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Perl Compatible Regular Expressions (PCRE) is a library written in C, which implements a regular expression engine, inspired by the capabilities of the Perl programming language. Philip Hazel started writing PCRE in summer 1997. [ 3 ]
In the context of an HTTP transaction, basic access authentication is a method for an HTTP user agent (e.g. a web browser) to provide a user name and password when making a request. In basic HTTP authentication, a request contains a header field in the form of Authorization: Basic <credentials> , where <credentials> is the Base64 encoding of ID ...
Every regular expression can be written solely in terms of the Kleene star and set unions over finite words. This is a surprisingly difficult problem. As simple as the regular expressions are, there is no method to systematically rewrite them to some normal form. The lack of axiom in the past led to the star height problem.
In the case of a web application, the programmer may use the same regular expression to validate input on both the client and the server side of the system. An attacker could inspect the client code, looking for evil regular expressions, and send crafted input directly to the web server in order to hang it.
Oniguruma (鬼車) is a free and open-source regular expression library that supports a variety of character encodings, written by K. Kosako.The Ruby programming language, in version 1.9, as well as PHP's multi-byte string module (since PHP5), use Oniguruma as their regular expression engine. [2]
In the table section click "edit source" (wikitext editing). Click on "Advanced" in the editing toolbar. Then click on the "search and replace" icon on the right. In the popup form check the box for "Treat search string as a regular expression". Fill in the "Search for" box with (\|-\n\|) Fill in the "replace with" box with $1style=text-align:left|
On this smaller file use the "Pivot Table" method described in the previous section to put the dates as column heads. Select all from the edit menu. Then click on the "Pivot Table" command from the Insert menu. Click OK in the popup box. In the next dialog box drag "Date reported" to the "Column Fields" box, and drag "Country" to the "Row ...
For referential integrity to hold in a relational database, any column in a base table that is declared a foreign key can only contain either null values or values from a parent table's primary key or a candidate key. [2] In other words, when a foreign key value is used it must reference a valid, existing primary key in the parent table.