Regular expression for validating special characters

We want to allow the username to contain letters, numbers, underscores and hyphens.We also want to limit the number of characters in username so it does not look ugly.We use the following regular expression to validate a username:.The regular expression is matched against an input string by comparing each character in the regularexpression to each character in the input string, one after another.Different applications and programming languages might have different implementations for regular expressions but underlying concepts are mostly the same.In this post, I am going to explain everything that you need to know about regular expressions.Regularexpressions are normally case-sensitive so the regular expression Test the regular expression Meta characters are the building blocks of the regular expressions.

Would you like to answer one of these unanswered questions instead?Some meta characters have a special meaning and are written inside square brackets.The meta characters are as follows: Test the regular expression Character sets are also called character class. Use a hyphen inside a character set to specify the characters’ range.For example, the regular expression is used to define alternation.Alternation is like a condition between multiple expressions.

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