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

Optionally, convert the extracted substring to the indicated type.

extract("x=([0-9.]+)", 1, "hello x=45.6|wo") == "45.6"


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


  • regex: A regular expression.
  • captureGroup: A positive int constant indicating the capture group to extract. 0 stands for the entire match, 1 for the value matched by the first '('parenthesis')' in the regular expression, 2 or more for subsequent parentheses.
  • text: A string to search.
  • typeLiteral: An optional type literal (e.g., typeof(long)). If provided, the extracted substring is converted to this type.


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

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


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 is 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)