1907ec3a61
depend on new devname_r(3) as heart. Add /dev/pts magic directly to devname(3). While it can lead to returning non-existing paths, the behavior is more consistent that way. Drop caching layer in devname(3), it doesn't buy anything for the common case of having access to the database. Teach devname(3) proper fallback behavior of scanning /dev. Create both old-style and new-style database for now in /etc/rc.d/sysdb.
205 lines
5.2 KiB
Groff
205 lines
5.2 KiB
Groff
.\" $NetBSD: ttyname.3,v 1.24 2012/06/03 21:42:46 joerg Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. 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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.\" @(#)ttyname.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 1, 2012
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.Dt TTYNAME 3
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.Os
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.Sh NAME
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.Nm ttyname ,
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.Nm ttyname_r ,
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.Nm isatty ,
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.Nm ttyslot
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.Nd get name of associated terminal (tty) from file descriptor
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft char *
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.Fn ttyname "int fd"
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.Ft int
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.Fn ttyname_r "int fd" "char *buf" "size_t len"
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.Ft int
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.Fn isatty "int fd"
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.In stdlib.h
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.Ft int
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.Fn ttyslot "void"
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.Sh DESCRIPTION
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These functions operate on the system file descriptors for terminal
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type devices.
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These descriptors are not related to the standard
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.Tn I/O
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.Dv FILE
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typedef, but refer to the special device files found in
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.Pa /dev
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and named
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.Pa /dev/tty Ns Em xx
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and for which an entry exists in the initialization file
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.Pa /etc/ttys
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(see
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.Xr ttys 5 ) ,
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or for pseudo-terminal devices created in ptyfs and named
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.Pa /dev/pts/ Ns Em n .
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.Pp
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The
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.Fn isatty
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function
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determines if the file descriptor
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.Fa fd
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refers to a valid terminal type device.
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.Pp
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The
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.Fn ttyname
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function gets the related device name of a file descriptor for
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which
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.Fn isatty
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is true.
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The
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.Fn ttyname_r
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is the reentrant version of the above, and it places the results in
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.Fa buf .
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If there is not enough space to place the results (indicated by
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.Fa len ) ,
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then it returns an error.
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.Pp
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The
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.Fn ttyslot
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function
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fetches the current process' control terminal number from the
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.Xr ttys 5
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file entry.
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If the terminal is a pseudo-terminal, and there is no special entry
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in the
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.Xr ttys 5
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file for it, the slot number returned is 1 + (last slot number) +
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minor(tty).
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This will return a consistent and unique number for each pseudo-terminal
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device without requiring one to enumerate all of them in
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.Xr ttys 5 .
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.Sh IMPLEMENTATION NOTES
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As an optimisation, these functions attempt to obtain information about
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all devices from the
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.Pa /var/run/dev.cdb
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database, if it exists.
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If the database exists but is out of date, then these functions
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may produce incorrect results.
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The database should be updated using the
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.Xr dev_mkdb 8
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command.
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.Sh RETURN VALUES
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The
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.Fn ttyname
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function returns the NUL-terminated name if the device is found and
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.Fn isatty
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is true; otherwise
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a
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.Dv NULL
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pointer is returned and
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.Va errno
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is set to indicate the error.
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.Pp
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The
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.Fn ttyname_r
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functions returns 0 on success and an error code on failure.
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.Pp
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The
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.Fn isatty
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function returns 1 if
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.Fa fd
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is associated with a terminal device; otherwise it returns 0 and
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.Va errno
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is set to indicate the error.
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.Pp
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The
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.Fn ttyslot
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function
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returns the unit number of the device file if found; otherwise
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the value zero is returned.
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.Sh FILES
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.Bl -tag -width /etc/ttys -compact
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.It Pa /dev/\(**
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.It Pa /etc/ttys
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.El
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.Sh ERRORS
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The
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.Fn ttyname ,
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.Fn ttyname_r ,
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and
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.Fn isatty
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functions will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument is not a valid file descriptor.
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.It Bq Er ENOTTY
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The
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.Fa fd
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argument does not refer to a terminal device.
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.El
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.Pp
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The
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.Fn ttyname_r
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function will also fail if:
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.Bl -tag -width Er
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.It Bq Er ENOENT
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The terminal device is not found.
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This can happen if the device node has been removed after it was opened.
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.It Bq Er ERANGE
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The buffer provided is not large enough to fit the result.
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.El
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.Sh SEE ALSO
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.Xr ioctl 2 ,
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.Xr ttys 5 ,
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.Xr dev_mkdb 8
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.Sh STANDARDS
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The
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.Fn ttyname
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and
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.Fn isatty
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functions conform to
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.St -p1003.1-90 .
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.Sh HISTORY
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.Fn isatty ,
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.Fn ttyname ,
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and
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.Fn ttyslot
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functions appeared in
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.At v7 .
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.\" Use of the .Pa /var/run/dev.cdb file was added in netBSD 6.0.
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.Sh BUGS
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The
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.Fn ttyname
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function leaves its result in an internal static object and returns
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a pointer to that object.
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Subsequent calls to
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.Fn ttyname
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will modify the same object.
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