CURLOPT_READDATA - pointer passed to the read callback

Added in curl 7.9.7

stdin

Data pointer to pass to the file read function. If you use the CURLOPT_READFUNCTION(3) option, this is the pointer you get as input in the fourth argument to the callback. If you do not 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 are using libcurl as a DLL on Windows, you must use the CURLOPT_READFUNCTION(3) callback if you set this option, otherwise you might experience crashes.

struct MyData { void *custom; }; int main(void) { CURL *curl = curl_easy_init(); struct MyData this; if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "https://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.

CURLOPT_READDATA - pointer passed to the read callback

This functionality affects all supported protocols

This returns CURLE_OK.

CURLOPT_HEADERDATA(3), CURLOPT_READFUNCTION(3), CURLOPT_WRITEDATA(3), CURLOPT_WRITEFUNCTION(3) libcurl 2025-06-16 CURLOPT_READDATA(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_READDATA, void *pointer);