CURLOPT_XFERINFODATA - pointer passed to the progress callback

Added in curl 7.32.0

NULL

Pass a pointer that is untouched by libcurl and passed as the first argument in the progress callback set with CURLOPT_XFERINFOFUNCTION(3). This is an alias for CURLOPT_PROGRESSDATA(3).

struct progress { char *private; size_t size; }; static int progress_cb(void *clientp, curl_off_t dltotal, curl_off_t dlnow, curl_off_t ultotal, curl_off_t ulnow) { struct progress *memory = clientp; printf("private ptr: %p\n", memory->private); /* use the values */ return 0; /* all is good */ } int main(void) { CURL *curl = curl_easy_init(); if(curl) { struct progress data; /* pass struct to callback */ curl_easy_setopt(curl, CURLOPT_XFERINFODATA, &data); curl_easy_setopt(curl, CURLOPT_XFERINFOFUNCTION, progress_cb); } }

CURLOPT_XFERINFODATA - pointer passed to the progress callback

This functionality affects all supported protocols

curl_easy_setopt(3) returns a CURLcode indicating success or error. CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

CURLOPT_NOPROGRESS(3), CURLOPT_VERBOSE(3), CURLOPT_XFERINFOFUNCTION(3) libcurl 2025-06-16 CURLOPT_XFERINFODATA(3)

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