CURLOPT_SSH_PUBLIC_KEYFILE - set public key file for SSH auth
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_PUBLIC_KEYFILE,
Pass a char * pointing to a filename
for your public key. If not used,
libcurl defaults to $HOME/.ssh/id_dsa.pub
if the HOME environment
variable is set, and just "id_dsa.pub" in the current directory if
HOME is not set.
If NULL (or an empty string) is passed, libcurl will pass no public key to
libssh2, which then tries to compute it from the private key. This is known to
work with libssh2 1.4.0+ linked against OpenSSL.
The application does not have to keep the string around after setting this
SFTP and SCP
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/file");
ret = curl_easy_perform(curl);
The "" trick was added in 7.26.0
Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or
CURLE_OUT_OF_MEMORY if there was insufficient heap space.