rule NameOfRule
{
    strings:
    $test_string1= "James"
    $test_string2= {8C 9C B5 L0}
    Conditions:
    $test_string1 or $test_string2
}

yara -s yararule1.yar .

Rule DNS
{
    strings:
    $test_string1= " (#cmd='whoami')"
    $test_string2= " (#cmd='nslookup')"
    $test_string3= {9D J5 G8 P9}
    Conditions:
    $test_string1 or $test_string2 or $test_string3
}

yara -rs /files/myyararules/clamav1.yar

yara ~/Desktop/myrules/James1 ~/Desktop/myrules/James2 .