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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 (consult 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  descrip-
       tor, 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 file associated with the fildes argument is not 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 POSIX.1-2008, <unistd.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           ISATTY(3P)