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explanation of ? and ^ in regex

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

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

^(.*\.)?acme\.org$
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Question by:al4629740
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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 .
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