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Annotation of 43BSDReno/usr.bin/tip/uucplock.c, revision 1.1.1.1

1.1       root        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: (1) source distributions retain this entire copyright
                      7:  * notice and comment, and (2) distributions including binaries display
                      8:  * the following acknowledgement:  ``This product includes software
                      9:  * developed by the University of California, Berkeley and its contributors''
                     10:  * in the documentation or other materials provided with the distribution
                     11:  * and in all advertising materials mentioning features or use of this
                     12:  * software. Neither the name of the University nor the names of its
                     13:  * contributors may be used to endorse or promote products derived
                     14:  * from this software without specific prior written permission.
                     15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     18:  */
                     19: 
                     20: #ifndef lint
                     21: static char sccsid[] = "@(#)uucplock.c 5.5 (Berkeley) 6/1/90";
                     22: #endif /* not lint */
                     23: 
                     24: #include <sys/types.h>
                     25: #include <sys/file.h>
                     26: #include <sys/dir.h>
                     27: #include <errno.h>
                     28: #include "pathnames.h"
                     29: 
                     30: /* 
                     31:  * uucp style locking routines
                     32:  * return: 0 - success
                     33:  *       -1 - failure
                     34:  */
                     35: 
                     36: uu_lock(ttyname)
                     37:        char *ttyname;
                     38: {
                     39:        extern int errno;
                     40:        int fd, pid;
                     41:        char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
                     42:        off_t lseek();
                     43: 
                     44:        (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
                     45:        fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660);
                     46:        if (fd < 0) {
                     47:                /*
                     48:                 * file is already locked
                     49:                 * check to see if the process holding the lock still exists
                     50:                 */
                     51:                fd = open(tbuf, O_RDWR, 0);
                     52:                if (fd < 0) {
                     53:                        perror("lock open");
                     54:                        return(-1);
                     55:                }
                     56:                if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) {
                     57:                        (void)close(fd);
                     58:                        perror("lock read");
                     59:                        return(-1);
                     60:                }
                     61: 
                     62:                if (kill(pid, 0) == 0 || errno != ESRCH) {
                     63:                        (void)close(fd);        /* process is still running */
                     64:                        return(-1);
                     65:                }
                     66:                /*
                     67:                 * The process that locked the file isn't running, so
                     68:                 * we'll lock it ourselves
                     69:                 */
                     70:                if (lseek(fd, 0L, L_SET) < 0) {
                     71:                        (void)close(fd);
                     72:                        perror("lock lseek");
                     73:                        return(-1);
                     74:                }
                     75:                /* fall out and finish the locking process */
                     76:        }
                     77:        pid = getpid();
                     78:        if (write(fd, (char *)&pid, sizeof(pid)) != sizeof(pid)) {
                     79:                (void)close(fd);
                     80:                (void)unlink(tbuf);
                     81:                perror("lock write");
                     82:                return(-1);
                     83:        }
                     84:        (void)close(fd);
                     85:        return(0);
                     86: }
                     87: 
                     88: uu_unlock(ttyname)
                     89:        char *ttyname;
                     90: {
                     91:        char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
                     92: 
                     93:        (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
                     94:        return(unlink(tbuf));
                     95: }

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