pipe.c

#include <sys/wait.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int main(int argc, char *argv[]){

  //write end [1] read end [0]
  int pipe_p_c1[2];
  int pipe_c1_p[2];
  int pipe_c1_c2[2];
  int pipe_c2_p[2];

  pipe(pipe_p_c1);
  pipe(pipe_c1_p);
  pipe(pipe_c1_c2);
  pipe(pipe_c2_p);

  if (fork() == 0) {    // C1
    printf("C1 Here.\n");

    char ch[7];
    read(pipe_p_c1[0], &ch, 7);
    printf("From P in C1 %s \n", ch);

    write(pipe_c1_p[1], "Kyrenia", 7);
    write(pipe_c1_c2[1], "Baphos", 6);

  } else { 
    if (fork() == 0) {    // C2
      printf("C2 Here.\n");

      char ch[6];
      read(pipe_c1_c2[0], &ch, 6);
      printf("From C1 in C2 %s \n", ch);

      write(pipe_c2_p[1], "Larnaca", 7);

    }else{
      printf("P Here.\n");
      write(pipe_p_c1[1], "Nicosia",7);

      char ch[7];
      read(pipe_c1_p[0], &ch, 7);
      printf("From C1 in P %s \n", ch);

      read(pipe_c2_p[0], &ch, 7);
      printf("From C2 in P %s \n", ch);
      
      wait(NULL);
    }
  }
}