bash remove lines from file that are in another file code example

Example 1: awk how to remove lines in one file that are found in another file

# Example 1
awk 'NR==FNR{a[$0];next} !($0 in a)' file_2 file_1
# This returns all lines in file_1 that are not found in file_2
# See source for more info on how the command works

Example 2: bash print lines unique to one file

# Example usage using awk:
awk 'FNR==NR { b[$0] = 1; next } !b[$0]' input_file_1 input_file_2
# This command prints all lines of input_file_2 that aren't found in
#	input_file_1 (i.e. lines that are unique to input_file_2). Another
#	way of saying this is that this removes all lines of input_file_2
#	that are found in input_file_1. 
#	It does this by first adding all unique lines of input_file_1 to an 
#	associative array, which works like a dictionary with a key value
#	pair. Then each line of input_file_2 is compared against the array
#	and if it isn't found in the array, it is printed.

# Note, change $0 to $# if you want to remove lines based on values in
#	specific fields (which don't have to be the same in each file)
# Note, unlike some comm and diff commands, this solution doesn't require
#	the files to be sorted.