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Linux man pages : tty (4)
TTY(4)			   Linux Programmer's Manual			TTY(4)


tty - controlling terminal


The file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and root.tty. It is a syn- onym for the controlling terminal of a process, if any. In addition to the ioctl() requests supported by the device that tty refers to, the following ioctl() request is supported: TIOCNOTTY Detach the current process from its controlling terminal, and remove it from its current process group, without attaching it to a new process group (that is, set its process group ID to zero). This ioctl() call only works on file descriptors con- nected to /dev/tty; this is used by daemon processes when they are invoked by a user at a terminal. The process attempts to open /dev/tty; if the open succeeds, it detaches itself from the terminal by using TIOCNOTTY, while if the open fails, it is obviously not attached to a terminal and does not need to detach itself.




mknod(1), chown(1), getty(1), termios(3), console(4), ttys(4) Linux 1992-01-21 TTY(4)