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. ---------------------------------------------------------------- Ed Vance edv (at) macrolink (dot) com Macrolink, Inc. 1500 N. Kellogg Dr Anaheim, CA 92807 ---------------------------------------------------------------- -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
