NAME

       CURLOPT_ALTSVC - alt-svc cache file name

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC, char *filename);

DESCRIPTION

       Pass  in a pointer to a filename to instruct libcurl to use that file as the Alt-Svc cache
       to read existing cache contents from and  possibly  also  write  it  back  to  a  after  a
       transfer, unless CURLALTSVC_READONLYFILE is set in CURLOPT_ALTSVC_CTRL(3).

       Specify a blank file name ("") to make libcurl not load from a file at all.

DEFAULT

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

PROTOCOLS

       HTTPS

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1);
         curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
         curl_easy_perform(curl);
       }

FILE FORMAT

       A  text  based  file with one line per alt-svc entry and each line consists of nine space-
       separated fields.

       An example line could look like

        h2 www.example 8443 h3 quic.example 443 "20190808 06:18:37" 1 0

       The fields of that line are:

       h2     ALPN id for the source origin

       www.example
              Host name for the source origin

       8443   Port number for the source origin

       h3     ALPN id for the destination host

       quic.example
              Host name for the destination host

       443    Port number for the destination host

       2019*  Expiration date and time of this entry within double quotes.  The  date  format  is
              "YYYYMMDD HH:MM:SS" and the time zone is GMT.

       1      Boolean (1 or 0) if "persist" was set for this entry

       0      Integer priority value (not currently used)

AVAILABILITY

       Added in 7.64.1

RETURN VALUE

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

SEE ALSO

       CURLOPT_ALTSVC_CTRL(3), CURLOPT_CONNECT_TO(3), CURLOPT_RESOLVE(3), CURLOPT_COOKIEFILE(3),