used by the task, in kilobytes, is shown here. For ELF processes
used library pages are counted here, for a.out processes not. SHARE The amount
of shared memory used by the task is shown in this column. STAT The state of the
task is shown here. The state is either S for sleeping, D for uninterruptible
sleep, R for running, Z for zombies, or T for stopped or traced. These states
are modified by trailing < for a process with negative nice value, N for a
process with positive nice value, W for a swapped out process (this does not
work correctly for kernel processes). WCHAN depending on the availability of
either /boot/psdatabase or the kernel link map /boot/System.map this shows the
address or the name of the kernel function the task currently is sleeping in.
TIME Total CPU time the task has used since it started. If cumulative mode is
on, this also includes the CPU time used by the process's children which have
died. You can set cumulative mode with the S command line option or toggle it
with the interactive command S. The header line will then be changed to CTIME.
%CPU The task's share of the CPU time since the last screen update, expressed as
a percentage of total CPU time per processor. %MEM The task's share of the
physical memory. COMMAND The task's command name, which will be truncated if it
is too long to be displayed on one line. Tasks in memory will have a full
command line, but swapped-out tasks will only have the name of the program in
parentheses (for example, "(getty)"). "A , WP" these fields from the kmem top
are not supported.
INTERACTIVE COMMANDSSeveral single-key
commands are recognized while top is running. Some are disabled if the s option
has been given on the command line. space Immediately updates the display. ^L
Erases and redraws the screen. "h or ?" Displays a help screen giving a brief
summary of commands, and the status of secure and cumulative modes. k Kill a
process. You will be prompted for the PID of the task, and the signal to send to
it. For a normal kill, send signal 15. For a sure, but rather abrupt, kill, send
signal 9. The default signal, as with kill(1), is 15,
SIGTERM. This command is not available in secure mode. i Ignore idle and zombie
processes. This is a toggle switch. I Toggle between Solaris (CPU percentage
divided by total number of CPUs) and Irix (CPU percentage calculated solely by
amount of time) views. This is a toggle switch that affects only SMP systems. "n
or #" Change the number of processes to show. You will be prompted to enter the
number. This overrides automatic determination of the number of processes to
show, which is based on window size measurement. If 0 is specified, then top
will show as many processes as will fit on the screen; this is the default. q
Quit. r Re-nice a process. You will be prompted for the PID of the task, and the
value to nice it to. Entering a positve value will cause a process to be niced
to negative values, and lose priority. If root is running top, a negative value
can be entered, causing a process to get a higher than normal priority. The
default renice value is 10. This command is not available in secure mode. S This
toggles cumulative mode, the equivalent of ps -S, i.e., that CPU times will
include a process's defunct children. For some programs, such as compilers,
which work by forking into many separate tasks, normal mode will make them
appear less demanding than they actually are. For others, however, such as
shells and init, this behavior is correct. In any case, try cumulative mode for
an alternative view of CPU use. s Change the delay between updates. You will be
prompted to enter the delay time, in seconds, between updates. Fractional values
are recognized down to microseconds. Entering 0 causes continuous updates. The
default value is 5 seconds. Note that low values cause nearly unreadably fast
displays, and greatly raise the load. This command is not available in secure
mode. "f or F" Add fields to display or remove fields from the display. See
below for more information. "o or O" Change order of displayed fields. See below
for more information. l toggle display of load average and uptime information. m
toggle display of memory information. t toggle display of processes and CPU
states information. c toggle display of command name or full command line. N
sort tasks by pid (numerically). A sort tasks by age (newest first). P sort
tasks by CPU usage (default). M sort tasks by resident memory usage. T sort
tasks by time / cumulative time. W Write current setup to ~/.toprc. This is the
recommended way to write a top configuration file.
The
Field and Order ScreensAfter pressing f, F, o or O you will be shown a screen
specifying the field order on the top line and short descriptions of the field
contents. The field order string uses the following syntax: If the letter in the
filed string corresponding to a field is upper case, the field will be
displayed. This is furthermore indicated by an asterisk in front of the field
description. The order of the fields corresponds to the order of the letters in
the string. From the field select screen you can toggle the display of a field
by pressing the corresponding letter. From the order screen you may move a field
to the left by pressing the corresponding upper case letter resp. to the right
by pressing the lower case one.
Configuration FilesTop
reads it's default configuration from two files, /etc/toprc and ~/.toprc. The
global configuration file may be used to restrict the usage of top to the secure
mode for non-non-privileged users. If this is desired, the file should contain a
's' to specify secure mode and a digit d (2<=d<=9) for the default delay
(in seconds) on a single line. The personal configuration file contains two
lines. The first line contains lower and upper letters to specify which fields
in what order are to be displayed. The letters correspond to the letters in the
Fields or Order screens from top. As this is not very instructive, it is
recommended to select fields and order in a running top process and to save this
using the W interactive command. The second line is more interesting (and
important). It contains information on the other options. Most important, if you
have saved a configuration in secure mode, you will not get an insecure top
without removing the lower 's' from the second line of your ~/.toprc. A digit
specifies the delay time between updates, a capital 'S' cumulative mode, a lower
'i' no-idle mode, a capital 'I' Irix view. As in interactive mode, a lower 'm',
'l', and 't' suppresses the display of memory, uptime resp. process and CPU
state information. Currently changing the default sorting order (by CPU usage)
is not supported.
SEE ALSOps(1), free(1), uptime(1), kill(1), renice(1).
Important: Use the man command (% man) to see how a command is
used on your particular computer.