Extract data between two xml tag.

Xml File:

<instance ab=1 >
<a1>aa</a1>
    <a2>aa</a2>
</instance>
<instance ab=2 >
<b1>bb</b1>
    <b2>bb</b2>
</instance>
<instance ab=3 >
<c1>cc</c1>
    <c2>cc</c2>
</instance>

Looking for output by using sed or awk like following.

<a1>aa</a1><a2>aa</a2>
<b1>bb</b1><b2>bb</b2>
<c1>cc</c1><c2>cc</c2>

It's not working with following sed command.

sed -n '/<Sample/,/<\/Sample/p' ab

Given a specific XML element (i.e. a specific tag name) and a snippet of XML data, I want to extract the children from each occurrence of that element. More specifically, I have the following snippet of (not quite valid) XML data:

<!-- data.xml -->

<instance ab=1 >
    <a1>aa</a1>
    <a2>aa</a2>
</instance>
<instance ab=2 >
    <b1>bb</b1>
    <b2>bb</b2>
</instance>
<instance ab=3 >
    <c1>cc</c1>
    <c2>cc</c2>
</instance>

I would like a script or command which takes this data as input and produces the following output:

<a1>aa</a1><a2>aa</a2>
<b1>bb</b1><b2>bb</b2>
<c1>cc</c1><c2>cc</c2>

I would like for the solution to use standard text-processing tools such as sed or awk.

I tried using the following sed command, but it did not work:

sed -n '/<Sample/,/<\/Sample/p' data.xml

Extract data between two xml tag.

Xml File:

<instance ab=1 >
<a1>a1</a1>
    <a2>a2</a2>
</instance>
<instance ab=2 >
<b1>a1</b1>
    <b2>a2</b2>
</instance>
<instance ab=3 >
<c1>a1</c1>
    <c2>a2</c2>
</instance>

Looking for output by using sed or awk like following.

<a1>a1</a1><a2>a1</a2>
<b1>a1</b1><b2>a2</b2>
<c1>a1</c1><c2>a2</c2>

It's not working with following sed command.

sed -n '/<Sample/,/<\/Sample/p' ab

Extract data between two xml tag.

Xml File:

<instance ab=1 >
<a1>aa</a1>
    <a2>aa</a2>
</instance>
<instance ab=2 >
<b1>bb</b1>
    <b2>bb</b2>
</instance>
<instance ab=3 >
<c1>cc</c1>
    <c2>cc</c2>
</instance>

Looking for output by using sed or awk like following.

<a1>aa</a1><a2>aa</a2>
<b1>bb</b1><b2>bb</b2>
<c1>cc</c1><c2>cc</c2>

It's not working with following sed command.

sed -n '/<Sample/,/<\/Sample/p' ab