dotlock(1) User Manuals dotlock(1)NAMElbdb_dotlock - Lock mail spool files.
SYNOPSISlbdb_dotlock [-t|-f|-u|-d] [-r retries] file
DESCRIPTION
dotlock implements the traditional mail spool file locking method: To
lock file, a file named file.lock is created.
OPTIONS-t Just try. dotlock won't actually lock a file, but inform the
invoking process if it's at all possible to lock file.
-f Force the lock. If another process holds a lock on file longer
than a certain amount of time, dotlock will break that lock by
removing the lockfile.
-u Unlock. dotlock will remove file.lock.
-d Delete. dotlock will lock file, remove it if it has length 0,
and afterwards remove file.lock.
-r retries
This command line option tells dotlock to try locking retries
times before giving up or (if invoked with the -f command line
option) break a lock. The default value is 5. dotlock waits
one second between successive locking attempts.
FILES
file.lock
The lock file dotlock generates.
SEE ALSOfcntl(2), flock(2), lockfile(1), lbdb-fetchaddr(1)DIAGNOSTICS
dotlock gives all diagnostics in its return values:
0 - DL_EX_OK
The program was successful.
1 - DL_EX_ERROR
An unspecified error such as bad command line parameters, lack
of system memory and the like has occured.
3 - DL_EX_EXIST
The user wants to lock a file which has been locked by another
process already. If dotlock is invoked with the -f command line
option, dotlock won't generate this error, but break other pro‐
cesses' locks.
4 - DL_EX_NEED_RPIVS
This return value only occurs if dotlock has been invoked with
the -t command line option. It means that dotlock will have to
use its group mail privileges to lock file.
5 - DL_EX_IMPOSSIBLE
This return value only occurs if dotlock has been invoked with
the -t command line option. It means that dotlock is unable to
lock file.
NOTES
dotlock tries to implement an NFS-safe dotlocking method which was bor‐
rowed from lockfile(1).
If the user can't open file for reading with his normal privileges,
dotlock will return the DL_EX_ERROR exit value to avoid certain attacks
against other users' spool files. The code carefully avoids race condi‐
tions when checking permissions; for details of all this see the com‐
ments in dotlock.c.
HISTORY
dotlock is part of the Mutt mail user agent package. It has been cre‐
ated to avoid running mutt with group mail privileges.
AUTHOR
Thomas Roessler <roessler@guug.de>
Unix OCTOBER 2005 dotlock(1)
