Overview

What Are Regular Expressions?

The term Regular Expressions refers to a nomenclature set that allows for powerful string matching in computer programs

Various languages offer support for the concept of Regular Expressions, and Argent employs the Microsoft Visual Basic Script implementation of Regular Expressions in our products

Which Products Use Regular Expressions?

All the Argent Advanced Technology products that include the Windows System Performance Rule Type support the use of Regular Expressions in the “How To Test Multiple Instances” of the Rule criteria

In addition, the Argent Guardian Ultra supports the use of Regular Expressions in the “Content Of Command Line Output Contains” criteria of System Command Rules and the “File Path” of a System File Rule

Also, the Argent Data Consolidator supports the use of Regular Expressions in the “File Path” of an ASCII Log Rule as well as in the Filter and Alert tabs to precisely archive and alert on the log file contents, respectively

Common Uses For Regular Expressions

Position Matching

^string                Match the beginning of a string

Example:      “^Failed” matches “Failed to authenticate” but not “Backup Failed“

string$                Match the end of a string

Example:       “Failed$” matches “Backup Failed“, but not “Failed to Authenticate“

\b                          Match word boundary

Example:       “failure\b” matches ‘failure’ in “Error: Redundancy failure in PS 3/4“

Literal Character Matching

Any Alphanumeric            Matches alphabetic and numeric characters

Example:

Special Characters

\n                          Matches new line

\t                          Matches horizontal tab

\.                          Matches dot (.)

\\                          Matches slash (\)

Character Classes

[a-zA-Z]                Matches a single alphabetic character

[0-9]                      Matches a single numeric character

\d                          Matches any digit (same as [0-9])

\s                          Matches any space character (same as [\t\r\n\v\f])

A ^ as the first character inside the brackets negates the character class

Example:      [a-zA-Z] matches the first ‘C’ in the string “35077-22C-PN6C“

Example:       [0-9] matches the ‘3’ in the string “35077-22C-PN6C“

Example:       [^0-9\.] matches ‘b’ in the string “2.0.54b“

Repetition

{x}                         Matches exactly x number of occurrences of the preceding regular expression

{x,}                        Matches x or more occurrences of the preceding regular expression

{x,y}                      Matches x to y number of occurrences of the preceding regular expression

Example:       “\d{3}” Matches “345” in the string “AB-C345-ZZ“

Example:       “\d{3,}” Matches “3456” in the string “AB-C3456-ZZ” but does not match anything in “ZZ-C32YY-4A“

Alternation & Grouping

()                        Allows you to group individual clauses

|                          Allows you to combine clauses into a single regular expression (think OR)

Example:       “(“error”|”failed”|”incomplete”)” matches strings containing “error”, “failed”, or “incomplete”

Argent Examples

RegEx Example: Argent Guardian Ultra W200X Performance Rule

In this example, we want to test the Rule criteria (under-loaded CPU) against only the enumerated instances of the CPU, not the _Total instance

Here is the Rule definition, screen by screen:

Screen G10, Argent Guardian Ultra W200x Performance Rule Definition

Screen A1B, Events And Alerts Tab In Applications

RegEx Example: Argent for Compliance

In this example, we are using a Regular Expression both to determine which Log file entries are archived into the backend database and another Regular Expression to determine which entries will post Events to the Argent Console

Here is the Rule definition, screen by screen:

Screen P6, Windows File Rule Definition Of WIN_LOG_TEST

Screen A1B, Events And Alerts Tab In Events

Additional Resources:

Microsoft Beefs Up VBScript With Regular Expressions

Microsoft Regular Expression Syntax