On Thu, Jan 09, 2003 at 02:13:42PM -0800, Ed Vance wrote: > On Thu, Jan 09, 2003 at 12:42 PM, Jan Hudec wrote: > > > > On Thu, Jan 09, 2003 at 12:29:45PM -0800, Ed Vance wrote: > > > Hi Jan, > > > > > > IIRC, a process must first have no controlling tty to get a > > > new one assigned on the next open of a tty. Controlling tty > > > assignments are sticky and are unaffected by closing. Once > > > assigned, the assignment persists even if the process > > > closes or redirects all streams open to that tty. For > > > example, a process still receives signals generated the > > > keyboard of its controlling tty, even if all streams have > > > been redirected. By default, a child process inherits the > > > parent's controlling tty assignment. So, the child process > > > must use the TIOCNOTTY ioctl on its controlling tty to > > > remove the controlling tty assignment. It does not matter > > > that a stream is already open to the previous controlling > > > tty. Then, the next open of a tty will assign that tty as > > > the new controlling tty, unless it is opened with the > > > O_NOCTTY flag or the tty is already the controlling tty of > > > another process, which it will be if there was a getty on it. > > > > > > I hope I got that right ... > > > > Thanks, this should help. The trick is, that I have a program > > that correctly claims controling tty, but I want to redirect > > it to a different tty. And a terminal can not be a controling > > terminal of more than one session. So I need something, that > > will keep the pty (terminal emulator) open, but not a > > controling terminal of anything. > > Do you mean something like the following sequence? > > process A has serial port as CTTY. > process A opens a master pseudo terminal. > process A forks child process B. > process B ioctl TIOCNOTTY serial port to remove B's CTTY assignment. > process B closes serial port streams. > process B opens corresponding slave pseudo terminal, becomes B's CTTY. 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 proces 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 commad. But I need to make a tty available (under X, that is in some terminal emulator). ------------------------------------------------------------------------------- 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/
