TTYNAME(3)                 Linux Programmer's Manual                TTYNAME(3)

       ttyname, ttyname_r - return name of a terminal

       #include <unistd.h>

       char *ttyname(int fd);

       int ttyname_r(int fd, char *buf, size_t buflen);

       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.

       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.

       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-

       For an  explanation  of  the  terms  used  in  this  section,  see  at-

       |Interface   | Attribute     | Value                  |
       |ttyname()   | Thread safety | MT-Unsafe race:ttyname |
       |ttyname_r() | Thread safety | MT-Safe                |
       POSIX.1-2001, POSIX.1-2008, 4.2BSD.

       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.

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

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Linux                             2019-10-10                        TTYNAME(3)
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