如何使用libcurl打印远程FTP目录列表？

Question

I think I'm supposed to use CURLOPT_DIRLISTONLY but I'm not really sure how to proceed.

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DIRLISTONLY, long listonly);

I'm not sure how to make the call to actually print the list.

Answer 1

Enabling the CURLOPT_DIRLISTONLY option for FTP has the effect of retrieving only file names instead of file details (eg file size, date, etc.) basically as the difference between using a plain ls (only names) or a ls -l (listing with details) on UNIX. At the FTP protocol level, enabling CURLOPT_DIRLISTONLY will make libcurl issue a NLST command rather than a LIST . Then to get the directory listing you do the same as a file transfer, with the difference that your ftp:// URL will point to a directory (and not to a file). The contents of that transfer will be your directory listing.

To display the directory listing, rather than saving it to a file, you can use the CURLOPT_WRITEFUNCTION option to have libcurl call a callback function you supply for every block of data. That function only needs to fwrite the data to stdout to display it. It should look something like this:

void write_callback(void* data, size_t size, size_t nmemb, void* ptr)
{
  fwrite(data, size, nmemb, stdout);
}

int main()
{
  // ...
  curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, write_callback);
  // ...
  ret = curl_easy_perform(handle);
}