Tribblix: manual page: CURLOPT

CURLOPT_ALTSVC(3) Introduction to Library Functions CURLOPT_ALTSVC(3)

NAME

CURLOPT_ALTSVC - alt-svc cache filename

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 after a transfer, unless
CURLALTSVC_READONLYFILE is set in CURLOPT_ALTSVC_CTRL(3).

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

The application does not have to keep the string around after setting
this option.

Using this option multiple times makes the last set string override
the previous ones. Set it to NULL to disable its use again.

SECURITY CONCERNS

libcurl cannot fully protect against attacks where an attacker has
write access to the same directory where it is directed to save
files. This is particularly sensitive if you save files using
elevated privileges.

DEFAULT

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

PROTOCOLS

This functionality affects http only

EXAMPLE

int main(void)
{
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.com 8443 h3 second.example.com 443 "20190808 06:18:37" 1 0

The fields of that line are:

h2 ALPN id for the source origin

www.example.comp
Hostname for the source origin

8443 Port number for the source origin

h3 ALPN id for the destination host

second.example.com
Hostname 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 curl 7.64.1

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).