Job Control

[Moderator, John Quarterman]

From: ihnp4!iwtpu!katzung (Brian Katzung)
Date: Sat, 8 Nov 86 14:59:33 CST

     I guess I'm being sort of lazy... I haven't even figured out the
relationship between "P1003" and "POSIX" (I got in late on the discussion),
[ IEEE P1003 is the committee; P1003.1 is the subcommittee that produced
the POSIX Trial Use Standard.  -mod ]
but I wanted to point out one shortcoming of the 4.xBSD implementation of
job control so that it might be avoided in the future.

     The wait3 system call has provisions for informing the parent when a
child is suspended, but not when it resumes.  Thus, if an agent other than
the parent resumes the child, the parent doesn't know about it.  This is
rare, but not unimaginable.  I've had applications that could have been
enhanced if the mechanism were "balanced".

     I haven't checked 4.3, but the 4.2 csh, in particular, won't send a
STOP or TSTP to a process that it believes is already stopped.
-- Brian Katzung  ihnp4!{laidbak,iwtpu}!katzung

Volume-Number: Volume 8, Number 51