strtok function not splitting at the given delimiter

Question

Strtok is called like this:

char *headers = strtok(NULL, "\n\n");

on this string:

"Host: 172.27.34.56\nConnection: keep-alive\nDNT: 1\nUpgrade-Insecure-Requests: 1\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36\nAccept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,/*;q=0.8,application/signed-exchange;v=b3;q=0.7\ncp-extension-installed: Yes\nAccept-Encoding: gzip, deflate\nAccept-Language: de-DE,de;q=0.9,en-US;q=0.8,en;q=0.7\nRange: bytes=85-85\nIf-Range: Wed, 19 Jul 2023 19:15:56 GMT\n\n123"

but it splits on the first \n instead of \n\n. why?

Answer 1

std::strtok takes a list of delimiting characters as its second argument. It doesn't split by a string/substring.

Cf. The example on cppreference

If you're not against using std::string, you can make a tokUntil function as follows:

std::string tokUntil(std::string str, std::string delimiter) {
  auto pos = str.find(delimiter);
  return pos === std::string::npos ? str : str.substr(0, pos);
}