Add extracted strings to a collection in order to generate a report.įor many applications that deal with strings or that parse large blocks of text, regular expressions are an indispensable tool.Extract, edit, replace, or delete text substrings.Validate text to ensure that it matches a predefined pattern (such as an email address).The extensive pattern-matching notation of regular expressions enables you to quickly parse large amounts of text to:
In contrast, the search with search and != in the following example doesn't return any events because all of the events with field City where the field Country is null are excluded.Regular expressions provide a powerful, flexible, and efficient method for processing text. Also, the Country field is displayed, but the values are null. As a result, 5 events are displayed for the City field, even though a Country field was not defined for those events. This search returns the union of two groups of events: events where the field Country is defined and has a value not equal to "Canada" and events where the field Country is not defined. | makeresults count=5 | eval city="Ontario" | makeresults count=5 | eval Country="Canada" The search with regex and != in the following example creates 5 events with Country="Canada" and 5 events with City="Ontario", and filters on events where Country does not equal "Canada". This example uses a negative lookbehind assertion at the beginning of the expression. If you use != in the context of the regex command, keep this behavior in mind and make sure you want to include null fields in your results.Įxample 1: Keep only search results whose "_raw" field contains IP addresses in the non-routable class A (10.0.0.0/8). For example, this search will not include events that do not define the field Location. You can use a search command with != to filter for events that don't contain a field matching the search string, and for which the field is defined. The search command behaves the opposite way. For example, this search will include events that do not define the field Location.
You can use a regex command with != to filter for events that don't have a field value matching the regular expression, or for which the field is null. If you use regular expressions in conjunction with the regex command, note that != behaves differently for the regex command than for the search command. Use the rex command to either extract fields using regular expression named groups, or replace or substitute characters in a field using sed expressions. Use the regex command to remove results that match or do not match the specified regular expression. The difference between the regex and rex commands See SPL and regular expressions in the Search Manual.Īlthough != is valid within a regex command, NOT is not valid.įor general information about regular expressions, see About Splunk regular expressions in the Knowledge Manager Manual. When you use regular expressions in searches, you need to be aware of how characters such as pipe ( | ) and backslash ( \ ) are handled. The regex command is a distributable streaming command. To keep results that do not match, specify !=. You can specify that the regex command keeps results that match the expression by using =. Optional arguments Syntax: Description: Specify the field name from which to match the values against the regular expression. The regular expression must be a Perl Compatible Regular Expression supported by the PCRE library. Regex (= | != | ) Required arguments Syntax: "" Description: An unanchored regular expression. Removes results that match or do not match the specified regular expression.
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