I have two text files on Linux. One contains a list of valid IDs. E.g:
abcd efgh ijkl etc.
The other contains a list of invalid IDs. But, some of these also appear on the list of valid IDs, in this example "efgh":
mnop qrst efgh etc.
How can I easily construct a text file that contains all the lines from the invalid list that do not appear in the valid list? That is, I want to end up with a text file that has:
mnop qrst etc.
I'd like either some Linux commandline magic of some clever Vim trickery. Thanks in advance!