CURLOPT_HSTSREADFUNCTION(3) - Man pages

CURLOPT_HSTSREADFUNCTION(3) Library Functions ManualCURLOPT_HSTSREADFUNCTION(3)

NAME
       CURLOPT_HSTSREADFUNCTION - read callback for HSTS hosts

SYNOPSIS
       #include <curl/curl.h>

       struct curl_hstsentry {
         char *name;
         size_t namelen;
         unsigned int includeSubDomains:1;
         char expire[18]; /* YYYYMMDD HH:MM:SS [null-terminated] */
       };

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

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADFUNCTION, hstsread);

DESCRIPTION
       Pass a pointer to your callback function, as the prototype shows above.

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

       Set the clientp argument with the CURLOPT_HSTSREADDATA(3) option  or  it
       is NULL.

       When  this  callback  is  invoked, the sts pointer points to a populated
       struct: Copy the hostname 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 CURLSTS_OK if it returns a name and is pre-
       pared to be called again (for another host) or CURLSTS_DONE if it has no
       entry to return. It can also return CURLSTS_FAIL to  signal  error.  Re-
       turning  CURLSTS_FAIL  stops  the transfer from being performed and make
       CURLE_ABORTED_BY_CALLBACK get returned.

       This option does not enable HSTS, you need to  use  CURLOPT_HSTS_CTRL(3)
       to do that.

DEFAULT
       NULL - no callback.

PROTOCOLS
       This functionality affects http only

EXAMPLE
       struct priv {
         void *custom;
       };

       static CURLSTScode hsts_cb(CURL *easy, struct curl_hstsentry *sts,
                                  void *clientp)
       {
         /* populate the struct as documented */
         return CURLSTS_OK;
       }

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           struct priv my_stuff;
           CURLcode res;

           /* set HSTS read callback */
           curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hsts_cb);

           /* pass in suitable argument to the callback */
           curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &my_stuff);

           res = curl_easy_perform(curl);
         }
       }

AVAILABILITY
       Added in curl 7.74.0

RETURN VALUE
       This returns CURLE_OK.

SEE ALSO
       CURLOPT_HSTS(3),  CURLOPT_HSTSREADDATA(3), CURLOPT_HSTSWRITEFUNCTION(3),
       CURLOPT_HSTS_CTRL(3)

libcurl                            2026-07-12       CURLOPT_HSTSREADFUNCTION(3)

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