From: Rob Biedenharn <Rob@...>
Date: 2009-12-30T07:23:22+09:00
Subject: Re: awk print $4 in ruby, NEW QUESTION?


On Dec 29, 2009, at 3:24 PM, Derek Smith wrote:

>> Mike Stok wrote:
>
> Thanks to all who replied!  :)
>
> I am trying to understand why my code is not entering my rundf method?

Well, mostly because you never tell it to. ;-)

>
> class FsData
>    def initialize
>        @rawdisk = @used = @available = @capacity = @filesystem = ""
>        if ARGV.empty?
>            puts "ARGV0 is required else script will not run"
>            exit 1
>        else
>            @filesystem = ARGV[0]
>        end
>    end

I'd suggest that this is not right for the initialize method. (Mostly  
because of the 'exit 1', but also because the FsData probably  
shouldn't refer to ARGV at all).

How about:
   def initialize(filesystem)
     @rawdisk = @used = @available = @capacity = nil
     @filesystem = filesystem
   end


>
>    def rundf
>        puts "entering rundf method"
>        df = %x(df -m |tail +2)
>        df.each do |ln|
>            @rawdisk    = ln.chomp.split[1].to_i
>            @used       = ln.chomp.split[2].to_i
>            @available  = ln.chomp.split[3].to_i
>            @capacity   = ln.chomp.split[4]
>            @filesystem = ln.chomp.split[5]
>        end
>        puts @available
>        if @available <= 4557
>            p "#{@available} is low as testing"
>        end
>    end

Ooh, I'll come back to this...

> end
>
> p dff = FsData.new

if ARGV.empty?
   $stderr.puts "The filesystem is required as an argument to this  
script"
   exit 1
end

dff = FsData.new(ARGV[0])

dff.rundf


>
> __OUTPUT__
>
> ruby  filesys_chk.rb /
> #<FsData:0x8115370 @filesystem="/", @rawdisk="", @capacity="",
> @available="", @used="">
> -- 


OK, now back to that rundf method. I'm assuming that:
* the calls to split are OK (I think you mean to get 0..4 not 1..5,  
but your df output wins)
* the three fields where you use to_i need it
* you mean to get just the line for the given filesystem
* your df output doesn't have any spaces in the non-numeric fields  
that mess up String#split

Now, understand that the original filesystem provided is doing nothing  
(and is overwritten if the df.each loop runs).

   def rundf
     puts "entering rundf method"
     df = %x(df -m | tail +2)
     df.each do |ln|
       df_fields = ln.chomp.split
       next unless df_fields.last == @filesystem

       @rawdisk   = df_fields[1].to_i
       @used      = df_fields[2].to_i
       @available = df_fields[3].to_i
       @capacity  = df_fields[4]
     end
     p "#{@available} is low as testing" if @available && @available  
<= 4557
     @available
   end

And perhaps a #to_s method as well:

   def to_s
     str =  "#{@filesystem} :"
     str << " raw #{@rawdisk}"         if @rawdisk
     str << " used #{@used}"           if @used
     str << " available #{@available}" if @available
     str << " capacity #{@capacity}"   if @capacity
     str
   end

I'm relying on the fact that in my version of your FsData class, the  
instance variables are initialized to nil (not an empty string).   
Others may not like the approach to building the string representation  
in parts in this case, but it illustrates a more general technique for  
when those variables might not all exist at the same time.

The end of the script could then be:
   puts FsData.new(ARGV[0])

You could also treat the whole exercise as a class method, give rundf  
an argument (the filesystem), and call:
   puts FsData.rundf(ARGV[0])
and not bother with an instance at all (since you don't do anything  
else with it).

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com