1.\" 2.\" $FreeBSD$ 3.\" 4.Dd February 24, 1995 5.Dt SNP 4 6.Os 7.Sh NAME 8.Nm snp 9.Nd tty snoop interface 10.Sh SYNOPSIS 11.In sys/snoop.h 12.Ft int 13.Fn ioctl fd SNPSTTY &dev 14.Ft int 15.Fn ioctl fd SNPGTTY &dev 16.Ft int 17.Fn ioctl fd FIONREAD &result 18.Sh DESCRIPTION 19.Pa /dev/snp? 20are snoop devices which allow users to attach to any tty 21and watch activities on it. 22The kernel must be compiled with 23.Cd "device snp" , 24or the 25.Nm 26module must be loaded, 27for these devices to be available. 28.Pp 29To associate a given 30.Nm 31device with a tty to be observed, open the 32.Nm 33device and then use the 34.Dv SNPSTTY 35ioctl. 36The argument passed to the 37.Xr ioctl 2 38is the address of a variable of type 39.Vt dev_t . 40To detach the 41.Nm 42device from a tty use a pointer to a value of 43.Po Vt dev_t Pc Ns \-1 . 44.Pp 45The 46.Dv SNPGTTY 47ioctl returns information about the current tty attached to 48the open 49.Nm 50device. 51.Pp 52The 53.Dv FIONREAD 54ioctl returns a positive value equal to the number of characters 55in a read buffer. 56Special values defined are: 57.Bl -tag -width ".Dv SNP_TTYCLOSE" 58.It Dv SNP_OFLOW 59device overflow occurred, device detached. 60.It Dv SNP_TTYCLOSE 61tty not attached. 62.It Dv SNP_DETACH 63.Nm 64device has been detached by user or tty device has been closed 65and detached. 66.El 67.Sh SEE ALSO 68.Xr pty 4 , 69.Xr sio 4 , 70.Xr kldload 8 , 71.Xr watch 8 72.Sh BUGS 73Caveat emptor! 74This manual page is horribly stale and wildly inaccurate in some places. 75.Pp 76While in line mode, user input cannot be seen. 77No signals may be sent to the observed tty. 78.Sh AUTHORS 79.An Ugen J.S. Antsilevich Aq ugen@NetVision.net.il 80.Sh HISTORY 81The 82.Nm 83device first appeared in 84.Fx 2.1 . 85