Regular expression for validating first name
Input validation is your first line of defense when creating a secure application, but it's often done insufficiently, in a place that is easy to bypass, or simply not done at all.Since this is a common issue I see in our assessments and something that has such a great impact on security I'd like to spend a bit of time outlining input validation best practices and give you some concrete examples of how to do it well.e-mail address e-mail addresses are notoriously difficult to match if you get too caught up in the RFC.Additionally if you try to be too compliant you may open yourself up to other issues, such as command or SQL injection or Cross Site Scripting.One example of this might be a phone number, which could be stored as a string in memory and a varchar in the database, however there is much more information about the context of that phone number that we can use to ensure we limit our attack surface by verifying the validity of that input.
Simply type your regular expression into the top text box and the text you wish to match in the lower text box. Download Regex Matcher We can define usernames to be as restrictive as we'd like, but let's start with something easy such as simply "The username must contain only upper and lowercase letters" Therefore the following list of usernames is valid: This will allow one or more of any "word" character that includes numbers, letters and underscores, which means S4MIE slips through.
There are some really great resources out there to find examples of regular expressions and to learn how they work.
I highly suggest you learn this incredibly powerful piece of computer science.
DOTALL is a flag in most recent regex libraries that makes the . There is no 100% reliable solution since the RFC is way too complex. ] )*@([a-z0-9_][-a-z0-9_]*(\.[-a-z0-9_] )*\.(aero|arpa|biz|com|coop|edu|gov|info|int|mil|museum|name|net|org|pro|travel|mobi|[a-z][a-z])|([0-9]\.[0-9]\.[0-9]\.[0-9]))(:[0-9])? $ This will make sure that every number in the IP address is between 0 and 255, unlike the version using \d which would allow for 999.999.999.999.
metacharacter match anything INCLUDING line breaks. Java Script by default does not support this since the . This is the best solution and should work 99% of the time is. If you want to match an IP within a string, get rid of the leading ^ and trailing $ to use \b (word boundaries) instead. The regular expression is only useful to validate the format of the date as entered by a user.Consult the regular expression documentation or the regular expression solutions to common problems section of this page for examples. You can create range of characters using the hyphen character such as A-Z (A to Z).