curl_share_init (3) - Linux Manuals
curl_share_init: Create a shared object
NAMEcurl_share_init - Create a shared object
DESCRIPTIONThis function returns a CURLSH handle to be used as input to all the other share-functions, sometimes referred to as a share handle in some places in the documentation. This init call MUST have a corresponding call to curl_share_cleanup when all operations using the share are complete.
This share handle is what you pass to curl using the CURLOPT_SHARE option with curl_easy_setopt(3), to make that specific curl handle use the data in this share.