This is a full reference on those
 functions and fields exposed by the
 kernel to processes and libraries.

Firstly, it is important to note that
 a process runs within a coroutine.

This allows a highly "traditional"
 form of mixing async and synchronous
 code with event-loop nesting and
 such designs. If this is not to your
 taste then you can just use one, not
 nested event loop.

As it runs in a coroutine, events are
 received via coroutine.yield() -
 sandboxers beware! You may have to
 use coroutine.running() in order to
 successfully hide the implementation
 details of your sandbox (also events
 and potentially accesses headed in
 its direction...)

An example KittenOS NEO program,
 solely using kernel APIs,
 that you will likely have to kill:

neo.scheduleTimer(os.uptime() + 1)
while true do
 local ev = coroutine.yield()
 if ev == "k.timer" then
  neo.emergency("Hello...")
  neo.scheduleTimer(os.uptime() + 1)
 end
end

This will say "Hello..." via the
 neo.emergency mechanism once every
 second, independently of anything
 else on the system.

While this is obviously not a sane
 sys-init for actual use, if you have
 a disk that you can copy the kernel
 to and a copy of this, it might make
 a fun experiment.

The way to exit the program is to
 return from your process's main
 function.

The first field to note is:

_VERSION: _VERSION from the host.

The following are just wrapMeta'd
 host libraries (*: altered):

math, table, string, unicode*,
 coroutine, os*, debug

unicode is extended with:
 safeTextFormat(s, p):
  Takes a string s, and a position p,
   (the position is optional, and is
     assumed to be 1 otherwise)
   and returns a space-padded string,
    with a space after each wide char
    to make unicode.len & co. act in
    screen units, along with the
    position translated.
 undoSafeTextFormat(s):
  Takes a string in padded-widechar
   format, and gets rid of the pad.
  Note that if padding is *missing*,
   wide characters become spaces.
  This leaves a string that's usually
   safe to pass to a GPU without any
   odd graphical glitches.

os is replaced with:
 totalMemory = computer.totalMemory,
 freeMemory = computer.freeMemory,
 energy = computer.energy,
 maxEnergy = computer.maxEnergy,
 clock = os.clock, date = os.date,
 difftime = os.difftime,
 time = os.time,
 uptime = computer.uptime,
 address = computer.address

The following are just wrapMeta'd
 host functions
 (*: wrapped for security):

 assert, ipairs, load, next*,
 pairs, pcall, xpcall, select,
 type, error, tonumber, tostring,
 setmetatable, getmetatable*,
 rawset*, rawget, rawlen, rawequal

"require" and "neo" are the parts of
 the environment where a NEO-specific
 nature presents itself.

require takes a string, and returns
 the value returned by the library at
 "libs/" .. str .. ".lua" on the
 primary disk.
The library name must be a valid path
 component, and the library path must
 also be valid - see
 ensurePathComponent, ensurePath for
 more info.

The "neo" table is where most of the
 NEO-specificness is hiding, which is
 probably shown by its name.

It is also where libraries differ to
 processes, as libraries get a subset
 of the table.

