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.\" $OpenBSD: openpty.3,v 1.7 2001/07/13 22:14:07 millert Exp $
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.\" Copyright (c) 1995
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software developed by the Computer Systems
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.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract
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.\" BG 91-66 and contributed to Berkeley.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd November 4, 1996
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.Dt OPENPTY 3
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.Os
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.Sh NAME
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.Nm openpty ,
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.Nm login_tty ,
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.Nm forkpty
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.Nd tty utility functions
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.Sh SYNOPSIS
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.Fd #include <termios.h>
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.Fd #include <util.h>
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.Ft int
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.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp"
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.Ft int
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.Fn login_tty "int fd"
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.Ft pid_t
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.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp"
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.Sh DESCRIPTION
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The
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.Fn openpty ,
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.Fn login_tty ,
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and
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.Fn forkpty
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functions perform manipulations on ttys and pseudo-ttys.
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.Pp
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The
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.Fn openpty
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function finds an available pseudo-tty and returns file descriptors
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for the master and slave in
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.Fa amaster
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and
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.Fa aslave .
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If
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.Fa name
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is non-null, the filename of the slave is returned in
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.Fa name
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(a string of at least 16 characters).
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If
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.Fa termp
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is non-null, the terminal parameters of the slave will be set to the
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values in
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.Fa termp .
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If
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.Fa winp
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is non-null, the window size of the slave will be set to the values in
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.Fa winp .
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.Pp
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The
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.Fn login_tty
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function prepares for a login on the tty
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.Fa fd
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(which may be a real tty device, or the slave of a pseudo-tty as
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returned by
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.Fn openpty )
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by creating a new session, making
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.Fa fd
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the controlling terminal for the current process, setting
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.Fa fd
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to be the standard input, output, and error streams of the current
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process, and closing
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.Fa fd .
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.Pp
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The
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.Fn forkpty
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function combines
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.Fn openpty ,
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.Fn fork ,
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and
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.Fn login_tty
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to creates a new process operating in a pseudo-tty. The file
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descriptor of the master side of the pseudo-tty is returned in
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.Fa amaster ,
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and the filename of the slave in
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.Fa name
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if it is non-null. The
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.Fa termp
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and
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.Fa winp
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parameters, if non-null, will determine the terminal attributes and
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window size of the slave side of the pseudo-tty.
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.Sh RETURN VALUES
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If a call to
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.Fn openpty ,
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.Fn login_tty ,
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or
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.Fn forkpty
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is not successful, \-1 is returned and
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.Va errno
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is set to indicate the error. Otherwise,
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.Fn openpty ,
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.Fn login_tty ,
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and the child process of
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.Fn forkpty
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return 0, and the parent process of
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.Fn forkpty
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returns the process ID of the child process.
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.Sh ERRORS
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.Fn openpty
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will fail if:
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.Bl -tag -width Er
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.It Bq Er ENOENT
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There are no available ttys.
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.El
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.Pp
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.Fn login_tty
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will fail if
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.Fn ioctl
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fails to set
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.Fa fd
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to the controlling terminal of the current process.
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.Fn forkpty
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will fail if either
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.Fn openpty
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or
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.Fn fork
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fails.
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.Sh FILES
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.Bl -tag -width /dev/[pt]ty[pqrstuvwxyzPQRST][0123456789abcdef] -compact
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.It Pa /dev/[pt]ty[pqrstuvwxyzPQRST][0123456789abcdef]
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.El
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.Sh SEE ALSO
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.Xr fork 2
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