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)