CURLINFO_CONN_ID(3)

💅 CURLINFO_CONN_ID — like, the ID of the last connection, bestie

okay so this is a page from the Library Functions Manual (that's the manual name, mwah 💖) and it's all about CURLINFO_CONN_ID. Buckle in, it's short and iconic.

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✨ NAME ✨

CURLINFO_CONN_ID — the ID of the last connection 🎀

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🌸 SYNOPSIS 🌸

#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CONN_ID,
                           curl_off_t *conn_id);

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🦋 DESCRIPTION 🦋

okay so you pass in a pointer to a curl_off_t and it receives the connection identifier that the handle used last. that's it, that's the whole vibe 💅

and listen — if there was, like, no connection used at all? it stores -1. no cap, that's your "nobody home" signal 🙈

now the important part: the connection id is unique among all connections using the same connection cache. and since all connections in the same multi handle implicitly share that cache, yeah — that's the case for them too. iykyk ✨

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🔥 PROTOCOLS 🔥

this functionality affects all supported protocols — every single one, periodt 👑

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🧚 EXAMPLE 🧚

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;

    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    /* Perform the request */
    result = curl_easy_perform(curl);

    if(!result) {
      curl_off_t conn_id;
      result = curl_easy_getinfo(curl, CURLINFO_CONN_ID, &conn_id);
      if(!result) {
        printf("Connection used: %" CURL_FORMAT_CURL_OFF_T "\n", conn_id);
      }
    }
  }
}

look at that. curl_easy_init, curl_easy_setopt with CURLOPT_URL, curl_easy_perform, then curl_easy_getinfo with CURLINFO_CONN_ID grabbing your conn_id and printing "Connection used: %" CURL_FORMAT_CURL_OFF_T "\n". the printf ate, fr fr 💖

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⭐ AVAILABILITY ⭐

added in curl 8.2.0 — so if you're on anything older, sorry bestie, it's giving not-yet 😭

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🌈 RETURN VALUE 🌈

curl_easy_getinfo(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK. non-zero means an error occurred — go check libcurl-errors(3) for the deets 🫶

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👑 SEE ALSO 👑

• CURLINFO_XFER_ID(3)
• curl_easy_getinfo(3)
• curl_easy_setopt(3)

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go touch grass after this, but like, after you read the also-sees. balance 💅

libcurl · 2026-10-12 · that's the source/version and date, bestie — this page is a wrap, mwah 🎀🦋✨