1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)ttyname.3 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/gen/ttyname.3,v 1.14 2007/01/09 00:27:55 imp Exp $ 30.\" 31.Dd September 10, 2019 32.Dt TTYNAME 3 33.Os 34.Sh NAME 35.Nm ttyname , 36.Nm ttyname_r , 37.Nm isatty 38.Nd get name of associated terminal (tty) from file descriptor 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In unistd.h 43.Ft char * 44.Fn ttyname "int fd" 45.Ft int 46.Fn ttyname_r "int fd" "char *buf" "size_t len" 47.Ft int 48.Fn isatty "int fd" 49.Sh DESCRIPTION 50These functions operate on the system file descriptors for terminal 51type devices. 52These descriptors are not related to the standard 53.Tn I/O 54.Dv FILE 55typedef, but refer to the special device files found in 56.Pa /dev 57and named 58.Pa /dev/tty Ns Ar xx 59and for which an entry exists 60in the initialization file 61.Pa /etc/ttys . 62(See 63.Xr ttys 5 . ) 64.Pp 65The 66.Fn isatty 67function 68determines if the file descriptor 69.Fa fd 70refers to a valid 71terminal type device. 72.Pp 73The 74.Fn ttyname 75function 76gets the related device name of 77a file descriptor for which 78.Fn isatty 79is true. 80.Pp 81The 82.Fn ttyname 83function 84returns the name stored in a static buffer which will be overwritten 85on subsequent calls. 86The 87.Fn ttyname_r 88function 89takes a buffer and length as arguments to avoid this problem. 90.Sh RETURN VALUES 91The 92.Fn isatty 93function 94returns 1 if the file descriptor refers to a valid terminal 95device and 0 otherwise. 96.Pp 97The 98.Fn ttyname 99function 100returns the null terminated name if the device is found and 101.Fn isatty 102is true; otherwise 103a 104.Dv NULL 105pointer is returned. 106The 107.Fn ttyname_r 108function returns 0 if successful. 109Otherwise an error number is returned. 110.Sh FILES 111.Bl -tag -width ".Pa /etc/ttys" -compact 112.It Pa /dev/\(** 113.It Pa /etc/ttys 114.El 115.Sh ERRORS 116The 117.Fn ttyname , 118.Fn ttyname_r , 119and 120.Fn isatty 121functions 122may fail and return the following error codes: 123.Bl -tag -width Er 124.It Bq Er EBADF 125The 126.Fa fd 127is not a valid open file descriptor. 128.It Bq Er ENOTTY 129The 130.Fa fd 131is not associated with a terminal. 132.It Bq Er ERANGE 133The 134.Fa bufsize 135argument 136is smaller than the length of the string to be returned. 137.El 138.Sh SEE ALSO 139.Xr ioctl 2 , 140.Xr ttys 5 141.Sh HISTORY 142The 143.Fn isatty 144and 145.Fn ttyname 146functions 147appeared in 148.At v7 . 149The 150.Fn ttyname_r 151function 152appeared in 153.Fx 6.0 . 154