If this variable is set, the temporary files will be created with this variable as the suffix, instead of the PID of the ‘cpt’ process. The advantage is that you can know exactly where the build directory is located, while the disadvantage is that there will be issues with multiple operations at the same time. So the best way to use this variable is during one-time ‘cpt’ calls.
CPT_PID=mesa cpt b mesa
By running the above, you will know that the created build directories will end with the ‘*-mesa’ suffix.