batch-rename-file-extension-in-a-for-loop

Thanks to basename, which is a unix bin file

https://stackoverflow.com/questions/38590165/how-to-rename-file-extentions-in-fish-in-a-for-loop

1
for file in *.md
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    mv -v -- "$file" (basename $file .md).txt
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end

use string replace is also nice.