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.\" $OpenBSD: posix_openpt.3,v 1.3 2012/12/05 06:40:59 jmc Exp $
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.\"
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.\" Copyright (c) 2012 Todd C. Miller <Todd.Miller@courtesan.com>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.Dd $Mdocdate: December 5 2012 $
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.Dt POSIX_OPENPT 3
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.Os
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.Sh NAME
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.Nm posix_openpt
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.Nd open a pseudo-terminal device
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.Sh SYNOPSIS
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.In stdlib.h
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.In fcntl.h
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.Ft int
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.Fn posix_openpt "int oflag"
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.Sh DESCRIPTION
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The
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.Fn posix_openpt
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function finds the next available pseudo-terminal and returns an open
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file descriptor for its master device.
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The path name of the slave device may be determined via the
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.Fn ptsname
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function.
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Note that the
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.Fn unlockpt
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and
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.Fn grantpt
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functions should be called before opening the slave device.
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.Pp
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The
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.Ar oflag
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argument is formed by bitwise-inclusive
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.Tn OR Ns 'ing
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the following values defined in
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.In fcntl.h :
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.Bl -tag -width O_NOCTTY -offset indent
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.It Dv O_RDWR
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Open for reading and writing.
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.It Dv O_NOCTTY
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Prevent the device from being made the controlling terminal for the session.
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This flag has no effect on
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.Ox
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and is included for compatibility with other systems.
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.El
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.Pp
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The
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.Dv O_RDWR
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flag must be specified in
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.Fa oflag .
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If
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.Fa oflag
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contains values other than those listed above,
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.Fn posix_openpt
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will return an error.
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.Sh RETURN VALUES
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If successful,
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.Fn posix_openpt
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returns a non-negative integer, the file descriptor for the
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pseudo-terminal master device.
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Otherwise, a value of \-1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn posix_openpt
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EMFILE
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The per-process descriptor table is full.
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.It Bq Er ENFILE
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The system file table is full.
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.It Bq Er EINVAL
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The value of
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.Fa oflag
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is not valid.
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.El
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.Sh SEE ALSO
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.Xr ptsname 3 ,
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.Xr pty 4 ,
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.Xr tty 4
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.Sh STANDARDS
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The
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.Fn posix_openpt
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function conforms to
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.St -p1003.1-2001 .
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.Sh HISTORY
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The
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.Fn posix_openpt
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function appeared in
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.Ox 5.3 .
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