Recently, there are lots of file related technical questions asked during the interview. Can anyone point me a good material where I can get the proper idea how to solve these problems:

1. Finding a file within a File System with multiple constrained like file name, file extensions, file size etc.
2. Create an API and develop find and replace functions like linux command
   find (eg linux command: find dir_name file_name)

these questions are already posted in various discussion but didn't get any clear answer.