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
1999-08-28 00:22:10 +00:00
.\" $FreeBSD$
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.\"
.Dd July 18, 2014
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.Dt TTYNAME 3
.Os
.Sh NAME
.Nm ttyname ,
.Nm ttyname_r ,
.Nm isatty
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.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"
.Sh DESCRIPTION
These functions operate on file descriptors for terminal type devices.
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.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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.Sh RETURN VALUES
The
.Fn isatty
function returns 1 if
.Fa fd
refers to a terminal type device;
otherwise, it returns 0 and may set
.Va errno
to indicate the error.
The
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.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.
.Sh ERRORS
These functions may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
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The
.Fa fd
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argument
is not a valid file descriptor.
.It Bq Er ENOTTY
The file associated with
.Fa fd
is not a terminal.
.El
.Pp
Additionally,
.Fn ttyname_r
may fail if:
.Bl -tag -width Er
.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 fdevname 3 ,
.Xr ptsname 3 ,
.Xr tcgetattr 3 ,
.Xr tty 4
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.Sh HISTORY
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The
.Fn isatty
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and
.Fn ttyname
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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 .