fflush
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header <stdio.h>
  | ||
| int fflush( FILE *stream ); | ||
Causes the output file stream to be synchronized with the actual contents of the file. If the given stream is of the input type, then the behavior of the function is undefined.
[edit] Parameters
| stream | - | the file stream to synchronize | 
[edit] Return value
Returns zero on success. Otherwise EOF is returned and the error indicator of the file stream is set.
[edit] See also
| opens a file (function) | |
| closes a file (function) | |