Regex: Check strings quickly and efficiently

  • by

You start writing scripts and programs and realize that you keep running into similar tasks. Instead of building cumbersome constructions of loops and queries, I recommend: Regex!

In this blog, I want to introduce you to what Regex can do specifically and what we use it for. My examples show: It’s not as complicated as it seems.

What is Regex?

In general computer science, a Regular Expression (abbreviated as Regex or RegExp) is a regular expression. That is, a string used to describe a series of strings using some syntax rules. These are mainly used in software development and web design. Regex is important, for example, in applications that expect input from the user. This is the case with online forms, for example. What you need a Regular Expression for. A regex can make your everyday life as a programmer and software developer easier in several ways.

  • Checking formats: A regular expression is used to check the correctness of a format or syntax.
  • Search texts: Helps to parse texts according to specific rules. Regex applies specific filters, for example, making it easier to search texts for keywords.
  • Examine input: Regex checks web forms for valid user input.
  • Consistent language: Everyone works with the same expressions, which simplifies communication.

What to look for when using regex. When working with regular expression statements, you have a lot of freedom, since there are always several solution options for each task to be solved with a regular expression.

However, it is not always advantageous to achieve a desired result in different ways: For example, the general instructions for a result may be too restrictive. I can also recommend an overview of the length. The more compact a regular expression is, the shorter its processing time.

How does a regular expression work?

Optionally, a regular expression can be formed using only normal characters (abc) or a combination of normal characters and metacharacters (ab * c). These are metacharacters: [ ] ( ) { } | ? + – * . ^ $ \

Meta characters have the task to describe certain constructions or arrangements of characters, like whether a character should be at the beginning of the line or whether a character can occur exactly once, more often or less often. The regex basic rules.

I have summarized some regex basic rules for you, which support me in my daily work. Use of predefined character classes. But there are also predefined character classes. They make regular expressions shorter and simpler. Regex on the more complex example: validation of e-mail addresses

The validation of an entered e-mail address requires a more complex expression. In the form the input type=email is used, but in the background the validation takes place with a regular expression. Like here for example:

[A-Za-z0-9\-\_\.\+]{1,64}@[A-Za-z0-9\-\_\.]+\.[a-zA-Z]+

The expression before the @ character defines the allowed characters and the maximum character length for the name used. After the @ sign it defines the allowed characters.

My conclusion

Regular expressions seem to be quite complicated at the beginning. When you get to grips with it you realize how quickly whole strings can be checked. And even if a regular expression can become very complex depending on the requirements, Regex is always a super support in software development for me.