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CURLOPT_READDATA - custom pointer passed to the read callback #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_READDATA, void *pointer); Data pointer to pass to the file read function. If you use the CURLOPT_READFUNCTION(3) option, this is the pointer you'll get as input in the 4th argument to the callback. If you don't specify a read callback but instead rely on the default internal read function, this data must be a valid readable FILE * (cast to 'void *'). If you're using libcurl as a win32 DLL, you MUST use a CURLOPT_READFUNCTION(3) if you set this option or you will experience crashes. By default, this is a FILE * to stdin. This is used for all protocols when sending data.

CURL *curl = curl_easy_init();
struct MyData this;
if(curl) {
 curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");

 /* pass pointer that gets passed in to the
 CURLOPT_READFUNCTION callback */
 curl_easy_setopt(curl, CURLOPT_READDATA, &this);

 curl_easy_perform(curl);
}

This option was once known by the older name CURLOPT_INFILE, the name CURLOPT_READDATA(3) was introduced in 7.9.7. This will return CURLE_OK. CURLOPT_READFUNCTION "(3), " CURLOPT_WRITEDATA "(3), "