https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&feedformat=atom&user=Vardis 2026-04-30T15:26:30Z User contributions MediaWiki 1.30.0 https://www.explainxkcd.com/wiki/index.php?title=1638:_Backslashes&diff=110500 2016-02-03T06:29:33Z

<p>Vardis: /* Explanation */ fixed incorrect use of &quot;it's&quot;</p> <hr /> <div>{{comic<br /> | number = 1638<br /> | date = February 3, 2016<br /> | title = Backslashes<br /> | image = backslashes.png<br /> | titletext = I searched my .bash_history for the line with the highest ratio of special characters to regular alphanumeric characters, and the winner was: cat out.txt &amp;#124; grep -o &quot;\\\[[(].*\\\[\])][^)\]]*$&quot; ... I have no memory of this and no idea what I was trying to do, but I sure hope it worked.<br /> }}<br /> <br /> ==Explanation==<br /> {{incomplete|Created by a regex noob.}}<br /> [[wikipedia:regular expression|Regular expressions]] are often used to search large bodies of text for strings that match a particular pattern. Several characters in regex are &quot;special characters&quot;, which by default do not match the literal character, but instead help indicate the pattern. To find a special character literally, you must &quot;escape&quot; it, by preceding it with a backslash. This, of course, means that the backslash is a special character, so to search for a literal backslash character, you need to type two backslashes -- \\. Occasionally, the text being searched will contain regular expressions, and occasionally you will need to search for an escaped backslash. To do ''that'', you need to escape two backspaces -- \\\\. This gets very silly, very quickly.<br /> <br /> Things get even worse when you have to embed a regexp in a language like Java, which both lacks perl's syntactic sugar to demarcate the beginning and end of a regexp, and uses the backslash for its own special characters. So, to create the regexp \\\\ in Java, you'd have to use the string &quot;\\\\\\\\&quot;, since each backslash needs to be quoted to get through the Java string parser before it can then be considered as a regular expression.<br /> <br /> The regex in the title text seems to be invalid. The left-parentheses character is a literal, causing it to fail to match up with the right-parentheses later in the expression. Whatever Randall was trying to do here, this expression didn't do the job.<br /> <br /> ==Transcript==<br /> \ - backslash<br /> <br /> \\ - real backslash<br /> <br /> \\\ - _real_ real backslash<br /> <br /> \\\\ - actual backslash, for real this time<br /> <br /> \\\\\ - elder backslash<br /> <br /> \\\\\\ - backslash which escapes the screen and enters your brain<br /> <br /> \\\\\\\ - backslash so real it transcends time and space<br /> <br /> \\\\\\\\ - backslash to end all other text<br /> <br /> \\\\\\\\\\\... - the true name of ba'al, the soul-eater<br /> <br /> {{comic discussion}}</div>

Vardis