Yeah, essentially, the NIL: device is "black hole." You can output anything to NIL and it'll just vanish. This is actually more helpful than you might think, especially in the startup-sequence. You can run something with output directed to NIL: so the Amiga doesn't try to open a screen for your output before workbench sets the proper resolution. :-)
for example to silently set an assignment, you'd:
c:assign >NIL: myassign: dh0:mydir/
this will output nothing whatsoever (even if dh0:mydir/ doesn't actually exist), but will still make the assignment, if possible. (Of course, if dh0: doesn't exist, I think this would still throw a requestor asking for dh0: to be inserted in any drive. :lol: )
(Linux probably one too)
/dev/null