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From: lm@cottage.WISC.EDU (Larry McVoy)
Newsgroups: comp.unix.questions
Subject: Re: SIGSTOP - what is it?
Message-ID: <3800@spool.WISC.EDU>
Date: Fri, 3-Jul-87 14:23:48 EDT
Article-I.D.: spool.3800
Posted: Fri Jul  3 14:23:48 1987
Date-Received: Sat, 4-Jul-87 13:55:32 EDT
References: <3786@spool.WISC.EDU> <13114@topaz.rutgers.edu>
Sender: news@spool.WISC.EDU
Reply-To: lm@cottage.WISC.EDU (Larry McVoy)
Organization: U of Wisconsin CS Dept
Lines: 34

In article <13114@topaz.rutgers.edu> ron@topaz.rutgers.edu (Ron Natalie) writes:
$ Programs that play around with the screen, use raw mode, or otherwise
$ want to perform some action when the SIGTSTP (the one generated by ^Z)
$ occurs use this.  They catch the SIGTSTP signal and when they really
$ want to stop themselves they send SIGSTOP to themselves.  It's sort
$ of analogous to SIGTERM and SIGKILL.

Yeah, that's what I thought, but can't you do something like this:

onstop()
{
    /* put the terminal back into whatever is normal state */
    normal();

    signal(SIGTSTP, SIG_DFL);
    kill(getpid(), SIGTSTP);

    /* come back to here */
    raw();

    signal(SIGTSTP, onstop);
    return;
}

I had something like this working once - but it was a while ago.  It doesn't 
work now and I think it might be because 4.3 does signals a little differently
than the SysV/enhanced system I was working on.  In particular, BSD blocks
further signals while in the handler, right?  So is that why the code above
might not work?

Surely you don't need two signals (on catchable, one not) for each "user"
signal, do you?

Larry McVoy 	        lm@cottage.wisc.edu  or  uwvax!mcvoy