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curl_multi_poll(3) Library Functions Manual curl_multi_poll(3) NAME curl_multi_poll - poll on all easy handles in a multi handle 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 de- tected on at least one of the handles or timeout_ms has passed. Alterna- tively, 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. 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. On completion, if numfds is non-NULL, it gets populated with the total num- ber of file descriptors on which interesting events occurred. This number can include both libcurl internal descriptors as well as descriptors pro- vided 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. If no extra file descriptors are provided and libcurl has no file descrip- tor 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 prob- lem with 1024 maximum file descriptors. 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 block- ing. 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) libcurl 2026-06-11 curl_multi_poll(3)
NAME | SYNOPSIS | DESCRIPTION | curl_waitfd | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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