I'm still new and learning a lot from these forums. Here's my ask:
I would like to have the options for a dropdown be a dynamic list of file names in a mounted folder, so that if a new file is created it is automatically added to the list. The idea being that the user can link a document to an entry without a risk of a typing error. I only need the name of the documents (which will always be PDF format) for the dropdown, which will be viewed later using a PDF Viewer component. (This last part is all setup and works fine as long as the name is typed correctly).
You would need to have a gateway script poll the folder(on the os) at a set interval and record the folder/file structure to a tag, and then use that tag as the source for the dropdown list.
If you are controlling who/what is uploading to the folder, you can call the script whenever the upload finishes to keep the structure data up to date.
Also, while in this area, be careful about path traversal information leaks/disclosure. Make sure you're hardcoding the OS path you're listing files in, that you're only listing files N folders deep, etc. Or, at the very least, make sure you don't get tempted to put in a webdev endpoint that says "give me all the files under X path you provided me in your query" 
Thank you.
This is a project for our internal use only and is hardcoded to a specific folder and filetype.
I've been very cautious about allowing users to input anything into queries and try to hard code as much as I can.