2.9BSD - /usr/src/ucb/Mail/lock.c

   1: #
   2: 
   3: /*
   4:  * A mailing program.
   5:  *
   6:  * Stuff to do version 7 style locking.
   7:  */
   8: 
   9: #include "rcv.h"
  10: #include <sys/stat.h>
  11: 
  12: static char *SccsId = "@(#)lock.c	2.3 10/5/82";
  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: }

Defined functions

Defined variables