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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 pathname of the terminal device that is open on the file descriptor fd, or NULL on error (for ex‐
ample, 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 │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴────────────────────────┘
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 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 2021-03-22 TTYNAME(3)