1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Title: CURLOPT_ALTSVC 5Section: 3 6Source: libcurl 7See-also: 8 - CURLOPT_ALTSVC_CTRL (3) 9 - CURLOPT_CONNECT_TO (3) 10 - CURLOPT_COOKIEFILE (3) 11 - CURLOPT_RESOLVE (3) 12Protocol: 13 - HTTP 14Added-in: 7.64.1 15--- 16<!-- markdown-link-check-disable --> 17# NAME 18 19CURLOPT_ALTSVC - alt-svc cache filename 20 21# SYNOPSIS 22 23~~~c 24#include <curl/curl.h> 25 26CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC, char *filename); 27~~~ 28 29# DESCRIPTION 30 31Pass in a pointer to a *filename* to instruct libcurl to use that file as 32the Alt-Svc cache to read existing cache contents from and possibly also write 33it back to after a transfer, unless **CURLALTSVC_READONLYFILE** is set in 34CURLOPT_ALTSVC_CTRL(3). 35 36Specify a blank filename ("") to make libcurl not load from a file at all. 37 38The application does not have to keep the string around after setting this 39option. 40 41Using this option multiple times makes the last set string override the 42previous ones. Set it to NULL to disable its use again. 43 44# DEFAULT 45 46NULL. The alt-svc cache is not read nor written to file. 47 48# %PROTOCOLS% 49 50# EXAMPLE 51 52~~~c 53int main(void) 54{ 55 CURL *curl = curl_easy_init(); 56 if(curl) { 57 curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1); 58 curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt"); 59 curl_easy_perform(curl); 60 } 61} 62~~~ 63 64# FILE FORMAT 65 66A text based file with one line per alt-svc entry and each line consists of 67nine space-separated fields. 68 69An example line could look like 70 71 h2 www.example.com 8443 h3 second.example.com 443 "20190808 06:18:37" 1 0 72 73The fields of that line are: 74 75## h2 76 77ALPN id for the source origin 78 79## www.example.comp 80 81Hostname for the source origin 82 83## 8443 84 85Port number for the source origin 86 87## h3 88 89ALPN id for the destination host 90 91## second.example.com 92 93Hostname for the destination host 94 95## 443 96 97Port number for the destination host 98 99## 2019* 100 101Expiration date and time of this entry within double quotes. The date format 102is "YYYYMMDD HH:MM:SS" and the time zone is GMT. 103 104## 1 105 106Boolean (1 or 0) if "persist" was set for this entry 107 108## 0 109 110Integer priority value (not currently used) 111 112# %AVAILABILITY% 113 114# RETURN VALUE 115 116Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. 117
