ncomm

ncomm is like comm, but for any number of files, not just two files.

Installation

go install github.com/ucarion/ncomm

Usage

To compare the contents of two (sorted) files a and b, run:

ncomm a b

The output will be exactly the same as comm a b. Unlike comm, you can pass additional files. To compare sorted files a, b, c, d, run:

ncomm a b c d

Whereas ncomm a b gave you three columns of output, ncomm a b c d will produce 15 columns; each column represents a different combination of a, b, c, or d that a line might appear in.

To make it more obvious what the columns mean, use --show-header for a legend:

ncomm --show-header a b c d

x---	-x--	xx--	--x-	x-x-	-xx-	xxx-	---x	x--x	-x-x	xx-x	--xx	x-xx	-xxx	xxxx	
[...]

You can also run ncomm --help for detailed information:

usage: ncomm [<options>] files...

like comm(1), but for any number of files

        --show-header    output a header to help explain what each column represents
    -h, --help           display this help and exit

Example

Here's a more fleshed-out example of how ncomm can start to be useful in the real world. In examples in this repo, there's a set of files:

• eu.txt lists members of the European Union
• nato.txt lists members of the North Atlantic Treaty Organization
• oecd.txt lists members of the Organisation for Economic Co-operation and Development

All three of these are clubs of countries. With ncomm, you can see how they overlap:

ncomm --show-header ./examples/eu.txt ./examples/nato.txt ./examples/oecd.txt

x--	-x-	xx-	--x	x-x	-xx	xxx	
	Albania
			Australia
				Austria
						Belgium
		Bulgaria
					Canada
			Chile
			Colombia
			Costa Rica
		Croatia
						Czech Republic
						Denmark
						Estonia
				Finland
						France
						Germany
						Greece
						Hungary
					Iceland
				Ireland
			Israel
						Italy
			Japan
			Korea
						Latvia
						Lithuania
						Luxembourg
Malta
			Mexico
	Montenegro
						Netherlands
			New Zealand
	North Macedonia
					Norway
						Poland
						Portugal
Republic of Cyprus
		Romania
			Slovak Republic
		Slovakia
						Slovenia
						Spain
				Sweden
			Switzerland
					Turkey
					United Kingdom
					United States

The first row comes from --show-header, and makes it a bit easier to figure out what each column represents. For instance, we can see that the 5th columns has a header x-x, indicating lines that are in the 1st and 3rd file but not the 2nd. In our example, that represents countries that are in the EU and OECD, but not NATO. We can extract just those countries with a bit of cut, and then remove blank lines with grep:

ncomm ./examples/eu.txt ./examples/nato.txt ./examples/oecd.txt | cut -s -f 5 | grep .

Austria
Finland
Ireland
Sweden

Alternatively, if we wanted to count how many countries fell into each of the seven possible "buckets", you could count how many tabs there are on each line, and then count how many lines have that number of tabs:

ncomm ./examples/eu.txt ./examples/nato.txt ./examples/oecd.txt | awk -F$'\t' '{print NF}' | sort | uniq -c

   2 1
   3 2
   4 3
  11 4
   4 5
   6 6
  17 7

As before, you could use --show-header to make sense of what each column number means.