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

You can use sed to replace lines in place in a file. However, it seems to be much slower than using grep for the inverse into a second file and then moving the second file over the original.

e.g.

sed -i '/pattern/d' filename      

or

grep -v "pattern" filename > filename2; mv filename2 filename

The first command takes 3 times longer on my machine anyway.