do
 _G.fs = {}
 local dfsattr = {read = "*", write = "*"}
 local fsattr = {}
 local fT,hT = {},{["_c"]=0}
 local function parseacl(acl)
  acl = acl or ""
  local tacl = {}
  if acl == "*" then
   setmetatable(tacl,{__index = function() return true end})
  else
   for n in acl:gmatch("[^,]+") do
    tacl[n] = true
    log(n)
   end
  end
  return tacl
 end
 local function canread(fn)
  fn = fs.canonical(fn)
  if os.getuid() == "nobody" then return false end
  if os.getuid() ~= "superuser" and fsattr[fn] then
   if not parseacl(fsattr[fn].read or "")[os.getuid()] then return false end
  end
  return true
 end
 local function canwrite(fn)
  fn = fs.canonical(fn)
  if os.getuid() == "nobody" then return false end
  if os.getuid() ~= "superuser" and fsattr[fn] then
   if not parseacl(fsattr[fn].write)[os.getuid()] then return false end
  end
  return true
 end
 fs.parseacl = parseacl
 fs.canread = canread
 fs.canwrite = canwrite
 local function getattr(fn,k)
  fn = fs.canonical(fn)
  if not canread(fn) then return false end
  if fsattr[fn] then
   return fsattr[fn][k]
  else
   return dfsattr[k]
  end
 end
 local function setattr(fn,k,v)
  fn = fs.canonical(fn)
  if not canwrite(fn) then return false end
  if k:find("\t") or v:find("\t") then return false end
  log(parseacl(getattr(fn,"write"))[os.getuid()])
  if not fsattr[fn] then
   fsattr[fn] = {}
   setmetatable(fsattr[fn],{__index=dfsattr})
  end
  fsattr[fn][k] = tostring(v)
 end
 function fs.mount(mp,pr)
  fT[mp] = pr
 end
 function fs.simplify(p)
  local pt,npt,rp = {},{},""
  for P in p:gmatch("[^/]+") do
   pt[#pt+1] = P
  end
  for k,v in pairs(pt) do
   if v == ".." then
    npt[#npt] = nil
   elseif v ~= "." then
    npt[#npt+1] = v
   end
  end
  for k,v in pairs(npt) do
   rp=rp.."/"..v
  end
  if p:sub(1,1) ~= "/" then rp = rp:sub(2) end
  return rp
 end
 function fs.resolve(p)
  if p:sub(1,1) ~= "/" then -- absolute/relative path
   p=(os.getenv("PWD") or "").."/"..p
  end
  p=fs.simplify(p)
  local pt,spt = {},""
  for P in p:gmatch("[^/]+") do
   pt[#pt+1] = P
  end
  for i = 2, #pt do
   spt=spt.."/"..pt[i]
  end
  return pt, pt[1], spt
 end
 function fs.canonical(p)
  local _,d,rp = fs.resolve(p)
  return fs.simplify("/"..d.."/"..rp)
 end
 function fs.exec(fc,m,...)
  return fT[fc][m](...)
 end
 function fs.open(p,m)
  if m:sub(1,1) == "r" then
   if not canread(p) then return false end
  elseif m:sub(1,1) == "w" or m:sub(1,1) == "a" then
   if not canwrite(p) then return false end
  end
  local _,d,p = fs.resolve(p)
  local d = fT[d]
  if d then
   local f,C=d.open(p,m),hT._c
   if f then
    hT._c = C + 1
    hT[C] = {d,f}
    return C
   end
   return false
  end
 end
 function fs.close(h)
  if hT[h] then
   hT[h][1].close(hT[h][2])
  end
  return false
 end
 function fs.read(h,n)
  if hT[h] then
   return hT[h][1].read(hT[h][2],n)
  end
  return false
 end
 function fs.readall(f)
  local s=""
  while true do
   c=fs.read(f,2048)
   if not c then break end
   s=s..c
  end
  return s
 end
 function fs.write(h,d)
  if hT[h] then
   return hT[h][1].write(hT[h][2],d)
  end
  return false
 end
 function fs.list(s)
  s=s or ""
  local _,d,p = fs.resolve(s)
  if not d then
   local kt = {}
   for k,v in pairs(fT) do
    kt[#kt+1] = k
   end
   return kt
  end
  return fT[d].list(p or "/")
 end
 function fs.mkdir(s)
  local _,d,p = fs.resolve(s)
  return fT[d].makeDirectory(p or "/")
 end
 function fs.rm(s)
  local _,d,p = fs.resolve(s)
  return fT[d].remove(p)
 end
 function fs.exists(s)
  local _,d,p = fs.resolve(s)
  if d then
   return fT[d].exists(p)
  end
 end
 function fs.isdir(s)
  local _,d,p = fs.resolve(s)
  return fT[d].isDirectory(p)
 end
 local function flushattr()
  local f = fs.open("/boot/sys/fsattr.dat","wb")
  if f then
   for k,v in pairs(fsattr) do
    fs.write(f,k.."\t")
    for l,m in pairs(v) do
     fs.write(f,"\t"..l.."="..m)
    end
    fs.write(f,"\n")
   end
   fs.close(f)
   return true
  end
  return false
 end
 local function readattr()
  local f=fs.open("/boot/sys/fsattr.dat","rb")
  if not f then return false end
  local C=fs.readall(f)
  fs.close(f)
  for line in C:gmatch("[^\n]+") do
   local ifn = true
   local fn = ""
   for kv in line:gmatch("[^\t]+") do
    if ifn then
     fn = kv
     ifn = false
    else
     local k,v = kv:match("(.+)%=(.+)")
     setattr(fn,k,v)
    end
   end
  end
 end
 spawn("read fs attributes",readattr)
 function fs.getattr(fn,k)
  if fs.exists(fn) then
   return getattr(fn,k)
  end
  return false
 end
 function fs.setattr(fn,k,v)
  if fs.exists(fn) then
   local res={setattr(fn,k,v)}
   flushattr()
   return table.unpack(res)
  end
  return false
 end
end
function fs.cd(p)
 if p:sub(1,1) ~= "/" then
  p=(os.getenv("PWD") or "").."/"..p
 end
 p=fs.simplify(p)
 if fs.exists(p) and fs.isdir(p) then
  os.setenv("PWD",p)
 else
  error("non-existent/not a dir")
 end
end
function fs.cp(s,d)
 local df = fs.open(d,"wb")
 local sf = fs.open(s,"rb")
 if df and sf then
  fs.write(df,fs.readall(sf))
  fs.close(df)
  fs.close(sf)
  return true
 end
 return false
end
function fs.mv(s,d)
 fs.cp(s,d)
 fs.rm(s)
end
function loadfile(fn)
 local f=io.open(fn,"rb")
 if not f then return false, "cannot read file" end
 local S=f:read("*a")
 f:close()
 return load(S,"=("..fn..")","bt",os.genenv())
end
function run(fn,...)
 local lf = loadfile(fn)
 if not lf then return false, "cannot load file" end
 local r = {pcall(lf,...)}
 if r[1] == true then
  table.remove(r,1)
 end
 print(table.unpack(r))
end
function srun(fn,...)
 local lf = loadfile(fn)
 if not lf then return false, "cannot load file" end
 spawn(fn,log(pcall(lf,...)))
end