UNIX环境高级编程：存储映射I/O（mmap函数）

运行结果：

huangcheng@ubuntu:~$ ./a data.txt  
aaaaaaaaaaaa  
bbbbbbbbbbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
      
aaaaaaaaaaaa  
bbbbbbb9bbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
      
aaaaaaaaaaaa  
bbbbbbb9bbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
............

如果进程B中的映射设置为私有映射，运行结果：

huangcheng@ubuntu:~$ ./a data.txt  
aaaaaaaaaaaa  
bbbbbbbbbbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
      
aaaaaaaaaaaa  
bbbbbbbbbbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
      
aaaaaaaaaaaa  
bbbbbbbbbbbb  
cccccccccccc  
dddddddddddd  
eeeeeeeeeeee  
ffffffffffff  
............

4. 匿名映射实现父子进程通信

#include <sys/mman.h>    
#include <stdio.h>    
#include <stdlib.h>    
#include <unistd.h>    
        
#define BUF_SIZE 100    
        
int main(int argc, char** argv)    
{    
    char    *p_map;    
        
    /* 匿名映射,创建一块内存供父子进程通信 */
    p_map = (char *)mmap(NULL, BUF_SIZE, PROT_READ | PROT_WRITE,    
            MAP_SHARED | MAP_ANONYMOUS, -1, 0);    
        
    if(fork() == 0) {    
        sleep(1);    
        printf("child got a message: %sn", p_map);    
        sprintf(p_map, "%s", "hi, dad, this is son");    
        munmap(p_map, BUF_SIZE); //实际上，进程终止时，会自动解除映射。    
        exit(0);    
    }    
        
    sprintf(p_map, "%s", "hi, this is father");    
    sleep(2);    
    printf("parent got a message: %sn", p_map);    
        
    return 0;    
}

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