regex - w3toppers.com

Regular expression to enforce complex passwords, matching 3 out of 4 rules

Don’t use one regex to check it then. if (password.length < 8) alert(“bad password”); var hasUpperCase = /[A-Z]/.test(password); var hasLowerCase = /[a-z]/.test(password); var hasNumbers = /\d/.test(password); var hasNonalphas = /\W/.test(password); if (hasUpperCase + hasLowerCase + hasNumbers + hasNonalphas < 3) alert(“bad password”); If you must use a single regex: ^(?:(?=.*[a-z])(?:(?=.*[A-Z])(?=.*[\d\W])|(?=.*\W)(?=.*\d))|(?=.*\W)(?=.*[A-Z])(?=.*\d)).{8,}$ This regex is not optimized … Read more

Regular expression pipe confusion

The first pattern without the parenthesis is equivalent to /(^a)|(b$)/. The reason is, that the pipe operator (“alternation operator”) has the lowest precedence of all regex operators: http://www.regular-expressions.info/alternation.html (Third paragraph below the first heading)

Collapse and Capture a Repeating Pattern in a Single Regex Expression

Read this first! This post is to show the possibility rather than endorsing the “everything regex” approach to problem. The author has written 3-4 variations, each has subtle bug that are tricky to detect, before reaching the current solution. For your specific example, there are other better solution that is more maintainable, such as matching … Read more

What is the difference between square brackets and parentheses in a regex?

These regexes are equivalent (for matching purposes): /^(7|8|9)\d{9}$/ /^[789]\d{9}$/ /^[7-9]\d{9}$/ The explanation: (a|b|c) is a regex “OR” and means “a or b or c”, although the presence of brackets, necessary for the OR, also captures the digit. To be strictly equivalent, you would code (?:7|8|9) to make it a non capturing group. [abc] is a … Read more

What regular expression will match valid international phone numbers?

\+(9[976]\d|8[987530]\d|6[987]\d|5[90]\d|42\d|3[875]\d| 2[98654321]\d|9[8543210]|8[6421]|6[6543210]|5[87654321]| 4[987654310]|3[9643210]|2[70]|7|1)\d{1,14}$ Is the correct format for matching a generic international phone number. I replaced the US land line centric international access code 011 with the standard international access code identifier of ‘+’, making it mandatory. I also changed the minimum for the national number to at least one digit. Note that if you … Read more

Searching for UUIDs in text with regex

The regex for uuid is: [0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12} If you want to enforce the full string to match this regex, you will sometimes (your matcher API may have a method) need to surround above expression with ^…$, that is ^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$

Regular Expressions and negating a whole character group [duplicate]

Using a character class such as [^ab] will match a single character that is not within the set of characters. (With the ^ being the negating part). To match a string which does not contain the multi-character sequence ab, you want to use a negative lookahead: ^(?:(?!ab).)+$ And the above expression disected in regex comment … Read more

Regex – Should hyphens be escaped? [duplicate]

Correct on all fronts. Outside of a character class (that’s what the “square brackets” are called) the hyphen has no special meaning, and within a character class, you can place a hyphen as the first or last character in the range (e.g. [-a-z] or [0-9-]), OR escape it (e.g. [a-z\-0-9]) in order to add “hyphen” … Read more

Is there something like a counter variable in regular expression replace?

FMTEYEWTK about Fancy Regexes Ok, I’m going to go from the simple to the sublime. Enjoy! Simple s///e Solution Given this: #!/usr/bin/perl $_ = <<“End_of_G&S”; This particularly rapid, unintelligible patter isn’t generally heard, and if it is it doesn’t matter! End_of_G&S my $count = 0; Then this: s{ \b ( [\w’]+ ) \b }{ sprintf … Read more

How can I match nested brackets using regex?

Many regex implementations will not allow you to match an arbitrary amount of nesting. However, Perl, PHP and .NET support recursive patterns. A demo in Perl: #!/usr/bin/perl -w my $text=”(outer (center (inner) (inner) center) ouer) (outer (inner) ouer) (outer ouer)”; while($text =~ /($([^()]|(?R))*$)/g) { print(“———-\n$1\n”); } which will print: ———- (outer (center (inner) (inner) center) … Read more