Path: utzoo!attcan!uunet!yale!cmcl2!phri!roy
From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.unix.wizards
Subject: What defines an "exceptional condition" in 4.[23]BSD
Message-ID: <3284@phri.UUCP>
Date: 25 May 88 14:59:22 GMT
Organization: Public Health Research Institute, NYC, NY
Lines: 17


	I've run across what seems to be an inconsistancy in the way
exceptional conditions are handled in 4.[23]BSD.  When OOB data is pending
on a socket, a select(2) for exceptions on the socket descriptor will
return; in addition, a SIGURG is sent.  If you have a pty in TIOCPKT or
TIOCUCNTL mode and a control packet or ioctl command comes in, you also
break out of a select(2), but no SIGURG is sent.

	Is there some reason why one sends a SIGURG but not the other?  Are
there any other conditions in the system other than OOB data and the
TIOCPKT/TIOCUCNTL cases described above which generate exceptional
conditions?  Do they send SIGURGs and/or break out of selects?  Should they?
-- 
Roy Smith, System Administrator
Public Health Research Institute
455 First Avenue, New York, NY 10016
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