Linux Commands - List the amount of memory and CPU used using the top command

By default, the top command can be used to view processes in real time, meaning that the top output will refresh every few seconds.

[root@server1 ]# top
top - 21:46:14 up 2 days, 29 min, 2 users, load average: 0.31, 0.40, 0.54
Tasks 160 total, 1 running, 158 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.5 us, 2.2 sy, 1.5 ni, 90.0 id, 4.8 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem:  3067824 total, 1498976 used, 1560456 free, 54168 buffers
KiB Swap: 3104837 total,       0 used, 3104872 free, 85747 cached Mem

PID    User   PR  NI     VIRT     RES     SHR   S  %CPU  %MEM    TIME+   COMMANDS
4594   root   20   0   417768  144754    5803   S   6.0   5.2  0:41:49       Xorg
2488   User1  20   0    92281   85793   84739   S   3.3   4.5  1:04:77 gnome-term
3794   User1  20   0   144384  209193   48473   S   5.7   3.2  0:32:99    firefox
. . .


The -n 1 option can be used to display a snap shot of top.

top -n 1


By default, top will only return the results that fit the current console window. The -b (batch) flag can be used to return the full top output.

top -b -n 1


Additionally, the -o option can be used to sort the output on a specific column. In this example, the output will be sorted on the %CPU column (which is the default anyways).

top -b -n 1 -o %CPU


If you need to capture the CPU over a period of time, such as over a 24 hour period, a script could be invoked once every minute, where the script outputs the overall CPU average to a file. In this example, a BASH shell script will output the CPU average to a file named cpu.txt.

date=$(date +%Y%m%d)
time=$(date +%H%M%S)
cpu=$(top -b -n 1 | grep ^%Cpu | awk '{print $2}')
echo [$date.$time] CPU Usage = ${cpu}% | tee -a cpu.txt


Running this script will produce a TXT file that contains something like this.

[20210708.214739] CPU Usage = 60.0%
[20210708.214746] CPU Usage = 70.4%


This script could then be scheduled to run once every minute via a crontab job, something like this.

* * * * * bash /path/to/


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