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



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

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 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.1-2017, <unistd.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                            ISATTY(3)
