Dosage is a comic strip downloader and archiver.
Dosage is designed to keep a local copy of specific webcomics and other picture-based content such as Picture of the Day sites. With the dosage commandline script you can get the latest strip of a webcomic, or catch-up to the last strip downloaded, or download a strip for a particular date/index (if the webcomic's site layout allows this).
Multiple webcomics can be downloaded in parallel, making the update of comic strips faster.
See http://dosage.rocks/ for more info.