I had a hard time finding my way to writing tools based on libapt. Amusingly, what got me started was to use Graphviz to work out header dependencies.

1 Libraries and Packages

In fairness, this post became more about working out header dependencies than libapt itself. So just for the sake doing justice to its title, a few words about libapt. The libapt-* development libraries provide the highest-level Debian package management interface and are available in the following packages:

• libapt-front-dev – the highest-level libraries;
• libapt-pkg-dev – high-level libraries, though not as high as libapt-front-dev.

Sadly, I couldn't get my hands on the documentation. This gave me a hard time understanding how to get started with these libraries, and that's how I got sidetracked and started looking for a way to identify header dependencies, instead, a way which will in fact work for any headers out there.

2 Header Dependencies

I wrote a little sed expression to draw dependencies between headers, which may be a start to using a library if there's otherwise little documentation. For instance, in the case of libapt, execute the following command line in /usr/include/apt-pkg:

grep "#include <apt-pkg/" * | sed -e 's/^\([a-z0-9\.-]\+\):#include <apt-pkg\/\([a-z0-9\.-]\+\)>/"\1" -> "\2"/'

This will generate a Graphviz graph which you can pass on to the dot command, that will turn it into this nice diagram:

For instance, this graph helps us see that the debfile.h may be a good starting point to get information from a .deb file. Food for thought.

3 References

• sed, a stream editor
• Graphviz