grep -w -e '(.)(.).21' file
grep -rH --include='*.c' 'hello' /home/gigi
grep --label=foo something
grep -E -e '^(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?).?987654321$' file
grep -H 'eli' /etc/passwd
ls -l | grep '^d' | awk '{print "rm -r "$9}' | sh
dd if=/dev/mem | hexdump -C | grep 'default'
grep -r 'hello' /home/gigi
grep --color=always -iw lm /proc/cpuinfo
cat /etc/passwd | grep root
cat /var/log/apache/access_log | grep 404