Debian Package of the Day (static archived copy)

Entry submitted by Bart van Kuik. DPOTD needs your help, please contribute!

Every now and then we need to see the differences between two files. You forgot exactly what you changed in that Perl script, or you’d like to check what changes the intern made in Apache’s configuration, et cetera.

For seeing changes between two files, diff used to be your friend for the command line. Although hard core hackers may disagree, diff its output takes quite a bit of exercise to parse with the human eye. And although diff has a side-by-side mode, a text terminal only offers so much freedom.

A graphical display offers much more possibilities and Meld tries to use them in an admirable fashion. It’s a utility that lets you graphically see the differences between two or three files. And unlike diff, Meld lets you edit (or merge) the files straight away. With the click of a mouse you can copy or move differences between files.

meld httpd.conf httpd.conf.default

Pressing and holding the Shift key will change the arrows to crosses, which lets you swiftly delete the additions that the intern made. (After sternly speaking to the lad!).

If you’re a programmer, you probably store your files in a version control repository like Subversion or CVS. Meld supports this, too. On the command line, type:

meld my/project/directory

Meld recognises a directory that’s under version control and will display any changed files. Double-clicking the file will show the differences between the current file that you’ve been working on, and the file in the repository. Meld is tab-based, so the changes will appear in a separate tab, making it easy to quickly return to the directory overview.

Although it’s not documented, meld seems to supports bzr, CVS, darcs, mercurial, monotone and subversion. Meld packs more features not discussed here, like a mode which displays the differences between directories, multiple languages et cetera. I encourage you to just install the package and look around.

Alternate tools

In the project’s homepage, one can find a little comparison with other similar tools:

Kdiff3

Very good for large merges. Automatic merge facility.

Xxdiff

Has some nice features such as CVS unmerge and good scriptability. Does 2 and 3 way file comparison but only 2 way directory comparison.

TkDiff

Two way file only diff viewer. Depends only on tk.

GtkDiff

Gtk1.x diff tool. Project seems dead.

Meld has been available in Debian since Sarge and in Ubuntu since Warty. It depends on the Python scripting language.