.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Portions of this software were developed under sponsorship from Snow
.\" B.V., the Netherlands.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" Portions of this text are reprinted and reproduced in electronic form
.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
.\" Portable Operating System Interface (POSIX), The Open Group Base
.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
.\" Electrical and Electronics Engineers, Inc and The Open Group.  In the
.\" event of any discrepancy between this version and the original IEEE and
.\" The Open Group Standard, the original IEEE and The Open Group Standard is
.\" the referee document.  The original Standard can be obtained online at
.\"	http://www.opengroup.org/unix/online.html.
.\"
.\" $FreeBSD: src/lib/libc/sys/posix_openpt.2,v 1.1.2.1.6.1 2010/12/21 17:09:25 kensmith Exp $
.\"
.Dd August 20, 2008
.Dt POSIX_OPENPT 2
.Os
.Sh NAME
.Nm posix_openpt
.Nd "open a pseudo-terminal device"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.In fcntl.h
.Ft int
.Fn posix_openpt "int oflag"
.Sh DESCRIPTION
The
.Fn posix_openpt
function allocates a new pseudo-terminal and establishes a connection
with its master device.
A slave device shall be created in
.Pa /dev/pts .
After the pseudo-terminal has been allocated, the slave device should
have the proper permissions before it can be used (see
.Xr grantpt 3 ) .
The name of the slave device can be determined by calling
.Xr ptsname 3 .
.Pp
The file status flags and file access modes of the open file description
shall be set according to the value of
.Fa oflag .
Values for
.Fa oflag
are constructed by a bitwise-inclusive OR of flags from the following
list, defined in
.In fcntl.h :
.Bl -tag -width ".Dv O_NOCTTY"
.It Dv O_RDWR
Open for reading and writing.
.It Dv O_NOCTTY
If set
.Fn posix_openpt
shall not cause the terminal device to become the controlling terminal
for the process.
.El
.Pp
The
.Fn posix_openpt
function shall fail when
.Fa oflag
contains other values.
.Sh RETURN VALUES
Upon successful completion, the
.Fn posix_openpt
function shall allocate a new pseudo-terminal device and return a
non-negative integer representing a file descriptor, which is connected
to its master device.
Otherwise, -1 shall be returned and errno set to indicate the error.
.Sh ERRORS
The
.Fn posix_openpt
function shall fail if:
.Bl -tag -width Er
.It Bq Er ENFILE
The system file table is full.
.It Bq Er EINVAL
The value of
.Fa oflag
is not valid.
.It Bq Er EAGAIN
Out of pseudo-terminal resources.
.El
.Sh SEE ALSO
.Xr pts 4 ,
.Xr ptsname 3 ,
.Xr tty 4
.Sh STANDARDS
The
.Fn posix_openpt
function conforms to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Fn posix_openpt
function appeared in
.Fx 5.0 .
In
.Fx 8.0 ,
this function was changed to a system call.
.Sh NOTES
The flag
.Dv O_NOCTTY
is included for compatibility; in
.Fx ,
opening a terminal does not cause it to become a process's controlling
terminal.
.Sh AUTHORS
.An Ed Schouten Aq ed@FreeBSD.org