标题：稀疏文件的trick: 凭空增加1T的“可用”空间
出处：Felix021
时间：Sun, 22 Aug 2010 21:58:26 +0000
作者：felix021
地址：https://www.felix021.com/blog/read.php?1918

内容：
一个简单的程序：
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>

int main(int argc, char *argv[])
{
    int fd = open(argv[1], O_CREAT | O_WRONLY);
    if (fd < 0)
    {
        printf("err open");
        return 1;
    }
    u_int64_t sz = lseek64(fd, (1ull << 40) - 1, SEEK_SET);
    if (sz < 0)
    {
        printf("err lseek64");
        return 2;
    }
    int nWrite = write(fd, &fd, 1);
    printf("nWrite = %d\n", nWrite);
    close(fd);
    return 0;
}


编译运行：引用
$ gcc -o hole hole.c -D_FILE_OFFSET_BITS=64
$ ./hole disk
$ ls -lh disk
-rwxr-S--- 1 felix021 felix021 1.0T 2010-08-20 14:36 disk



搞怪：引用
felix021@ubuntu-vbox:~/code$ mkdir mnt
felix021@ubuntu-vbox:~/code$ sudo mkfs.vfat disk 
mkfs.vfat 3.0.7 (24 Dec 2009)
felix021@ubuntu-vbox:~/code$ sudo mount -oloop disk mnt
felix021@ubuntu-vbox:~/code$ df -lh
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3             5.2G  1.5G  3.5G  30% /
...
/dev/sda1             2.3G  957M  1.3G  43% /home
/dev/loop0            1.0T   16K  1.0T   1% /home/felix021/code/mnt




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