powershell call cmake script, but some var it empty

[Sea_Sea]

cmake -P install.cmake -DHELLO=“hello”

#install.cmake
echo "result:   ${CMAKE_SYSTEM_NAME}" 
echo "result:     ${HELLO}" 

#output
result:  
result:  

[marc.chevrier]

Variable definitions (-D options) must be specified before the -P option.

I think variables describing the system are not available in script mode.

[Sea_Sea]

@marc.chevrier

Variable definitions (-D options) must be specified before the -P option.

what is the command line?
-P <file> = Process script mode.

[marc.chevrier]

As specified in the documentation:

Run a Script
 cmake [-D <var>=<value>]... -P <cmake-script-file>