curl/docs/libcurl/opts/CURLOPT_ALTSVC.md
Daniel Stenberg e3fe020089
docs/libcurl: generate PROTOCOLS from meta-data
Remove the PROTOCOLS section from the source files completely and
instead generate them based on the header data in the curldown files.

It also generates TLS backend information for options marked for TLS as
protocol.

Closes #13175
2024-03-23 18:13:03 +01:00

110 lines
2.0 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_ALTSVC
Section: 3
Source: libcurl
See-also:
- CURLOPT_ALTSVC_CTRL (3)
- CURLOPT_CONNECT_TO (3)
- CURLOPT_COOKIEFILE (3)
- CURLOPT_RESOLVE (3)
Protocol:
- HTTP
---
<!-- markdown-link-check-disable -->
# NAME
CURLOPT_ALTSVC - alt-svc cache filename
# SYNOPSIS
~~~c
#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.
# DEFAULT
NULL. The alt-svc cache is not read nor written to file.
# EXAMPLE
~~~c
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 7.64.1
# RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.