I have the following bash script.

while IFS= read -r filename;

  do [[ $(md5 path/to/"$filename-orig") = $(md5 path/to/"$filename") ]] || echo $filename differs;

  done < path/to/list-of-files-to-compare.txt

It's supposed to compare two files (by computing their MD5 hash digest) then report if they are different. It gets the files to compare from a list.

The problem is that if the file I am trying to read is at, say,

path/to/foo-orig.js

the script will look for the file at

path/to/foo.js-orig

and, obviously, this throws an error and fails.

How do I correct this bug in my script so that I handle the .js extension correctly?

Edit

TL;DR:

Given a string foo.bar how can I get foo-orig.bar?

Edit2:

I add the -orig extension because this project takes a template that's regularly updated by a third party, then I overlay my changes to it. So, I want to keep track of what files they change so I can go back and adapt my code when necessary.

list-of-files-to-compare.txt looks like the following.

public/assets/images/logos/logo.svg

README.md

src/auth/Auth.js

src/auth/store/actions/login.actions.js

src/auth/store/actions/user.actions.js

src/auth/store/reducers/user.reducer.js

src/firebaseService/firebaseService.js

src/firebaseService/firebaseServiceConfig.js

src/fuse-configs/fuseNavigationConfig.js

src/fuse-configs/fuseRoutesConfig.js

src/index.js

src/main/content/components/ComponentsConfig.js

src/main/content/login/Login.js

src/store.js

src/store/actions/index.js

src/store/reducers/index.js

In Bash you could use Pattern substitution:

while IFS= read -r filename;

do

    echo ${filename/.js/-orig.js}

done < list-of-files-to-compare.txt

If you want to be more generic you can first get an extension with cut and rev like that:

$ ext=$(echo public/assets/images/logos/logo.svg | rev | cut -d. -f1  | rev)

$ echo $ext

svg

And then replace it with sed:

$ echo public/assets/images/logos/logo.svg | sed "s,.${ext}$,-orig.${ext},"

public/assets/images/logos/logo-orig.svg

It would be easier if you appended .orig to the filename so that logo.svg would become logo.svg.orig.