CURLOPT_ALTSVC_CTRL(3)

1CURLOPT_ALTSVC_CTRL(3)     curl_easy_setopt options     CURLOPT_ALTSVC_CTRL(3)
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NAME

6       CURLOPT_ALTSVC_CTRL - control alt-svc behavior
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SYNOPSIS

9       #include <curl/curl.h>
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11       #define CURLALTSVC_READONLYFILE (1<<2)
12       #define CURLALTSVC_H1           (1<<3)
13       #define CURLALTSVC_H2           (1<<4)
14       #define CURLALTSVC_H3           (1<<5)
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16       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC_CTRL, long bitmask);
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DESCRIPTION

19       Populate  the long bitmask with the correct set of features to instruct
20       libcurl how to handle Alt-Svc for the transfers using this handle.
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22       libcurl will only accept Alt-Svc headers over a secure transport, mean‐
23       ing  HTTPS. It will also only complete a request to an alternative ori‐
24       gin if that origin is properly hosted over  HTTPS.  These  requirements
25       are  there to make sure both the source and the destination are legiti‐
26       mate.
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28       Setting any bit will enable the alt-svc engine.
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30       CURLALTSVC_READONLYFILE
31              Do not write the alt-svc cache back to the file  specified  with
32              CURLOPT_ALTSVC(3)  even  if  it  gets updated. By default a file
33              specified with that option will be read and written to as deemed
34              necessary.
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36       CURLALTSVC_H1
37              Accept alternative services offered over HTTP/1.1.
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39       CURLALTSVC_H2
40              Accept  alternative services offered over HTTP/2. This will only
41              be used if libcurl was also built to  actually  support  HTTP/2,
42              otherwise this bit will be ignored.
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44       CURLALTSVC_H3
45              Accept  alternative services offered over HTTP/3. This will only
46              be used if libcurl was also built to  actually  support  HTTP/3,
47              otherwise this bit will be ignored.
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DEFAULT

50       Alt-Svc  handling  is disabled by default. If CURLOPT_ALTSVC(3) is set,
51       CURLOPT_ALTSVC_CTRL(3)   has   a   default   value   corresponding   to
52       CURLALTSVC_H1  |  CURLALTSVC_H2 | CURLALTSVC_H3 - the HTTP/2 and HTTP/3
53       bits are only set if libcurl was built with support for those versions.
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PROTOCOLS

56       HTTPS
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EXAMPLE

59       CURL *curl = curl_easy_init();
60       if(curl) {
61         curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1);
62         curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
63         curl_easy_perform(curl);
64       }
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AVAILABILITY

67       Added in 7.64.1
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RETURN VALUE

70       Returns CURLE_OK if the option is supported,  and  CURLE_UNKNOWN_OPTION
71       if not.
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