1curl_easy_recv(3)               libcurl Manual               curl_easy_recv(3)
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NAME

6       curl_easy_recv - receives raw data on an "easy" connection
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SYNOPSIS

9       #include <curl/easy.h>
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11       CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);
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DESCRIPTION

14       This  function  receives  raw data from the established connection. You
15       may use it together with curl_easy_send(3) to implement  custom  proto‐
16       cols  using  libcurl.  This functionality can be particularly useful if
17       you use proxies and/or SSL encryption: libcurl will take care of  proxy
18       negotiation and connection setup.
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20       buffer is a pointer to your buffer that will get the received data. bu‐
21       flen is the maximum amount of data you can  get  in  that  buffer.  The
22       variable n points to will receive the number of received bytes.
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24       To  establish the connection, set CURLOPT_CONNECT_ONLY(3) option before
25       calling  curl_easy_perform(3)  or  curl_multi_perform(3).   Note   that
26       curl_easy_recv(3)  does not work on connections that were created with‐
27       out this option.
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29       The call will return CURLE_AGAIN if there is no  data  to  read  -  the
30       socket is used in non-blocking mode internally. When CURLE_AGAIN is re‐
31       turned, use your operating system facilities like select(2) to wait for
32       data.  The  socket  may  be  obtained  using  curl_easy_getinfo(3) with
33       CURLINFO_ACTIVESOCKET(3).
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35       Wait on the socket only if curl_easy_recv(3) returns CURLE_AGAIN.   The
36       reason for this is libcurl or the SSL library may internally cache some
37       data, therefore you should call curl_easy_recv(3)  until  all  data  is
38       read which would include any cached data.
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40       Furthermore if you wait on the socket and it tells you there is data to
41       read, curl_easy_recv(3) may return CURLE_AGAIN if the  only  data  that
42       was  read  was for internal SSL processing, and no other data is avail‐
43       able.
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EXAMPLE

46        curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
47        /* Do not do the transfer - only connect to host */
48        curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
49        res = curl_easy_perform(curl);
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51        if(res == CURLE_OK) {
52          /* Extract the socket from the curl handle -
53             we will need it for waiting. */
54          res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
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56          /* read data */
57          res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
58        }
59

AVAILABILITY

61       Added in 7.18.2.
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RETURN VALUE

64       On success, returns CURLE_OK, stores the received data into buffer, and
65       the number of bytes it actually read into *n.
66
67       On failure, returns the appropriate error code.
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69       The  function  may return CURLE_AGAIN. In this case, use your operating
70       system facilities to wait until data can be read, and retry.
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72       Reading exactly 0 bytes indicates a closed connection.
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74       If there's no socket available to use from the previous transfer,  this
75       function returns CURLE_UNSUPPORTED_PROTOCOL.
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SEE ALSO

78       curl_easy_setopt(3),     curl_easy_perform(3),    curl_easy_getinfo(3),
79       curl_easy_send(3)
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83libcurl 8.0.1                  January 02, 2023              curl_easy_recv(3)
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