Is there any kind of wildcard when downloading using sftp. Something like that:
BOOL success = [sftp DownloadFileByName:@"/home/user/*.txt" localFilePath:@"/mydir"];
I'm sorry to say that using a wildcard like you've described will not work.
To download all files matching a pattern such as "*.txt", you would write code that iterates over the files in a directory, such as shown here: http://www.example-code.com/objc/sftp_readDir.asp
and then within the loop, call DownloadFileByName for each filename that matches your pattern.