prg12_3.c

配套光盘网络编程进程间的通信,网络编程进程间的通信是一本很经典的好书

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

#define	SEM_NAME	"mysem"
#define	FILE_MODE	(S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
int main(int argc,char **argv)
{
  int  fd,i,nloop,zero = 0;
  int  *ptr;
  sem_t *mutex;
  
  if (argc !=3)
  {
    printf("usage:%s <pathname><#loops>",argv[0]);
    exit(0);
  }
  
  nloop = atoi(argv[2]);
  fd = open(argv[1],O_RDWR | O_CREAT, FILE_MODE);
  write(fd,&zero,sizeof(int));
  ptr = mmap(NULL,sizeof(int),PROT_READ | PROT_WRITE,MAP_SHARED,
     fd,0);
  close(fd);
  
  mutex = sem_open(SEM_NAME,O_CREAT | O_EXCL,
    FILE_MODE,1);
  sem_unlink(SEM_NAME);
  setbuf(stdout,NULL);
  
  if (fork() == 0)
  {
    for(i=0;i<nloop;i++)
    {
      sem_wait(mutex);
      printf("child:%d\n",(*ptr)++);
      sem_post(mutex);
    }
    exit(0);
  }
  
  for(i=0; i<nloop;i++)
  {
    sem_wait(mutex);
    printf("parent:%d\n",(*ptr)++);
    sem_post(mutex);
  }
  
  exit(0);
}