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CentOS 7.0 - man page for rrdlua (centos section 1)

RRDLUA(1)				     rrdtool					RRDLUA(1)

NAME
       RRDLua -  Lua binding for RRDTool

SYNOPSIS
	 require 'rrd'
	 rrd.create(...)
	 rrd.dump(...)
	 rrd.fetch(...)
	 rrd.first(...)
	 rrd.graph(...)
	 rrd.graphv(...)
	 rrd.info(...)
	 rrd.last(...)
	 rrd.resize(...)
	 rrd.restore(...)
	 rrd.tune(...)
	 rrd.update(...)
	 rrd.updatev(...)

DESCRIPTION
   Calling Sequence
       This module accesses RRDtool functionality directly from within Lua.  The arguments to the
       functions listed in the SYNOPSIS are explained in the regular RRDtool documentation. The
       command-line call

	   rrdtool update mydemo.rrd --template in:out N:12:13

       gets turned into

	   rrd.update ("mydemo.rrd", "--template", "in:out", "N:12:13")

       Note that --template=in:out is also valid.

   Using with Lua 5.1
       Start your programs with:

	   ---------------------------------------------------------------
	   package.cpath = '/usr/local/rrdtool-1.3.2/lib/lua/5.1/?.so;' ..
			   package.cpath
	   require 'rrd'
	   ---------------------------------------------------------------

       OBS: If you configured with --enable-lua-site-install, you don't need to set package.cpath
       like above.

   Using with Lua 5.0
       The Lua binding for RRDtool needs the Lua module compat-5.1 to work with Lua 5.0. Some
       Linux distros, like Ubuntu gutsy and hardy, have it already integrated in Lua 5.0 -dev
       packages, so you just have to require it:

	   require 'compat-5.1'

       For other platforms, the compat-5.1 module that comes with this binding will be installed
       for you in the same dir where RRDtool was installed, under the subdir .../lib/lua/5.0. In
       this case, you must tell your Lua programs where to find it by changing the Lua var
       LUA_PATH:

	   -- compat-5.1.lua is only necessary for Lua 5.0 ----------------
	   -- try only compat-5.1 installed with RRDtool package
	   local original_LUA_PATH = LUA_PATH
	   LUA_PATH = '/usr/local/rrdtool-1.3.2/lib/lua/5.0/?.lua'
	   require 'compat-5.1'
	   LUA_PATH = original_LUA_PATH
	   original_LUA_PATH = nil
	   --- end of code to require compat-5.1 ---------------------------

	   Now we can require the rrd module in the same way we did for 5.1 above:

	   ---------------------------------------------------------------
	   package.cpath = '/usr/local/rrdtool-1.3.2/lib/lua/5.0/?.so;' ..
			   package.cpath
	   require 'rrd'
	   ---------------------------------------------------------------

   Error Handling
       The Lua RRDTool module functions will abort your program with a stack traceback when they
       can not make sense out of the arguments you fed them.  However, you can capture and handle
       the errors yourself, instead of just letting the program abort, by calling the module
       functions through Lua protected calls - 'pcall' or 'xpcall'.

	    Ex: program t.lua

	    --- compat-5.1.lua is only necessary for Lua 5.0 ----------------
	    -- uncomment below if your distro has not compat-5.1
	    -- original_LUA_PATH = LUA_PATH
	    -- try only compat-5.1.lua installed with RRDtool package
	    -- LUA_PATH = '/usr/local/rrdtool-1.3.2/lib/lua/5.0/?.lua'

	    -- here we use a protected call to require compat-5.1
	    local r = pcall(require, 'compat-5.1')
	    if not r then
	      print('** could not load compat-5.1.lua')
	      os.exit(1)
	    end

	    -- uncomment below if your distro has not compat-5.1
	    -- LUA_PATH = original_LUA_PATH
	    -- original_LUA_PATH = nil
	    --- end of code to require compat-5.1 ---------------------------

	    -- If the Lua RRDTool module was installed together with RRDTool,
	    -- in /usr/local/rrdtool-1.3.2/lib/lua/5.0, package.cpath must be
	    -- set accordingly so that 'require' can find the module:

	    package.cpath = '/usr/local/rrdtool-1.3.2/lib/lua/5.0/?.so;' ..
			    package.cpath

	    local rrd = require 'rrd'
	    rrd.update ("mydemo.rrd","N:12:13")

       If we execute the program above we'll get:

	    $ lua t.lua

	    lua: t.lua:27: opening 'mydemo.rrd': No such file or directory
	    stack traceback:
		  [C]: in function `update'
		  t.lua:27: in main chunk
		  [C]: ?

   Return Values
       The functions rrd.first, rrd.last, rrd.graph, rrd.info and rrd.fetch return their
       findings.

       rrd.first returns a single INTEGER representing the timestamp of the first data sample in
       an RRA within an RRD file. Example returning the first timestamp of the third RRA (index
       2):

	    local firstdate = rrd.first('example.rrd', '--rraindex', 2)

       rrd.last returns a single INTEGER representing the last update time.

	    local lastupdate = rrd.last('example.rrd')

       rrd.graph returns the x-size and y-size of the created image and a table with the results
       of the PRINT arguments.

	    local xsize, ysize, averages = rrd.graph ...
	    print(string.format("Image size: %dx%d", xsize, ysize)
	    print("Averages: ", table.concat(averages, ', '))

       rrd.info returns a table where the keys and the values represent property names and
       property values of the RRD.

	    local info = rrd.info("test.rrd")
	    for key, value in pairs(info) do
	      print(key, ' = ', value)
	    end

       rrd.graphv takes the same parameters as rrd.graph but it returns a table only. The table
       returned contains meta information about the graph, like its size as well as the position
       of the graph area on the image. When called with and empty filename, the contents of the
       graph will be returned in the table as well (key 'image').

       rrd.updatev also returns a table. The keys of the table are strings formed by the
       concatenation of timestamp, RRA index and data source name for each consolidated data
       point (CDP) written to disk as a result of the current update call. The key values are CDP
       values.

       rrd.fetch is the most complex of the pack regarding return values. It returns 5 values:
       the initial timestamp, the step, two parallel arrays containing the data source names and
       their data points respectively, and the final timestamp.

	    --require compat-5.1 if necessary

	    package.cpath = '/usr/local/rrdtool-1.3.2/lib/lua/5.0/?.so;' ..
			    package.cpath

	    local rrd = require "rrd"
	    local first, last = rrd.first("test.rrd"), rrd.last("test.rrd")
	    local start, step, names, data =
	      rrd.fetch("test.rrd", "--start", first, "--end", last, "AVERAGE")
	    io.write(string.format("Start:	 %s (%d)\n",
				   os.date("%c", start),start))
	    io.write("Step size:   ", step, " seconds\n")
	    io.write("DS names:    ", table.concat(names, ', '), "\n")
	    io.write("Data points: ", #data[1], "\n")
	    io.write("Data:\n")
	    for i,dp in ipairs(data) do
	      io.write(os.date("%t", start), " (", start, "): ")
	      start = start + step
	      for j,v in ipairs(dp) do
		io.write(v, " ")
	      end
	    io.write("\n")
	    end

AUTHOR
       Fidelis Assis <fidelis@pobox.com>

1.4.8					    2013-05-23					RRDLUA(1)


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