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POMatch overlapping patterns with capture using a MATLAB regular expression
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  1. POMatch overlapping patterns with capture using a MATLAB regular expression
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    copied!<p>I'm trying to parse a log file that looks like this:</p> <pre><code>%%%% 09-May-2009 04:10:29 % Starting foo this is stuff to ignore %%%% 09-May-2009 04:10:50 % Starting bar more stuff to ignore %%%% 09-May-2009 04:11:29 ... </code></pre> <p>This excerpt contains two time periods I'd like to extract, from the first delimiter to the second, and from the second to the third. I'd like to use a regular expression to extract the start and stop times for each of these intervals. This mostly works:</p> <pre><code>p = '%{4} (?&lt;start&gt;.*?)\n% Starting (?&lt;name&gt;.*?)\n.*?%{4} (?&lt;stop&gt;.*?)\n'; times = regexp(c,p,'names'); </code></pre> <p>Returning:</p> <pre><code>times = 1x16 struct array with fields: start name stop </code></pre> <p>The problem is that this only captures every other period, since the second delimiter is consumed as part of the first match.</p> <p>In other languages, you can use lookaround operators (lookahead, lookbehind) to solve this problem. The <a href="http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_prog/f0-42649.html" rel="nofollow noreferrer">documentation on regular expressions</a> explains how these work in MATLAB, but I haven't been able to get these to work while still capturing the matches. That is, I not only need to be able to match every delimiter, but also I need to extract part of that match (the timestamp).</p> <p>Is this possible?</p> <p>P.S. I realize I can solve this problem by writing a simple state machine or by matching on the delimiters and post-processing, if there's no way to get this to work.</p> <p><strong>Update:</strong> Thanks for the workaround ideas, everyone. I heard from the developer and there's currently no way to do this with the regular expression engine in MATLAB.</p>
 

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