[CMake] How to test environment variable in IF command

[Philippe Fremy]

Mike Talbot wrote:
> Hi,
> 
> I'm trying to work out how to test for an environment variable in an IF
> command, the following doesn't work:
> 
> SET(ENV{FOO} ON)
> MESSAGE("FOO = $ENV{FOO}")    # prints "FOO = ON"
> IF(ENV{FOO})
>  MESSAGE("FOO is set")
> ENDIF(ENV{FOO})
> 
> Does anyone know what the right syntax for doing this is, please?
> 
> Thanks,
> Mike
> 


I can't tell you why because the syntax rules of CMake are still obscure
to me but this works:

SET(ENV{FOO} ON)
MESSAGE(FOO = $ENV{FOO})    # prints "FOO = ON"
SET( A $ENV{FOO} )
MESSAGE(A = ${A})
IF(A)
 MESSAGE("FOO is set")
ELSE(A)
 MESSAGE("FOO is not set")
ENDIF(A)

EXECUTE_PROCESS( COMMAND bash -c 'echo EDITOR=$EDITOR' )
EXECUTE_PROCESS( COMMAND bash -c 'echo FOO=$FOO' )