Grep Invert Match

Grep is a powerful tool for searching files for text matching a pattern. Have you ever thought to use it to search for lines that do not match a search pattern? Grep can do that! Add the --invert-match flag, or -v for short.

~ % cat words.txt
art
article
cities
name
nonsense
part
tart
~ % grep art words.txt
art
article
part
tart
~ % grep art --invert-match words.txt
cities
name
nonsense

Now you can use grep to search for presence or absence of a search pattern.