#include <string.h>

#include <stdio.h>

#include <fcntl.h>

int main()

{

  char *p1 = "This is a c test code";

  volatile int len = 0;

  int fp = open("/home/test.txt", O_RDWR|O_CREAT);

  for(;;)

  {

     int n;

     if((n=write(fp, p1+len, (strlen(p1)-len)))== 0)   //if((n=write(fp, p1+len, 3)) == 0)

     {                                                 //strlen(p1) = 21

         printf("n = %d \n", n);

         break;

     }

     len+=n;

  }

  return 0;

}