/dev/snp
is a snoop device which allows users to attach to any tty
and watch activities on it.
The kernel must be compiled with
device snp,
or the
snp
module must be loaded,
for these devices to be available.
To associate a given
snp
device with a tty to be observed, open the
snp
device and a tty device, and then issue the
SNPSTTY
ioctl on
snp
device.
The argument passed to the
ioctl(2)
is the address of a variable of type
int,
holding the file descriptor of a tty device.
To detach the
snp
device from a tty use a pointer to a value of
-1.
The
SNPGTTY
ioctl returns information about the current tty attached to
the open
snp
device.
The
FIONREAD
ioctl returns a positive value equal to the number of characters
in a read buffer.
Special values defined are:
|
| SNP_OFLOW
|
device overflow occurred, device detached.
|
| SNP_TTYCLOSE
|
| |
tty not attached.
|
| SNP_DETACH
|
snp
device has been detached by user or tty device has been closed
and detached.
|
|
