Comparing plain text files

Franklin Bristow

Compare plain text files

Compare plain text files.

The last thing we’ll do this week is look at comparing plain text files to one another. You’ve actually been introduced to this topic already when we looked at the output from git diff: when you run git diff you’re comparing the files as they were in the last commit to the current state that the files are in now!

We also sometimes want to be able to compare files directly to one another when, for example, they aren’t under version control (we don’t have the files in our repository).

For this, we’re going to use a program called diff.

Let’s get back one more time to the root of crazy-directories. Once you’re there, let’s compare the differences between b/5/s/bananas.md and b/5/s/bAnAnAs.md:

diff -u b/5/s/bananas.md b/5/s/bAnAnAs.md

You should see output that looks something like this:

--- b/5/s/bananas.md    2022-10-04 19:34:34.327980126 -0500
+++ b/5/s/bAnAnAs.md    2022-10-04 19:34:03.496980478 -0500
@@ -1,4 +1,4 @@
-bananas
+bAnAnAs
 =======
 
-You found me! That's bananas :banana:!
+You found me! That's ... wait, what?

diff is reporting to us the differences between the first file we passed and the second file. It indicates which file lines belong to using the - and + characters, and it’s showing us how we can change the file on the left to turn into the file on the right. The @@ -1,4 +1,4 @@ line is cryptically telling us that it’s showing us 4 lines from the file on the left (-) starting at line 1, and 4 lines from the file on the right (+) starting at line 1.

For full clarity: the learning outcome here is “Compare plain text files”, not “interpret the output from diff”. Being able to run diff on the command line to see the differences between files is all we’re looking for.