snp(4) [linux man page]

SNP(4)                                                     BSD 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 is a snoop device which allows users to attach to any tty and watch activities on it.  The kernel must be compiled with device snp,
     or the snp module 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 a tty device, and then issue the SNPSTTY ioctl on snp
     device.  The argument passed to the ioctl(2) is the address of a variable of type int, holding the file descriptor of a tty device.  To
     detach the snp device from a tty use a pointer to a value of -1.

     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 characters 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)

HISTORY

     The snp device first appeared in FreeBSD 2.1.  In FreeBSD 8.0 the snp driver was rewritten to work with the replaced TTY subsystem.

AUTHORS

     The author of the current implementation is Ed Schouten <ed@FreeBSD.org>.  Previous versions of snp were based on code written by
     Ugen J.S. Antsilevich <ugen@NetVision.net.il>.

BUGS

     This version of snp does not return proper error codes when calling FIONREAD.  It also does not allow SNPSTTY to detach itself from the TTY.

BSD                                                              November 5, 2008                                                              BSD

PTS(4)							   BSD Kernel Interfaces Manual 						    PTS(4)

NAME

     pts -- pseudo-terminal driver

DESCRIPTION

     The pts driver provides support for a device-pair termed a pseudo-terminal.  A pseudo-terminal is a pair of character devices, a master
     device and a slave device.  The slave device provides to a process an interface identical to that described in tty(4).  However, whereas all
     other devices which provide the interface described in tty(4) have a hardware device of some sort behind them, the slave device has, instead,
     another process manipulating it through the master half of the pseudo-terminal.  That is, anything written on the master device is given to
     the slave device as input and anything written on the slave device is presented as input on the master device.

     The following ioctl(2) calls apply only to pseudo-terminals:

     TIOCPKT	   Enable/disable packet mode.	Packet mode is enabled by specifying (by reference) a nonzero parameter and disabled by specifying
		   (by reference) a zero parameter.  When applied to the master side of a pseudo-terminal, each subsequent read(2) from the termi-
		   nal will return data written on the slave part of the pseudo-terminal preceded by a zero byte (symbolically defined as
		   TIOCPKT_DATA), or a single byte reflecting control status information.  In the latter case, the byte is an inclusive-or of zero
		   or more of the bits:

		   TIOCPKT_FLUSHREAD   whenever the read queue for the terminal is flushed.

		   TIOCPKT_FLUSHWRITE  whenever the write queue for the terminal is flushed.

		   TIOCPKT_STOP        whenever output to the terminal is stopped a la '^S'.

		   TIOCPKT_START       whenever output to the terminal is restarted.

		   TIOCPKT_DOSTOP      whenever VSTOP is '^S' and VSTART is '^Q'.

		   TIOCPKT_NOSTOP      whenever the start and stop characters are not '^S/^Q'.

		   While this mode is in use, the presence of control status information to be read from the master side may be detected by a
		   select(2) for exceptional conditions.

		   This mode is used by rlogin(1) and rlogind(8) to implement a remote-echoed, locally '^S/^Q' flow-controlled remote login with
		   proper back-flushing of output; it can be used by other similar programs.

     TIOCGPTN	   Obtain device unit number, which can be used to generate the filename of the pseudo-terminal slave device. This ioctl(2) should
		   not be used directly. Instead, the ptsname(3) function should be used.

     TIOCPTMASTER  Determine whether the file descriptor is pointing to a pseudo-terminal master device.  This ioctl(2) should not be used
		   directly. It is used to implement routines like grantpt(3).

FILES

     The files used by this pseudo-terminals implementation are:

     /dev/pts/[num]  Pseudo-terminal slave devices.

DIAGNOSTICS

     None.

SEE ALSO

     posix_openpt(2), grantpt(3), ptsname(3), pty(4), tty(4)

HISTORY

     A pseudo-terminal driver appeared in 4.2BSD.  In FreeBSD 8.0, it was replaced with the pts driver.

BSD
								  August 20, 2008							       BSD