$ grep -Fvxf FileE.txt FileP.txt > output.txt

grep: memory exhausted

core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
open files                      (-n) 256
pipe size            (512 bytes, -p) 8
stack size              (kbytes, -s) 2032
cpu time               (seconds, -t) unlimited
max user processes              (-u) 256
virtual memory          (kbytes, -v) unlimited