Module 4: Filtering Results and Manipulating Data Flashcards
What does the eval command allow you to do?
The eval command allows you to calculate and manipulate field values in your report and it supports a variety of functions
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What happens if the destination field exists when using the eval command?
The values of the field are replaced by the results of eval command
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Is the index data modified when using the eval command?
No, the data is not modified and no new data is written into the index
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Are field values treated as case sensitive when using the eval command?
Yes, field values are treated in a case sensitive manner when using the eval command
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Three things the eval command allows you to?
- Calculate expressions
- Place the results in a field
- Use that field in searches or other expressions
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What are the operator types that the eval commands effects?
Arithmetic/Operators
+, -, *, /, %
Concatenation/Operators
+, .
Boolean/Operators
AND OR NOT XOR
Comparison/Operators
, <=, >=, !=, =, ==, LIKE
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What is another function the eval command can do to values?
It can convert values. For example, the eval command can convert bytes into megabytes
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The eval command must do what in order to successfully convert values?
It must be set to a new or existing field
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The eval command also has another function that will help readability?
The round (field/number, decimals) function sets the value of a field to the number of decimals you specify
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What will the result be if decimals are unspecified when using the round function in the eval command?
The result is a whole number will be present
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What command would you use if you wanted to remove a field in the search window?
Use the fields - command
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You can perform mathematical functions against fields with what when using the eval command?
You can use mathematical functions against fields with numeric field values
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When using the eval command, what does the tostring function allow you to do?
tostring allows you to convert a numeric field value to a string
example: tostring(field, “option”)
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What are some of the options of the tostring function when using the eval command?
- “commas”: applies commas. If the number includes decimals, it rounds to two decimal places
- “duration”: formats the number as “hh:mm:ss”
- “hex”: formats the number in hexadecimal
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When using the eval command, give a scenario where you would use the range function?
Use the range function to return the difference between the max and min values of _time
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True or False: eval with added characters converts numeric field values to strings?
Yes it does
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When formatting and sorting values numerically what is the proper order to accomplish this?
To order numerically, first sort, then use eval command
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Can multiple expressions be used in the eval command?
Yes multiple expressions can be used in the eval command
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What are some of the rules when using expressions with the eval command?
- Each subsequent expression references the results of previous expressions
- Expressions must be separated by commas
example: eval fieldname1 = expression1,
fieldname2 = expression2,
fieldname3 = expression3
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What are some of the rules when using the if function with the eval command?
- The if function takes 3 arguments (X,Y,Z)
- The first argument, X, is a Boolean expression
- If it evaluates to TRUE, the result evaluates to the second argument, Y
- If it evaluates to FALSE, the result evaluate to the 3rd argument, Z
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What must be included with non-numeric values (arguments) when using the if function with the eval command?
Non-numeric values must be enclosed in “double quotes”
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Are field values treated in a case sensitive manner when using the if function with the eval command?
Yes they are case sensitive
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How would you use the case function with the eval command?
case(X1, Y1, X2, Y2…)
- the 1st argument, X1, is a Boolean expression
- if it evaluates to TRUE, the result evaluates to Y1
- if it evaluates to FALSE, the next Boolean expression, X2, is evaluated, etc.
- if you want an “otherwise: clause, just test for a condition you know is true at the end
(e. g., 0=0)
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Explain when and how to use the eval function?
You would use the eval function to count the number of events that contain a specific field value, use the count and eval functions
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