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Friday, March 7, 2008

It is about Time ... a process

Sometimes, it is easy to overlook the simple Linux commands. Take the command time, for example.

It simply times how long a command takes to run, and gives you 3 statistics:

  1. Elapsed real time (in seconds).
  2. Total number of CPU-seconds that the command spent in user mode.
  3. Total number of CPU-seconds that the command spent in kernel mode.


I use time a lot to benchmark network performance, e.g.,
$ time scp some-file  peter@192.168.22.104:/home/peter/some/location/
real 0m17.742s
user 0m0.364s
sys 0m0.476s


You can be creative with time, and run it like this:
$ time cat 


What does it do? It starts a timer, and stops when you enter Control D (to terminate the input stream to the cat command). It is a quick timer.

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