clearerr

/* writing errors */
#include <stdio.h>
int main ()
{
  FILE * pFile;
  pFile = fopen("myfile.txt","r");
  if (pFile==NULL) perror ("Error opening file");
  else
  {
    fputc ('x',pFile);
    if (ferror (pFile))
      {
      printf ("Error Writing to myfile.txt\n");
      clearerr (pFile);
      }
    fgetc (pFile);
    if (!ferror (pFile))
      printf ("No errors reading myfile.txt\n"); 
    fclose (pFile);
  }
  return 0;
}