function updateFileData(objFile)
    local f = io.open(objFile, "r")
    local fileData = f:read("*all")
    f:close()
    fileData = fileData:gsub("g (%w+)", "usemtl %1")
	
	f = io.open(objFile, "w")
	f:write(fileData)
	f:close()
	--print (fileData)
	
end

-- main function body

-- get the selected mesh
local selectedRt = octane.project.getSelection()[1]
if not selectedRt or selectedRt.type ~= octane.NT_GEO_MESH then
	showError("no mesh selected")
	return nil
end
--print (selectedRt)

-- get the file path for the mesh
local objFileName = octane.node.getAttribute( selectedRt , 29 ) 

--print (objFileName )
updateFileData(objFileName)

--reload mesh
octane.node.setAttribute(selectedRt, 94, true, true)