NAME
	9lua
SYNOPSIS
	
DESCRIPTION
	fd = p9.open(file [,mode])
	mode: "r", "w", "rw", "wr", the default "r"

	p9.read(fd [,size])
	size: integer (>0).
	if size is nil then read all data
	if size is given, p9.read() behaved sane as Plan9 read()

	p9.write(fd,data)
	data: string value (no default)

	p9.seek(fd,offset [,how])
	offset:	integer. the default is 0
	how: "set","cur","end". the default is "set"

	p9.close(fd)
	same as Plan9 close()

	p9.bind(name,old [,flag])
	same ad Plan9 command bind
	flag is "a","b","c"

	p9.unmount([name,] old)
	name may be absent, then old is assumed
	same ad Plan9 command unmount

	p9.dirstat(path)
	same as Plan9 dirstat()

	p9.dirwstat(path,dir)
	dir is a Lua table with mode, mtime, uid, gid
	for example dir={mode="755", gid="glenda"}

	p9.mkdir(path [,mode])
	mode default is "777". note that created dir mode follows the mode of parent dir.

	p9.readdir(path [,flag]) -- returns table
	flag is true or nil, the default is nil
	if nil, the returnd table contains only true or false for each name,
	which denotes dir or not.
	if true, the returnd table contains dir attributes for the names

	p9.bit(n,op,m)
	n,m is a number
	op is "&", "|", "^", "<<", ">>"
	NB: now Lua support bit wise operation. p9.bit is obolete.
	
	p9.popen(prog)
	prog is rc command list. the usage example is
		f = p9.popen("ps")
		s = p9.read(f)
		p9.close(f)
		print(s)

	p9.fork()  -- returns pid
	the usage example is
		pid = p9.fork()
		if pid > 0 then -- parent
			print("I am parent. My child is "..pid)
			print("waiting child to finish")
			s = p9.wait(pid)
			print("msg="..s)
		else
			print("I am child. I don't know my parent")
			p9.sleep(3)
		end		

	p9.wait(pid)

	p9.alarm(timeout [,killflag])
	I wander this is useful without notify? maybe obsoleted.
	execute with alarm timeout is much useful.

	p9.sleep(time)
	time in unit of second