alsaloop(1) on Linux
The text cb42cced6c34, as Debian 7 (Wheezy) shipped it.
command-line PCM loopback
Flags it lists
-
--daemonize -
--help -
--nblock -
--resample -
--verbose -
--xrun -
-U -
-b -
-d -
-h -
-n -
-v