Bleakley:

Given a .txt file with a list of files named:

2015_273_2_1_1__Your_Favorite_Home_Movie_1.mov
2015_273_2_1_1__Your_Favorite_Home_Movie_2.mov
2015_273_2_1_1__Your_Favorite_Home_Movie_3.mov

How do I Rename all the _ in between the numerals to a . without changing the ones between the letters?

I want the output to be:

2015.0273.2.1.1__Your_Favorite_Home_Movie_1.mov
2015.0273.2.1.1__Your_Favorite_Home_Movie_2.mov
2015.0273.2.1.1__Your_Favorite_Home_Movie_3.mov

etc.

sed -E '/s/{0..9}_{0..9}/{0..9}.{0..9}/' /Users/medialab/Desktop/ls.txt 

give me a error, invalid command code .

While I'm asking, how would this work with rename or mv if the target was files in a directory rather than a list of files in a .txt file?