curl_multi_info_read(3)

🌸 NAME 🌸

curl_multi_info_read — read multi stack information.

Okay so hi bestie, welcome to the curl_multi_info_read(3) page from the Library Functions Manual. This is the function that lets you ask the multi handle if it has any messages from the individual transfers. It's giving "check the group chat for updates," but for libcurl, and it lowkey slays. ✨

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLMsg *curl_multi_info_read(CURLM *multi_handle, int *msgs_in_queue);

💖 DESCRIPTION 💖

Ask the multi handle if there are any messages from the individual transfers. Messages may include information such as an error code from the transfer, or just the fact that a transfer is completed. More details on these should be written down as well. 💅

Repeated calls to this function return a new struct each time, until a NULL is returned as a signal that there is no more to get at this point. The integer pointed to with msgs_in_queue contains the number of remaining messages after this function was called. 🫶

When you fetch a message using this function, it is removed from the internal queue, so calling this function again does not return the same message again. It instead returns new messages at each new invoke until the queue is emptied. No cap, it's a one-way ticket out of the queue. 🎟️

⚠️ WARNING: the data the returned pointer points to does not survive calling curl_multi_cleanup(3), curl_multi_remove_handle(3), or curl_easy_cleanup(3). Like, do not keep that pointer around and expect it to be valid after those calls, bestie. 😭

The CURLMsg struct is simple and only contains basic information. If more involved information is wanted, the particular "easy handle" is present in that struct and can be used in subsequent regular curl_easy_getinfo(3) calls (or similar):

struct CURLMsg {
  CURLMSG msg;       /* what this message means */
  CURL *easy_handle; /* the handle it concerns */
  union {
    void *whatever;    /* message-specific data */
    CURLcode result;   /* return code for transfer */
  } data;
};

When msg is CURLMSG_DONE, the message identifies a transfer that is done, and then result contains the return code for the easy handle that just completed. 🏁

At this point, there are no other msg types defined. That's the whole menu, periodt. 💀

🌈 PROTOCOLS 🌈

This functionality affects all supported protocols. Every single supported protocol is invited to the party. 🎉

🎀 EXAMPLE 🎀

Here's the example, bestie — do not freestyle this part, fr fr. 🧚

int main(void)
{
  CURLM *multi = curl_multi_init();
  CURL *curl = curl_easy_init();
  if(curl) {
    struct CURLMsg *m;

    /* call curl_multi_perform or curl_multi_socket_action first, then loop
       through and check if there are any transfers that have completed */

    do {
      int msgq = 0;
      m = curl_multi_info_read(multi, &msgq);
      if(m && (m->msg == CURLMSG_DONE)) {
        CURL *e = m->easy_handle;
        /* m->data.result holds the error code for the transfer */
        curl_multi_remove_handle(multi, e);
        curl_easy_cleanup(e);
      }
    } while(m);
  }
}

🦋 AVAILABILITY 🦋

Added in curl 7.9.6. Vintage but still iconic. 💖

💅 RETURN VALUE 💅

A pointer to a filled-in struct, or NULL if it failed or ran out of structs. It also writes the number of messages left in the queue (after this read) in the integer the second argument points to. ngl, that second argument is doing main character work. 🫡

🔥 SEE ALSO 🔥

• curl_multi_cleanup(3)
• curl_multi_init(3)
• curl_multi_perform(3)

Go read these next, bestie — they're literally the supporting cast. 👑

mwah 💋 — source/version: libcurl; date: 2026-10-12; page: curl_multi_info_read(3). bye bestie, go read your messages 🫶