ARM Template Functions and Conditions

ARM templates include a rich library of built-in functions and support conditional resource deployment. In this lesson, you will learn the most important template functions, how to write conditions, and how to use copy loops for creating multiple resources.

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Template Functions Overview

ARM template functions follow the syntax:

"[functionName(arg1, arg2)]"

All expressions are enclosed in square brackets. Functions can be nested:

"[format('vm-{0}-{1}', parameters('environment'), uniqueString(resourceGroup().id))]"

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Essential Function Categories

String Functions

Function	Description	Example
format()	String formatting with placeholders	format('vm-{0}', parameters('env'))
concat()	Concatenate strings	concat('prefix-', parameters('name'))
toLower()	Convert to lowercase	toLower(parameters('name'))
toUpper()	Convert to uppercase	toUpper('hello')
substring()	Extract part of a string	substring('HelloWorld', 0, 5) → 'Hello'
replace()	Replace substring	replace('hello-world', '-', '_')
split()	Split string into array	split('a,b,c', ',')
trim()	Remove whitespace	trim(' hello ')

Resource Functions