From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-10-22T00:02:04+09:00
Subject: Re: gnuplot on ruby

On Fri, 21 Oct 2005, gordon.j.miller@gmail.com wrote:

> Ara.T.Howard wrote:
>> On Fri, 21 Oct 2005, soxinbox wrote:
>>
>>> I installed gnuplot gem, and I am getting some syntax errors when I try to
>>> run the samples on the projects web page.
>>>
>>>> ruby test.rb
>>> c:/programs/ruby/lib/ruby/gems/1.8/gems/gnuplot-2.1/lib/gnuplot.rb:20:in
>>> `popen': No such file or directory - which gnuplot (Errno::ENOENT)
>>> from
>>
>> it looks like the code must do
>>
>>    IO::popen `which gnuplot`
>>
>> so either
>>
>>    - gnuplot is not on your system
>>
>>    - gnuplot is not in your path
>>
>> can you verify both of these?  from the shell do
>>
>>    ~:> which -a gnuplot
>>
>
> Ara is completely correct with his diagnosis.  You have two choices, either
> ensure that gnuplot is in your path or hardcode the path in the gnuplot.rb
> file.  I've struggled for a number of years on how to improvie this but
> haven't been able to come up with something better that satisfies my sense
> of right and wrong.  Suggestions would be appreciated.

maybe somthing like (un-tested):

   def which bin
     path = ENV['PATH'] # || ENV['WHAT_EVER_WINDOWS_PATH_VAR_IS']
     path.split(File::PATH_SEPARATOR).each do |dir|
       candidate = File::join dir, bin
       return candidate if File::executable? candidate
     end
     return nil
   end

   gnuplot = ENV['RB_GNUPLOT'] || 'gnuplot'

   gnuplot = which gnuplot or raise 'gnuplot is not in your path'

or, if windows isn't a concern

   gnuplot = `which gnuplot`

   raise 'gnuplot not in your path' unless $? == 0

   IO::popen gnuplot


thanks for the good work on gnuplot btw - i've used in many times.

cheers.

-a
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