| 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 %G%"; |
| 13 | |
| 14 | char *maillock = ".mail"; /* 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 | } |