/*
 * non_blocking.c -- slightly modified from APUE book by Muhammad Abdulla.
 */

#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

char buf[1000 * 1000];

int main()
{
   int ntowrite, nwrite;
   char *str;
   int  val;

   ntowrite = read(STDIN_FILENO, buf, sizeof(buf));
   fprintf(stderr, "read %d bytes\n", ntowrite);

   // set standard output as non-blocking
   val = fcntl(STDOUT_FILENO, F_GETFL, 0); 
   if ( val < 0 ) {
      fprintf(stderr, "F_GETFL error.\n");
      exit(EXIT_FAILURE);
   }

   val = fcntl(STDOUT_FILENO, F_SETFL, val | O_NONBLOCK); 
   if ( val < 0 ) {
      fprintf(stderr, "F_SETFL error.\n");
      exit(EXIT_FAILURE);
   }

   for ( str = buf; ntowrite > 0; ) {
      errno = 0;   // clear the global errno variable
      nwrite = write ( STDOUT_FILENO, str, ntowrite);
      fprintf(stderr, "nwrite = %d, errno = %d\n", nwrite, errno);

      if ( nwrite > 0 ) {
         str += nwrite;
         ntowrite -= nwrite; 
      }
   }

   exit(0);
}