Report version of libcurl in use.
libcurlVersion()A character string, with value the libcurl version in use or
"" if none is. If libcurl is available, has attributes
A character string naming the SSL implementation
and version, possibly "none". It is intended for the version
of OpenSSL used, but not all implementations of libcurl use
OpenSSL --- for example macOS reports "SecureTranspart", its
wrapper for SSL/TLS.
A character string naming the libssh version,
which may or may not be available (it is used for
e.g.scp and sftp protocols). Where present,
something like "libssh2/1.5.0".
A character vector of the names of supported protocols, also known as ‘schemes’ when part of a URL.
extSoftVersion for versions of other third-party
software.
curlGetHeaders, download.file and
url for functions which (optionally) use libcurl.
http://curl.haxx.se/docs/sslcerts.html and
http://curl.haxx.se/docs/ssl-compared.html for more details on
SSL versions. Normally libcurl used with R uses
SecureTransport on macOS, OpenSSL on Windows and GnuTLS, NSS or OpenSSL
on Unix-alikes. (At the time of writing Debian-based Linuxen use
GnuTLS, RedHat-based ones use NSS.)