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Post By AdminLast Updated At 2020-06-11
What is Splunk Rex?

We all know that Splunk is a widely used software for Information monitoring and analysis. It offers searching designs to get Desired Data and Sequence them in a tabular method. By utilizing the table, chart, stats inbuilt features of splunk eval. They are very simple and easy to use, when you have Raw Information Data that aligned in a correct format. That the required data values tagged to direct in Splunk. In our blog what is Splunk Rex we will discuss more about it.

Basic Syntax with Splunk REX command

what is splunk rex

Here the total and cashout were fixed, the value amount is between ($22.00!) modifications. For example, we can design a field so, that I can filter events by cash out Amount. Equally Important We need to dollar amount, in particular, that to field without any ! at end.

What is Splunk Rex?

Rex – Splunk Search Command

Rex or the Regular Expression command is useful when you have to extract a field during the searching time. That which has not extracted automatically. In particular, Rex command works well with multi-line Events. As an illustration the following Example command gets total versions of chrome browser that processed Eventually in Highlighted User Agent. To illustrate Which String part of below Raw Data. Now let us Say, this just your Raw Data and you have to get the highlighted values, with splunk query.

018-08-22 24:59:60:227303,, GET,/destination/LAX/Details,-,90,-,,Mozilla/8.0 (Macintosh; Intel Mac OS X 10_8_5)AppleWebkit/537.36 (KHTML; Like Gecko) Chrome/29.0.1547.76Safari/537.36, 500,0,0,823,3058You can also utilise, search commands below.SPL> index=main | rex field=http_user_agent“chrome/(?.+?)Safari” | in detail top chrome_Version

Using Splunk commands with : REX

Generally We know that REX is used for field extraction in search head.

This type of command is used for extracting the fields by utilizing traditional phrases.

This command also used for replacing or substituting aspects or Digit in the Fields by Sed remark.

You can specify any fields with it, otherwise, official style showed to _Raw field.

Splunk Regular Expressions

This primer Guides you to design certain usual phrases. For Discussing usual remark usability and syntax. We have to check online resources like WWW. traditional-styles.info, or just like a manual on the subject.

The Regular Expression matches the designs of sorts in certain text. Which utilize for offering default fields, recognizing the binary file types. Automatic assignation of source types. You have an option for using traditional phrases when you explain Correlate searches, route data, in particular, Filter events, custom field extractions. In the same way, Search Commands utilize official to remark that contains regex. They evaluate functions like test and replacing.

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Regular Expressions syntax and Terminology

Regular Expression

The Meta sorts that define designs used by splunk index software that trail against the literal.

Character class

Characters that enclosed in Square brackets that used for trailing a string. For Initiating a aspects class, we have to define certain range with a hyphen. Like [A-Z], for matching any type of uppercase letters. At any rate that start with types class with Caret (^), for defining a negative meeting. Like [^A-Z] to synchronize with any type of lower case letter.

Character Type

It is similar to wild card, sorts types that show certain specific literal engagements.


To enumerate aspects types that test text modification positions like Return \r and updated line \n.


In the same fashion exact text of types for matching using a traditional type of styles with online training.


Regular Expression accept groupings, that directed by type of bracket used to enclose updated definition sorts. The Groups can define aspect classes, named capture groups, repetition matches. You can also apply quantifies and utilize alternation within enclosed groups.


Generally it Refers to supplying alternate engagements patterns in latest official explanation. Consequently they use pipe types or vertical bar. For separating alternate designs that include total usual Interpretation. For instance, grey|gray tests like grey or grey with IT training.

Quantifiers or Repetitions

Use (*,+,?) to define how to match the groups to the literal pattern. For instance *trails  0 or many, + match 1 or more, and ? Matches 0 or 1.

Back References

Specifically the literal batches that you recall for later usability, consequently for directing a back reference to value specify a dollar $ and besides number which is not Zero.


It is away to Define a group for recognizing, position in an string. As an illustration this definition will meet regular definition in the group, but it gives up the test for keeping result. Equally Important For Instance we use a look around for engagements X, in the same way that followed by Y not meeting y.

Character Types

(Dot), this matches any characters that uses sparingly.\s Match a non-white space aspects.\D it is for matching a non-digit types.\d it match a digit character\W recognize non matching sort

Alternation, Quantifiers, Groups

Every time Regular expressions accept groupings, that indicated by type of bracket. To illustrate it used to enclose regular explanation characters. You can also apply for Quantifiers (*,+,?), furthermore to enclose group and utilize alternation in other words with in the group.

[[Double brackets define splunk login -specific,]] In particular modular regular Interpretation, in the same way these are validated to 0-255 range Integers.
  • Usually Angle brackets will define, the named capturing groups. In the mean time they use syntax (?P…), for setting up a named field extraction.
{} Curly brackets will define Repetitions( ) The parentheses defines capture or trail, groups, atomic, groups, look around.? it matches zero.However, To enumerate this goes with Zero or more and more times *

Especially this example shows two ways for matching too or to.

Generally First regular expression utilities quantifier for meeting up to one more “0” meanwhile for first one.

At the same time, the second regular expression however in the same way,  furthermore use alternation for specifying the pattern.

Non-capturing Group matching

As a matter of fact, Utilize the syntax (?.....) designing groups that tested, but these are not captured. However Note that here you do not need  to include certain field name in angle brackets. In addition, the colon character after? in other words Character identify it as non-capturing group.

For Instance (?:FOO | Bar ) events either Foo or bar, or a string which is captured.

Finally Modular Regular Expressions refer to small chunks of regular expressions. At the same time this defines longer regular expression definitions. Therefore Modular Expressions define transforms .conf.