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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)pty.4 8.2 (Berkeley) 11/30/93 33.\" $FreeBSD$ 34.\" 35.Dd August 20, 2008 36.Dt PTS 4 37.Os 38.Sh NAME 39.Nm pts 40.Nd pseudo-terminal driver 41.Sh DESCRIPTION 42The 43.Nm 44driver provides support for a device-pair termed a 45.Em pseudo-terminal . 46A pseudo-terminal is a pair of character devices, a 47.Em master 48device and a 49.Em slave 50device. 51The slave device provides to a process an interface identical 52to that described in 53.Xr tty 4 . 54However, whereas all other devices which provide the 55interface described in 56.Xr tty 4 57have a hardware device of some sort behind them, the slave 58device has, instead, another process manipulating 59it through the master half of the pseudo-terminal. 60That is, anything written on the master device is 61given to the slave device as input and anything written 62on the slave device is presented as input on the master 63device. 64.Pp 65The following 66.Xr ioctl 2 67calls apply only to pseudo-terminals: 68.Bl -tag -width TIOCPTMASTER 69.It Dv TIOCPKT 70Enable/disable 71.Em packet 72mode. 73Packet mode is enabled by specifying (by reference) 74a nonzero parameter and disabled by specifying (by reference) 75a zero parameter. 76When applied to the master side of a pseudo-terminal, each subsequent 77.Xr read 2 78from the terminal will return data written on the slave part of 79the pseudo-terminal preceded by a zero byte (symbolically 80defined as 81.Dv TIOCPKT_DATA ) , 82or a single byte reflecting control 83status information. 84In the latter case, the byte is an inclusive-or 85of zero or more of the bits: 86.Bl -tag -width TIOCPKT_FLUSHWRITE 87.It Dv TIOCPKT_FLUSHREAD 88whenever the read queue for the terminal is flushed. 89.It Dv TIOCPKT_FLUSHWRITE 90whenever the write queue for the terminal is flushed. 91.It Dv TIOCPKT_STOP 92whenever output to the terminal is stopped a la 93.Ql ^S . 94.It Dv TIOCPKT_START 95whenever output to the terminal is restarted. 96.It Dv TIOCPKT_DOSTOP 97whenever 98.Dv VSTOP 99is 100.Ql ^S 101and 102.Dv VSTART 103is 104.Ql ^Q . 105.It Dv TIOCPKT_NOSTOP 106whenever the start and stop characters are not 107.Ql ^S/^Q . 108.El 109.Pp 110While this mode is in use, the presence of control status information 111to be read from the master side may be detected by a 112.Xr select 2 113for exceptional conditions. 114.Pp 115This mode is used by 116.Xr rlogin 1 117and 118.Xr rlogind 8 119to implement a remote-echoed, locally 120.Ql ^S/^Q 121flow-controlled 122remote login with proper back-flushing of output; it can be 123used by other similar programs. 124.It Dv TIOCGPTN 125Obtain device unit number, which can be used to generate the filename of 126the pseudo-terminal slave device. This 127.Xr ioctl 2 128should not be used directly. Instead, the 129.Xr ptsname 3 130function should be used. 131.It Dv TIOCPTMASTER 132Determine whether the file descriptor is pointing to a pseudo-terminal 133master device. 134This 135.Xr ioctl 2 136should not be used directly. It is used to implement routines like 137.Xr grantpt 3 . 138.El 139.Sh FILES 140The files used by this 141pseudo-terminals implementation are: 142.Bl -tag -width ".Pa /dev/pts/[num]" 143.It Pa /dev/pts/[num] 144Pseudo-terminal slave devices. 145.El 146.Sh DIAGNOSTICS 147None. 148.Sh SEE ALSO 149.Xr grantpt 3 , 150.Xr posix_openpt 2 , 151.Xr ptsname 3 , 152.Xr pty 4 , 153.Xr tty 4 154.Sh HISTORY 155A 156pseudo-terminal driver appeared in 157.Bx 4.2 . 158In 159.Fx 8.0 , 160it was replaced with the 161.Nm 162driver. 163