Odd Wildcard Matching in Windows 10

I recently ran into an odd behavior of more files matching a pattern than I expected. I’d used exiftool to modify the dates on files my GoPro produced. It creates backup files of the original images when it modifies the tags. Here’s the command I ran.

exiftool.exe -r "-AllDates+=4:7:6 17:40:00" -ext jpg f:\GoPro\20170807

Now I had about 4000 files with the .JPG extension and another 4000 files with a .JPG_original extension.

I ran my program that parses the directory structure and turns all those images into a time lapse movie, and it seemed to be including both the file extensions, making a very disjointed movie.

I loaded my source code in the debugger and it seemed to be doing a findfirst / findnext specifically looking for .JPG files, and not some other extension, but it was definitely retrieving files both with .JPG and .JPG_original extensions.

I then ran a couple of commands at the windows command prompt and was surprised to find the same results there.

dir F:\GoPro\20170807\372GOPRO\G*.JPG /p
dir F:\GoPro\20170807\372GOPRO\G???????.JPG /p

Each command returned both the JPG and JPG_original files.

dir F:\GoPro\20170807\372GOPRO\G*.JPG_original /p

returned just the JPG_original files.

dir F:\GoPro\20170807\372GOPRO\G??????.JPG /p

had one less question mark and correctly returned no files.

This is all unexpected behavior, though I’m glad to see that it was consistent with the operating system and not something specific to the C runtime. I’d love an explanation of what’s going on.

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