Usage

$ cd folder/with/photos  
$ sortPhotos <numberOfChars>

numberOfChars indicate number of first characters in filename which will be used as folder name, where file will be moved.

For example, given the following file list:

20180501.jpg
20181005.jpg
20191005.jpg
20191010.jpg
20191014.jpg
20191119.jpg

if you run:

sortPhotos 6

then files will be moved to the following folders:

201805
201810
201910
201911