I have 2 simple files ...
This is file a.txt
A B D E F
This is file b.txt
F A B C D E
Obviously Item C is missing - but how do I find this automatically.
Yes grep, like this
grep -v -x -f a.txt b.txt
But take care - this is filename order dependant - as the switches in GREP are important.
|-v||Show non-matching lines|
|-x||Match whole lines|
|-f||Read Pattern from a file|
But if you reverse the file order - you will produce nothing.
I had never heard of this command utility....
But first we need sorted files.
sort -o a.txt a.txt sort -o b.txt b.txt
Now we run the comm command.
comm a.txt b.txt
And we see the output
A B C D E F
Which is nearly what we want ...
Using command switches we can now reduce this output.
comm -3 a.txt b.txt