pipe.c

#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#define MAXMSG 100

//fork产生的父子间使用管道通信

int main()
{
  char msg[][MAXMSG] = {"This is an awesome attempt to go far ",
                        "Go go go this is the light of the dawn",
                        "The Hobbit is something amazing"};
  sem_t sem;
  if(sem_init(&sem, 0, 1)==-1)
  {
    perror("sem_init");
    exit(-1);
  }
  // pipe
  int pfd[2];
  //int dummy;
  setbuf(stdout, NULL);
  if (pipe(pfd) == -1)
    perror("pipe");

  for (int i = 0; i < 3; ++i)
  {
    switch (fork())
    {
    case -1:
      perror("Fork Error\n");
    case 0: // child
      if (sem_wait(&sem) == -1)
      {
        perror("sem_wait");
        exit(-1);
      }

      // generate messages

      if (close(pfd[0]) == -1) // read end not used
      {
        perror("close");
        exit(-1);
      }
      write(pfd[1], msg[i], MAXMSG);
      if (sem_post(&sem) == -1)
      {
        perror("sem_post");
        exit(-1);
      }
      _exit(EXIT_SUCCESS);
    default:
      break;
    }
  }

  printf("Father\n");
  char buffer[MAXMSG];
  if (close(pfd[1]) == -1) /* Write end is unused */
    perror("close");
  for (int i = 0; i < 3; ++i)
  {
    printf("%d\n", wait(NULL));
    read(pfd[0], buffer, MAXMSG);
    printf("%s\n", buffer);
  }
  if (close(pfd[0]) == -1) /* Write end is unused */
    perror("close");

  exit(EXIT_SUCCESS);
}