do -- so local works
 -- task format:
 -- {
 --  ["n"] = "name",
 --  ["c"] = coroutine of task,
 --  ["e"] = { table, of, environment, variables },
 --  ["p"] = parent pid,
 --  ["u"] = user ID,
 --  ["ep"]= event queue pointer
 -- }
 local tT,nP,rg,eq,p = {},1,_G,{},1 -- taskTable,nextPid,real _G,event queue
 _G.cT,sbt,C,T,io = 0,{},coroutine,table,io -- currentTask,sandboxTable
 function _G.spawn(n,f,e)
  tT[nP] = {}
  local function nf()
   log(xpcall(f))
  end
  tT[nP].c = coroutine.create(nf)
  tT[nP].n = n
  tT[nP].p = cT or -1
  if tT[cT] then
   tT[nP].u,tT[nP].ep,tT[nP].e = tT[cT].u,tT[cT].ep,e or tT[cT].e or {["PWD"]="/boot",["PATH"]="/boot/exec:."}
  else
   tT[nP].u,tT[nP].ep,tT[nP].e = "superuser",1,{["PWD"]="/boot",["PATH"]="/boot/exec:."}
  end
  nP = nP + 1
  return nP-1
 end
 function _G.sched()
  _G.sched = nil
  while #tT > 0 do
   eq[#eq+1]={computer.pullSignal(p)} -- add the latest event to the eq
   if #eq > 16 then
    table.remove(eq,1) -- remove the earliest if the eq is full
    for pid,proc in pairs(tT) do
     if proc.ep > 1 then
      proc.ep = proc.ep - 1 -- decrement pointers for tasks to keep them on the same ones
     end
    end
   end
   for pid,proc in pairs(tT) do
    if coroutine.status(proc.c) == "dead" then
     tT[pid] = nil
    else
     cT=pid
     for i = 1,tT[pid].ep, #eq do
      _G.ev = eq[#eq] -- make an ev for MultICE compat
      coroutine.resume(proc.c)
     end
    end
   end
  end
 end
 _G.event = {}
 function event.get() -- get the next event in the queue, or nil
  if eq[tT[cT].ep] then
   tT[cT].ep = tT[cT].ep + 1
   if tT[cT].ep > 17 then
    tT[cT].ep = 17
   end
   return eq[tT[cT].ep - 1]
  end
 end
 function event.pull(t,time) -- return or wait for the next event, optionally with the first param matching t
  time = time or math.huge
  time = time + computer.uptime()
  while computer.uptime() < time do
   local e = event.get()
   if e then
    if t then
     if e[1] == t then
      return table.unpack(e)
     end
    else
     return table.unpack(e)
    end
   end
   coroutine.yield()
  end
 end
 event.push = computer.pushSignal
 function os.getenv(k) -- gets an envionment variable from tT[cT].e
  if tT[cT] then
   return tT[cT].e[k]
  end
 end
 function os.setenv(k,v) -- sets "
  if tT[cT] then
   tT[cT].e[k] = v
  end
 end
 function os.tasks() -- returns a table of tasks running on the system
  local t = {}
  for k,v in pairs(tT) do
   t[k] = v.n
  end
  return t
 end
 function os.taskinfo(pid) -- returns info on a task
  if tT[pid] then
   return tT[pid].n,tT[pid].p,tT[pid].u
  end
 end
 function os.genenv()
  local et = {}
  setmetatable(et,{__index=_G})
  return et
 end
 -- user stuff from here
 local ut = {}
 local function flushut()
  local f = fs.open("/boot/sys/users.dat","wb")
  if f then
   for k,v in pairs(ut) do
    fs.write(f,k.."\t"..v[1].."\t"..v[2].."\n")
   end
   fs.close(f)
   return true
  end
  return false
 end
 function os.readut()
  local f=fs.open("/boot/sys/users.dat","rb")
  if not f then return false end
  local C=fs.readall(f)
  fs.close(f)
  log(C)
  for line in C:gmatch("[^\n]+") do
   local username,hpass,salt = line:match("(.+)\t(.+)\t(.+)")
   if username and hpass and salt then
    ut[username] = {hpass,salt}
    log(username,hpass,salt)
   end
  end
 end
 function os.setuid(user)
  if tT[cT].u == "superuser" and ut[user] then
   tT[cT].u = user
   return true
  end
  return false
 end
 function os.getuid(pid)
  pid = pid or cT
  return tT[pid].u
 end
 function os.users()
  local t = {}
  for k,v in pairs(ut) do
   t[#t+1] = k
  end
  return t
 end
 function os.verifyuser(username,pass)
  if sha then
   if ut[username] then
    if sha.sha256(pass..ut[username][2]) == ut[username][1] then
     return true
    end
   end
   return false
  end
  return true
 end
 function os.gensalt(len)
  local S = ""
  for i = 1, len do
   S=S..string.char(math.random(32,126))
  end
  return S
 end
 function os.setuser(username,hpass,salt,...)
  if tT[cT].u == "superuser" then
   if hpass == nil then
    ut[username] = nil
   else
    ut[username] = {hpass, salt,...}
    flushut()
   end
  end
 end
 function os.su(user,pass)
  if os.verifyuser(user,pass) then
   log(tT[cT].u .. " su'd to "..user,6,1,true)
   tT[cT].u = user
   return true
  end
  return false
 end
 spawn("read users",os.readut)
end