Alex Ruben
How To Compare the Contents of Two Directories on Linux/Ubuntu
If you’ve ever needed to check what’s different between two folders on your Ubuntu machine, you probably noticed how quick it is to get overwhelmed or just end up doing a manual slog through files. That’s where the diff command really shines—it’s built for this kind of job, and while it’s pretty straightforward, there’s a bit of nuance in how you use it effectively. Basically, once you get it running, you’ll be able to see which files are missing, which are the same, and where differences sneak in, including subdirectories, without breaking a sweat. Perfect for backing stuff up, debugging, or just satisfying curiosity about how similar or different two directories really are, all from the terminal.
How to Compare Two Folders in Ubuntu
Use the diff Command with Recursive and Brief Options
This is the most common way, and it works well on most setups. The basic idea is to run diff with the -q and -r options, which tell diff to report only whether files differ (not how) and do it recursively, covering all subfolders. For instance:
diff -qr ~/folder1 ~/folder2
This command compares folder1 and folder2 in your home directory. You can swap out the paths with any directories you’re working with. On some setups, you might need to specify the full paths like /home/username/Projects/folder1, especially if you’re not in the right directory.
Why it helps: It quickly flags files that are different or missing, which is often enough to get a sense of the general state of your directories.
When to use it: When you want a quick overview—no need to see every line of diff, just the summary of what’s different.
What to expect: You’ll see lines like Only in folder1: file.txt or Files folder1/file.txt and folder2/file.txt differ.
Sometimes, a folder might appear to be same but have tiny differences—this command catches those without fuss. On one setup, I ran it and it gave me a clear gap, while on another, the output was a bit overwhelming—depends on the amount of data.
View Detailed Diffs for Content Changes
If it turns out you need more info—like the specific lines that differ—you can skip the -q option. Just run:
diff -r ~/folder1 ~/folder2
This one will show you line-by-line differences inside files that aren’t identical. Not always necessary, but super helpful when you need to pinpoint exactly what changed in your code or configs.
Keep in mind, on really big folders, this can be a lot of output—sometimes it’s worth redirecting it to a file or just using a GUI tool, but for most quick checks, it’s fine.
Extra Tips & Troubleshooting
- Paths matter — always double-check that you’re comparing the right directories with absolute paths if you’re not in the same location.
- If the output is too noisy, add the –brief flag for even simpler results:
- You can also explore other options like man diff to see all sorts of flags for specific needs.
- Sometimes, permissions or symlinks cause issues—run the command with
sudoif needed, or double-check your folder access rights.
diff --brief -r folderA folderB
Wrap-up
This should give you a solid base to compare directories quickly in Ubuntu. It’s not perfect—sometimes the output can get a little dense if folders are huge—but it’s reliable, fast, and doesn’t require extra apps. Once you get used to it, you’ll wonder how you ever did without.
Frequently Asked Questions
What exactly does the diff command do?
It compares files line by line, showing you what’s different. When you give it directories, it scans everything inside, letting you spot missing, new, or changed files without opening each one manually.
Can I compare just specific files or subfolders?
Absolutely. Just provide the relative paths to the two files or folders within the diff command, like diff file1.txt file2.txt or diff -r folderA/subfolder folderB/subfolder.
Are there graphical alternatives for comparing folders?
Yep. Tools like Meld or Beyond Compare make it visual and might be easier if you prefer clicking over command lines. But for quick checks, streaking it in terminal still gets the job done.
- Double-check directories with ls or file manager before diffing.
- If your directories are huge, consider filtering output or adding further options.