CURLOPT_FTP_ALTERNATIVE_TO_USER man page
CURLOPT_FTP_ALTERNATIVE_TO_USER — command to use instead of USER with FTP
#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_FTP_ALTERNATIVE_TO_USER, char *cmd);
Pass a char * as parameter, pointing to a string which will be used to authenticate if the usual FTP "USER user" and "PASS password" negotiation fails. This is currently only known to be required when connecting to Tumbleweed's Secure Transport FTPS server using client certificates for authentication.
The application does not have to keep the string around after setting this option.
Added in 7.15.5
Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.