How to delete from a text file, all lines that contain a specific string?

Question

How would I use sed to delete all lines in a text file that contain a specific string?

Answer 1

I was struggling with this on Mac. Plus, I needed to do it using variable replacement.

So I used:

sed -i '' "/$pattern/d" $file

where $file is the file where deletion is needed and $pattern is the pattern to be matched for deletion.

I picked the '' from this comment.

The thing to note here is use of double quotes in "/$pattern/d". Variable won't work when we use single quotes.