A Complete details about regular expression and its programming use

Programming languages are now ruling the earth. Whatever you see on website and in your cell phone is the result of such programming. You make a search there in the portal and find the things instantly. Have you ever thought what is behind it? There lies the type of programming, which is regarded to be most complex, even by the computer engineers. This part is not itself a programming.

It remains there in all languages, but the periphery of the programming code is so much vast, that it is often regarded as a language itself. The thing that is talked about here is regular expressions. This article will give you a brief idea about that. What it is, where from it came; relationship of it in programming and its analogy with different languages - all will be covered here in this article.

What is Regular Expression?

Regular expression is used in all languages. The use of the codes here is too complicated. However, for simple understanding, that has to be made simpler. Take an example to understand this expression. You might be searching for a word CAT in a text. There can be some spelling errors in the writing. It can return your search with no results. Now, to get a definite search result, you can go for [CK][EA]T. While you search with the above stated keyword, you will find the words KAT, KET, CET and CAT in the document. Overlooking all the tentative spelling errors, you will find the words. Now, you can easily go through the sentences, where they are written and from there find the words, you want to replace.                                                                                        Regular expression in programming and use of REGEX

Use of REGEX

Use of the regular expression is there in every place, where you avail the find or replace option. It is there in the search engines, it is there in all the databases or SQL files, in the computer languages and even in the word programs. In general widows also, you use this type of expressions. For example, you make a search with *.txt or *.doc or similar things. When you place those in the search panel of windows, you will find all the files that are in txt or doc format.

Regular expression email matching example

Now, this is a simple one, where you have no idea about the file name, but the file extension is known to you. If there is any error, that will be in the name of the file. So, you searched with *.doc. This means that all the files with doc extension will be visible before your eyes. Now, when this simple thing is applied in vast databases, just imagine the calculation, you will have to go through. Probabilities, permutation and combination - all will have to apply to find the right search result. Vast use of the same is in computer programming languages. So, go for the analogy of this expression in different languages. A Brief history of the same and about how it is related to programming is necessary before moving ahead.


There are three historical steps about progress of regular expression in programming languages.

  • The coding and the related mathematics was first evaluated and evolved by Stephen Cole. It was done in the year of 1956. At the beginning stage, it was known as the Automata Theory.
  • In 1970s, a form of the coding has been used in the Unix. That was an effort shown from Bell labs.
  • It was brought to POSIX.2 stage in the 1980s and the first time of its use is 1992 in Perl.

Relationship Details

The language is going to give you a support in every possible ways. For the engineers, this is the language that is an essential part of their profession. There are different languages that are used by the programmers now. The expression is used in all the languages, but the annotation and analogy of the things are not always same. A study of the analogy of the expression in the different languages will give a perfect idea to you.

                                                         Regex Relationship Details

Analogy of the Languages

  • Perl - There are few specific things that you must note in the use of Regular expression in PERL. The first thing is to identify the use of the codes in the program. It can be for the conversion of the Regex and it can simply be for the purpose of comparison. Then, the test and debug statement will make the program ready to adopt the expression. When that is finalized, you can go for the generation of the code snippet. Now, copy that and paste in the IDE.
  • PHP - In PHP programming, there are two types of coding. One is ereg and the other one is preg. You can convert the coding according to the version of PHP, you are using it. Next, the function is similar to that you have done in case of Perl.
  • JavaScript - In case of Java, the action style is bit different. You will have to initially define a regex. This is basically a library of regular expression, which will be updated as you continue to construct the pattern. Now as the pattern is ready, you can follow the same procedure as the earlier one.
  • .Net - In case of the .NET framework, there is a perfect application of the regex. In fact, the programming sense applied there is much more complicated than any other languages. Microsoft, on the other hand is having a pretty poor regex configuration. This is the reason, why for any bigger program, you will have to update the .net framework, in case of Microsoft.


One of the things that is to be considered in the use of the regular expression in languages is the time taken. Time taken for testing and debugging has to be adjusted, for the perfect functioning of the query. Now, there are several applications that are used in the IT industry, in order to reduce this time investment. If you are in need of that, there are different products in the market. They are not only good in case of debugging, but excellent in encoding the program. Have them and get the support.


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