1.\" 2.\" $FreeBSD: src/share/man/man4/snp.4,v 1.15.2.6 2002/08/03 12:04:15 schweikh Exp $ 3.\" $DragonFly: src/share/man/man4/snp.4,v 1.2 2003/06/17 04:36:59 dillon Exp $ 4.\" 5.Dd February 24, 1995 6.Dt SNP 4 7.Os 8.Sh NAME 9.Nm snp 10.Nd tty snoop interface 11.Sh SYNOPSIS 12.In sys/snoop.h 13.Ft int 14.Fn ioctl fd SNPSTTY &dev 15.Ft int 16.Fn ioctl fd SNPGTTY &dev 17.Ft int 18.Fn ioctl fd FIONREAD &result 19.Sh DESCRIPTION 20/dev/snp? are 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 26device 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 SNPSTTY ioctl. 34The argument passed to the ioctl is the address of a variable of type 35dev_t. 36To detach the snp device from a tty use a pointer to a value of (dev_t)-1. 37.Pp 38The SNPGTTY ioctl returns information about the current tty attached to 39the open 40.Nm 41device. 42.Pp 43The FIONREAD ioctl returns a positive value equal to the number of characters 44in a read buffer. 45Special values defined are: 46.Bl -tag -width SNP_TTYCLOSE 47.It Dv SNP_OFLOW 48device overflow occurred, device detached. 49.It Dv SNP_TTYCLOSE 50tty not attached. 51.It Dv SNP_DETACH 52.Nm 53device has been detached by user or tty device has been closed 54and detached. 55.El 56.Sh SEE ALSO 57.Xr pty 4 , 58.Xr sio 4 , 59.Xr kldload 8 , 60.Xr watch 8 61.Sh BUGS 62Caveat emptor! 63This manual page is horribly stale and wildly inaccurate in some places. 64.Pp 65While in line mode, user input can't be seen. 66No signals may be sent to the observed tty. 67.Sh AUTHORS 68.An Ugen J.S. Antsilevich Aq ugen@NetVision.net.il 69.Sh HISTORY 70The 71.Nm 72device first appeared in 73.Fx 2.1 . 74