freebsd-dev/lib/libc/gen/ttyname.3

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.\" Copyright (c) 1991, 1993
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.\" @(#)ttyname.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
.Dd May 14, 2005
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.Dt TTYNAME 3
.Os
.Sh NAME
.Nm ttyname ,
.Nm ttyname_r ,
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.Nm isatty ,
.Nm ttyslot
.Nd get name of associated terminal (tty) from file descriptor
.Sh LIBRARY
.Lb libc
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.Sh SYNOPSIS
.In unistd.h
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.Ft char *
.Fn ttyname "int fd"
.Ft int
.Fn ttyname_r "int fd" "char *buf" "size_t len"
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.Ft int
.Fn isatty "int fd"
.Ft int
.Fn ttyslot void
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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
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.Tn I/O
.Dv FILE
typedef, but refer to the special device files found in
.Pa /dev
and named
.Pa /dev/tty Ns Ar xx
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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.
.Pp
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The
.Fn ttyname
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function
returns the name stored in a static buffer which will be overwritten
on subsequent calls.
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The
.Fn ttyname_r
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function
takes a buffer and length as arguments to avoid this problem.
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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
is true; otherwise
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a
.Dv NULL
pointer is returned.
The
.Fn ttyname_r
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function returns 0 if successful.
Otherwise an error number is returned.
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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.
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.Sh FILES
.Bl -tag -width ".Pa /etc/ttys" -compact
.It Pa /dev/\(**
.It Pa /etc/ttys
.El
.Sh ERRORS
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The
.Fn ttyname_r
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may fail and return the following error codes:
.Bl -tag -width Er
.It Bq Er ENOTTY
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The
.Fa fd
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argument
is not a valid file descriptor.
.It Bq Er ERANGE
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The
.Fa bufsize
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argument
is smaller than the length of the string to be returned.
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.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr ttys 5
.Sh HISTORY
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The
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.Fn isatty ,
.Fn ttyname ,
and
.Fn ttyslot
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functions
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appeared in
.At v7 .
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The
.Fn ttyname_r
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function
appeared in
.Fx 6.0 .