# Command modifiers

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 [advanced command editor](https://chaoses-ib.gitbook.io/directory-opus/manual/customize/creating_your_own_buttons/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.

![](https://3597805814-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F3XSZSwWow0fDf6fQJobd%2Fuploads%2Fgit-blob-e558182c8e23a6cc2fa5453933154628f77a4316%2Fcommand_modifiers_001.png?alt=media)

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}**[external control code](https://chaoses-ib.gitbook.io/directory-opus/manual/reference/command_reference/external_control_codes) 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 [Command modifier reference](https://chaoses-ib.gitbook.io/directory-opus/manual/reference/command_reference/command_modifier_reference) page for a full list of the available command modifiers.


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