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Everywhere. In documentation and code comments. It is almost never a good word and almost always a filler that should be avoided. Closes #20793
131 lines
3.3 KiB
Markdown
131 lines
3.3 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_HTTP_VERSION
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Section: 3
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Source: libcurl
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Protocol:
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- HTTP
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See-also:
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- CURLOPT_ALTSVC (3)
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- CURLOPT_HTTP09_ALLOWED (3)
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- CURLOPT_HTTP200ALIASES (3)
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- CURLOPT_SSLVERSION (3)
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Added-in: 7.9.1
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---
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# NAME
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CURLOPT_HTTP_VERSION - HTTP protocol version to use
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTP_VERSION, long version);
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~~~
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# DESCRIPTION
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Pass *version* a long, set to one of the values described below. They ask
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libcurl to use the specific HTTP versions.
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Note that the HTTP version is a request. libcurl still prioritizes to reuse
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existing connections so it might then reuse a connection using an HTTP version
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you have not asked for.
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## CURL_HTTP_VERSION_NONE
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We do not care about what version the library uses. libcurl uses whatever it
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thinks fit.
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## CURL_HTTP_VERSION_1_0
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Enforce HTTP 1.0 requests.
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## CURL_HTTP_VERSION_1_1
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Enforce HTTP 1.1 requests.
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## CURL_HTTP_VERSION_2_0
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Attempt HTTP 2 requests. libcurl falls back to HTTP 1.1 if HTTP 2 cannot be
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negotiated with the server.
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When libcurl uses HTTP/2 over HTTPS, it does not itself insist on TLS 1.2 or
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higher even though that is required by the specification. A user can add this
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version requirement with CURLOPT_SSLVERSION(3).
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The alias *CURL_HTTP_VERSION_2* was added to better reflect the actual
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protocol name.
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## CURL_HTTP_VERSION_2TLS
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Attempt HTTP 2 over TLS (HTTPS) only. libcurl falls back to HTTP 1.1 if HTTP 2
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cannot be negotiated with the HTTPS server. For clear text HTTP servers,
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libcurl uses 1.1.
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## CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE
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Issue non-TLS HTTP requests using HTTP/2 without HTTP/1.1 Upgrade. It requires
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prior knowledge that the server supports HTTP/2 straight away. HTTPS requests
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still do HTTP/2 the standard way with negotiated protocol version in the TLS
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handshake.
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Since 8.10.0 if this option is set for an HTTPS request then the application
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layer protocol version (ALPN) offered to the server is only HTTP/2. Prior to
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that both HTTP/1.1 and HTTP/2 were offered.
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## CURL_HTTP_VERSION_3
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(Added in 7.66.0) This option makes libcurl attempt to use HTTP/3 to the host
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given in the URL, with fallback to earlier HTTP versions if needed.
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## CURL_HTTP_VERSION_3ONLY
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(Added in 7.88.0) Setting this makes libcurl attempt to use HTTP/3 directly to
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server given in the URL and does not downgrade to earlier HTTP version if the
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server does not support HTTP/3.
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# DEFAULT
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Since curl 8.13.0: CURL_HTTP_VERSION_NONE
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Since curl 7.62.0: CURL_HTTP_VERSION_2TLS
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Before that: CURL_HTTP_VERSION_1_1
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# %PROTOCOLS%
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode result;
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
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curl_easy_setopt(curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2TLS);
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result = curl_easy_perform(curl);
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if(result == CURLE_HTTP_RETURNED_ERROR) {
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/* an HTTP response error problem */
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}
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}
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}
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~~~
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# HISTORY
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**CURL_HTTP_VERSION_*** enums became `long` types in 8.13.0, prior to this
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version a `long` cast was necessary when passed to curl_easy_setopt(3).
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# %AVAILABILITY%
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# RETURN VALUE
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curl_easy_setopt(3) returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3).
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