Question

I have a textfile in which some words are printed in ALL CAPS. I want to be able to just convert everything in the textfile to lowercase, using sed. That means that the first sentence would then read, ‘i have a textfile in which some words are printed in all caps.’

Answer 1

Here are two methods for doing the conversion using tr and sed:

Using tr

Convert uppercase to lowercase

tr '[:upper:]' '[:lower:]' < input.txt > output.txt

Convert lowercase to uppercase

tr '[:lower:]' '[:upper:]' < input.txt > output.txt

Using sed on GNU (but not BSD or Mac)

Convert uppercase to lowercase

sed -e 's/\(.*\)/\L\1/' input.txt > output.txt

Convert lowercase to uppercase

sed -e 's/\(.*\)/\U\1/' input.txt > output.txt
 

The reason the sed version doesn’t work on BSD or Mac is because those systems don’t support the \L or \U flags