CURLOPT_SSLKEY (3) - Linux Man Pages
CURLOPT_SSLKEY: specify private keyfile for TLS and SSL client cert
NAMECURLOPT_SSLKEY - specify private keyfile for TLS and SSL client cert
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEY, char *keyfile);
DESCRIPTIONPass a pointer to a zero terminated string as parameter. The string should be the file name of your private key. The default format is "PEM" and can be changed with CURLOPT_SSLKEYTYPE(3).
(iOS and Mac OS X only) This option is ignored if curl was built against Secure Transport. Secure Transport expects the private key to be already present in the keychain or PKCS#12 file containing the certificate.
PROTOCOLSAll TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
AVAILABILITYIf built TLS enabled.
RETURN VALUEReturns CURLE_OK if TLS is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.
SEE ALSOCURLOPT_SSLKEYTYPE(3), CURLOPT_SSLCERT(3),