libcurl
in use.
libcurlVersion()
"none"
. It is intended for the version
of OpenSSL used, but not all implementations of libcurl
use
OpenSSL --- for example OS X reports "SecureTranspart"
, its
wrapper for SSL/TLS.libssh
version,
which may or may not be available (it is used for
e.g.\ifelse{latex}{\out{~}}{ } scp
and sftp
protocols). Where present,
something like "libssh2/1.5.0"
.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 OS X, 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.)