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.1-2001, 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)