CURLOPT_PREREQDATA(3) Library Functions Manual CURLOPT_PREREQDATA(3)
NAME
CURLOPT_PREREQDATA - pointer passed to the pre-request callback
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PREREQDATA, void *pointer);
DESCRIPTION
Pass a pointer that is untouched by libcurl and passed as the first ar-
gument in the pre-request callback set with CURLOPT_PREREQFUNCTION(3).
DEFAULT
NULL
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
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);
}
}
AVAILABILITY
Added in curl 7.80.0
RETURN VALUE
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).
SEE ALSO
CURLINFO_PRIMARY_IP(3), CURLINFO_PRIMARY_PORT(3), CURLOPT_PREREQFUNC-
TION(3)
libcurl 2026-07-12 CURLOPT_PREREQDATA(3)
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