Exit codes ($?) in Bash Scripting - Mini Project: Build & Apply

Understanding Exit Codes ($?) in Bash Scripts

📖 Scenario: You are writing a simple bash script to run commands and check if they worked correctly. Exit codes help you know if a command succeeded or failed.In real life, this is like checking if a light bulb is working after you install it. If it works, you get a green light (exit code 0). If it doesn't, you get a red light (non-zero exit code).

🎯 Goal: Build a bash script that runs a command, saves its exit code using $?, and prints the exit code to understand if the command succeeded or failed.

📋 What You'll Learn

Create a variable to run a command

Save the exit code of the command using $?

Print the exit code to the terminal

💡 Why This Matters

🌍 Real World

Exit codes are used in scripts to detect errors and decide what to do next, like retrying a command or stopping the script.

💼 Career

Understanding exit codes is essential for writing reliable automation scripts and troubleshooting problems in system administration and DevOps roles.

1

Run a command and save its exit code

Write a line that runs the command ls /tmp and then save its exit code in a variable called exit_code using $?.

Bash Scripting

# Run the command ls /tmp and save its exit code in exit_code
# Your code here

Need a hint?

Run the command first, then immediately save $? to exit_code.

2

Add a second command and save its exit code

Add a line that runs the command cat /not_exist_file and then save its exit code in a variable called exit_code using $?.

Bash Scripting

ls /tmp
exit_code=$?
# Run the command cat /not_exist_file and save its exit code in exit_code
# Your code here

Need a hint?

Run the second command and save its exit code just like the first.

3

Print the exit code after the second command

Add a line to print the text Exit code is: followed by the value of the variable exit_code.

Bash Scripting

ls /tmp
exit_code=$?
cat /not_exist_file
exit_code=$?
# Print the exit code
# Your code here

Need a hint?

Use echo to print the message and the variable.

4

Print exit code after the first command too

Add a line to print the text First command exit code: followed by the exit code of the first command. Save the first command's exit code in a variable called first_exit_code before running the second command.

Bash Scripting

ls /tmp
first_exit_code=$?
cat /not_exist_file
exit_code=$?
echo "First command exit code: $first_exit_code"
echo "Exit code is: $exit_code"  # Print the second command exit code
# Your code here

Need a hint?

Save the first exit code before running the second command, then print it.