There is a problem that often seems to happen to people when starting to use Lua scripting, which is that they run foul of the Lua "sandbox" which is a default set of restrictions placed on Lua scripts by MUSHclient.
The problem is that the original sandbox set various functions (like io.open, os.execute) to nil, and then attempts to use them were met with a confusing error message, like "attempt to index global 'io' (a nil value)".
Version 3.83 of MUSHclient changes this behaviour to replace such functions with a special "error" function that simply reports that the original function was disabled, like this:
To retrofit this functionality into existing MUSHclient installations, edit the Lua sandbox (in File -> Global Preferences) and change from:
... to read like this instead:
The problem is that the original sandbox set various functions (like io.open, os.execute) to nil, and then attempts to use them were met with a confusing error message, like "attempt to index global 'io' (a nil value)".
Version 3.83 of MUSHclient changes this behaviour to replace such functions with a special "error" function that simply reports that the original function was disabled, like this:
Function 'io.open' disabled in Lua sandbox - see MUSHclient global preferences
To retrofit this functionality into existing MUSHclient installations, edit the Lua sandbox (in File -> Global Preferences) and change from:
function MakeSandbox ()
---> down to ---->
end -- end of function MakeSandbox
... to read like this instead:
function MakeSandbox ()
local function ReportDisabled (pkg, func)
return function ()
error (string.format (
"Function '%s.%s' disabled in Lua sandbox - see MUSHclient global preferences",
pkg, func), 2)
end -- function
end -- ReportDisabled
package.loadlib = ReportDisabled ("package", "loadlib") -- disable loadlib function
package.loaders [3] = nil -- disable DLL loader
package.loaders [4] = nil -- disable all-in-one loader
for k, v in pairs (io) do
if type (v) == "function" then
io [k] = ReportDisabled ("io", k)
end -- type is function
end -- for
local orig_os = os -- so we know names of disabled ones
-- replace 'os' table with one containing only safe functions
os = {
date = os.date,
time = os.time,
setlocale = os.setlocale,
clock = os.clock,
difftime = os.difftime,
}
for k, v in pairs (orig_os) do
if not os [k] and type (v) == "function" then
os [k] = ReportDisabled ("os", k)
end -- not still active
end -- for
if warn_if_not_trusted then
ColourNote ("yellow", "black",
"Lua sandbox created, some functions disabled.")
end -- if warn_if_not_trusted
end -- end of function MakeSandbox