CURLOPT_HSTS(3)

NAME
CURLOPT_HSTS - HSTS cache filename

SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTS, char *filename);

DESCRIPTION
Make the filename point to a filename to load an existing HSTS cache from, and to store the cache in when the easy handle is closed. Setting a file name with this option also enables HSTS for this handle (the equivalent of setting CURLHSTS_ENABLE with CURLOPT_HSTS_CTRL(3)). If the given file does not exist or contains no HSTS entries at startup, the HSTS cache simply starts empty. Setting the filename to NULL allows HSTS without reading from or writing to any file. NULL also makes libcurl clear the list of files to read HSTS data from, if any such were previously set. If this option is set multiple times, libcurl loads cache entries from each given file but only stores the last used name for later writing.

FILE FORMAT
The HSTS cache is saved to and loaded from a text file with one entry per physical line. Each line in the file has the following format:
[host] [stamp]
[host] is the domain name for the entry and the name is dot-prefixed if it is an entry valid for all subdomains to the name as well or only for the exact name. [stamp] is the time (in UTC) when the entry expires and it uses the format "YYYYMMDD HH:MM:SS". Lines starting with "#" are treated as comments and are ignored. There is currently no length or size limit.

DEFAULT
NULL, no filename

PROTOCOLS
This functionality affects http only

EXAMPLE
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_HSTS, "/home/user/.hsts-cache");
    curl_easy_perform(curl);
  }
}

AVAILABILITY
Added in curl 7.74.0

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

SEE ALSO
CURLOPT_ALTSVC(3), CURLOPT_HSTS_CTRL(3), CURLOPT_RESOLVE(3)