Top command usages and examples in Unix/Linux

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Top command has an important role in Unix/Linux Administration side. The command “top” displays a dynamic view of process that are currently running under the system. Here I’m  explaining some of the useful usage of top command for My Admin Friends.
Top command is simple in usage and very interesting also. The simple top command output is shown below.

1. top
top

An important thing is we can observer the dynamic view of Load Average from “top” command and also uptime, total users logged in to the system, cpu & free memory details etc..

2. -d switch with top command
d means delay time. The syntax for ‘d’ is “top -d ss.tt”(seconds.tenths).
For example top -d 05.00 that means the top command’s output screen have a dynamic change with 5 second time interval.

3. top command’s output field description.

PID : Process ID.
USER : The user name who runs the process.
PR : Priority
NI : Nice value
%CPU : CPU usage
TIME : CPU Time
%MEM : Memory usage (RES)
VIRT : Virtual Image (kb)
SWAP : Swapped size (kb)
RES : Resident size (kb)
S : Process Status
The status of the task which can be one of:
'D' = uninterruptible sleep
'R' = running
'S' = sleeping
'T' = traced or stopped
'Z' = zombie

4. Interactive commands for top
Several single-key commands are recognized while top is running.
4.1 space

Immediately updates the display.

4.2 h or ?

This will display the help page (q for quit).

4.3 k :

For kill a process.

kill

In the image change PROCESS ID with the pid of process which you want to kill.
4.4 i

Ignore idle and zombie processes. This is a toggle switch.

4.5 I (shift 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.

4.6 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.

4.7 q

Quit.

4.8 M (shift m)

sort tasks by resident memory usage.

mem

4.9 T (shift t)

sort tasks by time / cumulative time.

time

4.10 c or P(shift p)

sort tasks by CPU usage (default).

cpu

4.11 A (shift a)

sort tasks by age (newest first).

age

4.12 N (shift n)

sort tasks by pid (numerically).

pid

These are some interesting usage of top command under UNIX/LINUX. Please let me know your suggestions by commending. Thank you for your time.

More:
groupdel, groupmems, groupmod, useradd , usermod , chgrp, chown, ls, head, tail, top, ps, find, crontab

Linux Server Admin, Infopark, Cochin, Kerala. Contact me : arun(at)crybit.com

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