How to to delete a line given with a variable in sed?

Question

I am attempting to use sed to delete a line, read from user input, from a file whose name is stored in a variable. Right now all sed does is print

Answer 1

You might have success with grep instead of sed

read -p "Enter a regex to remove lines: " filter
grep -v "$filter" "$file"

Storing in-place is a little more work:

tmp=$(mktemp)
grep -v "$filter" "$file" > "$tmp" && mv "$tmp" "$file"

or, with sponge

grep -v "$filter" "$file" | sponge "$file"

Note: try to get out of the habit of using ALLCAPSVARS: one day you'll accidentally use PATH=... and then wonder why your script is broken.