Re: Making terminal available for TIOCSCTTY

[Jan Hudec <bulb@ucw.cz>]

On Thu, Jan 09, 2003 at 03:05:56PM -0800, Ed Vance wrote:
> On Thu, Jan 09, 2003 at 2:21 PM, Jan Hudec wrote:
> > I think, that it's a bit different. It should look like following:
> > process A has pty/1 as ctty.
> > process A makes pty/1 available (presumably via TIOCNOTTY)
> > process B has no ctty (there is something about setsid I don't fully
> > understand)
> > process A tells process B that it can use pty/1
> > process B opens pty/1 and makes it it's controling terminal 
> > (TIOCSCTTY)
> > 
> > The reason behind this: I have a process that logs a LOT to
> > stdout/stderr, does "setterm" ioctls on it and needs WINCH 
> > signal (thus a controling tty). I want to run it from gdb 
> > and have gdb and this programs output separated. Thus I use 
> > gdb's tty command. But I need to make a tty available (under 
> > X, that is in some terminal emulator).
> > 
> 
> If B calls setsid() successfully, then B opening pty/1 should
> make pty/1 ctty of B. Should not need to use TIOCSCTTY ioctl 
> unless pty/1 still has a session attached, which it will if 
> process A was not the session leader. Then you would not need 
> the TIOCNOTTY and would need to use TIOCSCTTY with arg=1 to 
> wrestle pty/1 away from its current group. Which call is 
> returning an error?

The TIOCSCTTY. The problem is, that TIOCSCTTY with arg=1 only works for
superuser (at least seems so from kernel source). Thus I need to detach
the terminal properly...

-------------------------------------------------------------------------------
						 Jan 'Bulb' Hudec <bulb@ucw.cz>
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