Difference between top and ps output
You are comparing apples to oranges. top
is displaying what proportion of your computer's CPU power that process used during the last sampling interval (a few seconds, usually). ps
, with %C
, is displaying what proportion of the time that process was running over that process's lifetime. Because of the way process statistics are gathered, any command that does display CPU usage over the past few seconds has to run for a few seconds, and ps
doesn't have any options to do that. You can however use top
in batch mode, top -b -n 2 -d 0.001
. It will pause gathering data, and then give its listing over STDOUT. This will allow you to parse top
output or use it in scripts.
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Updated on September 18, 2022Comments
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Community almost 2 years
I have seen What is the difference between ps and top command? but I think my question is unrelated.
My system is Lubuntu 13.04.
I runtop
in one lxterminal window andps -eo %c%C --sort -%cpu | head -6
in another.
I play a YouTube video in Firefox.
Very quickly, the values forplugin-container
in thetop
screen "stabilize" whereas the values I get by repeatedly issuingps -eo %c%C --sort -%cpu | head -6
rise slowly.
Similarly, when I close the Firefox tab that was playing the YouTube video, the plugin-container entry intop
goes away promptly but it lingers on in the output ofps -eo %c%C --sort -%cpu | head -6
, declining slowly as can be seen below:[04:43 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 21.5 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:43 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 21.3 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:43 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 20.9 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:43 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 20.2 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:44 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 20.0 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:44 PM] ~ $ ps -eo %c%C --sort -%cpu | head -6 COMMAND %CPU plugin-containe 18.9 firefox 4.9 Xorg 1.6 lxpanel 0.2 dropbox 0.2 [04:44 PM] ~ $
plugin-container
does eventually go away, but how should I modifyps -eo %c%C --sort -%cpu | head -6
to make it go away quicker?(All this is done on a Dell 1545 Core2Duo laptop.)