From: ara.t.howard@...
Date: 2006-08-03T23:56:23+09:00
Subject: Re: How to tell when IO::popen is finished?

On Thu, 3 Aug 2006, Daniel N wrote:

>> I'm using Gnuplot the open method is

<snip>

this works fine on my box:

     harp:~ > cat a.rb
     require 'rubygems'
     require 'gnuplot'

     PNG = ARGV.shift || 'test.png'

     def Gnuplot.open( persist=true )
       cmd = Gnuplot.gnuplot( persist ) or raise 'gnuplot not found'
       IO::popen( cmd, "w") { |io| yield io }
     end


     def make_chart( )
     Gnuplot.open() do |gp|
       Gnuplot::Plot.new(gp) do |plot|
         plot.terminal  "png"
         plot.output  PNG

         plot.title  "Array Plot Example"
         plot.ylabel "x"
         plot.xlabel "x^2"

         x = (0..200).collect { |v| v.to_f }
         y = x.collect { |v| v ** 2 }

         plot.data << Gnuplot::DataSet.new( [x, y] ) do |ds|
           ds.with = "lines"
           ds.notitle
           ds.linewidth = 6

         end
       end

     end
     end

     make_chart

     p File.stat(PNG)

     # works if you have image magick installed
     system "display #{ PNG }"


     harp:~ > ruby a.rb
     #<File::Stat dev=0x306, ino=33786, mode=0100664, nlink=1, uid=447, gid=447, rdev=0x51e1, size=3583, blksize=4096, blocks=8, atime=Thu Aug 03 08:53:07 MDT 2006, mtime=Thu Aug 03 08:53:50 MDT 2006, ctime=Thu Aug 03 08:53:50 MDT 2006>


i think your issue was '/test2.png' - unless you're root i doubt you can open
that file.

regards.

-a
-- 
we can never obtain peace in the outer world until we make peace with
ourselves.
- h.h. the 14th dali lama