This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                       TTYNAME(3POSIX)

       The  ttyname()  function  shall return a pointer to a string containing a null-terminated pathname of the
       terminal associated with file descriptor fildes.  The application shall not modify the  string  returned.
       The returned pointer might be invalidated or the string content might be overwritten by a subsequent call
       to  ttyname().   The  returned  pointer  and  the string content might also be invalidated if the calling
       thread is terminated.

       The ttyname() function need not be thread-safe.

       The ttyname_r() function shall store the null-terminated pathname of the  terminal  associated  with  the
       file  descriptor fildes in the character array referenced by name.  The array is namesize characters long
       and should have space for the name and the terminating null character. The maximum length of the terminal
       name shall be {TTY_NAME_MAX}.

       The ttyname() function may fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       ENOTTY The file associated with the fildes argument is not a terminal.

       The ttyname_r() function may fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       ENOTTY The file associated with the fildes argument is not a terminal.

       ERANGE The  value  of  namesize  is  smaller  than  the length of the string to be returned including the
              terminating null character.

       Thefollowingsectionsareinformative.

       None.

       None.

       ttyname, ttyname_r — find the pathname of a terminal

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       The term ``terminal'' is used instead of the historical term ``terminal device''  in  order  to  avoid  a
       reference to an undefined term.

       The  thread-safe  version places the terminal name in a user-supplied buffer and returns a non-zero value
       if it fails. The non-thread-safe version may  return  the  name  in  a  static  data  area  that  may  be
       overwritten by each call.

       Upon successful completion, ttyname() shall return a pointer to a string. Otherwise, a null pointer shall
       be returned and errno set to indicate the error.

       If successful, the ttyname_r() function shall return zero. Otherwise, an error number shall  be  returned
       to indicate the error.

       The Base Definitions volume of POSIX.1‐2017, <unistd.h>

       #include <unistd.h>

       char *ttyname(int fildes);
       int ttyname_r(int fildes, char *name, size_t namesize);