Howto display the number of processors in Linux

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If you've just bought a new desktop,laptop or server and the box says the box is powered by 2 processors, you can actually verify that.

Here's how to display the number of processor of your linux box.

Simply issue the following command as root

# cat /proc/cpuinfo | grep processor

Everything in linux is files. This command simply retrieves the number of processors that linux detected from /proc/cpuinfo and displays it. Usually, the processor number comes at the first set of line from issuing the command.

Here's what the command returned for me:
~~~~~~~~~~~~~~~~~~~~~~~~
processor : 0
~~~~~~~~~~~~~~~~~~~~~~~~

which means You have 1 processor with a processor ID number 0. Processor counting starts with 0.
So if you have a PC with core duo, you will probably have 2 lines that says 0 and 1.That is 2 processors.

9 thoughts on “Howto display the number of processors in Linux

  1. Ever heard of hyperthreading? If it’s on in the BIOS, it’ll incorrectly double the number…

  2. Lev: I once ate that with some proliant server, it had only one CPU, and because of HyperThreading, I thought there are 2…

  3. There is a lot simpler solution. Just type ‘top’ at the command prompt and then press ‘1’ (number one).
    You will see the ACTUAL CPUs listed on the top of the page

  4. > Simply issue the following command as root

    *Not* as root, because:
    # ls -l /proc/cpuinfo
    -r–r–r– 1 root root 0 2007-09-03 15:49 /proc/cpuinfo

    (Unless your system uses other permissions than mine, but I don’t see why it should do that.)

    Misuse of cat:
    > # cat /proc/cpuinfo | grep processor

    Simply use:
    # grep processor /proc/cpuinfo

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    Thank you. Your comment has been approved.

  6. If your kernel does not have SMP support compiled in, `cat /proc/cpuinfo` will only show one processor, even if you have more than one cpu.

  7. You can run the command below and you will see number of physical processors in the server:

    [server][root][~]# grep "^physical is" /proc/cpuinfo | awk '{print $NF}' | uniq | wc -l
    1

    Now lets determine how many cores we have:

    [server][root][~]# cat /proc/cpuinfo | grep processor | wc -l
    4

    So from the above, we are able to determine that we have a single CPU quad core chip.

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