From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnold@skeeve.com (arnold@skeeve.com)
Date: Sat, 10 Sep 2016 23:01:49 -0600
Subject: [TUHS] Shell control through external commands
In-Reply-To: <alpine.BSF.2.11.1609111404230.78806@aneurin.horsfall.org>
References: <201607151647.u6FGlqvW037575@tahoe.cs.Dartmouth.EDU>
 <20160910174011.GF5970@dnied%tiscali.it>
 <alpine.BSF.2.11.1609110842190.78806@aneurin.horsfall.org>
 <006301d20bcb$43ae03b0$cb0a0b10$@ronnatalie.com>
 <201609110239.u8B2dgDJ010272@freefriends.org>
 <alpine.BSF.2.11.1609111404230.78806@aneurin.horsfall.org>
Message-ID: <201609110501.u8B51nCK016335@freefriends.org>

Dave Horsfall <dave at horsfall.org> wrote:

> On Sat, 10 Sep 2016, arnold at skeeve.com wrote:
>
> > I think that the way the shell "recognized" scripts was by having exec 
> > fail, otherwise how would it know?  I think we'll have to go grubbing in 
> > the source archives to be sure.
>
> Correct; if the exec failed then the invoking shell assumed that it was a 
> shell script, and spawned a shell to run it.

I think this happened in the "spawned" shell - so the exec would fail and
then this child shell would just run the script.

	if ((pid = fork()) != 0)
		wait for pid
	else {
		/* in the child */
		exec /path/to/program
		if (errno == ENOEXEC)	/* or whatever it is, I don't remember */
			interpret the script directly
	}

Arnold