response=curl_easy_perform(curl);
response返回的状态值

CURLE_OK = 0, 0: no error  
CURLE_UNSUPPORTED_PROTOCOL, 1: unsupported protocol  
CURLE_FAILED_INIT, 2: failed init  
CURLE_URL_MALFORMAT, 3: URL using bad/illegal format or missing URL  
CURLE_URL_MALFORMAT_USER, 4: unknown error  
CURLE_COULDNT_RESOLVE_PROXY, 5: couldn’t resolve proxy name  
CURLE_COULDNT_RESOLVE_HOST, 6: couldn’t resolve host name  
CURLE_COULDNT_CONNECT, 7: couldn’t connect to server  
CURLE_FTP_WEIRD_SERVER_REPLY, 8: FTP: weird server reply  
CURLE_FTP_ACCESS_DENIED,9  
CURLE_FTP_USER_PASSWORD_INCORRECT, 10: unknown error  
CURLE_FTP_WEIRD_PASS_REPLY, 11: FTP: unknown PASS reply  
CURLE_FTP_WEIRD_USER_REPLY, 12: FTP: unknown USER reply  
CURLE_FTP_WEIRD_PASV_REPLY, 13: FTP: unknown PASV reply  
CURLE_FTP_WEIRD_227_FORMAT, 14: FTP: unknown 227 response format  
CURLE_FTP_CANT_GET_HOST, 15: FTP: can’t figure out the host in the PASV response  
CURLE_FTP_CANT_RECONNECT, 16: FTP: can’t connect to server the response code is unknown  
CURLE_FTP_COULDNT_SET_BINARY, 17: FTP: couldn’t set binary mode  
CURLE_PARTIAL_FILE, 18: Transferred a partial file  
CURLE_FTP_COULDNT_RETR_FILE, 19: FTP: couldn’t retrieve (RETR failed) the specified file  
CURLE_FTP_WRITE_ERROR, 20: FTP: the post-transfer acknowledge response was not OK  
CURLE_FTP_QUOTE_ERROR, 21: FTP: a quote command returned error  
CURLE_HTTP_RETURNED_ERROR, 22: HTTP response code said error  
CURLE_WRITE_ERROR, 23: failed writing received data to disk/application  
CURLE_MALFORMAT_USER, 24: unknown error  
CURLE_UPLOAD_FAILED, 25: upload failed (at start/before it took off)  
CURLE_READ_ERROR, 26: failed to open/read local data from file/application  
CURLE_OUT_OF_MEMORY, 27: out of memory  
CURLE_OPERATION_TIMEOUTED, 28: a timeout was reached  
CURLE_FTP_COULDNT_SET_ASCII, 29: FTP could not set ASCII mode (TYPE A)  
CURLE_FTP_PORT_FAILED, 30: FTP command PORT failed  
CURLE_FTP_COULDNT_USE_REST, 31: FTP command REST failed  
CURLE_FTP_COULDNT_GET_SIZE, 32: FTP command SIZE failed  
CURLE_HTTP_RANGE_ERROR, 33: a range was requested but the server did not deliver it  
CURLE_HTTP_POST_ERROR, 34: internal problem setting up the POST  
CURLE_SSL_CONNECT_ERROR, 35: SSL connect error  
CURLE_BAD_DOWNLOAD_RESUME, 36: couldn’t resume download  
CURLE_FILE_COULDNT_READ_FILE, 37: couldn’t read a file
CURLE_LDAP_CANNOT_BIND, 38: LDAP: cannot bind  
CURLE_LDAP_SEARCH_FAILED, 39: LDAP: search failed  
CURLE_LIBRARY_NOT_FOUND, 40: a required shared library was not found