### Run Irb

Use the ```run_irb``` feature to execute markdown-embedded Ruby snippets in the Ruby interactive shell, ```irb```.

This allows you to interleave Ruby snippets with *any* markdown (usually explanatory text, but actually anything).

In the example template below, snippets of Ruby are interleaved with other markdown elements.

Each Ruby snippet that's to be executed in ```irb``` is bracketed by pragmas <code>\`\`\`#run_irb</code> and <code>\`\`\`</code>.

In the example, each snippet has some Ruby code that shows values using method ```p```.

<pre>
# About Hashes

Create a hash:

```#run_irb
h = {}
p h.class
p h
```

Initialize a hash:

```#run_irb
h = {:a => 0, :b => 1}
p h
```

Change a value:

```#run_irb
h[:b] = 2
p h
```

Add a new entry:

```#run_irb
h[:c] = 2
p h
```

Delete an entry:

```#run_irb
h.delete(:a)
p h
```</pre>

#### Run Irb Via <code>markdown_helper</code>
<details>
<summary>CLI</summary>

```sh
markdown_helper run_irb --pristine template.md markdown.md
```

(Option ```--pristine``` suppresses comment insertion.)
</details>
<details>
<summary>API</summary>

```run_irb.rb```:
```ruby
require 'markdown_helper'

# Option :pristine suppresses comment insertion.
markdown_helper = MarkdownHelper.new(:pristine => true)
markdown_helper.run_irb('template.md', 'markdown.md')
```

</details>

The resulting markdown (raw) shows the output from ```irb``` for each snippet:

<pre>
# About Hashes

Create a hash:

```ruby
h = {}
p h.class
Hash
p h
{}
```

Initialize a hash:

```ruby
h = {:a => 0, :b => 1}
p h
{:a=>0, :b=>1}
```

Change a value:

```ruby
h[:b] = 2
p h
{:a=>0, :b=>2}
```

Add a new entry:

```ruby
h[:c] = 2
p h
{:a=>0, :b=>2, :c=>2}
```

Delete an entry:

```ruby
h.delete(:a)
p h
{:b=>2, :c=>2}
```
</pre>

Resulting markdown (rendered):

---

# About Hashes

Create a hash:

```ruby
h = {}
p h.class
Hash
p h
{}
```

Initialize a hash:

```ruby
h = {:a => 0, :b => 1}
p h
{:a=>0, :b=>1}
```

Change a value:

```ruby
h[:b] = 2
p h
{:a=>0, :b=>2}
```

Add a new entry:

```ruby
h[:c] = 2
p h
{:a=>0, :b=>2, :c=>2}
```

Delete an entry:

```ruby
h.delete(:a)
p h
{:b=>2, :c=>2}
```

---