#include <stdio.h>

int main(void)
{
  const char *buffer = "This is a test";
  FILE *fp = fopen("hello.txt", "w");
  if(fp != NULL)
  {
    fprintf(fp, "%s\n", buffer);
    if(ferror(fp))
    {
      fprintf(stderr, "An error occurred while writing the file.\n");
    }
    fclose(fp);
  }
  else
  {
    fprintf(stderr, "An error occurred while opening the file.\n");
  }
  return 0;
}