Linux Pocket Guide

Name

top [options] — procps

Synopsis

/usr/bin stdin stdout - file -- opt --help --version

The top command lets you monitor the most active processes, updating the display at regular intervals (say, every second). It is a screen-based program that updates the display in place, interactively.

$ top
116 processes: 104 sleeping, 1 running, 0 zombie, 11 stopped
CPU states: 1.1% user, 0.5% system, 0.0% nice, 4.5% idle
Mem: 523812K av, 502328K used, 21484K free, 0K shrd, 160436K
buff
Swap:  530104K av,  0K used, 530104K free  115300K cached

PID   USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
26265 smith 10 0  1092 1092 840  R    4.7  0.2  0:00 top
    1 root   0 0   540  540 472  S    0.0  0.1  0:07 init
    2 root   0 0     0    0   0  SW   0.0  0.0  0:00 kflushd
...

While top is running, you can press keys to change its behavior, such as setting the update speed (s), hiding idle processes (i), or killing processes (k). Type h to see a complete list and q to quit.

Useful options
-n N	Perform N updates, then quit.
-d N	Update the display every N seconds.
-p N -p M …	Display only the processes with PID N, M, …, up to 20 processes.
-c	Display the command-line arguments of processes.
-b	Print on standard output noninteractively, without playing screen tricks. top -b -n1 > outfile saves a quick snapshot to a file.