7 .Nd tty snoop interface
11 .Fn ioctl fd SNPSTTY &dev
13 .Fn ioctl fd SNPGTTY &dev
15 .Fn ioctl fd FIONREAD &result
18 is a snoop device which allows users to attach to any tty
19 and watch activities on it.
20 The kernel must be compiled with
24 module must be loaded,
25 for these devices to be available.
29 device with a tty to be observed, open the
31 device and a tty device, and then issue the
36 The argument passed to the
38 is the address of a variable of type
40 holding the file descriptor of a tty device.
43 device from a tty use a pointer to a value of
48 ioctl returns information about the current tty attached to
55 ioctl returns a positive value equal to the number of characters
57 Special values defined are:
58 .Bl -tag -width ".Dv SNP_TTYCLOSE"
63 device has been detached by user or tty device has been closed
73 device first appeared in
79 driver was rewritten to work with the replaced TTY subsystem.
82 The author of the current implementation is
83 .An \&Ed Schouten Aq Mt ed@FreeBSD.org .
86 were based on code written by
87 .An Ugen J.S. Antsilevich Aq Mt ugen@NetVision.net.il .