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From: julian@acp.OZ (Julian Elischer)
Newsgroups: comp.unix.wizards
Subject: TERMIO wait /no wait operation
Message-ID: <403@acp.OZ>
Date: Fri, 2-Oct-87 00:44:02 EDT
Article-I.D.: acp.403
Posted: Fri Oct  2 00:44:02 1987
Date-Received: Fri, 9-Oct-87 04:40:38 EDT
Organization: Australian Computer Products, Perth, Australia
Lines: 45
Keywords: TERMIO ICANON TIMEOUT

Reading the unix system V.2 and V.3 manuals, I see that 
if ICANON is not set then a read will return an TIME 10ths 
of a second or when MIN characters are available.
I cannot however see how to get it to sit indefinitly
and wait for a character. Is this feature (timeouts) only
available if the O_NDELAY flag is set in the file or
is it always operational. Is this feature used widely?
Does anybody know of documentation that is clear on
this point? It is quite possible that the information 
I seek is actually somewhere in the 3b2 sysV manuals I have,
but you have to know what's in them already if you want to
find anything which is a bit of a pain. (for instance
to find out how to stop fork/exit from creating zombies,
you have to look under SIGNAL of all places!)(flame off)
Several items I would like to find out are:
1/ what is the exact configuration of termio needed
    give the standard RAW mode under sysV.
2/ is there a similar timeout facility available
   for pipes or do i HAVE to use ALARM/SIGNAL etc?
3/ is there any clearer description of SYSV.3 shared memory/
   massages/semaphore operations than the hopeless ATT
   "Documentation".. something that describes the whole
   thing in a useable way instead of drowning you in details.
4/ does a value of 255 or something disable the TIMEOUT in the
   affore mentioned TERMIO ~ICANON mode ? or does it have to be
  enabled by some hidden switch?? do I have to loop every 25.5 seconds?
  When I run programs trying this, they seem to just wait.
   (c_cc[5] = 0)  how do I then get it to come back straight away?

This is how I see it at the moment.. could someone give me
some idea what REALLY HAPPENS?
if you want immediate return, use the O_NDELAY flag with fcntl()
if you want to wait indefinitly, use c_cc[5] = 0 in ioclt with
		O_NDELAY not active.
if you want n 10ths  timeout, use c_cc[5] = n in ioctl() with
		O_DELAY inactive.
is this right?
		thanks for any replies from those ahead of myself.
		replies from thos not ahead will be laughed at
			according to merrit 8-).
   replies by mail please:
	julian elischer
	uucp: {lots of places }!munnari!acp.oz!julian
	ACSnet (that's within australia to those out there in usa land ):
		julian@acp.oz