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