How to compare two files

So basically what I want to do is compare two file by line by column 2. How could I accomplish this?

File_1.txt:

User1 US
User2 US
User3 US

File_2.txt:

User1 US
User2 US
User3 NG

Output_File:

User3 has changed

Solution 1:

Look into the diff command. It's a good tool, and you can read all about it by typing man diff into your terminal.

The command you'll want to do is diff File_1.txt File_2.txt which will output the difference between the two and should look something like this:

A quick note on reading the output from the third command: The 'arrows' (< and >) refer to what the value of the line is in the left file (<) vs the right file (>), with the left file being the one you entered first on the command line, in this case File_1.txt

Additionally you might notice the 4th command is diff ... | tee Output_File this pipes the results from diff into a tee, which then puts that output into a file, so that you can save it for later if you don't want to view it all on the console right that second.

Solution 2:

Or you can use Meld Diff

Meld helps you compare files, directories, and version controlled projects. It provides two- and three-way comparison of both files and directories, and has support for many popular version control systems.

Install by running:

sudo apt-get install meld

Your example:

Compare directory:

Example with full of text:

Solution 3:

You can use vimdiff.

Example:

vimdiff  file1  file2