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Annotation of 42BSD/ucb/Mail/lock.c, revision 1.1

1.1     ! root        1: #ifndef lint
        !             2: static char sccsid[] = "@(#)lock.c     2.4 (Berkeley) 8/11/83";
        !             3: #endif
        !             4: 
        !             5: /*
        !             6:  * A mailing program.
        !             7:  *
        !             8:  * Stuff to do version 7 style locking.
        !             9:  */
        !            10: 
        !            11: #include "rcv.h"
        !            12: #include <sys/stat.h>
        !            13: 
        !            14: char   *maillock       = ".lock";              /* Lock suffix for mailname */
        !            15: char   *lockname       = "/usr/spool/mail/tmXXXXXX";
        !            16: char   locktmp[30];                            /* Usable lock temporary */
        !            17: static char            curlock[50];            /* Last used name of lock */
        !            18: static int             locked;                 /* To note that we locked it */
        !            19: 
        !            20: /*
        !            21:  * Lock the specified mail file by setting the file mailfile.lock.
        !            22:  * We must, of course, be careful to remove the lock file by a call
        !            23:  * to unlock before we stop.  The algorithm used here is to see if
        !            24:  * the lock exists, and if it does, to check its modify time.  If it
        !            25:  * is older than 5 minutes, we assume error and set our own file.
        !            26:  * Otherwise, we wait for 5 seconds and try again.
        !            27:  */
        !            28: 
        !            29: lock(file)
        !            30: char *file;
        !            31: {
        !            32:        register int f;
        !            33:        struct stat sbuf;
        !            34:        long curtime;
        !            35: 
        !            36:        if (file == NOSTR) {
        !            37:                printf("Locked = %d\n", locked);
        !            38:                return(0);
        !            39:        }
        !            40:        if (locked)
        !            41:                return(0);
        !            42:        strcpy(curlock, file);
        !            43:        strcat(curlock, maillock);
        !            44:        strcpy(locktmp, lockname);
        !            45:        mktemp(locktmp);
        !            46:        remove(locktmp);
        !            47:        for (;;) {
        !            48:                f = lock1(locktmp, curlock);
        !            49:                if (f == 0) {
        !            50:                        locked = 1;
        !            51:                        return(0);
        !            52:                }
        !            53:                if (stat(curlock, &sbuf) < 0)
        !            54:                        return(0);
        !            55:                time(&curtime);
        !            56:                if (curtime < sbuf.st_ctime + 300) {
        !            57:                        sleep(5);
        !            58:                        continue;
        !            59:                }
        !            60:                remove(curlock);
        !            61:        }
        !            62: }
        !            63: 
        !            64: /*
        !            65:  * Remove the mail lock, and note that we no longer
        !            66:  * have it locked.
        !            67:  */
        !            68: 
        !            69: unlock()
        !            70: {
        !            71: 
        !            72:        remove(curlock);
        !            73:        locked = 0;
        !            74: }
        !            75: 
        !            76: /*
        !            77:  * Attempt to set the lock by creating the temporary file,
        !            78:  * then doing a link/unlink.  If it fails, return -1 else 0
        !            79:  */
        !            80: 
        !            81: lock1(tempfile, name)
        !            82:        char tempfile[], name[];
        !            83: {
        !            84:        register int fd;
        !            85: 
        !            86:        fd = creat(tempfile, 0);
        !            87:        if (fd < 0)
        !            88:                return(-1);
        !            89:        close(fd);
        !            90:        if (link(tempfile, name) < 0) {
        !            91:                remove(tempfile);
        !            92:                return(-1);
        !            93:        }
        !            94:        remove(tempfile);
        !            95:        return(0);
        !            96: }

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