Have a look at the docs here:

http://www.boost.org/build/doc/html/jam/language.html#jam.language.variables

 

> Specifically, I have a variable that captures the output of an external
> tool I have executed. How can I strip off the trailing newline from that
> when I assign that to another variable ?

 

The SHELL rule has an optional parameter that will automatically strip off the trailing newline

(this is not documented).

 

 

Use it like this:

 

local output = [ SHELL path/to/tool.py : strip-eol ] ;

 

And the newline will automatically be stripped.