fflush : <stdio.h> library function

The function int fflush(FILE *stream); causes the content of an output buffer to be written on a file. The stream remains open after a call to fflush function. If stream is a null pointer, then all such streams are flushed.
All buffers automatically gets flushed when program terminates or because of a call to fclose or when they become full.

Function prototype of fflush

int fflush(FILE *stream);
  • stream : A pointer to a FILE object which identifies a stream.

Return value of fflush

This function returns zero value on success. If an error occurs, It returns EOF and the error indicator is set.

C program to show the use of fflush function

#include <stdio.h>
#include <string.h>

int main(){
   char buffer[100];

   memset(buffer, '\0', sizeof(buffer));
   setvbuf(stdout, buffer, _IOFBF, 100);

   fputs("fflush C Standard library function\n", stdout);

Program Output
fflush C Standard library function