Unknown option: "-3" Unix manual page for curl_slist_free_all. (host=minya system=Darwin) 
curl_slist_free_all(3)          libcurl Manual          curl_slist_free_all(3)

NAME
       curl_slist_free_all - free an entire curl_slist list

SYNOPSIS
       #include <curl/curl.h>

       void curl_slist_free_all(struct curl_slist *list);

DESCRIPTION
       curl_slist_free_all()   removes   all  traces  of  a  previously  built
       curl_slist linked list.

RETURN VALUE
       Nothing.

SEE ALSO
       curl_slist_append(3),

libcurl 7.54.0                 February 03, 2016        curl_slist_free_all(3)