Read Only Tables

local blockTables = {getfenv()}
--local blockTables = {_G,getfenv()} --blocks _G even in a sub program

local FakeToRealTableMap = {} --shadowTable: fake --> orig mapping
local RealToFakeTableMap = {} --reverse

local tEnv

local ErrorOnIndex = function( tableToIndex,key,value )
  error(
    string.format( "attempt to %s global %s %q%s",
      FakeToRealTableMap[ tableToIndex ] and FakeToRealTableMap[ tableToIndex ][ key ] ~= nil and "change" or "create",
      type( FakeToRealTableMap[ tableToIndex ] and FakeToRealTableMap[ tableToIndex ][ key ] or value ),
      key or "Unknown",tableToIndex==_G and " in _G" or ( tableToIndex==getfenv(  ) or tableToIndex==tEnv ) and " in the current environment" or ""
     ),
  2 )
end
local writeBlockingMetatable
local createNewBlockedTable = function(  ) return setmetatable( {},writeBlockingMetatable ) end
local localType = type
local blockingIndex = function( tableToIndex,key )
  if localType( FakeToRealTableMap[ tableToIndex ][ key ] ) == "table" then
    if RealToFakeTableMap[ FakeToRealTableMap[ tableToIndex ][ key ] ] then
      return RealToFakeTableMap[ FakeToRealTableMap[ tableToIndex ][ key ] ]
    else
      local newBlockedTable = createNewBlockedTable(  )
      FakeToRealTableMap[ newBlockedTable ] = FakeToRealTableMap[ tableToIndex ][ key ]
      RealToFakeTableMap[ FakeToRealTableMap[ tableToIndex ][ key ] ] = newBlockedTable
      return newBlockedTable
    end
  else
    return FakeToRealTableMap[ tableToIndex ][ key ]
  end
end
writeBlockingMetatable = {__index=blockingIndex,__newindex=ErrorOnIndex,__metatable="Allready used"}

local args = {...}

local localPairs=pairs
local localRawset = rawset
local localGetmetatable = getmetatable
local localSetmetatable = setmetatable
local localNext = _G.next
_G.setmetatable = function( ... ) return select( 2,pcall( localSetmetatable,... ) ) end

if #args > 0 then
local env = {shell=shell,multishell=multishell}
setmetatable( env,{__index=_G} )
tEnv = createNewBlockedTable(  )
FakeToRealTableMap[ tEnv ] = env
RealToFakeTableMap[ env ] = tEnv
os.run( tEnv,shell.resolveProgram( args[ 1 ] ),unpack( args,2 ) )
_G.setmetatable = localSetmetatable
return
end

_G.next = function( tableToIndex,key )
  if FakeToRealTableMap[ tableToIndex ] then
    return localNext( FakeToRealTableMap[ tableToIndex ],key )
  else
    return localNext( tableToIndex,key )
  end
end
_G.pairs = function( tableToIndex ) return _G.next,tableToIndex,nil end

local CopyOfTable
for taskNumber,oTable in localPairs( blockTables ) do
  CopyOfTable = {}
  for i,j in localPairs( oTable ) do
    CopyOfTable[ i ] = j
  end
  FakeToRealTableMap[ oTable ]= CopyOfTable
  RealToFakeTableMap[ CopyOfTable ] = oTable
  local oldMeta = localGetmetatable( oTable )
  if oldMeta and type( oldMeta.__index ) == "table" then
    setmetatable( CopyOfTable,FakeToRealTableMap[ oldMeta.__index ] and rawset( oldMeta,"__index",FakeToRealTableMap[ oldMeta.__index ] ) or oldMeta )
  end
  setmetatable( oTable,writeBlockingMetatable )
  for i in localPairs( CopyOfTable ) do
localRawset( oTable,i,nil )
  end
end