The curl() and curl_download() functions provide highly configurable
drop-in replacements for base url() and download.file() with better
performance, support for encryption (https://, ftps://), 'gzip'
compression, authentication, and other 'libcurl' goodies. The core
of the package implements a framework for performing fully customized
requests where data can be processed either in memory, on disk, or
streaming via the callback or connection interfaces. Some knowledge
of 'libcurl' is recommended; for a more-user-friendly web client
see the 'httr' package which builds on this package with HTTP
specific tools and logic.