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+.\" Hey Emacs! This file is -*- nroff -*- source.
+.\"
+.\" Copyright (C) 2004 Michael Kerrisk
+.\"
+.\" Permission is granted to make and distribute verbatim copies of this
+.\" manual provided the copyright notice and this permission notice are
+.\" preserved on all copies.
+.\"
+.\" Permission is granted to copy and distribute modified versions of this
+.\" manual under the conditions for verbatim copying, provided that the
+.\" entire resulting derived work is distributed under the terms of a
+.\" permission notice identical to this one.
+.\" 
+.\" Since the Linux kernel and libraries are constantly changing, this
+.\" manual page may be incorrect or out-of-date.  The author(s) assume no
+.\" responsibility for errors or omissions, or for damages resulting from
+.\" the use of the information contained herein.  The author(s) may not
+.\" have taken the same level of care in the production of this manual,
+.\" which is licensed free of charge, as they might when working
+.\" professionally.
+.\" 
+.\" Formatted or processed versions of this manual, if unaccompanied by
+.\" the source, must acknowledge the copyright and authors of this work.
+.\"
+.TH POSIX_OPENPT 3 "2004-12-17" "PTY Control" "Linux Programmer's Manual"
+.SH NAME
+posix_openpt \- open a pseudo-terminal device
+.SH SYNOPSIS
+.nf
+.B #define _XOPEN_SOURCE
+.br
+.B #include <stdlib.h>
+.B #include <fcntl.h>
+.sp
+.BI "char *posix_openpt(int " flags ");"
+.fi
+.SH DESCRIPTION
+The
+.BR posix_openpt ()
+function opens an unused pseudo-terminal master device, returning a
+file descriptor that can be used to refer to that device.
+
+The
+.I flags
+argument is a bit mask that ORs together zero or more of
+the following flags:
+.TP
+.B O_RWDR
+Open the device for both reading and writing.
+It is usual to specify this flag.
+.TP
+.B O_NOCTTY
+Do not make this device the controlling terminal for the process.
+.SH "RETURN VALUE"
+On success,
+.BR ptsname ()
+returns a non-negative file descriptor which is the lowest
+numbered unused descriptor.
+On failure, -1 is returned, and
+.I errno
+is set to indicate the error.
+.SH ERRORS
+See
+.BR open (2).
+.SH "CONFORMING TO"
+.BR posix_openpt ()
+is part of the Unix98 pseudo-terminal support (see
+.BR pts (4)).
+This function is specified in POSIX 1003.1-2001.
+.SH NOTES
+This function is a recent invention in POSIX.
+Some Unix implementations that support System V
+(aka Unix 98) pseudo-terminals don't have this function, but it
+is easy to implement:
+.in +0.5i
+.nf
+
+int
+posix_openpt(int flags)
+{
+    return open("/dev/ptmx", flags);
+}
+.fi
+.in -0.5i
+.SH "SEE ALSO"
+.BR open (2),
+.BR getpt (3),
+.BR grantpt (3),
+.BR ptsname (3),
+.BR unlock (3),
+.BR pts (4)