Meld

Meld is a tool that can compare and merge files and directories. It is a GUI analog to the standard diff and patch command line tools. (See man diff and man patch for more details on those)

Also, lots of source control systems (such as bzr or git ) have the ability to create diffs between versions.

Diff is your friend.

diff -ur path1 path2

This will compare all files that are common between path1 and path2.

If you change -ur to -urN then that will also show the contents of files that are only present in one of the paths.

'Beyond Compare' is available for Linux, too. Check their download URL.
Their german site is at http://www.beyondcompare.de/.

Use the diff command:

diff -u file1 file2

diff -u selects a format with a few lines of context. A plain diff file1 file2 only lists the differing lines. There are many more options to control the output format, ignore whitespace-only differences, etc.

If you want to write the output to a file, redirect it:

diff -u file1 file2 >file1-file2.diff

Gnome Commander

The interface might not be real sexy, but it's extremely powerful!

And if you were used to other *Commander (like Norton, or the likes), you won't be lost.

Command line tools

Inspired by this blog entry.

diff

Listing different files:

diff -qr folder1 folder2

Listing also content:

diff -Naur folder1 folder2

rsync

If the two directories are not on the same machine, rsync might be the easiest solution. Usually rsync is used in order to sync directories, but you can run it in verbose and dry mode, so it will only list files it would have to change.

rsync -rvnc --delete folder1 server:/path/to/folder2

You can ommit c if you want to compare files based on timestamps and file sizes to speed up everything:

rsync -rvn --delete folder1 server:/path/to/folder2

KDiff3

It is a graphical front-end to diff for KDE users (or if you don't mind using Qt apps).

There is also dirdiff for directories.

Krusader

Krusader is a free tool (available in the Software Centre) that shows folder contents in comparison and you can synchronize with a lot of different options. You can filter while synchronising and comparing.

To compare file contents you simply mark two files select "file" > "compare content" and they are compared on a letter by letter basis. the default comparing tool used by krusader is the default KDE tool "Kompare". You can set krusader to use any other comparison tool - like for example one of the above.

This is the most complete solution I ever found and it's very convenient. And it supports all the function keybindungs used by midnight commander (norton commander syntax).

Maybe Meld is what you are looking for. Or here are some other alternatives.

I learned about hashdeep two weeks ago. And it has some strong advantages:

• In contrast to meld, it works well for very large folders. Where meld becomes extremely slow and the UI unresponsive (blocked), hashdeep just works at a constant speed
• In contrast to rsync, hashdeep detects moved files - files with the same content, just in a different directory.

Verbose output is like:

...
foo/bar.txt: Known file not used
x/foo/M0824_2L.JPG: Moved from y/P1010998.JPG

hashdeep: Audit failed
   Input files examined: 0
  Known files expecting: 0
          Files matched: 6233
Files partially matched: 0
            Files moved: 3695
        New files found: 19257
  Known files not found: 4713