For libraries, it contains:
 emergency: Equals ocemu.log, if
  available on the system. Else, NOP.
 readBufSize: The readBufSize kernel
  configuration value. Default: 2048.
  Adjusting this in the kernel allows
   adjusting how much the system will
   read at any given time, which can
   have non-obvious memory usage
   effects.
  Do note, following this limit is
   not a requirement and is not
   enforced - it's not a security
   matter, just optimization/memory.
 wrapMeta: A function that takes a
  value, and wraps it in such a way
  as to be immutable, returning the
   wrapped value.
  This is the first line of defense
   against memory use - by using this
   to protect a table, the result can
   be shared between untrusted code.
 listProcs: A function that returns a
  table of processes. Index is ipairs
  -friendly, values are:
  {pid, pkg, cpuUsageInSeconds}
 listApps: Returns an ipairs-friendly
  list of applications on the system,
  such as:
  {"app-out-of-sight-is-out-of-mind",
   "svc-i-see-the-ones-that-play"}
 listLibs: Returns an ipairs-friendly
  list of libraries on the system,
  such as:
  {"fmttext",
   "braille"}
 totalIdleTime: Returns the current
  kernel idle time total, useful for
  measuring current CPU usage, and in
  turn comparing to application CPU
  time to get various statistics.
 ensurePath: (s, root)
  Attempts to verify the
  safety of a path, and errors if any
  aspect seems incorrect.
  The root must be a prefix to the
   path, and the path must follow a
   strict standardized form that is
   guaranteed to always be supported
   and handled in the same way on any
   OC system.
  Essentially, "//" must not occur,
   and all "[^/]+" matches must be
   valid path components.
 ensurePathComponent: (s)
  Ensures that a string is a safe
   filename via a character list and
   some special filename checks.
  UTF-8 characters are just flat out
   disallowed until someone can give
   me proof they won't blow up
   something somewhere.
  (This restriction is Windows's
   fault - I can't trust the encoding
   mess to not find some new and
   imaginative way of breaking
   filenames, so I'd rather that they
   get avoided until someone can try
   actually using them.)
  This does NOT ACCOUNT for *all* the
   Windows total nonsense (aux, com1)
   because if OC doesn't cover up
   that then you're kinda doomed.
 ensureType: (v, ts)
  Checks that a value is of a given
   type, and errors otherwise. If the
   type is "table", it also errors if
   a metatable exists.

The additional things available to
 processes are those things that
 require a process to use:

 pid: A field that specifies the
  process ID of this process.
  Harmless, but not entirely useful.
 dead: Actually a field, that isn't
  set at first, but is set later to
  indicate deadness. Useful if your
  process does anything that might
  lead to functions being called in
  the afterlife, such as providing an
  API.
 executeAsync: Function that takes
  an app name (aka: pkg), and a
  set of arguments to give it.
  NOTE: sys- apps cannot be started
   from non sys- apps no matter how
   hard you try, without k.root
   alterations to runProgramPolicy.
  Your process pkg and ID is
   prepended to the arguments.
  NOTE: This uses the result, err
   return format, except for security
   errors in which case it uses a
   full error, because you might just
   ignore the return value.
  A successful result is the PID.
 executeExt: Like executeAsync, but
  firstly, synchronous, and secondly,
  with an extra first parameter that
  contains a function to call on
  events encountered during the time.
  As for the return values, it tries
   to emulate os.execute, so it
   returns -1 & reason on load error,
   and 0 & death-reason otherwise.
 execute: executeExt, but with the
  first parameter set to a blank
  function.
 requestAccessAsync: A function that
  takes an access ID (aka 'perm') as
  a string (see kn-perms for info),
  and starts a security request that
  is responded to with a
  k.securityresponse such as:
  "k.securityresponse", perm, obj
 requestAccess: A function with
  (perm, handler) as the arguments -
  runs requestAccessAsync, then sends
  events to handler (if any) while
  waiting for the response.
 requireAccess: requestAccess, but
  (perm, reason) - the reason is used
   in an error if the access cannot
   be gained.
 scheduleTimer: Given an os.uptime
  value, creates a timer and returns
  a completely meaningless table that
  is never touched by the kernel
  directly, called the "tag".
  The resulting event:
  "k.timer", tag, time, ofs
  These events are ONLY EVER sent as
   a consequence of this function,
   and this can be relied on safely.
  NOTE: Setting timers too far in the
   future has effects on system
   stability. So does using memory,
   and there's no way for me to stop
   that, either. So long as the timer
   is reached, alive or dead, things
   will work, but spamming timers has
   the consequence of memory use,
   and timers stick around after the
   process that owns them is dead.

With that, I hope I have documented
 the kernel's interface to programs.

-- This is released into
 the public domain.
-- No warranty is provided,
 implied or otherwise.