linux C学习笔记04--内存映射

内存映射代码，打开一个文件与映射到内存中，对内存和文件的修改都会反映到文件中来，反之亦然，先贴代码，以后再完善：

/*************************************************************************
    > File Name: memory_map.c
    > Author: hailin.ma
    > Mail: mhl2018@126.com
    > Created Time: Thu 28 May 2015 08:20:50 AM CST
 ************************************************************************/

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

#define MEM_MAP_SIZE 1000

int memory_map()
{
    char * pmap = NULL;
    int fd;
    char rdbuf[] = "\0";

    fd = open("memory.txt",O_RDWR|O_CREAT|O_TRUNC,);

    if(fd == -)
    {
        perror("open error");
        return -;
    }

    write(fd,"hello world!",MEM_MAP_SIZE);        //write data to file,the write size must as long as MEM_MAP_SIZE

    pmap = mmap(NULL,MEM_MAP_SIZE,PROT_READ|PROT_WRITE,MAP_SHARED,fd,);        //map memory with file

    printf("the memory is: %s\n",pmap);

    memset(pmap,'a',MEM_MAP_SIZE);
    memcpy(pmap,"this is memory map",);        //try to chang any charactor in memory

    lseek(fd,,SEEK_SET);            //move fd pointer to begin section

    memset(rdbuf,,sizeof(rdbuf));
    read(fd,rdbuf,);                //read the context in file

    printf("the file is: %s\n",rdbuf);

    munmap(pmap,);

    close(fd);

    return ;
}

main函数调用后运行效果图：