Just try. mutt_dotlock won't actually lock a file, but inform the invoking process if it's at all possible to lock file.
Force the lock. If another process holds a lock on file longer than a certain amount of time, mutt_dotlock will break that lock by removing the lockfile.
Unlock. mutt_dotlock will remove file.lock.
Delete. mutt_dotlock will lock file, remove it if it has length 0, and afterwards remove file.lock.
Use privileges. If given this option, mutt_dotlock will operate with group mail privileges when creating and deleting lock files.
mutt_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 mutt_dotlock is invoked with the -f command line option, mutt_dotlock won't generate this error, but break other processes' locks.
4 - DL_EX_NEED_RPIVS
This return value only occurs if mutt_dotlock has been invoked with the -t command line option. It means that mutt_dotlock will have to use its group mail privileges to lock file.
5 - DL_EX_IMPOSSIBLE
mutt_dotlock tries to implement an NFS-safe dotlocking method which was borrowed from lockfile (1).
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