Solved

explanation of ? and ^ in regex

Posted on 2014-12-27
1
125 Views
Last Modified: 2014-12-27
I am unfamiliar with regex statements

What is the meaning of the ? and ^ in the following example:

^(.*\.)?acme\.org$
0
Comment
Question by:al4629740
1 Comment
 
LVL 74

Accepted Solution

by:
käµfm³d   👽 earned 500 total points
ID: 40519833
? means "zero or one" of the thing to the left. In this case, the thing to the left is a capture group, so the ? applies to the entire group.

^ in this context means "start of string". It doesn't match character; rather it matches a position within the string. There is also the negated character class ( [^...] ) which uses ^, but that does not apply here.

Likewise, the $ means "end of string".

An excellent resource for learning regex is http://www.regular-expressions.info .
0

Featured Post

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

Join & Write a Comment

by Batuhan Cetin Regular expression is a language that we use to edit a string or retrieve sub-strings that meets specific rules from a text. A regular expression can be applied to a set of string variables. There are many RegEx engines for u…
Do you hate spam? I do, and I am willing to bet you do as well. I often wonder, though, "if people hate spam so much, why do they still post their email addresses on the web?" I'm not talking about a plain-text posting here. I am referring to the fa…
Learn how to match and substitute tagged data using PHP regular expressions. Demonstrated on Windows 7, but also applies to other operating systems. Demonstrated technique applies to PHP (all versions) and Firefox, but very similar techniques will w…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…

757 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now