File processing without upload to shiny server

Can I develop a application where I can process my local files and save it directly from shiny app ?
Can I process local files or I have to upload it to server first for processing and then again have to download the processed file ?

Please say me in a easier way.
Thank you

If the shiny app runs locally, you can process local files

So,I can't process local files after I publish my app to Shiny app ?
Am I correct ?

Files have to be local relative to the app that processes them. You might need to move files, like a file upload to facilitate that

Thank You. I understand this.