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Comparison functions for ARM templates

  • Artikkel

Resource Manager provides several functions for making comparisons in your Azure Resource Manager template (ARM template):

Tip

We recommend Bicep because it offers the same capabilities as ARM templates and the syntax is easier to use. To learn more, see the coalesce logical operator and comparison operators.

coalesce

coalesce(arg1, arg2, arg3, ...)

Returns first non-null value from the parameters. Empty strings, empty arrays, and empty objects are not null.

In Bicep, use the ?? operator instead. See Coalesce ??.

Parameters

Parameter Required Type Description
arg1 Yes int, string, array, or object The first value to test for null.
more args No int, string, array, or object More values to test for null.

Return value

The value of the first non-null parameters, which can be a string, int, array, or object. Null if all parameters are null.

Example

The following example template shows the output from different uses of coalesce.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "objectToTest": {
      "type": "object",
      "defaultValue": {
        "null1": null,
        "null2": null,
        "string": "default",
        "int": 1,
        "object": { "first": "default" },
        "array": [ 1 ]
      }
    }
  },
  "resources": [
  ],
  "outputs": {
    "stringOutput": {
      "type": "string",
      "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').string)]"
    },
    "intOutput": {
      "type": "int",
      "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').int)]"
    },
    "objectOutput": {
      "type": "object",
      "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').object)]"
    },
    "arrayOutput": {
      "type": "array",
      "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').array)]"
    },
    "emptyOutput": {
      "type": "bool",
      "value": "[empty(coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
stringOutput String default
intOutput Int 1
objectOutput Object {"first": "default"}
arrayOutput Array [1]
emptyOutput Bool True

equals

equals(arg1, arg2)

Checks whether two values are identical. The comparison is case-sensitive.

In Bicep, use the == operator instead. See Equals ==.

Parameters

Parameter Required Type Description
arg1 Yes int, string, array, or object The first value to check for equality.
arg2 Yes int, string, array, or object The second value to check for equality.

Return value

Returns True if the values are equal; otherwise, False.

Remarks

The equals function is often used with the condition element to test whether a resource is deployed.

{
  "condition": "[equals(parameters('newOrExisting'),'new')]",
  "type": "Microsoft.Storage/storageAccounts",
  "name": "[variables('storageAccountName')]",
  "apiVersion": "2022-09-01",
  "location": "[resourceGroup().location]",
  "sku": {
    "name": "[variables('storageAccountType')]"
  },
  "kind": "Storage",
  "properties": {}
}

Example

The following example checks different types of values for equality. All the default values return True.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstInt": {
      "type": "int",
      "defaultValue": 1
    },
    "secondInt": {
      "type": "int",
      "defaultValue": 1
    },
    "firstString": {
      "type": "string",
      "defaultValue": "demo"
    },
    "secondString": {
      "type": "string",
      "defaultValue": "Demo"
    },
    "firstArray": {
      "type": "array",
      "defaultValue": [ "a", "b" ]
    },
    "secondArray": {
      "type": "array",
      "defaultValue": [ "a", "b" ]
    },
    "firstObject": {
      "type": "object",
      "defaultValue": { "a": "b" }
    },
    "secondObject": {
      "type": "object",
      "defaultValue": { "a": "b" }
    }
  },
  "resources": [
  ],
  "outputs": {
    "checkInts": {
      "type": "bool",
      "value": "[equals(parameters('firstInt'), parameters('secondInt') )]"
    },
    "checkStrings": {
      "type": "bool",
      "value": "[equals(parameters('firstString'), parameters('secondString'))]"
    },
    "checkArrays": {
      "type": "bool",
      "value": "[equals(parameters('firstArray'), parameters('secondArray'))]"
    },
    "checkObjects": {
      "type": "bool",
      "value": "[equals(parameters('firstObject'), parameters('secondObject'))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value Note
checkInts Bool True
checkStrings Bool False The result is false becasue the comparison is case-sensitive.
checkArrays Bool True
checkObjects Bool True

The following example template uses not with equals.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
  ],
  "outputs": {
    "checkNotEquals": {
      "type": "bool",
      "value": "[not(equals(1, 2))]"
    }
  }
}

The output from the preceding example is:

Name Type Value
checkNotEquals Bool True

greater

greater(arg1, arg2)

Checks whether the first value is greater than the second value.

In Bicep, use the > operator instead. See Greater than >.

