-v lines that did not match
-i ignore case
-n show line numbers
-r look into the files recursively

-w match exact words only
-l print names of the files matched
-c count of lines matched

-B n   show n lines before the match.
-A n   show n lines after the match.
-C n   show n lines both before and after the match (up to 2*n+1 lines) (context).
examples/intro/grep.txt
$ cat examples/intro/words.txt 
foo
foo
bar
foo
bar

$ grep bar examples/intro/words.txt 
bar
bar

$ grep -v bar examples/intro/words.txt 
foo
foo
foo

$ grep -n bar examples/intro/words.txt 
3:bar
5:bar

$ grep -n -v bar examples/intro/words.txt 
1:foo
2:foo
4:foo