diff --git a/rnsh/process.py b/rnsh/process.py
index 8fe5a51..edd6836 100644
--- a/rnsh/process.py
+++ b/rnsh/process.py
@@ -4,14 +4,10 @@ import functools
 import signal
 import struct
 import threading
-import time
 import tty
 import pty
-import io
 import os
 import asyncio
-import subprocess
-import typing
 import sys
 
 import logging as __logging
@@ -22,37 +18,33 @@ import termios
 
 module_logger = __logging.getLogger(__name__)
 
-# _tattrs: dict[int, list] = {}
-# # _fl: dict[int, int] = {}
-#
-# def tty_set_now(fd: int):
-#     global _tattrs
-#     # fl = fcntl.fcntl(fd, fcntl.F_GETFL)
-#     # module_logger.debug(f"fl {fd} {fl:032b} {fl}")
-#     _tattrs[fd] = termios.tcgetattr(fd)
-#     # _fl[fd] = fl
-#     # termios.tcsetattr(fd, termios.TCSANOW, termios.)
-#     # tty.setcbreak(fd, termios.TCSANOW)
-#     # tty.setraw(fd)
-#     # fcntl.fcntl(fd, fcntl.F_SETFL, fl & ~(termios.TCSADRAIN | termios.TCSAFLUSH))
-#     # module_logger.debug(f"fl {fd} {fl:032b} {fl}")
-#
-# def tty_reset(fd: int):
-#     global _tattrs
-#     tattr = _tattrs.get(fd)
-#     if tattr is not None:
-#         termios.tcsetattr(fd, termios.TCSANOW, tattr)
-#
-#     # fl = _fl.get(fd)
-#     # if fl is not None:
-#     #     fcntl.fcntl(fd, fcntl.F_SETFL, fl)
+def tty_add_reader_callback(fd: int, callback: callable, loop: asyncio.AbstractEventLoop | None = None):
+    """
+    Add an async reader callback for a tty file descriptor.
 
-def tty_set_callback(fd: int, callback: callable, loop: asyncio.AbstractEventLoop | None = None):
+    Example usage:
+
+        def reader():
+            data = tty_read(fd)
+            # do something with data
+
+        tty_add_reader_callback(self._si, reader, self._loop)
+
+    :param fd: file descriptor
+    :param callback: callback function
+    :param loop: asyncio event loop to which the reader should be added. If None, use the currently-running loop.
+    """
     if loop is None:
         loop = asyncio.get_running_loop()
     loop.add_reader(fd, callback)
 
 def tty_read(fd: int) -> bytes | None:
+    """
+    Read available bytes from a tty file descriptor. When used in a callback added to a file descriptor using
+    tty_add_reader_callback(...), this function creates a solution for non-blocking reads from ttys.
+    :param fd: tty file descriptor
+    :return: bytes read
+    """
     if fd_is_closed(fd):
         return None
 
@@ -76,12 +68,22 @@ def tty_read(fd: int) -> bytes | None:
     return result
 
 def fd_is_closed(fd: int) -> bool:
+    """
+    Check if file descriptor is closed
+    :param fd: file descriptor
+    :return: True if file descriptor is closed
+    """
     try:
         fcntl.fcntl(fd, fcntl.F_GETFL) < 0
     except OSError as ose:
         return ose.errno == errno.EBADF
 
-def tty_unset_callbacks(fd: int, loop: asyncio.AbstractEventLoop | None = None):
+def tty_unset_reader_callbacks(fd: int, loop: asyncio.AbstractEventLoop | None = None):
+    """
+    Remove async reader callbacks for file descriptor.
+    :param fd: file descriptor
+    :param loop: asyncio event loop from which to remove callbacks
+    """
     try:
         if loop is None:
             loop = asyncio.get_running_loop()
@@ -89,17 +91,34 @@ def tty_unset_callbacks(fd: int, loop: asyncio.AbstractEventLoop | None = None):
     except:
         pass
 
