Here’s a command that will compare two files and display the only entries in the first file that are missing in the second file. To do this, there’s a compare command in Linux Bash called comm that comes with several options. The option we are interested in is the comm -23 which exactly does that. Let me demonstrate.
Let’s say file a.txt contains:
one two three four five six seven eight nine ten
And file b.txt contains:
one three four five nine
We then run comm command using the option -23.
comm -23 a.txt b.txt > c.txt
The contents of c.txt is:
two six seven eight ten