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(** Simple abstraction over Unix lockfiles *)

open Error_monad

(** [try_with_lock ?close_on_exec ?unlink_on_exit ~when_locked
    ~filename f] tries to take a lock on file [filename] and calls [f]
    if the lock was successfully taken. If the lock was previously
    taken, [when_locked] is called instead and [f] is ignored.

    This function may fail with an I/O exception wrapped in the error
    monad if something unexpected happened. *)
val try_with_lock :
  when_locked:(unit -> 'a tzresult Lwt.t) ->
  filename:string ->
  (unit -> 'a tzresult Lwt.t) ->
  'a tzresult Lwt.t