直接读取硬盘扇区

Linux系统下一切都是文件，可以像使用普通文件一样使用设备，可直接操作设备扇区内容,这种方式不经过文件系统。

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

static void usage(char *prog_name)
{
    fprintf(stderr, "usage: %s device start count\n", prog_name);
    fprintf(stderr, "example: %s /dev/sda 0 512\n", prog_name);
}

int main(int argc, char *argv[])
{
    char buf[4096];
    int fd = 0;
    int i = 0;
    int j = 0;
    int start = 0;
    int count = 0;
    char *device = NULL;

    if(argc != 4){
        usage(basename(argv[0]));
        exit(1);
    }
    
    device = argv[1];
    start = atol(argv[2]);
    count = atol(argv[3]);

    fd = open(device, O_RDONLY);
    if(-1 == fd){
        fprintf(stderr, "cannot open /dev/hda");
        exit(1);
    }    
    
    if(lseek(fd, start, SEEK_SET) != start){
        fprintf(stderr, "cannot seek at %d", start);
        exit(1);
    }
    
    while(count > 0){
        int size = count > sizeof(buf) ? sizeof(buf) : count;

        read(fd, buf, size);
        
        /* 每行显示16个字节 每两个字节间以空格分开 */
        for(i = 0; i < size/16; i++){
            fprintf(stdout,"%08x:", i*16+start);
            for(j = 0; j < 16; j++){
                fprintf(stdout, " %02x", (int)buf[i*16+j] & 0xFF);    
            }
            fprintf(stdout,"\n");
            fflush(stdout);
        }
        count -= size;
        start += size;
    }