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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

Required Description 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:

| 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)
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