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

Just in case someone wants to do it for exact matches of strings, you can use the -w flag in grep - w for whole. That is, for example if you want to delete the lines that have number 11, but keep the lines with number 111:

-bash-4.1$ head file
1
11
111

-bash-4.1$ grep -v "11" file
1

-bash-4.1$ grep -w -v "11" file
1
111

It also works with the -f flag if you want to exclude several exact patterns at once. If "blacklist" is a file with several patterns on each line that you want to delete from "file":

grep -w -v -f blacklist file