isatty - test for a terminal device
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 file associated with the fildes argument is not a terminal.
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.
First released in Issue 1. Derived from Issue 1 of the SVID.
The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:
The optional setting of errno to indicate an error is added.
The [EBADF] and [ENOTTY] optional error conditions are added.
SD5-XSH-ERN-100 is applied, correcting the definition of the [ENOTTY] error condition.
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