C - Libcurl - How to search for Mails with special chars (ä,ö,ü) - c

Question

i use libcurl to search for mails in my mailbox.
But i cannot search mails with mails that inlcudes special chars (ä,ö,ü) in the subject.
int main(void)
{
CURL *curl;
CURLcode res = CURLE_OK;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_USERNAME, "myuser");
curl_easy_setopt(curl, CURLOPT_PASSWORD, "mypassword");
curl_easy_setopt(curl, CURLOPT_URL, "imaps://imap.gmail.com:993/INBOX");
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "SEARCH SUBJECT Spülmaschine");
res = curl_easy_perform(curl);
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
curl_easy_cleanup(curl);
}
return (int)res;
}
The mail cannot be found.
I searching a while but i cannot find some tipps.
Have someone any ideas ?
EDIT:// No one of the following trys will work:
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "SEARCH CHARSET UTF-8 SUBJECT \x53\x70\xc3\xbc\x6c\x6d\x61\x73\x63\x68\x69\x6e\x65");
//try it with UTF-7
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "SEARCH SUBJECT Sp+APw-lmaschine");
sprintf(strSearchString, "SEARCH CHARSET UTF-8 SUBJECT {%i}\r\n\x53\x70\xc3\xbc\x6c\x6d\x61\x73\x63\x68\x69\x6e\x65", strlen("\x53\x70\xc3\xbc\x6c\x6d\x61\x73\x63\x68\x69\x6e\x65"));
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, strSearchString);

Answer 1

After a long time i found a solution:
int main(void) {
CURL *curl;
CURLcode res = CURLE_OK;
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_USERNAME, "myuser");
curl_easy_setopt(curl, CURLOPT_PASSWORD, "mypass");
curl_easy_setopt(curl, CURLOPT_URL, "imaps://imap.gmail.com:993");
// see RFC6855 IMAP Support for UTF-8
// imap.gmail.com states UTF8=ACCEPT in CAPABILITY response,
// so enable it to use UTF-8 in quoted strings.
// Must come after AUTHENTICATE and before SELECT.
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "ENABLE UTF8=ACCEPT");
res = curl_easy_perform(curl);
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
// SELECT INBOX broken out from URL
if (res == CURLE_OK) {
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "SELECT INBOX");
res = curl_easy_perform(curl);
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
}
if (res == CURLE_OK) {
// U+00FC LATIN SMALL LETTER U WITH DIAERESIS is \xC3\xBC in UTF-8
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "SEARCH
SUBJECT \"Sp\xC3\xBClmaschine\"");
res = curl_easy_perform(curl);
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
}
curl_easy_cleanup(curl);
}
return (int) res;
}

Answer 2

While technically against protocol for including 8-bit characters, try SEARCH CHARSET UTF-8 SUBJECT "spülmaschine", and make sure you really are sending UTF-8 and not some other encoding. This will work on many servers. I do not know if you can make libcurl do it the proper way with an IMAP literal.
Note: some server software just doesn't support search that well. Remember, you can always use a tool like socat or python's imaplib, which give you pretty low level access to the protocol for experimenting.