Saturday 2 August 2008

Linux commands list the processes

top command provides a dynamic real-time view of a running system. It can display system summary information as well as a list of tasks currently being managed by the Linux kernel. But if you want get something more specific, you must play some tricks on it. For example, I want a clean view of top ten busiest processes every seconds without those summary info, how should I do with top?

Batch mode operation
top is a real-time application that keeps display processes info sorted by cpu usage, if you redirects the outputs to a file like command line below, you will having your results mixed with ugly symbols, which is not what you want.

top > top.txt

Well, top support batch mode. By specified top on batch mode, top will display the outputs without arrange the views properly, but if you redirects it to a file, you won’t get those messy symbols mixed up.

top -b > top.txt

I just want to monitor top ten processes every seconds!
You can limits your views of top ten using head and tail, but this will STOP top from continuing to monitor the processes.

top -d 1 | head -n 17 | tail -n 11

Fortunately, we have watch to help, but you needs to put top in batch mode, and also you can ask top to stop after done displaying the result for one time. This will increase the accuracy of the result.

watch -n 1 "top -b -n 1 | head -n 17 | tail -n 11"

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