```[matheusmmo@bbrandsti-07:~]
[11:14:07] $ cat a.txt 
a
b

[matheusmmo@bbrandsti-07:~]
[11:14:47] $ cat b.txt 
b
c

[matheusmmo@bbrandsti-07:~]
[11:14:48] $ grep -xvFf a.txt b.txt
c

-x, --line-regexp         force PATTERN to match only whole lines
-v, --invert-match        select non-matching lines
-F, --fixed-strings       PATTERN is a set of newline-separated strings
-f, --file=FILE           obtain PATTERN from FILE
```