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 .