1dotlock(1) User Manuals dotlock(1)
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6 lbdb_dotlock - Lock mail spool files.
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9 lbdb_dotlock [-t|-f|-u|-d] [-r retries] file
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12 dotlock implements the traditional mail spool file locking method: To
13 lock file, a file named file.lock is created.
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16 -t Just try. dotlock won't actually lock a file, but inform the
17 invoking process if it's at all possible to lock file.
18 -f Force the lock. If another process holds a lock on file longer
20 than a certain amount of time, dotlock will break that lock by
21 removing the lockfile.
22 -u Unlock. dotlock will remove file.lock.
24 -d Delete. dotlock will lock file, remove it if it has length 0,
26 and afterwards remove file.lock.
27 -r retries
29 This command line option tells dotlock to try locking retries
30 times before giving up or (if invoked with the -f command line
31 option) break a lock. The default value is 5. dotlock waits
32 one second between successive locking attempts.
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35 file.lock
36 The lock file dotlock generates.
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39 fcntl(2), flock(2), lockfile(1), lbdb-fetchaddr(1)
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42 dotlock gives all diagnostics in its return values:
43 0 - DL_EX_OK
45 The program was successful.
46 1 - DL_EX_ERROR
48 An unspecified error such as bad command line parameters, lack
49 of system memory and the like has occurred.
50 3 - DL_EX_EXIST
52 The user wants to lock a file which has been locked by another
53 process already. If dotlock is invoked with the -f command line
54 option, dotlock won't generate this error, but break other pro‐
55 cesses' locks.
56 4 - DL_EX_NEED_RPIVS
58 This return value only occurs if dotlock has been invoked with
59 the -t command line option. It means that dotlock will have to
60 use its group mail privileges to lock file.
61 5 - DL_EX_IMPOSSIBLE
63 This return value only occurs if dotlock has been invoked with
64 the -t command line option. It means that dotlock is unable to
65 lock file.
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68 dotlock tries to implement an NFS-safe dotlocking method which was bor‐
69 rowed from lockfile(1).
70 If the user can't open file for reading with his normal privileges,
72 dotlock will return the DL_EX_ERROR exit value to avoid certain attacks
73 against other users' spool files. The code carefully avoids race condi‐
74 tions when checking permissions; for details of all this see the com‐
75 ments in dotlock.c.
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78 dotlock is part of the Mutt mail user agent package. It has been cre‐
79 ated to avoid running mutt with group mail privileges.
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82 Thomas Roessler <roessler@guug.de>
83Unix JANUARY 2016 dotlock(1)