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From: aiv@euraiv1.UUCP (Eelco van Asperen)
Newsgroups: comp.unix.questions
Subject: catching signals while writing to a tty-line
Message-ID: <589@euraiv1.UUCP>
Date: Thu, 3-Sep-87 10:26:28 EDT
Article-I.D.: euraiv1.589
Posted: Thu Sep  3 10:26:28 1987
Date-Received: Sat, 5-Sep-87 16:55:04 EDT
Organization: Erasmus University EF/AIV,Rotterdam,Netherlands
Lines: 30
Keywords: signal;slow i/o

Hi, I have a problem regarding the use of alarm() in combination with
writing to a tty-line. The tty-line is put in raw-mode and write() is
used to send data; I would like to use alarm() to detect timeouts and
warn the user of my program of this event. After displaying this warning, 
the program should continue sending data. Now, upon reading the man-page 
for signal() it said: 

	"when a signal that is to be caught occurs during a read, a write,
	an open, or an ioctl system call on a slow device (like a terminal;
	but not a file), during a pause system call, or during a wait system
	call that does not return immediately due to the existence of a 
	previously stopped or zombie process, the signal catching function
	will be executed and the interrupted system call will return -1 to
	the calling process with errno set to EINTR."

(btw, I use System V release 2.0 on an AT&T 3B2/300)

The problem is of course to detect the number of characters that has
already been written so that we don't send chars twice or not at all.

Thanks in advance for the brain-cycles you use to answer my question,

Eelco van Asperen.

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