sed in 4 steps

What this card says

Why do we need it?

Preview a replace.

sed "s/8080/9090/g" app.conf

What is it?

Edit with backup.

sed -i.bak "s/8080/9090/g" app.conf

How to do it

Print some lines.

sed -n "10,20p" app.log

Example

Delete comments.

sed "/^#/d" app.conf