Given a command like this:
command <inputfile> <outputfile>
And then called like this:
command FileA > FileC FileB
It takes A and B as input and outputs to C, but how can it parse the third argument, since the output redirection is between the arguments?
The shell parses the command-line, and sets up redirection. In this case, it sees > FileC, sets up the corresponding redirection, and removes those terms from the command: so what ends up being executed is
command FileA FileB
command itself never sees the > FileC part.
See What are the shell's control and redirection operators? for details on redirection in general.
