The fclose() function causes the stream pointed to by stream to be flushed and the associated file to be closed. Any unwritten buffered data for the stream
is written to the file; any unread buffered data is discarded. The stream is disassociated from the file. If the associated buffer was automatically allocated, it is deallocated.
The fclose() function marks for update the st_ctime and st_mtime fields of the underlying file if the stream is writable and if buffered data
has not yet been written to the file. It will perform a close(2)
operation on the file descriptor that is associated with the stream pointed to by stream.
After the call to fclose(), any use of stream causes undefined behavior.
The fclose() function is performed automatically for all open files upon calling exit(2).