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

       The  isatty()  function does not necessarily indicate that a human being is available for interaction via
       fildes.  It is quite possible that non-terminal devices are connected to the communications line.

       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                                        ISATTY(3POSIX)

       The  isatty()  function shall test whether fildes, an open file descriptor, is associated with a terminal
       device.

       The isatty() function may fail if:

       EBADF  The fildes argument is not a valid open file descriptor.

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

       Thefollowingsectionsareinformative.

       None.

       None.

       isatty — test for a terminal device

       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.

       None.

       The isatty() function shall return 1 if fildes is associated with a terminal; otherwise, it shall  return
       0 and may set errno to indicate the error.

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

       #include <unistd.h>

       int isatty(int fildes);