If the file’s read/write pointer is at the end of the file then a non-zero value is returned.
If the file’s read/write pointer is not at the end of the file, and no errors occur, then zero is returned and the task’s errno is also set to zero.
If an error prevents the function from determining the position of the file’s read/write pointer then zero is returned and the task’s errno is set to indicate the reason.
A task can obtain its errno value using the ff_errno() API function.
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