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.


int fflush(FILE *stream)

fflush() Parameters:

Name Description Required /Optional
stream Identifies an address for a file descriptor, which is an area of memory associated with an input or output stream. Required

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);
   printf("The result is: %d\n", result);
   if ((c = getc(stream)) != EOF)
      printf("The character is: %c\n", c);


The result is: 0

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C Programming: Tips of the Day

What's an object file in C?

An object file is the real output from the compilation phase. It's mostly machine code, but has info that allows a linker to see what symbols are in it as well as symbols it requires in order to work. (For reference, "symbols" are basically names of global objects, functions, etc.)

A linker takes all these object files and combines them to form one executable (assuming that it can, i.e.: that there aren't any duplicate or undefined symbols). A lot of compilers will do this for you (read: they run the linker on their own) if you don't tell them to "just compile" using command-line options. (-c is a common "just compile; don't link" option.)

Ref : https://bit.ly/3CbzF8M