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CURLOPT_ALTSVC(3) curl_easy_setopt options CURLOPT_ALTSVC(3)

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:

ALPN id for the source origin
Host name for the source origin
8443
Port number for the source origin
ALPN id for the destination host
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),

June 21, 2022 libcurl 7.84.0