C fflush() function

C library function - fflush()

The fflush() function is used to empty the buffer that is associated with the specified output stream, if possible. The fflush() function undoes the effect of any ungetc() function if the stream is open for input. The stream remains open after the call.

Syntax:

int fflush(FILE *stream)

fflush() Parameters:

Return value from fflush()

• Upon successful completion, fflush() shall return 0; otherwise, it shall set the error indicator for the stream, return EOF, and set errno to indicate the error.

Example: fflush() function

Following example deletes a stream buffer.

#include <stdio.h>
#include <ctype.h>
 
int main(void)
{
   FILE *stream;
   int c;
   unsigned int result = 0;
 
   stream = fopen("test.txt", "r");
   while ((c = getc(stream)) != EOF && isdigit(c))
      result = result * 10 + c - '0';
   if (c != EOF)
      ungetc(c, stream);
 
   fflush(stream);
 
   printf("The result is: %d\n", result);
   if ((c = getc(stream)) != EOF)
      printf("The character is: %c\n", c);
} 

Output:

The result is: 0

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