The Linux Newbie Guide

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Fundamentals

top - Process Performance Monitoring

top is an interactive command-line utility used for monitoring system processes, CPU usage, memory utilization, and other system statistics. It provides real-time insights into your system's performance, similar to the Windows Task Manager.

When you run top, you can perform various operations to interact with and monitor processes. Here are some common actions:

Press q to quit top.
Press P to sort processes by CPU usage.
Press M to sort processes by memory usage.
Press k to terminate a selected process, then enter the process ID (PID) to kill it.
Press H to toggle between displaying threads or hiding them.
Press 1 to show the usage of each CPU core.

The basic syntax of the top command is:
top [OPTIONS] .

Common options for the top command include:

-d: Specify the refresh interval.
-n: Specify the number of iterations to display.
-p: Monitor a specific process by specifying its PID.
-u: Monitor processes for a specific user.
-H: Show thread information.
-i: Hide idle processes.

Example:

$ top
top - 00:42:30 up 36 days, 1:08, 2 users, load average: 0.16, 0.02, 0.01
Tasks: 130 total,   4 running, 125 sleeping,   1 stopped,   0 zombie
Cpu(s): 0.2%us, 2.6%sy, 0.0%ni, 97.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem:    515156k total,   438756k used,    76400k free,    11520k buffers
Swap: 1020088k total,        0k used, 1020088k free,   253064k cached

PID USER      PR NI VIRT RES SHR S %CPU %MEM    TIME+ COMMAND
2295 root      20   0 32496 12m 5936 S 1.2 2.4   0:15.29 X
2571 aaa       20   0 64484 19m 10m S 0.9 3.9   0:04.20 gnome-terminal
2113 root      20   0 3388 1148 1012 S 0.2 0.2   0:00.20 hald-addon-inpu
2414 aaa       20   0 31500 3616 2940 S 0.2 0.7   0:01.01 exe
. . .

For more detailed instructions and usage examples of the top command, please refer to the provided link.