grep

# Show grep version
grep --version

# Print lines containing sys
grep sys /etc/passwd

# Print lines containing SYS case insensitive
grep SYS -i /etc/passwd

# Count lines containing sys
grep -c sys /etc/passwd 

# Print last 10 lines containing sys
tail -10 /etc/passwd  | grep sys

# Print lines fullfilling regex (put regex in single quotes)
grep '^[a-z]' /etc/passwd

# Print non empty lines
grep -v '^$' /etc/passwd

# Print 2 lines after the match (including the match)
# use B instead for before, C for before and after
grep proxy -A2 /etc/passwd