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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)pty.4 8.2 (Berkeley) 11/30/93 29.\" $FreeBSD$ 30.\" 31.Dd August 20, 2008 32.Dt PTS 4 33.Os 34.Sh NAME 35.Nm pts 36.Nd pseudo-terminal driver 37.Sh DESCRIPTION 38The 39.Nm 40driver provides support for a device-pair termed a 41.Em pseudo-terminal . 42A pseudo-terminal is a pair of character devices, a 43.Em master 44device and a 45.Em slave 46device. 47The slave device provides to a process an interface identical 48to that described in 49.Xr tty 4 . 50However, whereas all other devices which provide the 51interface described in 52.Xr tty 4 53have a hardware device of some sort behind them, the slave 54device has, instead, another process manipulating 55it through the master half of the pseudo-terminal. 56That is, anything written on the master device is 57given to the slave device as input and anything written 58on the slave device is presented as input on the master 59device. 60.Pp 61The following 62.Xr ioctl 2 63calls apply only to pseudo-terminals: 64.Bl -tag -width TIOCPTMASTER 65.It Dv TIOCPKT 66Enable/disable 67.Em packet 68mode. 69Packet mode is enabled by specifying (by reference) 70a nonzero parameter and disabled by specifying (by reference) 71a zero parameter. 72When applied to the master side of a pseudo-terminal, each subsequent 73.Xr read 2 74from the terminal will return data written on the slave part of 75the pseudo-terminal preceded by a zero byte (symbolically 76defined as 77.Dv TIOCPKT_DATA ) , 78or a single byte reflecting control 79status information. 80In the latter case, the byte is an inclusive-or 81of zero or more of the bits: 82.Bl -tag -width TIOCPKT_FLUSHWRITE 83.It Dv TIOCPKT_FLUSHREAD 84whenever the read queue for the terminal is flushed. 85.It Dv TIOCPKT_FLUSHWRITE 86whenever the write queue for the terminal is flushed. 87.It Dv TIOCPKT_STOP 88whenever output to the terminal is stopped a la 89.Ql ^S . 90.It Dv TIOCPKT_START 91whenever output to the terminal is restarted. 92.It Dv TIOCPKT_DOSTOP 93whenever 94.Dv VSTOP 95is 96.Ql ^S 97and 98.Dv VSTART 99is 100.Ql ^Q . 101.It Dv TIOCPKT_NOSTOP 102whenever the start and stop characters are not 103.Ql ^S/^Q . 104.El 105.Pp 106While this mode is in use, the presence of control status information 107to be read from the master side may be detected by a 108.Xr select 2 109for exceptional conditions. 110.Pp 111This mode is used by 112.Xr rlogin 1 113and 114.Xr rlogind 8 115to implement a remote-echoed, locally 116.Ql ^S/^Q 117flow-controlled 118remote login with proper back-flushing of output; it can be 119used by other similar programs. 120.It Dv TIOCGPTN 121Obtain device unit number, which can be used to generate the filename of 122the pseudo-terminal slave device. This 123.Xr ioctl 2 124should not be used directly. Instead, the 125.Xr ptsname 3 126function should be used. 127.It Dv TIOCPTMASTER 128Determine whether the file descriptor is pointing to a pseudo-terminal 129master device. 130This 131.Xr ioctl 2 132should not be used directly. It is used to implement routines like 133.Xr grantpt 3 . 134.El 135.Sh FILES 136The files used by this 137pseudo-terminals implementation are: 138.Bl -tag -width ".Pa /dev/pts/[num]" 139.It Pa /dev/pts/[num] 140Pseudo-terminal slave devices. 141.El 142.Sh DIAGNOSTICS 143None. 144.Sh SEE ALSO 145.Xr grantpt 3 , 146.Xr posix_openpt 2 , 147.Xr ptsname 3 , 148.Xr pty 4 , 149.Xr tty 4 150.Sh HISTORY 151A 152pseudo-terminal driver appeared in 153.Bx 4.2 . 154In 155.Fx 8.0 , 156it was replaced with the 157.Nm 158driver. 159