$FreeBSD: head/share/man/man4/snp.4 86868 2001-11-24 17:06:20Z dd $

.Dd February 24, 1995 .Dt SNP 4 .Os .Sh NAME .Nm snp .Nd tty snoop interface .Sh SYNOPSIS n sys/snoop.h .Ft int .Fn ioctl fd SNPSTTY &dev .Ft int .Fn ioctl fd SNPGTTY &dev .Ft int .Fn ioctl fd FIONREAD &result .Sh DESCRIPTION /dev/snp? are snoop devices which allow user to attach to any tty and watch activities on it. The kernel must be compiled with .Cd "device snp" , or the .Nm device must be loaded, for these devices to be available.

p To associate a given .Nm device with a tty to be observed, open the .Nm device and then use the SNPSTTY ioctl. The argument passed to the IOCTL is the address of a variable of type dev_t. By setting the value of the variable pointed to -1, the user may detach the snp device from a tty.

p The SNPGTTY ioctl returns information about the current tty attached to the open .Nm device.

p The FIONREAD ioctl returns a positive value equal to the number of characters in a read buffer. Special values defined are: l -tag -width SNP_TTYCLOSE t Dv SNP_OFLOW device overflow occured, device detached. t Dv SNP_TTYCLOSE tty not attached. t Dv SNP_DETACH .Nm device has been detached by user or tty device has been closed and detached. .El .Sh SEE ALSO .Xr pty 4 , .Xr sio 4 , .Xr kldload 8 , .Xr watch 8 .Sh BUGS Caveat emptor! This manual page is horribly stale and wildly inaccurate in some places.

p While in line mode, user input can't be seen. No signals may be sent to the observed tty. .Sh AUTHORS .An Ugen J.S. Antsilevich Aq ugen@NetVision.net.il .Sh HISTORY The .Nm device first appeared in .Fx 2.1 .