Regex in Grep: What Regular Expressions

Regular expressions, or regex, are used to describe text patterns. A distinction is made between basic and extended. Grep is a program for Unix or Unix derivatives that is used for searching and filtering predefined strings from files.

How to use Regex in Grep

Grep is a program developed primarily for Unix operating systems. With it, you can search and filter certain strings from files and also data streams. In order to properly use regex in Grep, it is important to know the different characters that are used with Grep.

1. "^A" searches for expressions that start with an A, whereas "A$" searches for strings that end with an A.
2. If you want to cover a certain range of characters, such as whether any number can be found within the file, then you must use square brackets. Use the "[0-9]" query to check if any number occurs.
3. Use the "^" to negate this statement. So you can check if any character other than this occurs inside the square bracket. To know if any characters other than numbers occur, use the expression "^[0-9]".
4. When using the expressions with grep, write "grep `[0-9]` file", for example. Verwenden Sie hierbei die einfachen Anführungszeichen, wenn Sie die Befehle über eine Konsole ausführen möchten.