ISATTY(3P)                                          POSIX Programmer's Manual                                         ISATTY(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    ISATTY(3P)