linux ½ø³Ì¼ä¹²ÏíÄÚ´æ

¿ÉÒÔ²ÉÓÃsysVµÄshmget £« shmat ʵÏÖ¡£
µ«ÊÇÎÒ¸üϲ»¶shm_open + mmap ¸ü¼òµ¥¡£
#---------------------writer.c----------------------------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>
struct ofs_stat
{
  int a;
  int b;
  int c;
};
int main(void)
{
        int fd;
    int count = 0;
    struct ofs_stat stat={0};
    struct ofs_stat *s;
    void *region=NULL;
    char *name;
        if((fd=shm_open("ofs_mmm", O_TRUNC|O_CREAT|O_RDWR,0644))==-1) {
      perror("open");
      exit(1);
        }
    ftruncate(fd, sizeof(stat));
    region = mmap(NULL, sizeof(struct stat), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if(region == (caddr_t)-1) {
      perror("mmap");
      shm_unlink("ofs_mmm");
      return 1;
    }
    s = (struct ofs_stat *)region;
    while(1) {
      s->a=count++;
      printf("%d \n",s->a);
      sleep(1);
    }
        shm_unlink("ofs_mmm");
    return 0;
}
#--------------------reader.c----------------------------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>
struct ofs_stat
{
  int a;
  int b;
&