int isatty(int fildes);
The isatty() function shall test whether fildes, an open file descriptor, is associated with a terminal device.
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.
The isatty() function may fail if:
- The fildes argument is not a valid open file descriptor.
The fildes argument is not associated with a terminal.
The following sections are informative.
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.
COPYRIGHTPortions 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 .