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SNP(4)		       FreeBSD Kernel Interfaces Manual			SNP(4)

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 with device snp, or
     the snp device 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	char-
     acters 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.

SEE ALSO
     pty(4), sio(4), kldload(8), watch(8)

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.

AUTHORS
     Ugen J.S. Antsilevich <ugen@NetVision.net.il>

HISTORY
     The snp device first appeared in FreeBSD 2.1.

FreeBSD	10.1		       February	24, 1995		  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | BUGS | AUTHORS | HISTORY

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