You can (usually) specify the input file name as “-“ (single hyphen) to read from stdin

Or you can use `/dev/stdin`, which has the upside of not needing tool support.

I somewhat regularly use this on Linux. I think it also works on OS X

	▲	mlegendre 4 hours ago \| parent [-]
		And conversely, `/dev/stdout` (resp. `/dev/stderr`) is a convenient way to "redirect" output to stdout (resp stderr) instead of a file