ttyname - Online Linux Manual Page

Section : 3
Updated : 2022-12-15
Source : Linux man-pages 6.03

NAME

ttyname, ttyname_r − return name of a terminal

LIBRARY

Standard C library

(

libc

−lc

)

SYNOPSIS

#include <unistd.h>

char *ttyname(int

);

int ttyname_r(int

, char

buf

buflen

], size_t

buflen

);

DESCRIPTION

The function ttyname(

)

returns a pointer to the null-terminated pathname of the terminal device that is open on the file descriptor fd

, or NULL on error (for example, if

is not connected to a terminal). The return value may point to static data, possibly overwritten by the next call. The function ttyname_r(

)

stores this pathname in the buffer

buf of length buflen

RETURN VALUE

The function ttyname(

)

returns a pointer to a pathname on success. On error, NULL is returned, and errno is set to indicate the error. The function ttyname_r(

)

returns 0 on success, and an error number upon error.

ERRORS

EBADF

Bad file descriptor.

ENODEV

fd refers to a slave pseudoterminal device but the corresponding pathname could not be found (see NOTES).

ENOTTY

fd does not refer to a terminal device.

ERANGE

(

ttyname_r

(

)

buflen was too small to allow storing the pathname.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
ttyname()	Thread safety	MT-Unsafe race:ttyname
ttyname_r()	Thread safety	MT-Safe

STANDARDS

POSIX.1-2001, POSIX.1-2008, 4.2BSD.

NOTES

A process that keeps a file descriptor that refers to a pts(4) device open when switching to another mount namespace that uses a different /dev/ptmx instance may still accidentally find that a device path of the same name for that file descriptor exists. However, this device path refers to a different device and thus can't be used to access the device that the file descriptor refers to. Calling ttyname(

)

or ttyname_r(

)

on the file descriptor in the new mount namespace will cause these functions to return NULL and set errno to ENODEV