curl_multi_poll(3)

curl_multi_poll(3) 💅✨

okay bestie, this is the Library Functions Manual page for curl_multi_poll(3) — the function that polls on all easy handles in a multi handle. iconic behavior only. 🦋

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💖 NAME 💖

curl_multi_poll — poll on all easy handles in a multi handle. literally the whole point, no cap. 💅

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLMcode curl_multi_poll(CURLM *multi_handle,
                          struct curl_waitfd extra_fds[],
                          unsigned int extra_nfds,
                          int timeout_ms,
                          int *numfds);

🦋 DESCRIPTION 🦋

curl_multi_poll(3) polls all file descriptors used by the curl easy handles contained in the given multi handle set. it blocks until activity is detected on at least one of the handles or timeout_ms has passed. ⏳

alternatively, if the multi handle has a pending internal timeout that has a shorter expiry time than timeout_ms, that shorter time is used instead to make sure timeout accuracy is reasonably kept. like it's not gonna sit there longer than it needs to, fr. 🕰️

the calling application may pass additional curl_waitfd structures which are similar to poll(2)'s pollfd structure to be waited on in the same call. bestie can bring her own fds to the party. 🎀

on completion, if numfds is non-NULL, it gets populated with the total number of file descriptors on which interesting events occurred. this number can include both libcurl internal descriptors as well as descriptors provided in extra_fds. 💅

the curl_multi_wakeup(3) function can be used from another thread to wake up this function and return faster. this is one of the details that makes this function different than curl_multi_wait(3) which cannot be woken up this way. thread wakeup slay 🧚

if no extra file descriptors are provided and libcurl has no file descriptor to offer to wait for, this function instead waits during timeout_ms milliseconds (or shorter if an internal timer indicates so). this is the other detail that makes this function different than curl_multi_wait(3). 😭

this function is encouraged to be used instead of select(3) when using the multi interface to allow applications to easier circumvent the common problem with 1024 maximum file descriptors. periodt, dodge that 1024 limit. 🔥

🎀 curl_waitfd 🎀

struct curl_waitfd {
  curl_socket_t fd;
  short events;
  short revents;
};

• CURL_WAIT_POLLIN — bit flag to curl_waitfd.events indicating the socket should poll on read events such as new data received. 📥
• CURL_WAIT_POLLPRI — bit flag to curl_waitfd.events indicating the socket should poll on high priority read events such as out of band data. 🚨
• CURL_WAIT_POLLOUT — bit flag to curl_waitfd.events indicating the socket should poll on write events such as the socket being clear to write without blocking. 📤

🌈 PROTOCOLS 🌈

this functionality affects all supported protocols ✨

🌸 EXAMPLE 🌸

extern void handle_fd(int);

int main(void)
{
  CURL *easy_handle;
  CURLM *multi_handle;
  int still_running = 0;
  int myfd = 2; /* this is our own file descriptor */

  multi_handle = curl_multi_init();
  easy_handle = curl_easy_init();

  /* add the individual easy handle */
  curl_multi_add_handle(multi_handle, easy_handle);

  do {
    CURLMcode mresult;
    int numfds;

    mresult = curl_multi_perform(multi_handle, &still_running);

    if(mresult == CURLM_OK) {
      struct curl_waitfd myown;
      myown.fd = myfd;
      myown.events = CURL_WAIT_POLLIN; /* wait for input */
      myown.revents = 0; /* clear it */

      /* wait for activity on curl's descriptors or on our own,
         or timeout */
      mresult = curl_multi_poll(multi_handle, &myown, 1, 1000, &numfds);

      if(myown.revents) {
        /* did our descriptor receive an event? */
        handle_fd(myfd);
      }
    }

    if(mresult != CURLM_OK) {
      fprintf(stderr, "curl_multi failed, code %d.\n", mresult);
      break;
    }

  } while(still_running);

  curl_multi_remove_handle(multi_handle, easy_handle);
}

👑 AVAILABILITY 👑

Added in curl 7.66.0 ✨

⭐ RETURN VALUE ⭐

This function returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3). 💖

🫶 SEE ALSO 🫶

• curl_multi_fdset(3)
• curl_multi_perform(3)
• curl_multi_wait(3)
• curl_multi_wakeup(3)

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k that's the page, bestie! this was libcurl, dated 2026-10-12, and the page is curl_multi_poll(3) — slay and stay polled 💖🦋