extract()

Get a match for a regular expression from a source string.

Optionally, convert the extracted substring to the indicated type.

Syntax

extract(regex, captureGroup, source [, typeLiteral])

Learn more about syntax conventions.

Parameters

Name	Type	Required	Description
regex	string	✔️	A regular expression.
captureGroup	int	✔️	The capture group to extract. 0 stands for the entire match, 1 for the value matched by the first '('parenthesis')' in the regular expression, and 2 or more for subsequent parentheses.
source	string	✔️	The string to search.
typeLiteral	string		If provided, the extracted substring is converted to this type. For example, typeof(long).

Returns

If regex finds a match in source: the substring matched against the indicated capture group captureGroup, optionally converted to typeLiteral.

If there's no match, or the type conversion fails: null.

Examples

The example string Trace is searched for a definition for Duration. The match is converted to real, then multiplied it by a time constant (1s) so that Duration is of type timespan. In this example, it's equal to 123.45 seconds:

T
| extend Trace="A=1, B=2, Duration=123.45, ..."
| extend Duration = extract("Duration=([0-9.]+)", 1, Trace, typeof(real)) * time(1s) 

This example is equivalent to substring(Text, 2, 4):

extract("^.{2,2}(.{4,4})", 1, Text)