Well, you can use a write function to save the partial content.

Yes, I can! But if I use curl multi functions, I can also use write function to save the partial content. So why is there curl_multi_getcontent function?

Moreover, it's very difficult to use write function (I must create new function, set up it for callback, manualy handle and store written data).

Same for case, when I can initialize curl_multi and use it only for download 1 file (I must call curl_init, curl_multi_init, curl_multi_add_handle then call curl_multi_exec in do-while cycle and more..)

In both of these case, the source code lost its brilliant simplicity :-(

As I wrote, there is no SIMPLE way how to do that. And if is requested function already implemented for multi curl, it should be easy make it for single curl.

The getcontent functions are not vital functions for cURL. As you said, everybody can use write function to save the partial content - this applies to single curl and also for multi curl!

I really don't understand, why is function implemented only for multi curl and not for single curl? Why to want make easy life only for multi curl and no for single curl? For both case of use, there is "ugly" alternative way (write function) to solve problem. And there should be great function getcontent also for both, not only for one...

curl_multi_getcontent() is a misnomer; actually, the function has
nothing to do with cURL multi handles, but works on vanilla cURL
handles.  As such there is nothing to add.