grammar

[unix-history] / usr / src / usr.bin / mail / lock.c

/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/

#ifndef lint
static char *sccsid = "@(#)lock.c       5.2 (Berkeley) %G%";
#endif not lint

/*
* A mailing program.
*
* Stuff to do version 7 style locking.
*/

#include "rcv.h"
#include <sys/stat.h>

char    *maillock       = ".mail";              /* Lock suffix for mailname */
char    *lockname       = "/usr/spool/mail/tmXXXXXX";
char    locktmp[30];                            /* Usable lock temporary */
static char             curlock[50];            /* Last used name of lock */
static  int             locked;                 /* To note that we locked it */

/*
* Lock the specified mail file by setting the file mailfile.lock.
* We must, of course, be careful to remove the lock file by a call
* to unlock before we stop.  The algorithm used here is to see if
* the lock exists, and if it does, to check its modify time.  If it
* is older than 5 minutes, we assume error and set our own file.
* Otherwise, we wait for 5 seconds and try again.
*/

lock(file)
char *file;
{
       register int f;
       struct stat sbuf;
       long curtime;

       if (file == NOSTR) {
               printf("Locked = %d\n", locked);
               return(0);
       }
       if (locked)
               return(0);
       strcpy(curlock, file);
       strcat(curlock, maillock);
       strcpy(locktmp, lockname);
       mktemp(locktmp);
       remove(locktmp);
       for (;;) {
               f = lock1(locktmp, curlock);
               if (f == 0) {
                       locked = 1;
                       return(0);
               }
               if (stat(curlock, &sbuf) < 0)
                       return(0);
               time(&curtime);
               if (curtime < sbuf.st_ctime + 300) {
                       sleep(5);
                       continue;
               }
               remove(curlock);
       }
}

/*
* Remove the mail lock, and note that we no longer
* have it locked.
*/

unlock()
{

       remove(curlock);
       locked = 0;
}

/*
* Attempt to set the lock by creating the temporary file,
* then doing a link/unlink.  If it fails, return -1 else 0
*/

lock1(tempfile, name)
       char tempfile[], name[];
{
       register int fd;

       fd = creat(tempfile, 0);
       if (fd < 0)
               return(-1);
       close(fd);
       if (link(tempfile, name) < 0) {
               remove(tempfile);
               return(-1);
       }
       remove(tempfile);
       return(0);
}