duti:tldr:bd39a

The command you provided, "duti -s ${org-videolan-vlc} ${m4v} viewer", is used to set the default viewer for files with the ".m4v" extension to VLC media player.

Here's a breakdown of the command:

• "duti" is a command-line utility used in macOS to manage default applications for file types.
• "-s" is an option provided by duti that allows you to set the default application for a specific file type.
• "${org-videolan-vlc}" is a placeholder that represents the bundle identifier of the application you want to set as the default viewer for the file type.
• "${m4v}" is another placeholder that represents the file extension or UTI (Uniform Type Identifier) for the file type you want to associate with the default viewer.
• "viewer" is another placeholder that represents the role you want to set for the default application. In this case, it is "viewer" to indicate the application should be the default viewer for the file type.

To make this command work, you need to replace the placeholders "${org-videolan-vlc}" with the actual bundle identifier of the VLC media player, and "${m4v}" with the file type you want to associate with VLC.