ttyname, ttyname_r - return name of a terminal

       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                │
       └──────────────────────────────────────────────────────────────┴───────────────┴────────────────────────┘

       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.

EBADF  Bad file descriptor.

       ENODEVfd  refers to a slave pseudoterminal device but the corresponding pathname could not be found (see
              NOTES).

       ENOTTYfd does not refer to a terminal device.

       ERANGE (ttyname_r()) buflen was too small to allow storing the pathname.

       POSIX.1-2001, 4.2BSD.

       Standard C library (libc, -lc)

       ttyname, ttyname_r - return name of a terminal

       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.

       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.

tty(1), fstat(2), ctermid(3), isatty(3), pts(4)

Linux man-pages 6.9.1                              2024-05-02                                         ttyname(3)

       POSIX.1-2008.

#include<unistd.h>char*ttyname(intfd);intttyname_r(intfd,charbuf[.buflen],size_tbuflen);