linux下进程间通信mmap()实现内存共享的例子

在我的博客（传送门）里详细描述了mmap实现内存共享的手段，这里只是贴出需要的代码，谢谢：

normalfile1.c

/*
 * Copyright (c) 2010-~ zhouyongfei
 *
 * The source code is released for free distribution under the terms of the GNU General Public License
 *
 *
 * Author: alen Chou
 * Created Time: 2010年08月15日 星期日 11时24分36秒
 * File Name: normalfile.c
 * Description:
 * 使用mmap映射文件到内存空间，向内存空间写入数据，同时也会对相应的文件进行相应的操作。
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

typedef struct{
    char name[4];
    int age;
}people;

int main(int argc, char *argv[])
{
    int fd,i;
    people *p_map;
    char temp;

    fd = open(argv[1],O_CREAT|O_RDWR|O_TRUNC,0777);
    lseek(fd,sizeof(people)*5 - 1,SEEK_SET);//设置文件的大小

    write(fd,"",1);

    p_map = (people *)mmap(NULL,sizeof(people)*10,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
    //注意，mmap只能在进程中映射这么大的空间，而不能改变文件的大小

    close(fd);
    temp = 'a';
    for(i =0;i<10;i++){
        temp += 1;
        memcpy((*(p_map+i)).name,&temp,1);
        (*(p_map+i)).age = 20 + i;
    }
    printf("initialize over\n");
    sleep(10);
    munmap(p_map,sizeof(people)*10);
    printf("unmap OK\n");
    return 0;
}

normalfile2.c

/*
 * Copyright (c) 2010-~ zhouyongfei
 *
 * The source code is released for free distribution under the terms of the GNU General Public License
 *
 *
 * Author: alen Chou
 * Created Time: 2010年08月15日 星期日 11时33分35秒
 * File Name: normalfile2.c
 * Description:
 * 使用mmap映射shmtmp文件到内存区域，并读取这块内存上的东西，相当于读取文件中的东西。
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>

typedef struct {
    char name[4];
    int age;
}people;

int main(int argc, char *argv[])
{
    int fd,i;
    people *p_map;
    fd = open(argv[1],O_CREAT|O_RDWR,00777);
    p_map = (people *)mmap(NULL,sizeof(people)*10,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);

    for(i = 0;i < 10;i++){
        printf("name:%s age: %d;\n ",(*(p_map+i)).name,(*(p_map+i)).age);
    }

    munmap(p_map,sizeof(people)*10);

    return 0;
}

normalfile4.c

/*
 * Copyright (c) 2010-~ zhouyongfei
 *
 * The source code is released for free distribution under the terms of the GNU General Public License
 *
 *
 * Author: alen Chou
 * Created Time: 2010年08月15日 星期日 15时30分39秒
 * File Name: normalfile4.c
 * Description:
 * 父子进程间通过匿名映射实现共享内存
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

typedef struct{
    char name[4];
    int age;
}people;

main(int argc, char** argv)
{
    int i;
    people *p_map;
    char temp;
    p_map=(people*)mmap(NULL,sizeof(people)*10,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,-1,0);//fd = -1 表示只是创建内存区域，不对文件进行映射。

    if(fork() == 0)
    {
        sleep(2);
        for(i = 0;i<5;i++)
            printf("child read: the %d people's age is %d\n",i+1,(*(p_map+i)).age);
        (*p_map).age = 100;
        munmap(p_map,sizeof(people)*10); //实际上，进程终止时，会自动解除映射。

        exit(0);
    }
    temp = 'a';
    for(i = 0;i<5;i++)
    {
        temp += 1;
        memcpy((*(p_map+i)).name, &temp,2);
        (*(p_map+i)).age=20+i;
    }
    sleep(5);
    printf( "parent read: the first people,s age is %d\n",(*p_map).age );
    printf("umap\n");
    munmap( p_map,sizeof(people)*10 );
    printf( "umap ok\n" );
}