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, ORDWR, CHEXCL|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 if (dirfstat(fd, &statbuf) == -1 || statbuf.Length.length == 0) 42 break; 43 if (write(fd, "", 0) < 0) 44 break; 45 sleep(3000); 46 } 47 48 close(fd); 49 postnote(PNGROUP, ppid, "kill"); 50 exits(""); 51 } 52