Path: utzoo!attcan!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.lang.c
Subject: Re: Catching Signals in 'C'
Message-ID: <1990Sep28.231904.24123@virtech.uucp>
Date: 28 Sep 90 23:19:04 GMT
References: <1990Sep28.120043.17628@NCoast.ORG>
Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill)
Organization: Virtual Technologies Inc., Sterling VA
Lines: 44

In article <1990Sep28.120043.17628@NCoast.ORG> ramsey@NCoast.ORG (Cedric Ramsey) writes:
>main()
>{
>  signal (SIGINT, (*handler1) ());
>  signal (SIGQUIT, (*handler2) ());

On initial inspection I would say there was a problem with your call to signal.
This is probably due to the fact that you left off some important code. 
Normally the signal would be used as follows:

	main()
	{
		int	handler1();
		int	handler2();

		(void) signal(SIGINT,handler1);
		(void) signal(SIGQUIT,handler2);


Anyway, on to the real problem....

>But, when I type a control-c the program handles the signal as
>expected; however, when I type the control-c a second time the program 
>doesn't catch it and simply exits. 

To solve this problem you have to know that whenever a signal is caught
the action for that signal is automatically reset to the default state.
To fix this you must call signal() each time the handler is executed.

For example,

handler1(sig)
	int	sig;
{
	signal(sig,handler1);
	.
	.
	.


-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170