explainshell.com - comm.1posix -23 %3C%28cat source %7C cut -d%27 %27 -f 1 %7C sort -u%29 %3C%28cat output %7C cut -d%27 %27 -f 2 %7C sort -u%29

-23 %3C%28cat source %7C cut -d%27 %27 -f 1 %7C sort -u%29 %3C%28cat output %7C cut -d%27 %27 -f 2 %7C sort -u%29

select or reject lines common to two files

-2     Suppress the output column of lines unique to file2.

-3     Suppress the output column of lines duplicated in file1 and file2.

source manpages: comm