Yes,the sector size is 512 bytes,but this is not the beginning of my
fourth partition.Please check the code below,and if you can please test
it..
mbr.c
------
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
struct mbr {
unsigned char boot_indicator;
unsigned char s_head;
unsigned char s_sector;
unsigned char s_cylinder;
unsigned char f_desc;
unsigned char e_head;
unsigned char e_sector;
unsigned char e_cylinder;
unsigned int rs_sector;
unsigned int n_sectors;
} __attribute__((packed));
int main()
{
int fd;
struct mbr s;
fd= open("/dev/hdb",O_RDONLY);
lseek(fd,0x01ee,SEEK_SET); /* This is the 4rth entry,extended for
me*/
read(fd,&s,sizeof(struct mbr));
printf("Partition Entry 1:\n");
printf("Boot Indicator: %#x\n",s.boot_indicator);
printf("Starting head %u, cylinder %u, sector
%u.\n",s.s_head,((s.s_sector &
0xc0)<<2)+s.s_cylinder,s.s_sector&0x3f);
printf("Filesystem descriptor: %#x\n",s.f_desc);
printf("Ending head %u, cylinder %u, sector
%u.\n",s.e_head,((s.e_sector & 0xc0)<<2)+
s.e_cylinder,s.e_sector&0x3f);
printf("Starting sector: %u\n",s.rs_sector);
printf("Number of sectors in partition: %u\n",s.n_sectors);
fd= open("/dev/hdb4",O_RDONLY); /* Where is this in hdb,offset??*/
lseek(fd,446L,SEEK_SET);
read(fd,&s,sizeof(struct mbr));
printf("\nPartition Entry 4: Extended partition\n");
printf("Boot Indicator: %#x\n",s.boot_indicator);
printf("Starting head %u, cylinder %u, sector
%u.\n",s.s_head,((s.s_sector &
0xc0)<<2)+s.s_cylinder,s.s_sector&0x3f);
printf("Filesystem descriptor: %#x\n",s.f_desc);
printf("Ending head %u, cylinder %u, sector
%u.\n",s.e_head,((s.e_sector & 0xc0)<<2)+
s.e_cylinder,s.e_sector&0x3f);
printf("Starting sector: %u\n",s.rs_sector);
printf("Number of sectors in partition: %u\n",s.n_sectors);
return 0;
}
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