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 .