dotlock(1) User Manuals dotlock(1)
NAME
lbdb_dotlock - Lock mail spool files.
SYNOPSIS
lbdb_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 ALSO
fcntl(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 processes' 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 borrowed 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 conditions 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 created to avoid running mutt with group mail privileges.
AUTHOR
Thomas Roessler <roessler@guug.de>
Unix OCTOBER 2005 dotlock(1)
