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From: haral@unisol.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: HELP: stop job (csh) su because of tty output
Message-ID: <277@unisol.UUCP>
Date: Mon, 25-May-87 20:57:06 EDT
Article-I.D.: unisol.277
Posted: Mon May 25 20:57:06 1987
Date-Received: Wed, 27-May-87 03:15:17 EDT
References: <275@dcc1.UUCP>
Reply-To: haral@unisol.UUCP (Haral Tsitsivas)
Organization: UniSolutions Associates, Culver City, CA
Lines: 30
Keywords: stop jobs, csh, su

> douglas@dcc1.UUCP (Douglas B. Jones) writes:
> After compiling (instruction in program) the program below, I
> execute it with:
> %a.out username
> %^D> > > > (now in users csh shell)
> (I typed in the control-d above and exited back to my shell).
> After leaving the shell, I get the message that my a.out program
> is stopped due to tty output. I must then do a:
> %fg
> to get it to continue the program.
> ...
>Xsprintf(buf,"/bin/su %s",argv[1]);

Your problem will go away if you execute the user's shell directly and
don't use "su" or other programs that set the first character of the
shell to "-" as in "-csh" to signify a login shell.

I am not sure why this is true but you will notice the same problem
when you set argv[0] to "-anything" as part of the exec system call.
I first noticed this on the Mt. Xinu 4.3 release and I guess is part
of the standard 4.3 release.  I don't think the problem (or feature)
existed in 4.2.

Note that if you don't call "su" you have to "setuid" and maybe "setgid"
(in a sub-process) to get the same effect.

--Haral Tsitsivas
  UniSolutions Associates
  (213) 641-6739
  ...!seismo!scgvaxd!ashtate!unisol!haral