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Jun 14, 2013

The power of regular expression and testing tools like regexpal.com

Regular expressions are also known as regex, and they are very powerful and used widely in JavaScript, Unix scripting,  development tools, monitoring tools like Tivoli, and programming languages. So, it really pays to have good knowledge of regexes. This post is about a handy tool named "regexpal.com" that helps you not only learn regex, but also to quickly verify your regexes while working on a project. If you google for "regex online validator" you will find other similar online validating tools.



Step 1: Open up a browser and type regexpal.com on the address bar. Yo will get the online validator.

Step 2: Type or copy/paste the regex at the top window and the text to apply the regex on the second window.


As indicated in the footer, use RegexBuddy for a more powerful regex testing. The regex keywords are highlighted in blue. Also the matched phrase is also highlighted. In blue for the exact match and in yellow for any other string match.

The above example matches any string followed by one of "Monitoring", "MYAPP", or "CASHFORECAST". The "|" in regex means "OR". What if you want to literally match "Monitoring|MYAPP|CASHFORECAST"? You can escape "|" with "\" as shown below.


Now, the  "|" is not highlighted in blue as it is escaped.

Change the text as shown below. The "CASHFORECAST" is changed to "TRADEFORECAST" and match is no longer found as the text is not highlighted.

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