I was testing out the linux api while working on something but got stuck on the following output.

[Abhii@localhost net]$ cat /proc/uptime
39135.53 149657.73

As per specs the first number should be the Uptime and the second number should be the time system has stayed idle.

So why is the former less then latter ???

As an extra piece of info my version information

Linux version 3.5.2-3.fc17.x86_64 (mockbuild@) (gcc version 4.7.0 20120507 (Red Hat 4.7.0-5) (GCC) ) #1 SMP Tue Aug 21 19:06:52 UTC 2012

1 Answer 1


Idle time is the sum of all your CPU/core idle times, while uptime is the wall-clock time your system has been up.

I'm guessing you have four CPUs/cores/threads.

  • 1
    Wow , thats brilliant & confusing ! Commented Oct 22, 2012 at 6:54

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