---
name: "CURLOPT_PREREQDATA"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_PREREQDATA"
---

# CURLOPT\_PREREQDATA(3)

pointer passed to the pre-request callback

## 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 argument in the pre-request callback set with *[CURLOPT\_PREREQFUNCTION(3)](/CURLOPT_PREREQFUNCTION/3.md)*.

## 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) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_PREREQFUNCTION, prereq_callback);
    curl_easy_setopt(curl, CURLOPT_PREREQDATA, &prereq_data);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.80.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLINFO\_PRIMARY\_IP**(3)](/CURLINFO_PRIMARY_IP/3.md), [**CURLINFO\_PRIMARY\_PORT**(3)](/CURLINFO_PRIMARY_PORT/3.md), [**CURLOPT\_PREREQFUNCTION**(3)](/CURLOPT_PREREQFUNCTION/3.md)