CURLOPT_ALTSVC(3)

1CURLOPT_ALTSVC(3)                   libcurl                  CURLOPT_ALTSVC(3)
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NAME

6       CURLOPT_ALTSVC - alt-svc cache file name
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SYNOPSIS

9       #include <curl/curl.h>
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11       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC, char *filename);
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DESCRIPTION

14       Pass in a pointer to a filename to instruct libcurl to use that file as
15       the Alt-Svc cache to read existing cache  contents  from  and  possibly
16       also  write it back to after a transfer, unless CURLALTSVC_READONLYFILE
17       is set in CURLOPT_ALTSVC_CTRL(3).
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19       Specify a blank file name ("") to make libcurl not load from a file  at
20       all.
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DEFAULT

23       NULL. The alt-svc cache is not read nor written to file.
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PROTOCOLS

26       HTTPS
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EXAMPLE

29       CURL *curl = curl_easy_init();
30       if(curl) {
31         curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1);
32         curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
33         curl_easy_perform(curl);
34       }
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FILE FORMAT

37       A  text  based  file with one line per alt-svc entry and each line con‐
38       sists of nine space-separated fields.
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40       An example line could look like
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42        h2 www.example 8443 h3 second.example 443 "20190808 06:18:37" 1 0
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44       The fields of that line are:
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47       h2     ALPN id for the source origin
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49       www.example
50              Host name for the source origin
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52       8443   Port number for the source origin
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54       h3     ALPN id for the destination host
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56       second.example
57              Host name for the destination host
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59       443    Port number for the destination host
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61       2019*  Expiration date and time of this entry within double quotes. The
62              date format is "YYYYMMDD HH:MM:SS" and the time zone is GMT.
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64       1      Boolean (1 or 0) if "persist" was set for this entry
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66       0      Integer priority value (not currently used)
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AVAILABILITY

69       Added in 7.64.1
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RETURN VALUE

72       Returns  CURLE_OK  if the option is supported, and CURLE_UNKNOWN_OPTION
73       if not.
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