CURLMOPT_NOTIFYDATA(3)

📦
version 8.23.0 · 11 versions
, in alpine 3.23, alpine 3.24

💅 CURLMOPT_NOTIFYDATA(3) 💅

ok so bestie, welcome to the Library Functions Manual — this one's a short one, but it's lowkey iconic. let's get into it ✨

🌸 NAME 🌸

CURLMOPT_NOTIFYDATA — the custom pointer you hand off to your notification callback. that's it. that's the vibe 🫶

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_NOTIFYDATA, void *pointer);

like, one function call, one void *, no drama 💅

💖 DESCRIPTION 💖

so this is a data pointer that gets passed along to the notification callback — the one you set up with the CURLMOPT_NOTIFYFUNCTION(3) option. think of it as slipping your bestie a little note that says "hey, this is mine, use it" 🎀

and listen — libcurl does not touch this pointer. like, at all. no peeking, no modifying, no main-character interference. it's literally just handed straight in as the notification callback's clientp argument. that's the whole job. iconic behavior honestly 👑

🦋 DEFAULT 🦋

NULL

(yeah, it starts out empty — no pointer, no problem 🌈)

🌼 PROTOCOLS 🌼

this functionality affects all supported protocols — every single one, fr fr 💜

⭐ EXAMPLE ⭐

ok here's the whole thing in action, copy it, love it, run it:

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);
}

see how &setup just slides right into notifyp? chef's kiss 🧚 no cap, that's the whole flow.

🎀 AVAILABILITY 🎀

added in curl 8.17.0 — so if your curl is older than that, bestie, it's giving "not yet" 😭 go update 💀

👑 RETURN VALUE 👑

returns CURLM_OK. that's it. slay, no error codes to stress about 💖

💜 SEE ALSO 💜

go read those next, iykyk 📚

and that's the page, bestie 🫶 brought to you by libcurl, dated 2026-10-25 — mwah, go forth and notify 💅✨

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