1.\" 2.\" $FreeBSD$ 3.\" 4.Dd September 18, 2005 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 a tty device, and then issue the 34.Dv SNPSTTY 35ioctl on 36.Nm 37device. 38The argument passed to the 39.Xr ioctl 2 40is the address of a variable of type 41.Vt int , 42holding the file descriptor of a tty device. 43To detach the 44.Nm 45device from a tty use a pointer to a value of 46\-1. 47.Pp 48The 49.Dv SNPGTTY 50ioctl returns information about the current tty attached to 51the open 52.Nm 53device. 54.Pp 55The 56.Dv FIONREAD 57ioctl returns a positive value equal to the number of characters 58in a read buffer. 59Special values defined are: 60.Bl -tag -width ".Dv SNP_TTYCLOSE" 61.It Dv SNP_OFLOW 62device overflow occurred, device detached. 63.It Dv SNP_TTYCLOSE 64tty not attached. 65.It Dv SNP_DETACH 66.Nm 67device has been detached by user or tty device has been closed 68and detached. 69.El 70.Sh SEE ALSO 71.Xr pty 4 , 72.Xr sio 4 , 73.Xr kldload 8 , 74.Xr watch 8 75.Sh HISTORY 76The 77.Nm 78device first appeared in 79.Fx 2.1 . 80.Sh AUTHORS 81.An Ugen J.S. Antsilevich Aq ugen@NetVision.net.il 82.Sh BUGS 83Caveat emptor! 84This manual page is horribly stale and wildly inaccurate in some places. 85.Pp 86While in line mode, user input cannot be seen. 87No signals may be sent to the observed tty. 88