07-07-2008
Daemons can have any ppid and a ppid of 1 is no guarantee that you're a daemon. I like the open /dev/tty idea. It's portable. But of course it can fail for other reasons. No one ever did a
rm /dev/tty
on any of your systems? Also the process could be out of fd's, etc. Still it's the best way. Depending on the unix system, ther may be a non-portable way. Get the source code for ps and see how it finds this stuff out. But that is a lot of trouble to avoid opening /dev/tty. I would go with that.
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TTY(4) Linux Programmer's Manual TTY(4)
NAME
tty - controlling terminal
DESCRIPTION
The file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and owner.group root.tty. It is a syn-
onym for the controlling terminal of a process, if any.
In addition to the ioctl(2) requests supported by the device that tty refers to, the ioctl(2) request TIOCNOTTY is supported.
TIOCNOTTY
Detach the calling process from its controlling terminal.
If the process is the session leader, then SIGHUP and SIGCONT signals are sent to the foreground process group and all processes in the
current session lose their controlling tty.
This ioctl(2) call only works on file descriptors connected to /dev/tty. It 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.
FILES
/dev/tty
SEE ALSO
chown(1), mknod(1), ioctl(2), termios(3), console(4), tty_ioctl(4), ttyS(4), agetty(8), mingetty(8)
COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2003-04-07 TTY(4)