-def tty_get_size(fd: int) -> [int, int, int ,int]:
+def tty_get_winsize(fd: int) -> [int, int, int , int]:
+    """
+    Ge the window size of a tty.
+    :param fd: file descriptor of tty
+    :return: (rows, cols, h_pixels, v_pixels)
+    """
     packed = fcntl.ioctl(fd, termios.TIOCGWINSZ, struct.pack('HHHH', 0, 0, 0, 0))
     rows, cols, h_pixels, v_pixels = struct.unpack('HHHH', packed)
     return rows, cols, h_pixels, v_pixels
 
-def tty_set_size(fd: int, rows: int, cols: int, h_pixels: int, v_pixels: int):
+def tty_set_winsize(fd: int, rows: int, cols: int, h_pixels: int, v_pixels: int):
+    """
+    Set the window size on a tty.
+    :param fd: file descriptor of tty
+    :param rows: number of visible rows
+    :param cols: number of visible columns
+    :param h_pixels: number of visible horizontal pixels
+    :param v_pixels: number of visible vertical pixels
+    """
     packed = struct.pack('HHHH', rows, cols, h_pixels, v_pixels)
     fcntl.ioctl(fd, termios.TIOCSWINSZ, packed)
 
-def process_exists(pid):
-    """ Check For the existence of a unix pid. """
+def process_exists(pid) -> bool:
+    """
+    Check For the existence of a unix pid.
+    :param pid: process id to check
+    :return: True if process exists
+    """
     try:
         os.kill(pid, 0)
     except OSError:
@@ -109,37 +128,61 @@ def process_exists(pid):
 
 class TtyRestorer:
     def __init__(self, fd: int):
+        """
+        Saves termios attributes for a tty for later restoration
+        :param fd: file descriptor of tty
+        """
         self._fd = fd
         self._tattr = termios.tcgetattr(self._fd)
 
     def raw(self):
+        """
+        Set raw mode on tty
+        """
         tty.setraw(self._fd, termios.TCSADRAIN)
 
     def restore(self):
+        """
+        Restore termios settings to state captured in constructor.
+        """
         termios.tcsetattr(self._fd, termios.TCSADRAIN, self._tattr)
 
 class CallbackSubprocess:
-
+    # time between checks of child process
     PROCESS_POLL_TIME: float = 0.1
 
-    def __init__(self, command: [str], term: str, loop: asyncio.AbstractEventLoop, stdout_callback: callable,
-                terminated_callback: callable):
-
+    def __init__(self, argv: [str], term: str | None, loop: asyncio.AbstractEventLoop, stdout_callback: callable,
+                 terminated_callback: callable):
+        """
+        Fork a child process and generate callbacks with output from the process.
+        :param argv: the command line, tokenized. The first element must be the absolute path to an executable file.
+        :param term: the value that should be set for TERM. If None, the value from the parent process will be used
+        :param loop: the asyncio event loop to use
+        :param stdout_callback: callback for data, e.g. def callback(data:bytes) -> None
+        :param terminated_callback: callback for termination/return code, e.g. def callback(return_code:int) -> None
+        """
         assert loop is not None, "loop should not be None"
         assert stdout_callback is not None, "stdout_callback should not be None"
         assert terminated_callback is not None, "terminated_callback should not be None"
 
         self.log = module_logger.getChild(self.__class__.__name__)
-        self.log.debug(f"__init__({command},{term},...")
-        self._command = command
+        self.log.debug(f"__init__({argv},{term},...")
+        self._command = argv
         self._term = term
         self._loop = loop
         self._stdout_cb = stdout_callback
         self._terminated_cb = terminated_callback
         self._pid: int | None = None
 
-    def terminate(self):
+    def terminate(self, kill_delay: float = 1.0):
+        """
+        Terminate child process if running
+        :param kill_delay: if after kill_delay seconds the child process has not exited, escalate to SIGHUP and SIGKILL
+        """
         self.log.debug("terminate()")
+        if not self.running:
+            return
+
         try:
             os.kill(self._pid, signal.SIGTERM)
         except:
@@ -164,28 +207,65 @@ class CallbackSubprocess:
 
