where commands come from

[janet tuma]

Ok, I read and re read Rich's note but am still a bit confused. At the end of his post on Feb 22 regarding Unix command getting input from command line it is stated the clear command has no options or arguments. Therefore, the clear command does not get any input from the command line. So I assume the command who which has options one can add, would qualify? Yet with that thinking so would ls because you can add options...but ls comes from the OS. ?? What am I missing? Would the answer be "who" with an option added on?