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99 lines
4.0 KiB
Groff
99 lines
4.0 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" * SPDX-License-Identifier: curl
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.\" *
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.\" **************************************************************************
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.\"
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.TH curl_easy_recv 3 "29 April 2008" "libcurl" "libcurl"
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.SH NAME
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curl_easy_recv - receives raw data on an "easy" connection
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.SH SYNOPSIS
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.nf
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#include <curl/easy.h>
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CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);
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.fi
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.SH DESCRIPTION
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This function receives raw data from the established connection. You may use
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it together with \fIcurl_easy_send(3)\fP to implement custom protocols using
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libcurl. This functionality can be particularly useful if you use proxies
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and/or SSL encryption: libcurl takes care of proxy negotiation and connection
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setup.
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\fBbuffer\fP is a pointer to your buffer memory that gets populated by the
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received data. \fBbuflen\fP is the maximum amount of data you can get in that
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buffer. The variable \fBn\fP points to receives the number of received bytes.
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To establish the connection, set \fICURLOPT_CONNECT_ONLY(3)\fP option before
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calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that
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\fIcurl_easy_recv(3)\fP does not work on connections that were created without
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this option.
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The call returns \fBCURLE_AGAIN\fP if there is no data to read - the socket is
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used in non-blocking mode internally. When \fBCURLE_AGAIN\fP is returned, use
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your operating system facilities like \fIselect(2)\fP to wait for data. The
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socket may be obtained using \fIcurl_easy_getinfo(3)\fP with
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\fICURLINFO_ACTIVESOCKET(3)\fP.
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Wait on the socket only if \fIcurl_easy_recv(3)\fP returns \fBCURLE_AGAIN\fP.
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The reason for this is libcurl or the SSL library may internally cache some
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data, therefore you should call \fIcurl_easy_recv(3)\fP until all data is
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read which would include any cached data.
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Furthermore if you wait on the socket and it tells you there is data to read,
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\fIcurl_easy_recv(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was
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read was for internal SSL processing, and no other data is available.
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.SH EXAMPLE
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.nf
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* Do not do the transfer - only connect to host */
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curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
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res = curl_easy_perform(curl);
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if(res == CURLE_OK) {
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/* Extract the socket from the curl handle - we need it for waiting. */
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res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
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/* read data */
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res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
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}
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.fi
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.SH AVAILABILITY
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Added in 7.18.2.
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.SH RETURN VALUE
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On success, returns \fBCURLE_OK\fP, stores the received data into
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\fBbuffer\fP, and the number of bytes it actually read into \fB*n\fP.
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On failure, returns the appropriate error code.
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The function may return \fBCURLE_AGAIN\fP. In this case, use your operating
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system facilities to wait until data can be read, and retry.
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Reading exactly 0 bytes indicates a closed connection.
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If there is no socket available to use from the previous transfer, this function
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returns \fBCURLE_UNSUPPORTED_PROTOCOL\fP.
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.SH "SEE ALSO"
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.BR curl_easy_getinfo (3),
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.BR curl_easy_perform (3),
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.BR curl_easy_send (3),
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.BR curl_easy_setopt (3)
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