ttyname(3) Library Functions Manual ttyname(3)
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 path-
name 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 er-
ror.
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 path-
name.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(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 tty-
name_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 6.03 2022-12-15 ttyname(3)
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