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

# CURLMOPT\_NOTIFYDATA(3)

custom pointer passed to the notification callback

## NAME

CURLMOPT\_NOTIFYDATA - custom pointer passed to the notification callback

## SYNOPSIS

```
#include <curl/curl.h>
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_NOTIFYDATA, void *pointer);
```

## DESCRIPTION

A data *pointer* to pass to the notification callback set with the *[CURLMOPT\_NOTIFYFUNCTION(3)](/CURLMOPT_NOTIFYFUNCTION/3.md)* option.

This pointer is not touched by libcurl but is only passed in as the notification callback's **clientp** argument.

## DEFAULT

NULL

## PROTOCOLS

This functionality affects all supported protocols

## EXAMPLE

```
struct priv {
  void *ours;
};
static void notify_cb(CURLM *multi, unsigned int notification,
                      CURL *easy, void *notifyp)
{
  struct priv *p = notifyp;
  printf("my ptr: %p\n", p->ours);
  /* ... */
}
int main(void)
{
  struct priv setup;
  CURLM *multi = curl_multi_init();
  /* ... use socket callback and custom pointer */
  curl_multi_setopt(multi, CURLMOPT_NOTIFYFUNCTION, notify_cb);
  curl_multi_setopt(multi, CURLMOPT_NOTIFYDATA, &setup);
  curl_multi_notify_enable(multi, CURLMNOTIFY_INFO_READ);
}
```

## AVAILABILITY

Added in curl 8.17.0

## RETURN VALUE

Returns CURLM\_OK.

## SEE ALSO

[**CURLMOPT\_NOTIFYFUNCTION**(3)](/CURLMOPT_NOTIFYFUNCTION/3.md), [**curl\_multi\_notify\_disable**(3)](/curl_multi_notify_disable/3.md), [**curl\_multi\_notify\_enable**(3)](/curl_multi_notify_enable/3.md)