How to know the motherboard BIOS version using the command line

I got the solution.

Using dmidecode (of course), but the problem was with the result...

I don't want to list block result about my bios I just need the version..

The command is:

sudo dmidecode -s bios-version

The output will just print the version:

SIX7910J.86A.0537.2012.0723.1217

Try this command,

sudo dmidecode | less

dmidecode usually returns, amongst other things, a block with information about your BIOS. It should look something like this:

BIOS Information
    Vendor: American Megatrends Inc.
    Version: 0309
    Release Date: 04/18/2013
    Address: 0xF0000
    Runtime Size: 64 kB
    ROM Size: 8192 kB
    Characteristics:
        PCI is supported
        APM is supported
        BIOS is upgradeable
        BIOS shadowing is allowed
        Boot from CD is supported
        Selectable boot is supported
        BIOS ROM is socketed
        EDD is supported
        5.25"/1.2 MB floppy services are supported (int 13h)
        3.5"/720 kB floppy services are supported (int 13h)
        3.5"/2.88 MB floppy services are supported (int 13h)
        Print screen service is supported (int 5h)
        8042 keyboard services are supported (int 9h)
        Serial services are supported (int 14h)
        Printer services are supported (int 17h)
        ACPI is supported
        USB legacy is supported
        BIOS boot specification is supported
        Targeted content distribution is supported
        UEFI is supported
    BIOS Revision: 4.6

The information here includes both version and BIOS revision. If dmidecode does not include that data on your machine, I'm afraid you will have to reboot and actually look at the BIOS.