Parameters

Parameter Required Type Description
arg1 Yes int or string The first value for the greater comparison.
arg2 Yes int or string The second value for the greater comparison.

Return value

Returns True if the first value is greater than the second value; otherwise, False.

Example

The following example checks whether the one value is greater than the other.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstInt": {
      "type": "int",
      "defaultValue": 1
    },
    "secondInt": {
      "type": "int",
      "defaultValue": 2
    },
    "firstString": {
      "type": "string",
      "defaultValue": "A"
    },
    "secondString": {
      "type": "string",
      "defaultValue": "a"
    }
  },
  "resources": [
  ],
  "outputs": {
    "checkInts": {
      "type": "bool",
      "value": "[greater(parameters('firstInt'), parameters('secondInt') )]"
    },
    "checkStrings": {
      "type": "bool",
      "value": "[greater(parameters('firstString'), parameters('secondString'))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
checkInts Bool False
checkStrings Bool True

greaterOrEquals

greaterOrEquals(arg1, arg2)

Checks whether the first value is greater than or equal to the second value.

In Bicep, use the >= operator instead. See Greater than or equal >=.

Parameters

Parameter Required Type Description
arg1 Yes int or string The first value for the greater or equal comparison.
arg2 Yes int or string The second value for the greater or equal comparison.

Return value

Returns True if the first value is greater than or equal to the second value; otherwise, False.

Example

The following example checks whether the one value is greater than or equal to the other.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstInt": {
      "type": "int",
      "defaultValue": 1
    },
    "secondInt": {
      "type": "int",
      "defaultValue": 2
    },
    "firstString": {
      "type": "string",
      "defaultValue": "A"
    },
    "secondString": {
      "type": "string",
      "defaultValue": "a"
    }
  },
  "resources": [
  ],
  "outputs": {
    "checkInts": {
      "type": "bool",
      "value": "[greaterOrEquals(parameters('firstInt'), parameters('secondInt') )]"
    },
    "checkStrings": {
      "type": "bool",
      "value": "[greaterOrEquals(parameters('firstString'), parameters('secondString'))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
checkInts Bool False
checkStrings Bool True

less

less(arg1, arg2)

Checks whether the first value is less than the second value.

In Bicep, use the < operator instead. See Less than <.

Parameters

Parameter Required Type Description
arg1 Yes int or string The first value for the less comparison.
arg2 Yes int or string The second value for the less comparison.

Return value

Returns True if the first value is less than the second value; otherwise, False.

Example

The following example checks whether the one value is less than the other.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstInt": {
      "type": "int",
      "defaultValue": 1
    },
    "secondInt": {
      "type": "int",
      "defaultValue": 2
    },
    "firstString": {
      "type": "string",
      "defaultValue": "A"
    },
    "secondString": {
      "type": "string",
      "defaultValue": "a"
    }
  },
  "resources": [
  ],
  "outputs": {
    "checkInts": {
      "type": "bool",
      "value": "[less(parameters('firstInt'), parameters('secondInt') )]"
    },
    "checkStrings": {
      "type": "bool",
      "value": "[less(parameters('firstString'), parameters('secondString'))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
checkInts Bool True
checkStrings Bool False

lessOrEquals

lessOrEquals(arg1, arg2)

Checks whether the first value is less than or equal to the second value.

In Bicep, use the <= operator instead. See Less than or equal <=.

Parameters

Parameter Required Type Description
arg1 Yes int or string The first value for the less or equals comparison.
arg2 Yes int or string The second value for the less or equals comparison.

Return value

Returns True if the first value is less than or equal to the second value; otherwise, False.

Example

The following example checks whether the one value is less than or equal to the other.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstInt": {
      "type": "int",
      "defaultValue": 1
    },
    "secondInt": {
      "type": "int",
      "defaultValue": 2
    },
    "firstString": {
      "type": "string",
      "defaultValue": "A"
    },
    "secondString": {
      "type": "string",
      "defaultValue": "a"
    }
  },
  "resources": [
  ],
  "outputs": {
    "checkInts": {
      "type": "bool",
      "value": "[lessOrEquals(parameters('firstInt'), parameters('secondInt') )]"
    },
    "checkStrings": {
      "type": "bool",
      "value": "[lessOrEquals(parameters('firstString'), parameters('secondString'))]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
checkInts Bool True
checkStrings Bool False

Next steps