> When I offer a pipeline as a solution I expect it to be reusable. It is quite likely that a pipeline would be added at the end of or spliced into another pipeline. In that case having a file argument to grep screws up reusability, and quite possibly do so silently without an error message if the file argument exists. I. e. `grep foo xyz | grep bar xyz | wc` will give you how many lines in xyz contain bar while you are expecting the number of lines that contain both foo and bar. Having to change arguments to a command in a pipeline before using it is prone to errors. Add to it the possibility of silent failures and it becomes a particularly insidious practice.
