Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!ames!amdahl!nsc!taux01!gil
From: gil@taux01.UUCP (Gil Shwed)
Newsgroups: comp.unix.wizards
Subject: Re: Trapping SIGTSTP and then suspeding
Message-ID: <2697@taux01.UUCP>
Date: 10 Oct 89 06:45:26 GMT
References: <T45126.89Oct6084404@iemisi.dhc>
Reply-To: gil@taux01.nsc.com (Gil Shwed)
Distribution: comp
Organization: National Semiconductor (IC) Ltd, Israel
Lines: 41

In article <T45126.89Oct6084404@iemisi.dhc> t45126@iemisi.dhc (John Durko) writes:
>Can someone help me with a problem.  I am trying to trap signal 18 (SIGTSTP)
>so that i can reset some terminal stuff before program is suspend by ^Z.

The following code should be used on 4.3BSD (SunOS included)
[ 4.2BSD derived systems should replace sigmask(i) with 1<<(i-1) ]:

in your main program:

	signal(SIGTSTP, tstp);

Handler code:

tstp() {
	/* Restore tty values, or whatever you like. */

	/* First, Use the default action - STOP process */
	signal(SIGTSTP, SIG_DFL);
	/*
	 * Turn off blocking of SIGTSTP from blocked signals. Otherwise
	 * It will be masked until we get out of the handler.
	 */
	sigsetmask(sigblock(0) & ~sigmask(SIGTSTP));
	/*
	 * Stop myself
	 */
	kill(getpid(), SIGTSTP);
	/*
	 * Set handler again for next use.
	 */
	signal(SIGTSTP, tstp);

	/* Restore/Set tty values back to programs' */

}

	

Hope that helps.

-- Gil