# Write Out Then Read In Hash of Two-element Arrays

**URL:** <https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294>\
**Category:** Ruby\
**Created:** [April 20, 2006, 11:00am UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294 "2006-04-20T11:00:29Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 11:00am UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/1 "2006-04-20T11:00:29Z")

</div>

Kind All,

I wonder if one of you knowledgeble folks can steer me in he right  
direction:

I’m trying to get a hash I’ve created read back in after after writing  
it out to a file, so that it is exactly the same afterward. The hash  
has zero-based integer keys and two-element array values.

After I create and populate the hash:  
Length of histHash after creation = 5

When I write out the hash, the output to STDOUT looks like this:  
Write histHash[0] = 101  
Write histHash[1] = 112  
Write histHash[2] = 123  
Write histHash[3] = 134  
Write histHash[4] = 145  
5 histHash lines written  
histHash written = 01011112212331344145

After I delete the elements of the hash:  
Length of histHash after deletion = 0

But when I read it back in, it looks like this:  
Read histHash[0] = 10; line = 10  
Read histHash[1] = 1; line = 1  
Read histHash[2] = 11; line = 11  
Read histHash[3] = 2; line = 2  
Read histHash[4] = 12; line = 12  
Read histHash[5] = 3; line = 3  
Read histHash[6] = 13; line = 13  
Read histHash[7] = 4; line = 4  
Read histHash[8] = 14; line = 14  
Read histHash[9] = 5; line = 5  
10 histHash lines read  
histHash read = 5301061311742118143295412  
Length of histHash after read = 10

As you can see, it’s length is five lines when I initially write it to  
the file, but ten lines when I read it back in. I’ve been pawing though  
the docs, but I can’t figure out what I’m doing wrong. Any help will be  
greatly appreciated.

Here is the errant code:

# write out and then read in hash of two-element arrays

# create and populate the hash

histHash = Hash.new  
histHash[0] = [10, 1]  
histHash[1] = [11, 2]  
histHash[2] = [12, 3]  
histHash[3] = [13, 4]  
histHash[4] = [14, 5]  
puts  
puts “Length of histHash after creation = #{histHash.length}”  
puts

# write the hash to the file

fileOut = File.new(“savedHash.sdo”, “w”)  
histHash.length.times do |i|  
fileOut.puts(histHash[i])  
puts “Write histHash[#{i}] = #{histHash[i]}”  
end  
fileOut.close

puts “#{histHash.length} histHash lines written”  
puts “histHash written = #{histHash}”  
puts

# Delete the hist hash elements

histHash.length.times do |i|  
histHash.delete(i)  
end  
puts “Length of histHash after deletion = #{histHash.length}”  
puts

# load (read) the saved file

fileIn = File.new(“savedHash.sdo”, “r”)  
i = 0  
fileIn.each\_line{|line|histHash[i]=[line.to\_i]; puts “Read  
histHash[#{i}] = #{histHash[i]}; line = #{line}”;i+=1}  
fileIn.close  
puts “#{histHash.length} histHash lines read”  
puts “histHash read = #{histHash}”  
puts “Length of histHash after read = #{histHash.length}”  
puts

---

<div class="post-metadata">

**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 11:19am UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/2 "2006-04-20T11:19:21Z")

</div>

David,

My initial guess:

> puts “Write histHash[#{i}] = #{histHash[i]}”

replaced with

fileOut.print("#{histHash[i]}\n")

This is what you want?

HTH,  
Peter

---

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**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 11:22am UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/3 "2006-04-20T11:22:25Z")

</div>

Sorry,

fileOut.puts(histHash[i])

should be replaced with

fileOut.print("#{histHash[i]}\n")

Cheers,  
Peter

---

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**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 11:22am UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/4 "2006-04-20T11:22:29Z")

</div>

Instead of writing your own de/serialization code why not give  
Marshal.dump and Marshal.load a try:

> > dumped\_histHash = Marshal.dump(histHash)  
> > =\>  
> > “\004\010{\ni\000[\ai\017i\006i\006[\ai\020i\ai\a[\ai\021i\010i\010[\ai\022i  
> > ti\t[\ai\023i\n”
> 
> > loaded\_histHash = Marshal.load(dumped\_histHash)  
> > =\> {0=\>[10, 1], 1=\>[11, 2], 2=\>[12, 3], 3=\>[13, 4], 4=\>[14, 5]}

If you need a human readable/editable file consider using YAML:

> > require ‘yaml’  
> > =\> true
> 
> > puts yaml\_histHash = histHash.to\_yaml

* * *

0:

- 10
- 1  
1:
- 11
- 2  
2:
- 12
- 3  
3:
- 13
- 4  
4:
- 14
- 5  
=\> nil

> > loaded\_histHash = YAML.load(yaml\_histHash)  
> > =\> {0=\>[10, 1], 1=\>[11, 2], 2=\>[12, 3], 3=\>[13, 4], 4=\>[14, 5]}

Farrel

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**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 8:56pm UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/5 "2006-04-20T20:56:15Z")

</div>

Farrel L. wrote:

> Instead of writing your own de/serialization code why not give  
> Marshal.dump and Marshal.load a try:
> 
> > > dumped\_histHash = Marshal.dump(histHash)  
> > > =\>  
> > > “\004\010{\ni\000[\ai\017i\006i\006[\ai\020i\ai\a[\ai\021i\010i\010[\ai\022i  
> > > ti\t[\ai\023i\n”
> > 
> > > loaded\_histHash = Marshal.load(dumped\_histHash)  
> > > =\> {0=\>[10, 1], 1=\>[11, 2], 2=\>[12, 3], 3=\>[13, 4], 4=\>[14, 5]}
> 
> If you need a human readable/editable file consider using YAML:
> 
> > > require ‘yaml’  
> > > =\> true
> > 
> > > puts yaml\_histHash = histHash.to\_yaml
> 
> * * *
> 
> 0:
> 
> - 10
> - 1  
> 1:
> - 11
> - 2  
> 2:
> - 12
> - 3  
> 3:
> - 13
> - 4  
> 4:
> - 14
> - 5  
> =\> nil
> 
> > > loaded\_histHash = YAML.load(yaml\_histHash)  
> > > =\> {0=\>[10, 1], 1=\>[11, 2], 2=\>[12, 3], 3=\>[13, 4], 4=\>[14, 5]}
> 
> Farrel

Farrel,

Good suggestion. Had I not forgotten about marshal and yaml (after  
having read about it a while back in the pickaxe book), I would have  
done so initally. At any rate, thank you for the suggestion. And for  
jogging my memory!

David

---

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**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\
**Post date:** [April 20, 2006, 8:58pm UTC](https://www.ruby-forum.com/t/write-out-then-read-in-hash-of-two-element-arrays/58294/6 "2006-04-20T20:58:36Z")

</div>

Peter S. wrote:

> David,
> 
> My initial guess:
> 
> > puts “Write histHash[#{i}] = #{histHash[i]}”
> 
> replaced with
> 
> fileOut.print("#{histHash[i]}\n")
> 
> This is what you want?
> 
> HTH,  
> Peter

Peter,

After a number of suggestions from gracious Rubyists, I am happy to say  
that I am now all set. Thank you very much for your help. Best  
regards,

David