I have successfully built boost with the following options:

./b2 install --prefix=~/development/cots/boost stage <various other options>

I notice that a directory ~/development/cots/boost is created in $BOOST_ROOT which contains lib and include sub directories. The contents of the include directory appears to be the same as what is in $BOOST_ROOT/boost and the lib contains the build output.

A directory $BOOST_ROOT/stage/lib is also created which contains the build output.

I expected the latter but not the former.

What is the --prefix option for? Should it be used when the stage option is used? And why does it appear to result in the include files being duplicated in another directory?