Regex commands for beginners

Regular expressions, also known as regex, are a powerful tool for working with text. They allow you to search for, match, and manipulate specific patterns of characters within a body of text.

Here are a few basic regex commands that every beginner should know:

1. ^ - Matches the start of a line. For example, the regex ^Hello would match the string “Hello” at the beginning of a line.
2. $ - Matches the end of a line. For example, the regex World$ would match the string “World” at the end of a line.
3. . - Matches any single character (except a newline). For example, the regex H.llo would match the strings “Hello”, “Hillo”, and “Hxllo”, but not “Hollo”.
4. ** - Matches zero or more occurrences of the preceding character or group. For example, the regex “H*llo” would match the strings “Hello”, “Hllo”, and “Hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhllo”.
5. + - The plus symbol (+) matches one or more occurrences of the preceding character or group. For example, the regex H+llo would match the strings “Hello” and “Hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhllo”, but not “Hllo”.
6. ? - The question mark (?) matches zero or one occurrence of the preceding character or group. For example, the regex H?llo would match the strings “Hello” and “Hllo”, but not “Hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhllo”.
7. [ ] - Brackets enclose a character set, which matches any single character within the set. For example, the regex H[ae]llo would match the strings “Hello” and “Hallo”, but not “Hxllo”.
8. [^ ] - When the caret symbol is placed within brackets, it negates the character set. For example, the regex H[^ae]llo would match the string “Hxllo”, but not “Hello” or “Hallo”.

9. | - The pipe symbol (

   ) represents a logical OR. For example, the regex H(e|a)llo would match the strings “Hello” and “Hallo”.

10. \d - The backslash and “d” combination matches any single digit. For example, the regex \d\d\d-\d\d-\d\d\d\d would match a string in the format “XXX-XX-XXXX”, where “X” is a digit.

These are just a few basic regex commands that can help you get started working with regular expressions. With practice and a bit of creativity, you can use these commands to perform a wide range of tasks, such as searching for and replacing specific patterns of text within a document, validating forms, and more.