NAME

       isatty - test for a terminal device

SYNOPSIS

       #include <unistd.h>

       int isatty(int fildes);

DESCRIPTION

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

RETURN VALUE

       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.

ERRORS

       The isatty() function may fail if:

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

       ENOTTY The fildes argument is not associated with a terminal.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       The Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .