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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 .