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SNP(4) FreeBSD Kernel Interfaces Manual SNP(4) NAME snp -- tty snoop interface SYNOPSIS #include <sys/snoop.h> int ioctl(fd, SNPSTTY, _dev); int ioctl(fd, SNPGTTY, _dev); int ioctl(fd, FIONREAD, _result); 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 device snp, or the snp device must be loaded, for these devices to be available. To associate a given snp device with a tty to be observed, open the 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. The SNPGTTY ioctl returns information about the current tty attached to the open snp device. The FIONREAD ioctl returns a positive value equal to the number of char- acters in a read buffer. Special values defined are: SNP_OFLOW device overflow occurred, device detached. SNP_TTYCLOSE tty not attached. SNP_DETACH snp device has been detached by user or tty device has been closed and detached. SEE ALSO pty(4), sio(4), kldload(8), watch(8) BUGS Caveat emptor! This manual page is horribly stale and wildly inaccurate in some places. While in line mode, user input can't be seen. No signals may be sent to the observed tty. AUTHORS Ugen J.S. Antsilevich <ugen@NetVision.net.il> HISTORY The snp device first appeared in FreeBSD 2.1. FreeBSD 11.1 February 24, 1995 FreeBSD 11.1
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