use of cpus in building

[Adam Dershowitz]

> On May 27, 2016, at 1:47 PM, Ryan Schmidt <ryandesign at macports.org> wrote:
> 
> 
> On May 25, 2016, at 5:07 PM, Justin C. Walker wrote:
> 
>> On May 25, 2016, at 14:42 , Adam Dershowitz wrote:
>> 
>>> You can also manually change it for a single install, for example by using build.jobs.  Such as:
>>> sudo port install port_whatever_name build.jobs=4 
>>> and then, for that specific install it will attempt to use 4 cores.  This can be handy to reduce the number of cores used, from the default, so that you can do other things on the machine while building. 
> 
> Instead, consider changing buildnicevalue in macports.conf from 0 to a greater number, up to 20. When MacPorts is configured to be "nice" it means that if other programs running on your computer need CPU time, they'll get it first.
> 

Can this also be done on the command line for a specific install, instead of changing the config file?