CURLOPT_PREREQDATA - pointer passed to the pre-request callback

Added in curl 7.80.0

NULL

Pass a pointer that is untouched by libcurl and passed as the first argument in the pre-request callback set with CURLOPT_PREREQFUNCTION(3).

struct priv { void *custom; }; static int prereq_callback(void *clientp, char *conn_primary_ip, char *conn_local_ip, int conn_primary_port, int conn_local_port) { printf("Connection made to %s:%d\n", conn_primary_ip, conn_primary_port); return CURL_PREREQFUNC_OK; } int main(void) { struct priv prereq_data; CURL *curl = curl_easy_init(); if(curl) { curl_easy_setopt(curl, CURLOPT_PREREQFUNCTION, prereq_callback); curl_easy_setopt(curl, CURLOPT_PREREQDATA, &prereq_data); curl_easy_perform(curl); } }

CURLOPT_PREREQDATA - pointer passed to the pre-request 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).

CURLINFO_PRIMARY_IP(3), CURLINFO_PRIMARY_PORT(3), CURLOPT_PREREQFUNCTION(3) libcurl 2025-06-16 CURLOPT_PREREQDATA(3)

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