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3rdparty/curl/share/man/man3/CURLOPT_HTTP_VERSION.3 3.72 KB
a86c63ca   Hu Chunming   提交三方库文件
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  .\" **************************************************************************
  .\" *                                  _   _ ____  _
  .\" *  Project                     ___| | | |  _ \| |
  .\" *                             / __| | | | |_) | |
  .\" *                            | (__| |_| |  _ <| |___
  .\" *                             \___|\___/|_| \_\_____|
  .\" *
  .\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
  .\" *
  .\" * This software is licensed as described in the file COPYING, which
  .\" * you should have received as part of this distribution. The terms
  .\" * are also available at https://curl.se/docs/copyright.html.
  .\" *
  .\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
  .\" * copies of the Software, and permit persons to whom the Software is
  .\" * furnished to do so, under the terms of the COPYING file.
  .\" *
  .\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  .\" * KIND, either express or implied.
  .\" *
  .\" **************************************************************************
  .\"
  .TH CURLOPT_HTTP_VERSION 3 "November 04, 2020" "libcurl 7.77.0" "curl_easy_setopt options"
  
  .SH NAME
  CURLOPT_HTTP_VERSION \- specify HTTP protocol version to use
  .SH SYNOPSIS
  #include <curl/curl.h>
  
  CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTP_VERSION, long version);
  .SH DESCRIPTION
  Pass \fIversion\fP a long, set to one of the values described below. They ask
  libcurl to use the specific HTTP versions.
  
  Note that the HTTP version is just a request. libcurl will still prioritize to
  re-use an existing connection so it might then re-use a connection using a
  HTTP version you haven't asked for.
  
  .IP CURL_HTTP_VERSION_NONE
  We don't care about what version the library uses. libcurl will use whatever
  it thinks fit.
  .IP CURL_HTTP_VERSION_1_0
  Enforce HTTP 1.0 requests.
  .IP CURL_HTTP_VERSION_1_1
  Enforce HTTP 1.1 requests.
  .IP CURL_HTTP_VERSION_2_0
  Attempt HTTP 2 requests. libcurl will fall back to HTTP 1.1 if HTTP 2 can't be
  negotiated with the server. (Added in 7.33.0)
  
  The alias \fICURL_HTTP_VERSION_2\fP was added in 7.43.0 to better reflect the
  actual protocol name.
  .IP CURL_HTTP_VERSION_2TLS
  Attempt HTTP 2 over TLS (HTTPS) only. libcurl will fall back to HTTP 1.1 if
  HTTP 2 can't be negotiated with the HTTPS server. For clear text HTTP servers,
  libcurl will use 1.1. (Added in 7.47.0)
  .IP CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE
  Issue non-TLS HTTP requests using HTTP/2 without HTTP/1.1 Upgrade. It requires
  prior knowledge that the server supports HTTP/2 straight away. HTTPS requests
  will still do HTTP/2 the standard way with negotiated protocol version in the
  TLS handshake. (Added in 7.49.0)
  .IP CURL_HTTP_VERSION_3
  (Added in 7.66.0) Setting this value will make libcurl attempt to use HTTP/3
  directly to server given in the URL. Note that this cannot gracefully
  downgrade to earlier HTTP version if the server doesn't support HTTP/3.
  
  For more reliably upgrading to HTTP/3, set the preferred version to something
  lower and let the server announce its HTTP/3 support via Alt-Svc:. See
  \fICURLOPT_ALTSVC(3)\fP.
  .SH DEFAULT
  Since curl 7.62.0: CURL_HTTP_VERSION_2TLS
  
  Before that: CURL_HTTP_VERSION_1_1
  .SH PROTOCOLS
  HTTP
  .SH EXAMPLE
  .nf
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode ret;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2TLS);
    ret = curl_easy_perform(curl);
    if(ret == CURLE_HTTP_RETURNED_ERROR) {
      /* an HTTP response error problem */
    }
  }
  .fi
  .SH AVAILABILITY
  Along with HTTP
  .SH RETURN VALUE
  Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.
  .SH "SEE ALSO"
  .BR CURLOPT_SSLVERSION "(3), " CURLOPT_HTTP200ALIASES "(3), "
  .BR CURLOPT_HTTP09_ALLOWED "(3), " CURLOPT_ALTSVC "(3) "