May 28, 2021 Regular expression
Unless you have used regular expressions before, you may not be familiar with the term. However, there is no doubt that you have used some regular expression concepts that do not involve scripts.
For example, you are likely to use ? a nd a wildcard to find files on your hard drive. W ildcards match individual characters in the file name, while wildcards match zero or more characters. L ike data?. A pattern like dat looks for the following files:
data1.dat data2.dat datax.dat dataN.dat
Use the character instead of ? C haracters expand the number of files found. Data*.dat all of the following files:
data.dat data1.dat data2.dat data12.dat datax.dat dataXYZ.dat
Although this search method is useful, it is limited. The concept on which regular expressions depend is introduced by understanding how the wildcard works, but regular expressions are more powerful and flexible.
Regular expressions can be used in a simple way to achieve powerful functionality. Here's a simple example:
^.+@.+\\..+$
Continuing with this tutorial will give you the freedom to apply this code.
Typical search and replace operations require you to provide exact text that matches the expected search results. While this technique may be sufficient for performing simple search and replace tasks for static text, it is inflexible and can be difficult, if not impossible, to search for dynamic text in this way.
By using regular expressions, you can:
For example, you might want to search the entire site, remove outdated material, and replace some HTML formatting tags. I n this case, you can use regular expressions to determine whether the material or the HTML-formatted tag appears in each file. T his process narrows the list of affected files to those that contain material that needs to be deleted or changed. Y ou can then use regular expressions to remove outdated material. Finally, you can use regular expressions to search for and replace tags.
The "ancestors" of regular expressions can be traced back to early studies of how the human nervous system works. Two neurophysiologists, Warren McCulloch and Walter Pitts, have developed a mathematical way to describe these neural networks.
In 1956, a mathematician named Stephen Kleene, based on the early work of McCulloch and Pitts, published a paper entitled "The Notation of Neural Network Events", introducing the concept of regular expressions. Regular expressions are expressions that describe what he calls "alge of regular sets" and therefore use the term regular expressions.
It was then discovered that this work could be applied to some early research using Ken Thompson, the main inventor of Unix, using the computational search algorithm. The first utility application for regular expressions is the qed editor in Unix.
What remains, as they say, is well-known history. Regular expressions have been an important part of text-based editors and search tools ever since.
At present, regular expressions have been widely used in many software, including operating systems such as nix (Linux, Unix, etc.), HP, PHP, C#, Java and many other development environments, as well as many applications, you can see the shadow of regular expressions.
In our C# tutorial, this section of the chapter on C# regular expressions is devoted to the knowledge of C# regular expressions.
In our Java tutorial, this section of Java Regular Expressions is devoted to knowledge of Java regular expressions.
In our JavaScript tutorial, this section of JavaScript RegExp Objects focuses on JavaScript regular expressions, and we also provide a complete JavaScript RegExp object reference manual.
In our Python basic tutorial, the Python Regular Expressions section is devoted to knowledge of Python regular expressions.
In our Ruby tutorial, ruby regular expressions This section is devoted to knowledge of Ruby regular expressions.