1 #include <u.h>
2 #include <libc.h>
3 
4 void
5 usage(void)
6 {
7 	fprint(2, "usage: fossil/last disk\n");
8 	exits("usage");
9 }
10 
11 void
12 main(int argc, char **argv)
13 {
14 	int fd, bs, addr;
15 	char buf[20];
16 
17 	ARGBEGIN{
18 	default:
19 		usage();
20 	}ARGEND
21 
22 	if(argc != 1)
23 		usage();
24 
25 	if((fd = open(argv[0], OREAD)) < 0)
26 		sysfatal("open %s: %r", argv[0]);
27 
28 	werrstr("end of file");
29 	if(seek(fd, 131072, 0) < 0 || readn(fd, buf, 20) != 20)
30 		sysfatal("error reading %s: %r", argv[0]);
31 	fmtinstall('H', encodefmt);
32 	if(memcmp(buf, "\x37\x76\xAE\x89", 4) != 0)
33 		sysfatal("bad magic %.4H != 3776AE89", buf);
34 	bs = buf[7]|(buf[6]<<8);
35 	addr = (buf[8]<<24)|(buf[9]<<16)|(buf[10]<<8)|buf[11];
36 	if(seek(fd, (vlong)bs*addr+34, 0) < 0 || readn(fd, buf, 20) != 20)
37 		sysfatal("error reading %s: %r", argv[0]);
38 	print("vac:%.20lH\n", buf);
39 	exits(0);
40 }