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CURLOPT_SSH_KEYDATA - pointer passed to the SSH key callback #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_KEYDATA, void *pointer); Pass a void * as parameter. This pointer will be passed along verbatim to the callback set with CURLOPT_SSH_KEYFUNCTION(3). NULL SFTP and SCP

static int keycb(CURL *easy,
 const struct curl_khkey *knownkey,
 const struct curl_khkey *foundkey,
 enum curl_khmatch,
 void *clientp)
{
 /* 'clientp' points to the callback_data struct */
 /* investigate the situation and return the correct value */
 return CURLKHSTAT_FINE_ADD_TO_FILE;
}
{
 curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/thisfile.txt");
 curl_easy_setopt(curl, CURLOPT_SSH_KEYFUNCTION, keycb);
 curl_easy_setopt(curl, CURLOPT_SSH_KEYDATA, &callback_data);
 curl_easy_setopt(curl, CURLOPT_SSH_KNOWNHOSTS, "/home/user/known_hosts");

 curl_easy_perform(curl);
}

Added in 7.19.6 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. CURLOPT_SSH_KEYDATA "(3), " CURLOPT_SSH_KNOWNHOSTS "(3), "