include
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The include directive (include::path[attributes]) let’s you import content from another file into the current document. You can use it multiple times in the same document.
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The include directive has the following anatomy:
<div class="example">
include::path[leveloffset=offset,lines=ranges,tag(s)=name(s),indent=depth]
</div>
The leveloffset, lines, tag(s) and indent attributes are optional, making the simplest case look like:
<div class="example">
include::content.adoc[]
</div>
The sections that follow go into detail about when the include is processed, how the include file 
is resolved, and how each attribute is used.
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For more information please refer to online documentation.