idnits:tldr:81d16

The command "idnits --doctype ${select} ${filename-txt}" runs the idnits tool with certain options and arguments.

Here's a breakdown of the command:

• "idnits" is the name of the tool or program being executed.
• "--doctype" is an option flag for idnits that specifies the type of document being checked.
• "${select}" is a placeholder for the specific document type that you want to check. It should be replaced with the appropriate value, such as "rfc" or "draft".
• "${filename-txt}" is another placeholder for the name of the input file that you want to analyze. It should be replaced with the actual filename and the ".txt" extension.

In summary, the command runs the idnits tool to check a specific type of document (${select}) given a certain file (${filename-txt}). The specific type of document to check and the filename need to be provided to make the command work correctly.