# Reading lines from a file into an array

**URL:** <https://www.ruby-forum.com/t/reading-lines-from-a-file-into-an-array/187911>\
**Category:** Ruby\
**Created:** [May 1, 2010, 2:19pm UTC](https://www.ruby-forum.com/t/reading-lines-from-a-file-into-an-array/187911 "2010-05-01T14:19:46Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jimb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/f4b2a3/32.png) [@jimb](https://www.ruby-forum.com/u/jimb)\
**Post date:** [May 1, 2010, 2:19pm UTC](https://www.ruby-forum.com/t/reading-lines-from-a-file-into-an-array/187911/1 "2010-05-01T14:19:46Z")

</div>

Using ruby, I am trying to read in lines from a two column html table  
and store each line in a two element array. This two element array is in  
turn stored in one large array.

The table rows look like this:

 Row 1 - Column 1 Row 1 - Column 2 ...

And, when I’m done, I hoping for this:  
[[“row1 - col1”, “row1, col2”], [“row2 - col1”, “row2, col2”], …]

Can anyone give me any pointers on the correct way to do this.  
The code I have come up with so far is this:

f = File.open(“file\_containing\_table.txt”, “r”)  
lines = f.readlines  
array\_to\_hold\_rows= []  
index = 0  
loop do  
if lines[index] == nil  
break  
elsif lines[index].match “\<td”  
array\_to\_hold\_rows \<\< ["#{lines[index]}", “#{lines[index+1]}”]  
index +=2  
else  
index +=1  
end  
end

This works and does what I want, but I would like to know if this is the  
best / most effective way to go about what I am trying to achieve.

Would be grateful for any help.

---

<div class="post-metadata">

**Author:** ![jimb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/f4b2a3/32.png) [@jimb](https://www.ruby-forum.com/u/jimb)\
**Post date:** [May 1, 2010, 2:50pm UTC](https://www.ruby-forum.com/t/reading-lines-from-a-file-into-an-array/187911/2 "2010-05-01T14:50:15Z")

</div>

On Sat, May 1, 2010 at 2:19 PM, Jim B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> …  
> index = 0  
> loop do  
> if lines[index] == nil  
> break  
> elsif lines[index].match “\<td”  
> array\_to\_hold\_rows \<\< [“#{lines[index]}”, “#{lines[index+1]}”]  
> index +=2  
> else  
> index +=1  
> end  
> end

Usually parsing html with regular expressions is risky. I’d use a  
parser instead, if possible, for example nokogiri:

require ‘nokogiri’  
html =\<\<END

| Row 1 - Column 1 | Row 1 - Column 2 |
| Row2 - col1 | row2 - col2 |

END doc = Nokogiri::HTML(html) result = [] doc.xpath('//tr[@class="odd"]/td').each\_slice(2) do |first, second| result \<\< [first.inner\_html, second.inner\_html] end

result #=\> [[“Row 1 - Column 1”, “Row 1 - Column 2”], [" Row2 -  
col1", " row2 - col2"]]

> This works and does what I want, but I would like to know if this is the  
> best / most effective way to go about what I am trying to achieve.

I think in your solution you are not stripping the markup, so your  
array still contains the and tags.  
Now that I think about it you might want to tweak the Xpath I wrote,  
because maybe not all the trs have class=“odd”.

Hope this helps,

Jesus.

---

<div class="post-metadata">

**Author:** ![jimb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/f4b2a3/32.png) [@jimb](https://www.ruby-forum.com/u/jimb)\
**Post date:** [May 1, 2010, 3:32pm UTC](https://www.ruby-forum.com/t/reading-lines-from-a-file-into-an-array/187911/3 "2010-05-01T15:32:39Z")

</div>

Hi Jesus,

Thanks for your reply. That really helped.

> Usually parsing html with regular expressions is risky. I’d use a  
> parser instead, if possible, for example nokogiri:

You are of course correct.  
I have followed your suggestion, installed ‘nokogiri’ and am currently  
looking at some examples. I will then tweak what you wrote and use that  
in my final version as it is very neat and concise.

However, this:

> doc.xpath(’//tr[@class=“odd”]/td’).each\_slice(2) do |first, second|  
> result \<\< [first.inner\_html, second.inner\_html]  
> end

gave me the idea of writing this:

lines.each\_slice(4){|one,two,three,four| result \<\<  
[two.chomp,three.chomp]}

which also does exactly what I want, so thanks again!

Essentially, I have just finished reading the first part of the Pickaxe  
book and am trying to implement some of their suggestions and think  
about the code I write as opposed to doing the “quick and dirty” method.