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127 lines
3.9 KiB
Markdown
127 lines
3.9 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_ACCEPT_ENCODING
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_HTTPHEADER (3)
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- CURLOPT_HTTP_CONTENT_DECODING (3)
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- CURLOPT_TRANSFER_ENCODING (3)
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Protocol:
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- HTTP
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Added-in: 7.21.6
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---
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# NAME
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CURLOPT_ACCEPT_ENCODING - automatic decompression of HTTP downloads
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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_ACCEPT_ENCODING, char *enc);
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~~~
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# DESCRIPTION
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Pass a char pointer argument specifying what encoding you would like.
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Sets the contents of the `Accept-Encoding:` header sent in an HTTP request,
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and enables decoding of a response when a `Content-Encoding:` header is
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received.
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libcurl potentially supports several different compressed encodings depending
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on what support that has been built-in.
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To aid applications not having to bother about what specific algorithms this
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particular libcurl build supports, libcurl allows a zero-length string to be
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set ("") to ask for an `Accept-Encoding:` header to be used that contains all
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built-in supported encodings.
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Alternatively, you can specify exactly the encoding or list of encodings you
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want in the response. The following encodings are supported: *identity*,
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meaning non-compressed, *deflate* which requests the server to compress its
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response using the zlib algorithm, *gzip* which requests the gzip algorithm,
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(since curl 7.57.0) *br* which is brotli and (since curl 7.72.0) *zstd* which
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is zstd. Provide them in the string as a comma-separated list of accepted
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encodings, like: **"br, gzip, deflate"**.
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Set CURLOPT_ACCEPT_ENCODING(3) to NULL to explicitly disable it, which makes
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libcurl not send an `Accept-Encoding:` header and not decompress received
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contents automatically.
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You can also opt to include the `Accept-Encoding:` header in your request with
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CURLOPT_HTTPHEADER(3) but then there is no automatic decompressing when
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receiving data.
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Setting this option is a request, not an order; the server may or may not do
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it. It must be set (to any non-NULL value) or else any encoding done by the
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server is ignored.
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Servers might respond with `Content-Encoding:` even without getting a
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`Accept-Encoding:` in the request. Servers might respond with a different
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content encoding than what was asked for in the request.
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The `Content-Length:` header field servers send for a compressed response is
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supposed to indicate the length of the compressed content so when auto
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decoding is enabled it may not match the sum of bytes reported by the write
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callbacks (although, sending the length of the non-compressed content is a
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common server mistake).
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The application does not have to keep the string around after setting this
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option.
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Using this option multiple times makes the last set string override the
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previous ones.
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**WARNING:** when decompressing data, even tiny transfers might be expanded
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and generate a huge amount of bytes. You might want to limit using this option
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to only known and trusted sites using secure protocols, perhaps in combination
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with CURLOPT_MAXFILESIZE_LARGE(3).
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# HISTORY
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This option was called CURLOPT_ENCODING before 7.21.6
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# NOTES
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The specific libcurl you are using must have been built with zlib to be able to
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decompress gzip and deflate responses, with the brotli library to
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decompress brotli responses and with the zstd library to decompress zstd
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responses.
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# DEFAULT
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NULL
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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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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* enable all supported built-in compressions */
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curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "");
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/* Perform the request */
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curl_easy_perform(curl);
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}
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}
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~~~
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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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