Lookaheads do not consume any characters. It just checks if the lookahead can be matched or not: a(?!b)c So here after matching a it just checks if it is followed not by b but does not consume that not character (which is c) and is followed by c. How a(?!b)c matches ac ac | a … Read more
([A-Z][a-z0-9]+)+ Assuming English. Use appropriate character classes if you want it internationalizable. This will match words such as “This”. If you want to only match words with at least two capitals, just use ([A-Z][a-z0-9]+){2,} UPDATE: As I mentioned in a comment, a better version is: [A-Z]([A-Z0-9]*[a-z][a-z0-9]*[A-Z]|[a-z0-9]*[A-Z][A-Z0-9]*[a-z])[A-Za-z0-9]* It matches strings that start with an uppercase letter, … Read more
This looks like a behavior difference in the handling of \s between grep 2.5 and newer versions (a bug in old grep?). I confirm your result with grep 2.5.4, but all four of your greps do work when using grep 2.6.3 (Ubuntu 10.10). Note: GNU grep 2.5.4 echo “foo bar” | grep “\s” (doesn’t match) … Read more
\b is a zero width assertion. That means it does not match a character, it matches a position with one thing on the left side and another thing on the right side. The word boundary \b matches on a change from a \w (a word character) to a \W a non word character, or from … Read more
You can capture the strings, then count them. It can be done by applying a list context to the capture with (): my $x = “foo”; my $y = “foo foo foo bar”; my $c = () = $y =~ /$x/g; # $c is now 3 You can also capture to an array and count … Read more
You’re looking for a non-greedy (or lazy) match. To get a non-greedy match in regular expressions you need to use the modifier ? after the quantifier. For example you can change .* to .*?. By default grep doesn’t support non-greedy modifiers, but you can use grep -P to use the Perl syntax.
If you want to validate email then use input with type=”email” instead of type=”text”. AngularJS has email validation out of the box, so no need to use ng-pattern for this. Here is the example from original documentation: <script> function Ctrl($scope) { $scope.text=”[email protected]”; } </script> <form name=”myForm” ng-controller=”Ctrl”> Email: <input type=”email” name=”input” ng-model=”text” required> <br/> <span … Read more
Here is one way one can grab the RewriteBase in an environment variable which you can then use in your other rewrite rules: RewriteCond %{REQUEST_URI}::$1 ^(.*?/)(.*)::\2$ RewriteRule ^(.*)$ – [E=BASE:%1] Then you can use %{ENV:BASE} in your rules to denote RewriteBase, i.e.: #redirect in-existent files/calls to index.php RewriteCond %{REQUEST_FILENAME} !-f RewriteRule . %{ENV:BASE}/index.php [L] Explanation: … Read more
Russ Cox has a very detailed article about why this is and the history of regexes (part 2, part 3). Regular expression matching can be simple and fast, using finite automata-based techniques that have been known for decades. In contrast, Perl, PCRE, Python, Ruby, Java, and many other languages have regular expression implementations based on … Read more
Don’t parse XML/HTML with regex, use a proper XML/HTML parser. theory : According to the compiling theory, HTML can’t be parsed using regex based on finite state machine. Due to hierarchical construction of HTML you need to use a pushdown automaton and manipulate LALR grammar using tool like YACC. realLife©®™ everyday tool in a shell … Read more