Uppercasing and lowercasing is a common task when working with text. Below are examples of doing this with standard Linux/Unix utilities.
Lowercasing text with tr
tr 'A-Z' 'a-z'
Uppercasing text with tr
tr 'a-z' 'A-Z'
Lowercasing text with awk
awk '{print tolower($0)}'
Uppercasing text with awk
awk '{print toupper($0)}'
Lowercasing text with sed
sed 's/[A-Z]/\L&/g'
Uppercasing text with sed
sed 's/[a-z]/\U&/g'