I have thousands of textfiles inside a directory and they are named in a certain way. For eg:

Image_234_Data_7778_n0.txt
Image_234_Data_7778_n1.txt
Image_234_Data_7778_n2.txt

Image_954_Data_4478_n0.txt
Image_954_Data_4478_n1.txt
Image_954_Data_4478_n2.txt

Image_104_Data_9878_n0.txt
Image_104_Data_9878_n1.txt
Image_104_Data_9878_n2.txt

and so on...

I would like to make a sourcefile (which would be used to rename the files and keep track of 'which is which') that should read:

1_1.txt:Image_234_Data_7778_n0.txt
1_2.txt:Image_234_Data_7778_n1.txt
1_3.txt:Image_234_Data_7778_n2.txt

2_1.txt:Image_954_Data_4478_n0.txt
2_2.txt:Image_954_Data_4478_n1.txt
2_3.txt:Image_954_Data_4478_n2.txt

3_1.txt:Image_104_Data_9878_n0.txt
3_2.txt:Image_104_Data_9878_n1.txt
3_3.txt:Image_104_Data_9878_n2.txt

and so on...

Can anyone help me with some code which would do this for me? Any help would be highly appreciated !

what have you tried so far and where are you suck ?

mayde cut bytes 7-9 from the file name then sort | uniq them ?

Are there only 3 of each type of name, as shown?