docs/libcurl/opts: clarify the return values

Expand a little.

- mention the type name of the return code
- avoid stating which exact return codes that might be returned, as that
  varies over time, builds and conditions
- avoid stating some always return OK
- refer to the manpage documenting all the return codes

Closes #15900

docs/libcurl/opts/CURLINFO_ACTIVESOCKET.md

@@ -78,4 +78,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_APPCONNECT_TIME.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_APPCONNECT_TIME_T.md

@@ -68,4 +68,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CAINFO.md

@@ -64,4 +64,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CAPATH.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CERTINFO.md

@@ -103,4 +103,7 @@ Transport support added in 7.79.0. mbedTLS support added in 8.9.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONDITION_UNMET.md

@@ -76,4 +76,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONNECT_TIME.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONNECT_TIME_T.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONN_ID.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_DOWNLOAD.md

@@ -70,4 +70,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_DOWNLOAD_T.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD.md

@@ -69,4 +69,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD_T.md

@@ -62,4 +62,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_CONTENT_TYPE.md

@@ -71,4 +71,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_COOKIELIST.md

@@ -78,4 +78,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_EARLYDATA_SENT_T.md

@@ -72,4 +72,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_EFFECTIVE_METHOD.md

@@ -68,4 +68,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_EFFECTIVE_URL.md

@@ -64,4 +64,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_FILETIME.md

@@ -73,4 +73,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_FILETIME_T.md

@@ -74,4 +74,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_FTP_ENTRY_PATH.md

@@ -70,4 +70,7 @@ Works for SFTP since 7.21.4
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_HEADER_SIZE.md

@@ -61,4 +61,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_HTTPAUTH_AVAIL.md

@@ -71,4 +71,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_HTTPAUTH_USED.md

@@ -73,4 +73,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_HTTP_CONNECTCODE.md

@@ -61,4 +61,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_HTTP_VERSION.md

@@ -57,4 +57,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_LASTSOCKET.md

@@ -78,4 +78,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_LOCAL_IP.md

@@ -69,4 +69,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_LOCAL_PORT.md

@@ -68,4 +68,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_NAMELOOKUP_TIME.md

@@ -64,4 +64,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_NAMELOOKUP_TIME_T.md

@@ -65,4 +65,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_NUM_CONNECTS.md

@@ -61,4 +61,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_OS_ERRNO.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_POSTTRANSFER_TIME_T.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PRETRANSFER_TIME.md

@@ -69,4 +69,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PRETRANSFER_TIME_T.md

@@ -71,4 +71,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PRIMARY_IP.md

@@ -69,4 +69,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PRIMARY_PORT.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PRIVATE.md

@@ -64,4 +64,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PROTOCOL.md

@@ -73,4 +73,7 @@ Deprecated since 7.85.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PROXYAUTH_AVAIL.md

@@ -72,4 +72,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PROXYAUTH_USED.md

@@ -76,4 +76,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PROXY_ERROR.md

@@ -101,4 +101,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_PROXY_SSL_VERIFYRESULT.md

@@ -74,4 +74,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_QUEUE_TIME_T.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REDIRECT_COUNT.md

@@ -58,4 +58,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REDIRECT_TIME.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REDIRECT_TIME_T.md

@@ -68,4 +68,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REDIRECT_URL.md

@@ -65,4 +65,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REFERER.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_REQUEST_SIZE.md

@@ -59,4 +59,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RESPONSE_CODE.md

@@ -68,4 +68,7 @@ responses added in 7.25.0, for OpenLDAP in 7.81.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RETRY_AFTER.md

@@ -72,4 +72,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RTSP_CLIENT_CSEQ.md

@@ -57,4 +57,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RTSP_CSEQ_RECV.md

@@ -57,4 +57,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RTSP_SERVER_CSEQ.md

@@ -61,4 +61,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_RTSP_SESSION_ID.md

@@ -62,4 +62,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SCHEME.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SIZE_DOWNLOAD.md

@@ -73,4 +73,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SIZE_DOWNLOAD_T.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SIZE_UPLOAD.md

@@ -69,4 +69,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SIZE_UPLOAD_T.md

@@ -62,4 +62,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SPEED_DOWNLOAD.md

@@ -69,4 +69,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SPEED_DOWNLOAD_T.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SPEED_UPLOAD.md

@@ -67,4 +67,7 @@ Deprecated since 7.55.0.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SPEED_UPLOAD_T.md

@@ -61,4 +61,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SSL_ENGINES.md

@@ -63,4 +63,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_SSL_VERIFYRESULT.md

@@ -73,4 +73,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_STARTTRANSFER_TIME.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_STARTTRANSFER_TIME_T.md

@@ -69,4 +69,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_TLS_SESSION.md

@@ -77,4 +77,7 @@ Deprecated since 7.48.0
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_TLS_SSL_PTR.md

@@ -178,4 +178,7 @@ This option is exactly the same as that option except in the case of OpenSSL.
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_TOTAL_TIME.md

@@ -65,4 +65,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_TOTAL_TIME_T.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_USED_PROXY.md

@@ -65,4 +65,7 @@ int main(int argc, char *argv[])
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLINFO_XFER_ID.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE.md

@@ -57,4 +57,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE.md

@@ -56,4 +56,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_MAXCONNECTS.md

@@ -69,4 +69,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_MAX_CONCURRENT_STREAMS.md

@@ -55,4 +55,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_MAX_HOST_CONNECTIONS.md

@@ -74,4 +74,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_MAX_PIPELINE_LENGTH.md

@@ -60,4 +60,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_MAX_TOTAL_CONNECTIONS.md

@@ -71,4 +71,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_PIPELINING.md

@@ -79,4 +79,7 @@ Before that, default was **CURLPIPE_NOTHING**.
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_PIPELINING_SERVER_BL.md

@@ -66,4 +66,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_PIPELINING_SITE_BL.md

@@ -62,4 +62,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_PUSHDATA.md

@@ -83,4 +83,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_PUSHFUNCTION.md

@@ -144,4 +144,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_TIMERDATA.md

@@ -71,4 +71,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLMOPT_TIMERFUNCTION.md

@@ -103,4 +103,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
+curl_multi_setopt(3) returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_ABSTRACT_UNIX_SOCKET.md

@@ -67,4 +67,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_ACCEPTTIMEOUT_MS.md

@@ -57,4 +57,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_ACCEPT_ENCODING.md

@@ -114,5 +114,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
-CURLE_OUT_OF_MEMORY if there was insufficient heap space.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_ADDRESS_SCOPE.md

@@ -58,5 +58,8 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).
 Returns CURLE_BAD_FUNCTION_ARGUMENT if set to a negative value.

docs/libcurl/opts/CURLOPT_ALTSVC.md

@@ -113,4 +113,7 @@ Integer priority value (not currently used)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md

@@ -95,4 +95,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_APPEND.md

@@ -62,4 +62,7 @@ This option was known as CURLOPT_FTPAPPEND up to 7.16.4
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_AUTOREFERER.md

@@ -73,4 +73,7 @@ int main(void)
 
 # RETURN VALUE
 
-Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).

docs/libcurl/opts/CURLOPT_AWS_SIGV4.md

@@ -123,4 +123,7 @@ the special value "UNSIGNED-PAYLOAD".
 
 # RETURN VALUE
 
-Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).