>> when I read the code near ftp.c:1431 (in ftp_state_ul_setup) the
>> RESUME_FROM handling seems to mean that if resume_from is less than 0,
>> the transfer should resume from current size of the target file (and this
>> is perfect).
>>
>> This is not documented, is it to be documented or unreliable?
>
> This undocumented feature is in fact used by curl and we really should
> document how this works!
>
> You up to providing a patch for curl_easy_setopt.3 ?
here is a patch, i'm not very good at doc writing so if you want to rewrite
it, feel free.

now I've a question: enabling resume for FTP sets the 'dont_check' option,
which unconditionally prevents testing the server return code. I suspect
that this is because servers may return somewhat exotic return codes. isn't
it? (i wonder if we could find a way to still test them, for example,
accepting all 2xx code in 'dont_check', or something like that, but not
4xx/5xx...)

Armel