Regular Expressions
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Introduction
Regular expressions (often called regex or regexp) are powerful sequences of characters that define a search pattern. They're used for string matching within text, allowing you to search and match strings based on a specified pattern. A regular expression may contain literals or special characters with a predefined meaning.
Elements of a regular expression
- Anchors: Assert the start and end position of a line. ^ (caret) matches the start and $ (dollar sign) matches the end.
- Character class: Enclosed in square brackets [ ], defines a set of characters to match. For example, [aeiou] matches any vowel.
- Capturing group: Parentheses ( ) are used to create groups, used to treat multiple characters or subpatterns as a single unit.
- Quantifiers: Specify the number of occurrences of the preceding character, character class or group. Common quantifiers include * (zero or more), + (one or more), ? (zero or one), and {} (exact number or range).
- Alternation: | (pipe). It allows you to specify alternatives, matching either the pattern on the left or the one on the right.
- Negation: ^ (caret). Used inside a character class. Matches any character not listed in the character class. [^aeiou] matches any character that is not a vowel.
- Escape character: \ (backslash). It is used to escape a special character, allowing you to match it as a literal. Also used for encoded characters, e.g. \x20 matches a white space character.
Examples
Some example regular expressions to be used within Openscape Endpoint Management.
IP address range
The following examples can be used for matching IP address ranges
| Regular Expression | Description |
|---|---|
| 192\.168\.0\.((2[5-9])|(3[0-9])) | Starting at 192.168.0.25 until 192.168.0.39 |
| 192\.168\.1\.[0-9]{1,3} | All addresses within subnet 192.168.1.0/24 |
