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.TH CURLOPT_HSTSREADFUNCTION 3 "14 Sep 2020" "libcurl 7.74.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_HSTSREADFUNCTION \- read callback for HSTS hosts
.SH SYNOPSIS
#include <curl/curl.h>

CURLSTScode hstsread(CURL *easy, struct curl_hstsentry *sts, void *userp);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADFUNCTION, hstsread);
.SH EXPERIMENTAL
Warning: this feature is early code and is marked as experimental. It can only
be enabled by explicitly telling configure with \fB--enable-hsts\fP. You are
advised to not ship this in production before the experimental label is
removed.
.SH DESCRIPTION
Pass a pointer to your callback function, as the prototype shows above.

This callback function gets called by libcurl repeatedly when it populates the
in-memory HSTS cache.

Set the \fIuserp\fP argument with the \fICURLOPT_HSTSREADDATA(3)\fP option or
it will be NULL.

When this callback is invoked, the \fIsts\fP pointer points to a populated
struct: Copy the host name to 'name' (no longer than 'namelen' bytes). Make it
null-terminated. Set 'includeSubDomains' to TRUE or FALSE. Set 'expire' to a
date stamp or a zero length string for *forever* (wrong date stamp format
might cause the name to not get accepted)

The callback should return \fICURLSTS_OK\fP if it returns a name and is
prepared to be called again (for another host) or \fICURLSTS_DONE\fP if it has
no entry to return. It can also return \fICURLSTS_FAIL\fP to signal error.

This option doesn't enable HSTS, you need to use \fICURLOPT_HSTS_CTRL(3)\fP to
do that.
.SH DEFAULT
NULL - no callback.
.SH PROTOCOLS
This feature is only used for HTTP(S) transfer.
.SH EXAMPLE
.nf
{
  /* set HSTS read callback */
  curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hstsread);

  /* pass in suitable argument to the callback */
  curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &hstspreload[0]);

  result = curl_easy_perform(curl);
}
.fi
.SH AVAILABILITY
Added in 7.74.0
.SH RETURN VALUE
This will return CURLE_OK.
.SH "SEE ALSO"
.BR CURLOPT_HSTSREADDATA "(3), " CURLOPT_HSTSWRITEFUNCTION "(3), "
.BR CURLOPT_HSTS "(3), " CURLOPT_HSTS_CTRL "(3), "