mmap文件映射相关代码

mmap，flock，fsync等函数的用法。


#include<stdio.h>


#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/file.h>
#include <unistd.h>
#include <string.h>


int main()
{
    int fd;
    void *start;
    struct stat sb;
    //fd = open("/mnt/ceph-kernel/1.txt", O_RDONLY); /*打开/etc/passwd */
    fd = open("/mnt/ceph-kernel/1.txt",O_RDWR); /*打开/etc/passwd */
    if(fd < 0)
        printf("open file failed\n");
        fsync(fd);
        if(flock(fd, LOCK_EX) == 0)
        {
                printf("file is locked\n");
//              sleep(10);
        }


    fstat(fd, &sb); /* 取得文件大小 */
    //start = mmap(NULL, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
    start = mmap(NULL, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if(start == MAP_FAILED) /* 判断是否映射成功 */
        return;
        memcpy((char*)start,"a", 1);
        write(5, start, sb.st_size);
        fsync(fd);
    printf("%s", start); munmap(start, sb.st_size); /* 解除映射 */
    close(fd);


return 0;
}