You can do this in Lua with something like:
local mypds = pds.create()
pds.putString ( mypds, "directory", "/tmp")
pds.putString ( mypds, "file", "file.txt" )
pds.putInt ( mypds, "buffer_size", 10240000 )
output,return_status = nimbus.request ( "/domain/hub/robot/controller", "text_file_get", mypds )
print( output["file_content"] )
Make the obvious adjustments for your environment.
Garin