It sounds like @Craige_Hales might be right then in that your variable rp might already have that log info. Try running this:
names default to here(1);
RP = Run Program(
Executable(
exefilepathRoot || "CommonalityEngine\PyScript\get_data_from_cache.exe"
),
Options( Char( CAEngine_Main:ConfigFileName ) ),
ReadFunction( "text" )
);
New Window("Output", text box(RP));
Or, here is an example anyone on windows can run:
names default to here(1);
rp = Run Program(
Executable( "cmd.exe" ),
Options( {"/c", "TaskList\!n"} ),
Read Function( "text" ) // returns all text
);
New Window("Output", text box(rp));