Provided by: manpages-dev_6.7-2_all 
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(int fd, 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 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 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.1-2008.
HISTORY
POSIX.1-2001, 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.
SEE ALSO
tty(1), fstat(2), ctermid(3), isatty(3), pts(4)
Linux man-pages 6.7 2023-10-31 ttyname(3)