NAME
snp —
tty snoop interface
SYNOPSIS
#include
<sys/snoop.h>
int
ioctl(fd,
SNPSTTY,
&dev);
int
ioctl(fd,
SNPGTTY,
&dev);
int
ioctl(fd,
FIONREAD,
&result);
DESCRIPTION
/dev/snp? are snoop devices which allow users to attach to any tty and watch activities on it. The kernel must be compiled withdevice 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 then use the
SNPSTTY ioctl. The argument passed to the ioctl is
the address of a variable of type dev_t. To detach the
snp device from a tty use a pointer to a value of
(dev_t)-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_DETACHsnpdevice has been detached by user or tty device has been closed and detached.
SEE ALSO
HISTORY
The snp device first appeared in
FreeBSD 2.1.
AUTHORS
Ugen J.S. Antsilevich <ugen@NetVision.net.il>
BUGS
Caveat emptor! This manual page is horribly stale and wildly inaccurate in some places.
While in line mode, user input can't be seen. No signals may be sent to the observed tty.