OPTION

--noflock (-L)

Ordinarily, dotlock uses both flock and dotfile locking. (It uses flock first, but releases that lock in the even that dotfile locking fails, so as to avoid deadlocking with applications that proceed in the reverse order.) The -L option disables flock locking, so that dotlock only uses dotfile locking.

This is primarily useful as a wrapper around an application that already does flock locking, but to which you want to add dotfile locking. (Even if your mail delivery system doesn't use flock, flock actually improves the efficiency of dotlock, so there is no reason to disable it.)

--fcntl (-P)

This option enables fcntl (a.k.a. POSIX) file locking of mail spools, in addition to flock and dotfile locking. The advantage of fcntl locking is that it may do the right thing over NFS. However, if either the NFS client or server does not properly support fcntl locking, or if the file system is not mounted with the appropriate options, fcntl locking can fail in one of several ways. It can allow different processes to lock the same file concurrently--even on the same machine. It can simply hang when trying to acquire a lock, even if no other process holds a lock on the file. Also, on some OSes it can interact badly with flock locking, because those OSes actually implement flock in terms of fcntl.

--nowait (-W)

With this option, dotlock simply exits non-zero and does not run command if it cannot immediately acquire the lock.