Welcome to the Regular Expression Tutorial! If you're new to regular expressions, you've come to the right place. Regular expressions, often shortened to "regex," are patterns used to match sequences of characters in strings. They are very powerful and can be used for a wide range of text processing tasks.
Basic Syntax
Here's a quick overview of some basic regex syntax:
.matches any character except a newline.*matches zero or more of the preceding element.+matches one or more of the preceding element.?matches zero or one of the preceding element.[]defines a character class, matching any one of the enclosed characters.^asserts the position at the start of a line.$asserts the position at the end of a line.
Examples
Let's look at a few examples to get a feel for how regular expressions work.
Example 1: Matching a Single Character
To match any single character, you can use the dot .. For example:
a.c
This pattern will match any string that has an a followed by any character and then a c, such as "abc", "axc", or "agc".
Example 2: Matching Zero or More Characters
To match zero or more occurrences of a character, you can use the asterisk *. For example:
a.*
This pattern will match any string that starts with an a followed by any number of characters, such as "ax", "axx", "axxx", and so on.
Example 3: Matching One or More Characters
To match one or more occurrences of a character, you can use the plus sign +. For example:
a+
This pattern will match any string that starts with an a followed by at least one other character, such as "ax", "axx", "axxx", but not "a".
Resources
For more in-depth information, check out our comprehensive guide on Regular Expressions.