Is it safe to delete .DS_Store & .FBCIndex files?

I think I may have answered my own question! I did a search for "Find By Content" Mac and got this useful link:

http://www.westwind.com/reference/OS-X/invisibles.html

Apparently these are files SHERLOCK used to use! (I told you I have garbage that's been dragged from one computer to the next for a couple of decades.) Great, so I can delete them like a madwoman!

Wow, thanks! I just tried it and it works! That's really good to know.

Re my original question: I should have mentioned the .FBC.... files first and not even mentioned the .DS_Store files b/c I got several responses that told me what I already know (what .DS_Store files are). Weirdly, I have been all over this machine with the Finder and haven't seen a .DS_Store file yet, and those should be visible in any folder in the Finder. So that's weird, since they are supposed to be ubiquitous on Macs. I thought maybe they were no longer part of the Mac OS since High Sierra, b/c of the new filing system.

I do have a file in almost every Folder that says, "Icon?". I figure if this Mac OS doesn't even know what a file is, it's safe to delete it.

I have seen all kinds of weird things over the years in converting and transferring files. The .FBC.... files are new to me, though. Unless I find out otherwise, I agree with you that they are most likely remnants of old apps & filing systems and are safe to delete.

Thanks for that info. That would explain why other invisible files toggle but the .DS_Store files don't.

You wrote: "It appears from other places on the web that .FBCIndex files are Find by Content indexes..."

This seems to be the most information I or anyone who posted here has found on the .FBCIndex, .FBCSemaphores, & other .FBC files. I went ahead and deleted them but left them in the trash. If I don't have any problems, I'll eventually empty the trash. I used to have maintenance apps that would allow me to rebuild the Spotlight index, but I have jumped from Snow Leopard to Sierra (now High Sierra), and I no longer know what apps are safe to use, what processes the OS does automatically now (remember back in the day when we ran daily, weekly, & monthly maintenance tasks, (which the Mac would only do automatically if you had it running at 3:00am or something?) and ran Disk Utility to verify and repair permissions?), or other ways in which the system is different. I used to periodically scan for corrupted preference files. I suppose Onyx is the safest third party app for using to clean up junk from the system and run whatever maintenance might still be performed on command on High Sierra.

Thanks, everyone. I found an answer re the .FBCIndex files, and posted it here for others who may encounter these (rare as that might be). You can read that reply so I'm not going to repeat it here. I wanted to edit the original post to take out the question re the .DS_Store files, since I haven't even encountered any yet in High Sierra, to focus only on the .FBC files, but didn't see a way, so I had to leave it. Just know that I solved the .FBC files mystery and thanks to everyone who responded with whatever information they knew or could find.