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159 lines
4.2 KiB
Groff
159 lines
4.2 KiB
Groff
.\"
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.\" Copyright (c) 1996 Joerg Wunsch
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.\"
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.\" All rights reserved.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\" "
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.Dd June 2, 2018
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.Dt PTY 3
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.Os
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.Sh NAME
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.Nm openpty ,
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.Nm forkpty
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.Nd auxiliary functions to obtain a pseudo-terminal
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/ioctl.h
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.In termios.h
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.In libutil.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 forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp"
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.Sh DESCRIPTION
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The function
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.Fn openpty
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attempts to obtain the next available pseudo-terminal from the system (see
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.Xr pty 4 ) .
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If it successfully finds one, it subsequently changes the
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ownership of the slave device to the real UID of the current process,
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the group membership to the group
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.Dq tty
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(if such a group exists in the system), the access permissions for
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reading and writing by the owner, and for writing by the group, and
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invalidates any current use of the line by calling
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.Xr revoke 2 .
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.Pp
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If the argument
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.Fa name
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is not
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.Dv NULL ,
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.Fn openpty
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copies the pathname of the slave pty to this area.
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The caller is
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responsible for allocating the required space in this array.
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.Pp
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If the arguments
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.Fa termp
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or
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.Fa winp
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are not
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.Dv NULL ,
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.Fn openpty
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initializes the termios and window size settings from the structures
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these arguments point to, respectively.
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.Pp
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Upon return, the open file descriptors for the master and slave side
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of the pty are returned in the locations pointed to by
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.Fa amaster
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and
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.Fa aslave ,
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respectively.
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.Pp
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The
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.Fn forkpty
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function first calls
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.Fn openpty
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to obtain the next available pseudo-terminal from the system.
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Upon success,
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it forks off a new process.
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In the child process, it closes the descriptor
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for the master side of the pty, and calls
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.Xr login_tty 3
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for the slave pty.
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In the parent process, it closes the descriptor for the
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slave side of the pty.
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The arguments
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.Fa amaster ,
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.Fa name ,
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.Fa termp ,
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and
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.Fa winp
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have the same meaning as described for
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.Fn openpty .
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.Sh RETURN VALUES
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The
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.Fn openpty
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function returns 0 on success, or -1 on failure.
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.Pp
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The
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.Fn forkpty
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function returns -1 on failure, 0 in the slave process, and the process ID of
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the slave process in the parent process.
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.Sh ERRORS
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The
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.Fn openpty
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function may fail and set the global variable
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.Dv errno
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for any of the errors specified for the
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.Xr grantpt 3 ,
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.Xr posix_openpt 2 ,
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.Xr ptsname 3 ,
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and
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.Xr unlockpt 3
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functions and the
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.Xr revoke 2
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system call.
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.Pp
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In addition to this,
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.Fn forkpty
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may set it to any value as described for
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.Xr fork 2 .
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.Sh SEE ALSO
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.Xr chmod 2 ,
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.Xr chown 2 ,
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.Xr fork 2 ,
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.Xr getuid 2 ,
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.Xr open 2 ,
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.Xr revoke 2 ,
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.Xr login_tty 3 ,
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.Xr pty 4 ,
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.Xr termios 4 ,
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.Xr group 5
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.Sh HISTORY
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The
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.Fn openpty
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and
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.Fn forkpty
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functions first appeared in
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.Bx 4.3 Reno .
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.Sh BUGS
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.Fn openpty
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writes the slave terminal's name to
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.Fa name ,
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but does not check that sufficient space is available.
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It is advisable to use
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.Xr ptsname 3
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instead.
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