Scripting with variables and loops in Azure - Step-by-Step Execution

Process Flow - Scripting with variables and loops

Start Script

↓

Set Variable

↓

Check Loop Condition

↓

Execute Loop Body

↓

Update Variable

↩Back to Check Loop Condition

The script starts by setting a variable, then checks a loop condition. If true, it runs the loop body, updates the variable, and repeats until the condition is false.

Execution Sample

Azure

count=0
while [ $count -lt 3 ]; do
  echo "Count is $count"
  count=$((count + 1))
done

This script prints the count from 0 to 2 by increasing the variable in a loop.

Process Table

Step	Variable 'count'	Condition 'count < 3'	Action	Output
1	0	True	Print 'Count is 0'	Count is 0
2	1	True	Print 'Count is 1'	Count is 1
3	2	True	Print 'Count is 2'	Count is 2
4	3	False	Exit loop

💡 Loop ends because count reaches 3 and condition '3 < 3' is False

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
count	0	1	2	3	3

Key Moments - 2 Insights

Why does the loop stop when count is 3?

Because the condition 'count < 3' becomes False at step 4, so the loop exits as shown in the execution_table row 4.

What happens if we forget to update 'count' inside the loop?

The variable 'count' would stay the same, causing the condition to always be True and the loop to run forever, never reaching the exit shown in the execution_table.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'count' at step 2?

A 1

B 0

C 2

D 3

💡 Hint

Check the 'Variable count' column in execution_table row 2.

At which step does the loop condition become false?

A Step 3

B Step 4

C Step 2

D Step 1

💡 Hint

Look at the 'Condition' column in execution_table to find when it is False.

If we start 'count' at 1 instead of 0, how many times will the loop run?

A 1 time

B 3 times

C 2 times

D 4 times

💡 Hint

Refer to variable_tracker and execution_table logic for how count changes and loop condition.

Concept Snapshot

Scripting with variables and loops:
- Initialize a variable before the loop.
- Use a condition to control loop execution.
- Inside the loop, perform actions and update the variable.
- Loop stops when condition is false.
- Always update variables to avoid infinite loops.

Full Transcript

This visual execution shows a simple script using a variable and a loop. The variable 'count' starts at 0. The loop checks if 'count' is less than 3. If yes, it prints the count and increases it by 1. This repeats until 'count' reaches 3, then the loop stops. Key points include updating the variable inside the loop and understanding when the loop ends.

Practice

1. What is the main purpose of using variables in Azure scripting?

easy

A. To store values that can be reused throughout the script

B. To create loops that repeat commands

C. To delete resources automatically

D. To connect to the internet

Solution

1. Step 1: Understand what variables do

   Variables hold information like names or numbers that you want to use again without typing them multiple times.

2. Step 2: Identify the correct purpose in scripting

   Variables help scripts remember values so you can use them repeatedly and easily change them if needed.

3. Final Answer:

   To store values that can be reused throughout the script -> Option A

4. Quick Check:

   Variables = reusable values [OK]

Hint: Variables hold values to reuse in scripts [OK]

Common Mistakes:

• Confusing variables with loops
• Thinking variables delete resources
• Believing variables connect to internet

2. Which of the following is the correct way to declare a variable named count with value 5 in an Azure CLI script?

easy

A. var count = 5

B. let count = 5

C. set count=5

D. count=5

Solution

1. Step 1: Recall Azure CLI variable syntax

   In Azure CLI scripts (bash style), variables are assigned without keywords using name=value format.

2. Step 2: Match the correct syntax

   count=5 uses count=5, which is the correct bash style assignment.

3. Final Answer:

   count=5 -> Option D

4. Quick Check:

   Azure CLI variable = name=value [OK]

Hint: Use name=value to assign variables in Azure CLI [OK]

Common Mistakes:

• Using 'var' or 'let' which are not bash syntax
• Using 'set' which is Windows CMD syntax
• Adding spaces around '=' which breaks assignment

3. What will be the output of this Azure CLI script snippet?

for i in 1 2 3; do
  echo $((i * 2))
done

medium

A. 2 4 6

B. 0 1 2

C. 1 2 3

D. Syntax error

Solution

1. Step 1: Understand the loop iterations

   The loop runs with i values 1, then 2, then 3.

2. Step 2: Calculate the expression inside echo

   Each iteration prints i multiplied by 2: 1*2=2, 2*2=4, 3*2=6.

3. Final Answer:

   2 4 6 -> Option A

4. Quick Check:

   Loop * 2 = 2 4 6 [OK]

Hint: Multiply loop variable inside $(( )) for math [OK]

Common Mistakes:

• Confusing echo $i with echo $((i * 2))
• Expecting space-separated output on one line
• Thinking syntax error due to missing semicolons

4. Identify the error in this Azure CLI script snippet:

for i in 1 2 3 do
  echo $i
done

medium

A. echo command is incorrect

B. Variable $i is not defined

C. Missing semicolon or newline after for statement

D. done keyword is missing

Solution

1. Step 1: Check for correct for loop syntax

   In bash scripts, the for loop header must end with a semicolon or a newline before the do keyword.

2. Step 2: Identify the missing semicolon or newline

   The snippet has no semicolon or newline after for i in 1 2 3, causing syntax error.

3. Final Answer:

   Missing semicolon or newline after for statement -> Option C

4. Quick Check:

   For loop header needs semicolon/newline before do [OK]

Hint: Add semicolon or newline before do in for loops [OK]

Common Mistakes:

• Forgetting semicolon after for statement
• Assuming $i is undefined
• Thinking echo syntax is wrong

5. You want to create 3 Azure resource groups named rg1, rg2, and rg3 using a script with a loop and a variable prefix rg. Which script snippet correctly achieves this?

hard

A. prefix=rg
for i in 1 2 3; do
az group create --name $prefix + $i --location eastus
done

B. prefix=rg
for i in 1 2 3; do
az group create --name "$prefix$i" --location eastus
done

C. prefix=rg
for i in 1 2 3; do
az group create --name prefix$i --location eastus
done

D. for i in 1 2 3; do
az group create --name "rg" + i --location eastus
done

Solution

1. Step 1: Understand variable concatenation in bash

   To combine a variable and a number, use double quotes and place variables side by side like "$prefix$i".

2. Step 2: Check each option for correct syntax

   prefix=rg for i in 1 2 3; do az group create --name "$prefix$i" --location eastus done correctly uses "$prefix$i" to form names rg1, rg2, rg3. Others use invalid concatenation or miss quotes.

3. Final Answer:

   prefix=rg for i in 1 2 3; do az group create --name "$prefix$i" --location eastus done -> Option B

4. Quick Check:

   Use "$prefix$i" to join strings in bash [OK]

Hint: Use "$prefix$i" to join variable and number in bash [OK]

Common Mistakes:

• Using + for string concat in bash
• Not quoting variable expansions
• Writing variable names without $ sign