Edit signs

[xoft]

Usually you need to do something like this:

-- World is the cWorld of the sign, X, Y, Z are the sign's coords
World:DoWithBlockEntityAt(X, Y, Z,
  function (a_CBBlockEntity)
    local BlockType = a_CBBlockEntity:GetBlockType()
    if ((BlockType == E_BLOCK_WALLSIGN) or (BlockType == E_BLOCK_SIGNPOST)) then
      local Sign = tolua.cast(a_CBBlockEntity, "cSignEntity")
      Sign:SetLines("line1", "line2", "line3", "line4")
    end
  end
)

Note that I wrote this code off of my head, might not work