1 /* 2 * Copyright (c) 1988, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 static char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 06/06/93"; 10 #endif /* not lint */ 11 12 #include <sys/types.h> 13 #include <sys/file.h> 14 #include <sys/dir.h> 15 #include <errno.h> 16 #include "pathnames.h" 17 18 /* 19 * uucp style locking routines 20 * return: 0 - success 21 * -1 - failure 22 */ 23 24 uu_lock(ttyname) 25 char *ttyname; 26 { 27 extern int errno; 28 int fd, pid; 29 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN]; 30 off_t lseek(); 31 32 (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname); 33 fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660); 34 if (fd < 0) { 35 /* 36 * file is already locked 37 * check to see if the process holding the lock still exists 38 */ 39 fd = open(tbuf, O_RDWR, 0); 40 if (fd < 0) { 41 perror("lock open"); 42 return(-1); 43 } 44 if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) { 45 (void)close(fd); 46 perror("lock read"); 47 return(-1); 48 } 49 50 if (kill(pid, 0) == 0 || errno != ESRCH) { 51 (void)close(fd); /* process is still running */ 52 return(-1); 53 } 54 /* 55 * The process that locked the file isn't running, so 56 * we'll lock it ourselves 57 */ 58 if (lseek(fd, 0L, L_SET) < 0) { 59 (void)close(fd); 60 perror("lock lseek"); 61 return(-1); 62 } 63 /* fall out and finish the locking process */ 64 } 65 pid = getpid(); 66 if (write(fd, (char *)&pid, sizeof(pid)) != sizeof(pid)) { 67 (void)close(fd); 68 (void)unlink(tbuf); 69 perror("lock write"); 70 return(-1); 71 } 72 (void)close(fd); 73 return(0); 74 } 75 76 uu_unlock(ttyname) 77 char *ttyname; 78 { 79 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN]; 80 81 (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname); 82 return(unlink(tbuf)); 83 } 84