Regular expression search avoid nested results

问题

My document contains several instance of code blocks looking like:

{% highlight %}
//some code
{% endhighlight %}

In Atom.io, I am trying to write a regex search to capture those.

My first try was:
{% highlight .* %}([\S\s]+){% endhighlight %}

The problem is because there are several code blocks in the same document, it also catches the first code block until the last one, all in one match.

I though to exclude the { character:
{% highlight .* %}([^\{]+){% endhighlight %}

But the problem is that some of the code blocks contain valid { characters (such as function(){ ... }).

回答1:

Use non greedy matching:

{% highlight .* %}([\S\s]+?){% endhighlight %}
                          ^

回答2:

The problem with Karthik's lazy matching solution is that when you have large substrings between {% highlight %} and {% end highlight %} the [\s\S]*? will be storing more and more text into the backtracking buffer that can eventually overrun.

Using an unrolling-the-loop technique, you can avoid that:

{% highlight %}([^{]*(?:{(?!% endhighlight %})[^{]*)*){% endhighlight %}

See the regex demo

This way, the substrings inside the highlight blocks can be of any length and performance will stay fast.

Main regex parts:

• {% highlight %} - matches the {% highlight %} text literally
• ([^{]*(?:{(?!% endhighlight %})[^{]*)*) - matches and captures into group 1 everything that is not {% endhighlight %} matching:
  • [^{]* - 0 or more characters other than {
  • (?:{(?!% endhighlight %})[^{]*)* - 0 or more sequences of....
    • {(?!% endhighlight %}) - literal { not followed by % endhighlight %}
    • [^{]* - 0 or more characters other than {
• {% endhighlight %} - matches the {% endhighlight %} text literally

This is basically the same as {% highlight %}([\s\S]*?){% endhighlight %}, but "unwraped". The linear execution ensures safer and faster user experience.

回答3:

This regex you can get only content in {% highlight %} ... {% endhighlight %}:

(?<={% highlight %}).*(?={% endhighlight %})

Test: https://regex101.com/r/nX6wV8/1

---

Sorry for my fail, I hope this can help you

New expression: https://regex101.com/r/qX2cA1/1

来源：https://stackoverflow.com/questions/33805752/regular-expression-search-avoid-nested-results