see:tldr:5923d

The command "run-mailcap --action=view ${filename}" is used to open and view the content of a file, using the mailcap configuration.

Here's a breakdown of the command:

• "run-mailcap" is a command in Unix-based systems that runs a content-type-specific action as defined in the mailcap configuration file.

• "--action=view" is an option or argument specifying the action to be done on the file. In this case, the action is "view," which means the file will be opened for viewing.

• "${filename}" is a placeholder variable that represents the name of the file you want to view. You need to replace it with the actual file name or the path to the file you wish to open.

When this command is executed, it will look for the appropriate entry in the mailcap configuration file associated with the file's content type. Then, it will execute the corresponding program or action to display the file content. The actual action performed will depend on how it is configured in the mailcap file.