PROLOG

       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.

NAME

       ttyname, ttyname_r — find the pathname of a terminal

SYNOPSIS

       #include <unistd.h>

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

DESCRIPTION

       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}.

RETURN VALUE

       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.

ERRORS

       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.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       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.

FUTURE DIRECTIONS

       None.

SEE ALSO

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

COPYRIGHT

       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 .