Can anyone inform me why we need a callback in some curl options, like CURLOPT_WRITEFUNCTION?
I used the code below in C , and got the same result with or without a CURLOPT_WRITEFUNCTION callback, so it seems confusing to use a callback.
int main(){
CURL *curl = curl_easy_init();
CURLcode response;
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://www.example.com");
response=curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
CodePudding user response：
callback is an option that has it own specific properties that might be usefull for someone who wants to use that properties. see link below https://curl.se/libcurl/c/CURLOPT_WRITEFUNCTION.html
CodePudding user response：
By default, libcurl simply writes the downloaded data to STDOUT.
If you just want to change which FILE* it writes the data to, you can use the CURLOPT_WRITEDATA option.
But, if you want to change how it writes the data, for instance to write to something other than a FILE*, you can use a CURLOPT_WRITEFUNCTION callback.
For instance, see these examples, which use CURLOPT_WRITEFUNCTION to customize downloads:
https://curl.se/libcurl/c/ftpsget.html