Is there a way to focus lcov code coverage reports to just one or two directories?

I used the --no-external flag together with the --directory flag to exclude unwanted files.

The definition of external from the man:

External source files are files which are not located in one of the directories specified by –directory or –base-directory.

So my command looked like this:

$ lcov  --directory src -c -o report.info --no-external
Capturing coverage data from src
Found gcov version: 4.2.1
Scanning src for .gcda files ...
Found 4 data files in src
Processing src/C####.gcda
  ignoring data for external file /usr/include/c++/4.2.1/bits/allocator.h