9 .Nd tty snoop interface
13 .Fn ioctl fd SNPSTTY &dev
15 .Fn ioctl fd SNPGTTY &dev
17 .Fn ioctl fd FIONREAD &result
20 is a snoop device which allows users to attach to any tty
21 and watch activities on it.
22 The kernel must be compiled with
26 module must be loaded,
27 for these devices to be available.
31 device with a tty to be observed, open the
33 device and a tty device, and then issue the
38 The argument passed to the
40 is the address of a variable of type
42 holding the file descriptor of a tty device.
45 device from a tty use a pointer to a value of
50 ioctl returns information about the current tty attached to
57 ioctl returns a positive value equal to the number of characters
59 Special values defined are:
60 .Bl -tag -width ".Dv SNP_TTYCLOSE"
65 device has been detached by user or tty device has been closed
75 device first appeared in
81 driver was rewritten to work with the replaced TTY subsystem.
84 The author of the current implementation is
85 .An \&Ed Schouten Aq Mt ed@FreeBSD.org .
88 were based on code written by
89 .An Ugen J.S. Antsilevich Aq Mt ugen@NetVision.net.il .