How to validate a domain name using regular expression?

How to validate a domain name using regular expression?

How to validate a domain name using Regular Expression. Given string str, the task is to check whether the given string is a valid domain name or not by using Regular Expression. The domain name should be a-z or A-Z or 0-9 and hyphen (-). The domain name should be between 1 and 63 characters long.

Which is the equivalent of calling regex.matches?

The method is equivalent to calling the Regex.Matches (String, String, RegexOptions) method and passing each Match object in the returned MatchCollection collection to the evaluator delegate. The pattern parameter consists of regular expression language elements that symbolically describe the string to match.

How to replace a regular expression in regex?

In a specified input string, replaces all substrings that match a specified regular expression with a string returned by a MatchEvaluator delegate. Additional parameters specify options that modify the matching operation and a time-out interval if no match is found.

How to build regular expressions to match valid dates?

In my exploration of the issues, I have come up with a system that enables you to build a regular expression by arranging together four simpler sub-expressions that match on the delimiter, and valid ranges for the year, month and day fields in the order you require.

Do you need to validate the last name in regex?

It is probably better not to validate the name at all, apart from checking that it is empty. After going through all of these answers I found a way to build a tiny regex that supports most languages and only allows for word characters. It even supports some special characters like hyphens, spaces and apostrophes.

How many alphanumerics do you need for a name in regex?

Since those two are required, the name must be at least two characters long. This is your own regex, and it requires the string to start and end with two alphanumeric characters, and if there are two separators within the string, there have to be exactly two alphanumerics between them.

Which is the best way to validate a name?

Validating names is a difficult issue, because valid names are not only consisting of the letters A-Z. At least you should use the Unicode property for letters and add more special characters. A first approach could be e.g.:

How to check if a string matches a regex in Bash?

This way you can do: where commands after && are executed if the test is successful, and commands after || are executed if the test is unsuccessful. Note this is based on the solution by Aleks-Daniel Jakimenko in User input date format verification in bash. In other shells you can use grep.

How to check if a string matches a date?

A good way to test if a string is a correct date is to use the command date: I would use expr match instead of =~: This is better than the currently accepted answer of using =~ because =~ will also match empty strings, which IMHO it shouldn’t.

Can a hostname be valid in a regex?

In the proposed regex the dot might appear only once. I’d assume that abc.def.gh is a valid hostname as well, isn’t it. Strange, but also couldn’t find any .NET class that can validate hostname string (is it the situation?). Any advice will be highly appreciated.

How to regex a DNS hostname or IP address?

Looking for hostname validation regex. Regular expression to match DNS hostname or IP Address? In that link gentlemen propose a decent regex. I have a few problems/questions with that: In the proposed regex the dot might appear only once. I’d assume that abc.def.gh is a valid hostname as well, isn’t it.

Is there a regex for abc.def.gh?

In that link gentlemen propose a decent regex. I have a few problems/questions with that: In the proposed regex the dot might appear only once. I’d assume that abc.def.gh is a valid hostname as well, isn’t it. Strange, but also couldn’t find any .NET class that can validate hostname string (is it the situation?).