[CMake] execute_process spew test

[luxInteg]

Greetings

I tried an execute_process that  spits out a file. Llets call this  
${someDirectory}/someFile.

I then tried   to do a test like so 
  if( ${someDirectory}/someFile 1 )
  --- do something
endif( ${someDirectory}/someFile 1 )

but it does not seem to work

in  shell scripts{linux}   we can use   the following:-
 if  [-f  ${someDirectory}/someFile ] ;  do somehing
 or 
 if  [-r ${someDirectory}/someFile ];   do something else

advice on their equivalent in cmake scripts would be appreciated.

luxInteg