NetBSD/lib/libc/gen/ttyname.3

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.\" $NetBSD: ttyname.3,v 1.10 2001/09/16 02:57:05 wiz Exp $
.\"
.\" Copyright (c) 1991, 1993
.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
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.\" @(#)ttyname.3 8.1 (Berkeley) 6/4/93
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.\"
.Dd June 4, 1993
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.Dt TTYNAME 3
.Os
.Sh NAME
.Nm ttyname ,
.Nm isatty ,
.Nm ttyslot
.Nd get name of associated terminal (tty) from file descriptor
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.Sh LIBRARY
.Lb libc
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.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft char *
.Fn ttyname "int fd"
.Ft int
.Fn isatty "int fd"
.Fd #include <stdlib.h>
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.Ft int
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.Fn ttyslot
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.Sh DESCRIPTION
These functions operate on the system file descriptors for terminal
type devices. These descriptors are not related to the standard
.Tn I/O
.Dv FILE
typedef, but refer to the special device files found in
.Pa /dev
and named
.Pa /dev/tty Ns Em xx
and for which an entry exists
in the initialization file
.Pa /etc/ttys .
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(See
.Xr ttys 5 . )
.Pp
The
.Fn isatty
function
determines if the file descriptor
.Fa fd
refers to a valid
terminal type device.
.Pp
The
.Fn ttyname
function
gets the related device name of
a file descriptor for which
.Fn isatty
is true.
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.Pp
The
.Fn ttyslot
function
fetches the current process' control terminal number from the
.Xr ttys 5
file entry.
.Sh RETURN VALUES
The
.Fn ttyname
function
returns the null terminated name if the device is found and
.Fn isatty
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is true; otherwise
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a
.Dv NULL
pointer is returned and
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.Va errno
is set to indicate the error.
.Pp
The
.Fn isatty
function returns 1 if
.Fa fd
is associated with a terminal device; otherwise it returns 0 and
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.Va errno
is set to indicate the error.
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.Pp
The
.Fn ttyslot
function
returns the unit number of the device file if found; otherwise
the value zero is returned.
.Sh FILES
.Bl -tag -width /etc/ttys -compact
.It Pa /dev/\(**
.It Pa /etc/ttys
.El
.Sh ERRORS
The
.Fn ttyname
and
.Fn isatty
functions will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid file descriptor.
.It Bq Er ENOTTY
The
.Fa fd
argument does not refer to a terminal device.
.El
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.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr ttys 5
.Sh STANDARDS
The
.Fn ttyname
and
.Fn isatty
functions conform to
.St -p1003.1-90 .
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.Sh HISTORY
A
.Fn isatty ,
.Fn ttyname ,
and
.Fn ttyslot
function
appeared in
.At v7 .
.Sh BUGS
The
.Fn ttyname
function leaves its result in an internal static object and returns
a pointer to that object. Subsequent calls to
.Fn ttyname
will modify the same object.