Sorry, I'm back again. For the third quiz question I'm now having second thoughts. I know that in "sort dognames > dogsinorder" "dognames" is an argument to sort, which now is aware of it and opens it to gather what it needs. Slide 57 addresses this question. But to choose between answers b) the command line and c) opening and reading the file dognames for "where is sort getting its input from" is confusing me today. The shell parses the command line, telling "sort" to gather its info from "dognames". The sort program does open the dognames file to read it. "This is done by the sort process code, making requests to the kernel to read data from the file on the hard drive."
So first I thought the answer was c - opening and reading the file dognames is where sort is getting its input, but now I'm wondering; is "input" referring to "instruction" from the shell, which would make the answer b) "the command line", or is the input here referring to the information read in the 'dognames" file?