On Thu, Jan 09, 2003 at 03:50:52PM -0800, Ed Vance wrote: > On Thu, Jan 09, 2003 at 3:11 PM, Jan Hudec wrote: > > 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 controlling 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 controlling 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... > > I understand. TIOCNOTTY must be called from the session leader to > free up the tty. Otherwise, the calling process is removed from the > tty, but the tty remains attached to the other processes in the > session, which prevents TIOCSCTTY from using it. I don't see a > non-superuser way to do it yet, unless the actual session leader > can be made to do the TIOCNOTTY. Yes. Now, since it's a terminal emulator, the shell should be the session leader (it should be true even on console). Now I see two ways to make it give up controling tty. Either exec the script to give it up, or have the terminal emulator run it from the very start. Now I only have to find out, why is the script failing, when it's exec'd. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@ucw.cz> -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
