How do I use sed to make every letter in a file lowercase?

[hawksbill]

Link to GNU sed substitute documentation: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html

In this example we will be using the following:
\L - Turn the replacement to lowercase.

The sample file we're working with is:

this is my first ip 10.50.20.1
grapes
apples
pears
this is the first block
oranges
PLUMS

this is my second ip 10.50.20.2
this is my duplicate ip 10.50.20.2
grapes
apples
pears
this is the second block
oranges
PLUMS

this is my third ip 10.50.20.3
grapes
apples
pears
this is the third block
oranges
plumsp

This command will change the uppercase PLUMS to plums. This command send the output to the screen, redirect the output to another file to save it or use the -i option.

$ cat grepfile | sed -e 's/\(.*\)/\L\1/'