projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 0f5e4452 KS |
1 | /* Copyright (c) 1979 Regents of the University of California */ |
| 2 | char maillock[] = ".lock"; /* Lock suffix for mailname */ | |
| 3 | char locktmp[] = "/usr/spool/mail/tmXXXXXX"; | |
| 4 | char curlock[50]; /* Last used name of lock */ | |
| 5 | static int locked; /* To note that we locked it */ | |
| 6 | ||
| 7 | /* | |
| 8 | * Lock the specified mail file by setting the file mailfile.lock. | |
| 9 | * We must, of course, be careful to remove the lock file by a call | |
| 10 | * to unlock before we stop. The algorithm used here is to see if | |
| 11 | * the lock exists, and if it does, to check its modify time. If it | |
| 12 | * is older than 200 seconds, we assume error and set our own file. | |
| 13 | * Otherwise, we wait for 5 seconds and try again. | |
| 14 | */ | |
| 15 | ||
| 16 | lock(file) | |
| 17 | char *file; | |
| 18 | { | |
| 19 | register int f; | |
| 20 | struct stat sbuf; | |
| 21 | long curtime; | |
| 22 | ||
| 23 | if (locked) | |
| 24 | return(0); | |
| 25 | strcpy(curlock, mailname); | |
| 26 | strcat(curlock, maillock); | |
| 27 | mktemp(locktmp); | |
| 28 | unlink(locktmp); | |
| 29 | for (;;) { | |
| 30 | f = lock1(locktmp, curlock); | |
| 31 | if (f == 0) { | |
| 32 | locked = 1; | |
| 33 | return(0); | |
| 34 | } | |
| 35 | stat(curlock, &sbuf); | |
| 36 | time(&curtime); | |
| 37 | if (curtime < sbuf.st_ctime + 200) { | |
| 38 | sleep(5); | |
| 39 | continue; | |
| 40 | } | |
| 41 | unlink(curlock); | |
| 42 | cnt++; | |
| 43 | } | |
| 44 | return(-1); | |
| 45 | } | |
| 46 | ||
| 47 | /* | |
| 48 | * Remove the mail lock, and note that we no longer | |
| 49 | * have it locked. | |
| 50 | */ | |
| 51 | ||
| 52 | unlock() | |
| 53 | { | |
| 54 | ||
| 55 | unlink(curlock); | |
| 56 | locked = 0; | |
| 57 | } | |
| 58 | ||
| 59 | /* | |
| 60 | * Attempt to set the lock by creating the temporary file, | |
| 61 | * then doing a link/unlink. If it fails, return -1 else 0 | |
| 62 | */ | |
| 63 | ||
| 64 | lock1(tempfile, name) | |
| 65 | char tempfile[], name[]; | |
| 66 | { | |
| 67 | register int fd; | |
| 68 | ||
| 69 | fd = creat(tempfile, 0); | |
| 70 | if (fd < 0) | |
| 71 | return(-1); | |
| 72 | if (link(tempfile, name) < 0) { | |
| 73 | unlink(tempfile); | |
| 74 | return(-1); | |
| 75 | } | |
| 76 | unlink(tempfile); | |
| 77 | close(fd); | |
| 78 | return(0); | |
| 79 | } |