/* twin2.c -- One of two programs that use named pipes (or FIFOs)
 *            The other program is twin1.c.
 *            After you have compiled both programs into images twin1
 *            and twin2, execute both in the background passing
 *            as only parameter the name you want to use for the fifo.
 *            For example, you could use the name
 *                named_pipe_fifo
 *            Twin1 will write to twin2 two lines from a 
 *            limerick. Twin2 will read from the fifo and print out the 
 *            info.
 *            Whichever twin you launch first, it will
 *            hang in there until the other twin is launched. Then
 *            the communication takes place and both twins die.
 */

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

#define MAXBUFFER 256


#define FIFO_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH )
/* Default protection mode of fifo so that all can read only I can write */

int
main(int argc, char *argv[])
{
  int fd;
  char buffer[MAXBUFFER];
  int len;
  
  if (argc <2) {
    printf("usage: twin1 name-of-fifo\n");
    exit(0);
  }
  if ((mkfifo(argv[1],FIFO_MODE)<0) && (errno != EEXIST)) {
    perror("mkfifo");
    exit(0);
  }
  if ((fd = open(argv[1], O_RDONLY))<0) {
    perror("open");
    exit(0);
  }
  while ((len=read(fd,buffer, MAXBUFFER-1))>0) {
    buffer[len] = '\0';
    printf("%s", buffer);
  }
  close(fd);
  return 0;
}