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$Source: /home/ncvs/src/share/man/man4/snp.4,v $

.Dd February 24, 1995 .Dt SNP 4 .Os FreeBSD .Sh NAME .Nm snp .Nd tty snoop interface .Sh SYNOPSIS .Fd #include <sys/ioctl.h> .Fd #include <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. To associate a given .Nm snp device with a tty to be observed, open the .Nm snp 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 snp 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 snp device has been detached by user or tty device has been closed and detached. .Sh SEE ALSO .Xr pty 4 , .Xr sio 4 , .Xr watch 8 .Sh RESTRICTIONS Only the superuser may access the .Nm snp devices. .Sh BUGS While in line mode, user input can't be seen. No signals may be sent to the observed tty. .Sh AUTHOR Ugen J.S. Antsilevich <ugen@NetVision.net.il> .Sh HISTORY The .Nm snp device first appeared in FreeBSD 2.1.