TTYNAME(3) Linux Programmer's Manual TTYNAME(3)
NAME
ttyname, ttyname_r - return name of a terminal
SYNOPSIS
#include <unistd.h>
char *ttyname(int fd);
int ttyname_r(int fd, char *buf, 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 appropriately. The function
ttyname_r() returns 0 on success, and an error number upon error.
ERRORS
EBADF Bad file descriptor.
ENODEV File descriptor refers to a slave pseudoterminal device but the
corresponding pathname could not be found (see NOTES).
ENOTTY File descriptor 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 |
+------------+---------------+------------------------+
CONFORMING TO
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)
COLOPHON
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description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2019-10-10 TTYNAME(3)