--- Pads str to length len with char from right
string.lpad = function(str, len, char)
    if char == nil then char = ' ' end
    return str .. string.rep(char, len - #str)
end

--- Pads str to length len with char from right
function str_lpad(str, len, char)
    if char == nil then char = ' ' end
    while #str < len do str = str ..char end
    return str
end

str_lpad - pad string to the left

Lua