1 /* 2 * Copyright (c) 1988 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 */ 17 18 #ifndef lint 19 static char sccsid[] = "@(#)uucplock.c 5.3 (Berkeley) 09/02/88"; 20 #endif /* not lint */ 21 22 #include <sys/types.h> 23 #include <sys/file.h> 24 #include <sys/dir.h> 25 #include <errno.h> 26 27 /* pick the directory naming scheme you are using */ 28 29 #define LOCKDIRNAME "/usr/spool/uucp/LCK..%s" /**/ 30 /* #define LOCKDIRNAME "/usr/spool/uucp/LCK/LCK..%s" /**/ 31 32 /* 33 * uucp style locking routines 34 * return: 0 - success 35 * -1 - failure 36 */ 37 38 uu_lock(ttyname) 39 char *ttyname; 40 { 41 extern int errno; 42 int fd, pid; 43 char tbuf[sizeof(LOCKDIRNAME) + MAXNAMLEN]; 44 off_t lseek(); 45 46 (void)sprintf(tbuf, LOCKDIRNAME, ttyname); 47 fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660); 48 if (fd < 0) { 49 /* 50 * file is already locked 51 * check to see if the process holding the lock still exists 52 */ 53 fd = open(tbuf, O_RDWR, 0); 54 if (fd < 0) { 55 perror("lock open"); 56 return(-1); 57 } 58 if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) { 59 (void)close(fd); 60 perror("lock read"); 61 return(-1); 62 } 63 64 if (kill(pid, 0) == 0 || errno != ESRCH) { 65 (void)close(fd); /* process is still running */ 66 return(-1); 67 } 68 /* 69 * The process that locked the file isn't running, so 70 * we'll lock it ourselves 71 */ 72 if (lseek(fd, 0L, L_SET) < 0) { 73 (void)close(fd); 74 perror("lock lseek"); 75 return(-1); 76 } 77 /* fall out and finish the locking process */ 78 } 79 pid = getpid(); 80 if (write(fd, (char *)&pid, sizeof(pid)) != sizeof(pid)) { 81 (void)close(fd); 82 (void)unlink(tbuf); 83 perror("lock write"); 84 return(-1); 85 } 86 (void)close(fd); 87 return(0); 88 } 89 90 uu_unlock(ttyname) 91 char *ttyname; 92 { 93 char tbuf[sizeof(LOCKDIRNAME) + MAXNAMLEN]; 94 95 (void)sprintf(tbuf, LOCKDIRNAME, ttyname); 96 return(unlink(tbuf)); 97 } 98