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From: duvalj@bionette.cgrb.orst.edu (Joe Duval - Entomology)
Newsgroups: comp.lang.c
Subject: System V function calls to signal()
Message-ID: <13842@orstcs.CS.ORST.EDU>
Date: 15 Nov 89 22:58:01 GMT
Sender: usenet@orstcs.CS.ORST.EDU
Reply-To: duvalj@bionette.cgrb.orst.edu.UUCP (Joe Duval - Entomology)
Distribution: usa
Organization: Oregon State University - CMBL
Lines: 64

Hi,
  I would like some help using the signal function on a SYSV machine.  I am
using an AT&T 3b2. Here is what I want to do.
	I want to catch the action previously defined for a signal, lets say
	SIGINT, so I can reset that action later.  After I catch the previous
	action, I want to do something else and then call signal again to reset
	the previous action.  Redundant, huh?
	I have tried signal and ssignal both with no luck.  I am sure that is
	in my logic.

Any help will be appreciated.  I have included two pieces of code; one uses
signal and the next uses ssignal.

Here is my (attempt at) code USES SIGNAL:

#include <signal.h>

static Foo()
{
	static int (*sigint)();
	int catch_int();
    /* First I want to catch the action previously established for that
     * signal type */
     sigint = signal (SIGINT, catch_int);  /* An invalid pointer combination 
				   	      error occurs here. */ 

    /* Then I want to do something else, go kill a process in this case */ 
     kill(getpid(), SIGINT); 
     
    /*  Now I want to return to the previous action to that signal type */ 
     signal (SIGINT, sigint); } static catch_int(n) {
}


Here is my attempt at the code USING SSIGNAL:

#include <signal.h>

static Foo()
{
	static int (*sigint)();
	int catch_int();

      /*  In <signal.h>  ssignal is defined like this 
		int (*ssignal (sig, action))()
		int sig, (*action)();
       */

	sigint = (*)ssignal (SIGINT, catch_int);

	kill(getpid(), SIGINT);

	signal (SIGINT, sigint);
}

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