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ttyname

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

ttyname, ttyname_r - return name of a terminal

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <unistd.h>
char *ttyname(int fd);
int ttyname_r(size_t size;
              int fd, char buf[size], size_t size);

DESCRIPTION

The function ttyname() returns a pointer to the nul-terminated pathname of the terminal device that is open on the file descriptor fd, or NULL on error (for example, if fd 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 size size.

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()) size 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	M-Unsafe race:ttyname
ttyname_r()	Thread safety	M-Safe

STANDARDS

POSIX.-2008.

HISTORY

POSIX.-2001, 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.