line-printer spooling to non-tty-like devices

[Guy Riddle]

) Both the 4.2BSD and System V line printer spoolers invoke a
) printer-specific interface program with one file descriptor
) already open to "the device" (the printer).  On both systems the
) fd is open for writing, but the documentation states that the
) device can be opened for reading also under certain
) circumstances (specifying "rw" in the BSD printcap entry, or
) having the file (device) readable on SysV); however, you still
) only get one fd when you get called.  You do NOT get passed the
) name of the device (so you can't do your own open(2)).

On System V the interface script can get the name of the printer
by `basename $0` and use it to do an open or set up a network
connection or whatever.  For our network-attached printers, we just
tell lpadmin(1M) that the device to open is /dev/null and the real
open (and connect) is done by the programs invoked by the interface script.

		=== Guy Riddle == AT&T Bell Laboratories, New Jersey ===
				ggr.btl at csnet-relay.ARPA
					ihnp4!ggr