lee@sq.sq.com (Liam R. E. Quin) (06/08/90)
In article <779@mwtech.UUCP> martin@mwtech.UUCP (Martin Weitzel) writes: >In article <475@van-bc.wimsey.bc.ca> sl@van-bc.wimsey.bc.ca (Stuart Lynne) writes: >[about locking from interface programs of the SysV spool system] >Locking with FIFOs [...] > It is essential that the daemon keeps >the FIFO open for read and write, so that the character in it >is never discarded! All in all it's a bit tricky to get this >started, as you can open a FIFO from the shell only for read OR >for write You could investigate the <> syntax in the shell, which opens an existing file in read-write mode. This was documented briefly in System III as I recall, and also in a Unix quick-reference card of about 1983 or so, but I've not seen it since. Most shells actually use read/write in any case, although relying on this might be a bad idea. Script started on Thu Jun 7 20:49:38 1990 sqarc!lee> ls -l <> boy boy: cannot open sqarc!lee> date > boy sqarc!lee> cat <> boy Thu Jun 7 20:50:12 EDT 1990 sqarc!lee> cat boy Thu Jun 7 20:50:12 EDT 1990 sqarc!lee> date 1<> boy sqarc!lee> cat boy Thu Jun 7 20:50:41 EDT 1990 sqarc!lee> script done on Thu Jun 7 20:50:52 1990 Lee -- Liam R. E. Quin, lee@sq.com, {utai,utzoo}!sq!lee, SoftQuad Inc., Toronto ``It's just an idea, and admittedly a half-baked, unlikely one. Still, picking apart ideas is what the net is all about.'' [David Brin, _Earth_]