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`fflush'--flush buffered file output

     #include <stdio.h>
     int fflush(FILE *FP);
The `stdio' output functions can buffer output before delivering it to
the host system, in order to minimize the overhead of system calls.
   Use `fflush' to deliver any such pending output (for the file or
stream identified by FP) to the host system.
   If FP is `NULL', `fflush' delivers pending output from all open
`fflush' returns `0' unless it encounters a write error; in that
situation, it returns `EOF'.
ANSI C requires `fflush'.
   No supporting OS subroutines are required.