Ken's Blog | Converting Filename Wildcard to Standard RegEx

Tuesday, 27. September 2005

Converting Filename Wildcard to Standard RegEx09/27/2005 03:50 PM

In case you ever need to allow users to specify a wildcard listing for files, you can use this to convert a DOS/Windows/Unix wildcard style string into a regular regex for use with Java's built-in regular expression classes. It took a while for me to find in Google, so I'm putting this in my blog in case anyone else needs it

If you want to support case-sensitive matching, remember to remove the toLowerCase() call on the return statement:
/** * Converts a windows wildcard pattern to a regex pattern * * @param wildcard - Wildcard pattern containing * and ? * * @return - a regex pattern that is equivalent to the windows wildcard pattern */ private static String wildcardToRegex(String wildcard) { if (wildcard == null) return null; StringBuffer buffer = new StringBuffer(); char [] chars = wildcard.toCharArray(); for (int i = 0; i < chars.length; ++i) { if (chars[i] == '*') buffer.append(".*"); else if (chars[i] == '?') buffer.append("."); else if ("+()^$.{}[]|\\".indexOf(chars[i]) != -1) buffer.append('\\').append(chars[i]); // prefix all metacharacters with backslash else buffer.append(chars[i]); } return buffer.toString().toLowerCase(); }

Comments :

1. Greg12/30/2009 16:06:16

Thanks for the post, and Ray for your comment! This is just what I needed. In my case, I needed to work with multiple wildcard patterns, such as *.zip AND *.xml at the same time, as well as ignore anything with a .include extension, so I ended up sticking a (?!.*\.ignore$) at the start of the regex and called your code in a loop, resulting in the following, which I've posted in the hopes that someone would find it helpful:

^(?!.*\.ignore$)(.*\.xml)|(.*\.zip)$

2. Ray10/04/2008 19:18:03

One small improvement, make your return string start with ^ and end with $

At the moment if you supplied ello*.* it would match yellow.txt which it shouldn't!

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