bash return lines from one file that arent in another code example

Example: bash return lines from one file that arent in another

# Example usage:
awk 'NR==FNR { b[$0] = 1; next } !b[$0]' input_file_1 input_file_2
# This returns all lines of input_file_2 that aren't found in 
# input_file_1

# Note, remove the ! to return all lines in common between the files