I can think if one way of doing it in B3D without API calls, but it might not have a very low cpu usage.
Basically, write a function to scan the directory for the filetype, and call it once every few seconds.
The advantage of the API calls is that they will tell you when the directory has changed as opposed to you manually checking.
Basically, write a function to scan the directory for the filetype, and call it once every few seconds.
The advantage of the API calls is that they will tell you when the directory has changed as opposed to you manually checking.