1 #include <u.h>
2 #include <libc.h>
3 
4 /* MAXHOSTNAMELEN is in sys/param.h */
5 #define MAXHOSTNAMELEN	64
6 
7 char lockstring[MAXHOSTNAMELEN+8];
8 
9 void
10 main(int argc, char *argv[]) {
11 	char *lockfile;
12 	int fd, ppid, ssize;
13 	struct Dir *statbuf;
14 
15 	if (argc != 4) {
16 		fprint(2, "usage: LOCK lockfile hostname ppid\n");
17 		exits("lock failed on usage");
18 	}
19 	lockfile = argv[1];
20 	if ((fd=create(lockfile, OLOCK|ORDWR, 0666)) < 0) {
21 		exits("lock failed on create");
22 	}
23 	ppid = atoi(argv[3]);
24 	ssize = sprint(lockstring, "%s %s\n", argv[2], argv[3]);
25 	if (write(fd, lockstring, ssize) != ssize) {
26 		fprint(2, "LOCK:write(): %r\n");
27 		exits("lock failed on write to lockfile");
28 	}
29 
30 	switch(fork()) {
31 	default:
32 		exits("");
33 	case 0:
34 		break;
35 	case -1:
36 		fprint(2, "LOCK:fork(): %r\n");
37 		exits("lock failed on fork");
38 	}
39 
40 	for(;;) {
41 		statbuf = dirfstat(fd);
42 		if(statbuf == nil)
43 			break;
44 		if (statbuf->length == 0){
45 			free(statbuf);
46 			break;
47 		}
48 		free(statbuf);
49 		if (write(fd, "", 0) < 0)
50 			break;
51 		sleep(3000);
52 	}
53 
54 	close(fd);
55 	postnote(PNGROUP, ppid, "kill");
56 	exits("");
57 }