~~Title: Command modifiers ~~
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Opus supports various command modifiers that can be used in toolbar buttons and hotkeys to modify the behaviour of the function. A command modifier is not a command itself - for the most part you can think of them as options that control how the function is executed.

Each modifier is given on a separate line - therefore, to use command modifiers in a function, you must edit the function in the [[.command_editor:advanced_command_editor|advanced command editor]] (as the simple editor does not support multiple-line functions). Some modifiers (like **@async**) affect an individual command in the function, and are given on the same line as the command - others affect the whole function, and are supplied on a line by themselves.

{{:media:command_modifiers_001.png?nolink|}} 

This screenshot is an example of a simple function that makes use of two command modifiers:

  * The **@filesonly** modifier causes the function to only use selected files - any currently selected folders will be ignored. The **{f}**[[:reference:command_reference:external_control_codes|external control code]] means each filename will be passed in turn to Notepad. 
  * The **@async** modifier causes the command following it, **notepad.exe** in this instance, to run asynchronously. If multiple files are selected, an instance of notepad.exe will be executed for each file, without waiting for the previous instance to return. 



See the [[:reference:command_reference:command_modifier_reference|Command modifier reference]] page for a full list of the available command modifiers.