user23111: I want to filter a PGN database for games where one side plays a series of moves but I don't care what the other side does during that sequence. For example the bongcloud is where one side plays 1. e3 ... 2. Ke2. (I know there are lots of variations but that's ignore that for now). I don't really care what black does on turn one or two. How would I filter for that? I don't want to list out all the moves black can make and then input 20+ parameters. Is there a simpler way to achieve this?

user23111: I found an answer. After spending a few hours digging through PGN-Extract's website I found this:
* b6
means that you are interested in all games in which Black replied 1 ... b6 regardless of White's first move. The sequence:
d4 * c4 * Nc3 *
will pick up Nimzo-Indian, Grunfeld, King's Indian, etc. defenses. This notation is not possible with positional variations
Edit:
You put the above text in a file and then set it as a parameter when calling pgn-extract like this:
pgn-extract -v[file that contains the rules]

23111: <p>I want to filter a PGN database for games where one side plays a series of moves but I don't care what the other side does during that sequence. For example the bongcloud is where one side plays 1. e3 ... 2. Ke2. (I know there are lots of variations but that's ignore that for now). I don't really care what black does on turn one or two. How would I filter for that? I don't want to list out all the moves black can make and then input 20+ parameters. Is there a simpler way to achieve this?</p>
 23111: <p>I found an answer. After spending a few hours digging through PGN-Extract's website I found this:</p>
<p><code>* b6</code></p>
<p>means that you are interested in all games in which Black replied 1 ... b6 regardless of White's first move. The sequence:</p>
<p><code>d4 * c4 * Nc3 *</code></p>
<p>will pick up Nimzo-Indian, Grunfeld, King's Indian, etc. defenses. This notation is not possible with positional variations</p>
<p>Edit:
You put the above text in a file and then set it as a parameter when calling pgn-extract like this:</p>
<p><code>pgn-extract -v[file that contains the rules]</code></p>
