C3-2 TEST OF HOLE FILE &NOHOLE FILE

 首先生成一个带有空洞的文件

 生辰一个不带空洞的文件：

发现二者文件的大小是一样的，但是所分配的磁盘块是不一样的。

#include "apue.h"
#include <fcntl.h>

char buf1[] = "abcdefghij";
char buf2[] = "ABCDEFGHIJ";

int main(void )
{
    int fd;

    if(( fd=creat("file.hole",FILE_MODE)) < 0)
        err_sys("creat error ");
    /* offset now =10 */
    if(write(fd,buf1,10) != 10)
        err_sys("write error");

    if( lseek(fd,16384,SEEK_SET ) == -1 )
        err_sys("lseek error");

    /* offset now =16384 */

    if(write(fd,buf2,10) != 10)
        err_sys("write error");
    /* offet now =16394 */
    exit(0);
}

#include "apue.h"
#include <fcntl.h>

int main(void )
{
    int fd;

    if ((fd=creat("file.nohole",FILE_MODE)) < 0)
        err_sys("creat error ");
    int loop=1;
    char *p="c";
    for (loop =1; loop <=16394; loop++)
    {
        if (write(fd,p,1) != 1)
            err_sys("write error");
    }
    exit(0);
}

-rw-r--r-- 1 ubuntu ubuntu 16394 2011-12-27 19:50 file.hole
0000000   a   b   c   d   e   f   g   h   i   j  \0  \0  \0  \0  \0  \0
0000020  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
*
0040000   A   B   C   D   E   F   G   H   I   J
0040012
 8 -rw-r--r-- 1 ubuntu ubuntu 16394 2011-12-27 19:50 file.hole
20 -rw-r--r-- 1 ubuntu ubuntu 16394 2011-12-27 20:06 file.nohole