The legacy program for sending files to the printer queues from the command line is which of the following?

`lpd` is the Line Printer Daemon itself, the service that manages print queues, not the command to send print jobs.

`lpr` (line printer remote) is the traditional command-line utility for sending files or standard input to a print spooler, which then manages the job for printing.

`lpq` is used to view the status or contents of a printer queue, not to send files.

`lpp` is not a standard Unix/Linux command for sending files to a printer queue.