     @property
     def started(self) -> bool:
+        """
+        :return: True if child process has been started
+        """
         return self._pid is not None
 
     @property
     def running(self) -> bool:
+        """
+        :return: True if child process is still running
+        """
         return self._pid is not None and process_exists(self._pid)
 
     def write(self, data: bytes):
+        """
+        Write bytes to the stdin of the child process.
+        :param data: bytes to write
+        """
         self.log.debug(f"write({data})")
         os.write(self._si, data)
 
-    def set_winsize(self, r: int, c: int, h: int, w: int):
-        self.log.debug(f"set_winsize({r},{c},{h},{w}")
-        tty_set_size(self._si, r, c, h, w)
+    def set_winsize(self, r: int, c: int, h: int, v: int):
+        """
+        Set the window size on the tty of the child process.
+        :param r: rows visible
+        :param c: columns visible
+        :param h: horizontal pixels visible
+        :param v: vertical pixels visible
+        :return:
+        """
+        self.log.debug(f"set_winsize({r},{c},{h},{v}")
+        tty_set_winsize(self._si, r, c, h, v)
 
     def copy_winsize(self, fromfd:int):
-        r,c,h,w = tty_get_size(fromfd)
-        self.set_winsize(r,c,w,h)
+        """
+        Copy window size from one tty to another.
+        :param fromfd: source tty file descriptor
+        """
+        r,c,h,v = tty_get_winsize(fromfd)
+        self.set_winsize(r,c,h,v)
 
-    # def tcsetattr(self, val: list[int | list[int | bytes]]):
-    #     termios.tcsetattr(self._si, termios.TCSANOW, val)
+    def tcsetattr(self, when: int, attr: list[int | list[int | bytes]]):
+        """
+        Set tty attributes.
+        :param when: when to apply change: termios.TCSANOW or termios.TCSADRAIN or termios.TCSAFLUSH
+        :param attr: attributes to set
+        """
+        termios.tcsetattr(self._si, when, attr)
+
+    def tcgetattr(self) -> list[int | list[int | bytes]]:
+        """
+        Get tty attributes.
+        :return: tty attributes value
+        """
+        return termios.tcgetattr(self._si)
 
     def start(self):
+        """
+        Start the child process.
+        """
         self.log.debug("start()")
         parentenv = os.environ.copy()
         env = {"HOME": parentenv["HOME"],
@@ -224,14 +304,18 @@ class CallbackSubprocess:
             except:
                 pass
 
-        tty_set_callback(self._si, functools.partial(reader, self._si, self._stdout_cb), self._loop)
+        tty_add_reader_callback(self._si, functools.partial(reader, self._si, self._stdout_cb), self._loop)
 
 async def main():
+    """
+    A test driver for the CallbackProcess class.
+    python ./process.py /bin/zsh --login
+    """
     import testlogging
 
     log = module_logger.getChild("main")
     if len(sys.argv) <= 1:
-        print("no cmd")
+        print(f"Usage: {sys.argv} <absolute_path_to_child_executable> [child_arg ...]")
         exit(1)
 
     loop = asyncio.get_event_loop()
@@ -252,7 +336,6 @@ async def main():
     def sigint_handler(signal, frame):
         # log.debug("KeyboardInterrupt")
         if process is None or process.started and not process.running:
-            tr.restore()
             raise KeyboardInterrupt
         elif process.running:
             process.write("\x03".encode("utf-8"))
@@ -271,7 +354,7 @@ async def main():
             process.write(data)
             # sys.stdout.buffer.write(data)
 
-    tty_set_callback(sys.stdin.fileno(), stdin)
+    tty_add_reader_callback(sys.stdin.fileno(), stdin)
     process.start()
     # process.tcsetattr(termios.tcgetattr(sys.stdin))
 
@@ -285,5 +368,5 @@ if __name__ == "__main__":
         tr.raw()
         asyncio.run(main())
     finally:
-        tty_unset_callbacks(sys.stdin.fileno())
+        tty_unset_reader_callbacks(sys.stdin.fileno())
         tr.restore()
\ No newline at end of file