.. hook:: H_MODIFY_COMMAND

  :arg closure value: int|string <closure>(string cmd, object player)
  :arg string value: int|string <name>(string cmd)
  :arg mapping value: <mapping>

  Optional hook to modify commands (both entered or given by a call to :efun:`command`) before the parser sees them (this includes special commands like 'status').

  Hook setting can be any closure, the name of the function to call in the object, or a mapping.

  For interactives this hook is used only if the interactive object has no command modifier already set by the :efun:`set_modify_command`.

  If the hook is a closure, it is called with the entered command as first, and the command giving player as second argument. Lambda closures are bound to the command giving player, unbound-lambda closures remain unbound.

  If the hook is a string, it is used as the name of an lfun in the command giving player, which is called with the command as argument.

  If the hook is a mapping, it is queried with the given command as index, and the data retrieved is used as new command (defaults to 0 if no data is stored for a given command). If an entry is a closure instead of a string, it is called as::

    int|string <closure>(string cmd, object player)

  and the result from the call is used as 'the' command.

  The result is treated equal in all three cases:

  - If the result is a string, it is the new command to execute instead of the given one. Note that it is not possible to make several commands from one this way!
  - If the result is a non-zero number, the given command is to be ignored. In case of the closure/lfun setting this may mean that the closure/lfun already executed it.
  - If the result is 0, the originally given command is to be used.

  It is possible for the hook to change the command giver (``this_player()``) for the execution of the command. This means that even though the commands are execute for the original commandgiver, ``this_player()`` will return the changed commandgiver.

  .. history

  .. seealso:: :overview:`hook`, :hook:`command`, :hook:`modify_command_fname`, :hook:`notify_fail`, :hook:`send_notify_fail`