Custom exit codes (exit N) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to exit the script with status 5.

Bash Scripting

exit [1]

Drag options to blanks, or click blank then click option'

A5

B0

C1

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using exit 0 which means success, not a custom code.

Forgetting to put a number after exit.

Using exit 5 ends the script with exit code 5, which can be checked by the calling process.

2fill in blank

medium

Complete the code to exit with status stored in variable code.

Bash Scripting

code=7
exit [1]

Drag options to blanks, or click blank then click option'

A${code}

Bcode

C$code

D"code"

Attempts:

3 left

💡 Hint

Common Mistakes

Using exit code which tries to exit with a command named 'code'.

Using quotes around variable name which makes it a string, not a number.

Use ${code} to expand the variable value for exit status.

3fill in blank

hard

Fix the error in the script to exit with code 3 if count is less than 5.

Bash Scripting

count=3
if [ $count [1] 5 ]; then
  exit 3
fi

Drag options to blanks, or click blank then click option'

A>

B==

C-lt

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == which tests equality, not less than.

Using = which is for assignment, not comparison.

Use -lt inside [ ] to check if count is less than 5.

4fill in blank

hard

Fill both blanks to exit with code 2 if status equals 1.

Bash Scripting

status=1
if [ $status [1] 1 ]; then
  exit [2]
fi

Drag options to blanks, or click blank then click option'

A==

B!=

C2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using != which means not equal.

Exiting with wrong code like 1 instead of 2.

Use == to check equality and exit 2 to exit with code 2.

5fill in blank

hard

Fill all three blanks to exit with code 4 if error is true and count is greater than 10.

Bash Scripting

error=true
count=15
if [ $error == true ] && [ $count [1] [2] ]; then
  exit [3]
fi

Drag options to blanks, or click blank then click option'

A>

B10

C4

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > for comparison.

Exiting with wrong code like 10 or 1.

Use > to check if count is greater than 10, and exit 4 to exit with code 4.

Practice

1. What does the command exit 0 mean in a bash script?

easy

A. The script will continue running after this command.

B. The script encountered an error and stopped.

C. The script finished successfully without errors.

D. The script restarts from the beginning.

Solution

1. Step 1: Understand exit codes in bash

   In bash, exit 0 means the script ended without any errors.

2. Step 2: Interpret the meaning of 0

   Exit code 0 always signals success to the system or calling program.

3. Final Answer:

   The script finished successfully without errors. -> Option C

4. Quick Check:

   exit 0 = success [OK]

Hint: Remember: 0 means success, anything else means error [OK]

Common Mistakes:

• Thinking exit 0 means error
• Assuming script continues after exit
• Confusing exit 0 with restart

2. Which of the following is the correct syntax to exit a bash script with code 5?

easy

A. exit 5

B. exit code 5

C. exit(5)

D. exit -5

Solution

1. Step 1: Recall bash exit syntax

   The correct way to exit with a code is exit N, where N is a number.

2. Step 2: Check each option

   exit 5 uses exit 5, which is valid syntax. Others are invalid in bash.

3. Final Answer:

   exit 5 -> Option A

4. Quick Check:

   exit N syntax = exit 5 [OK]

Hint: Use just 'exit' followed by a number, no extra words [OK]

Common Mistakes:

• Adding 'code' after exit
• Using parentheses like a function
• Using negative numbers for exit

3. What will be the exit code of this script?

#!/bin/bash
if [ -f "/tmp/file.txt" ]; then
  exit 3
else
  exit 0
fi

medium

A. 0 if /tmp/file.txt exists, 3 if not

B. 3 if /tmp/file.txt exists, 0 if not

C. Always 0

D. Always 3

Solution

1. Step 1: Understand the if condition

   The script checks if the file /tmp/file.txt exists using -f.

2. Step 2: Analyze exit codes for each case

   If the file exists, it exits with code 3; otherwise, it exits with 0.

3. Final Answer:

   3 if /tmp/file.txt exists, 0 if not -> Option B

4. Quick Check:

   File exists -> exit 3; else -> exit 0 [OK]

Hint: Match exit code to condition true/false carefully [OK]

Common Mistakes:

• Mixing up the if and else branches
• Assuming exit 0 always means file exists
• Ignoring the file check condition

4. Identify the error in this script snippet:

#!/bin/bash
exit 256

medium

A. Exit code 256 is invalid; exit codes must be 0-255.

B. Missing quotes around 256.

C. exit command should be lowercase.

D. exit requires a string, not a number.

Solution

1. Step 1: Check valid exit code range

   Bash exit codes must be between 0 and 255 inclusive.

2. Step 2: Analyze the given exit code

   256 is outside this range, so it is invalid and will wrap around or cause unexpected behavior.

3. Final Answer:

   Exit code 256 is invalid; exit codes must be 0-255. -> Option A

4. Quick Check:

   Exit codes range 0-255 [OK]

Hint: Exit codes must be 0-255, no higher numbers [OK]

Common Mistakes:

• Using numbers above 255
• Thinking quotes are needed
• Confusing case sensitivity of exit

5. You want a script to exit with code 10 if a user is not root, and 0 if root. Which snippet correctly implements this?

hard

A. if [ "$USER" != "root" ]; then exit 10; else exit 0; fi

B. if [ "$UID" -eq 0 ]; then exit 10; else exit 0; fi

C. if [ "$USER" == "root" ]; then exit 10; else exit 0; fi

D. if [ "$UID" -ne 0 ]; then exit 10; else exit 0; fi

Solution

1. Step 1: Identify how to check root user

   Root user has UID 0, so checking $UID -ne 0 means user is not root.

2. Step 2: Match exit codes to condition

   If user is not root, exit 10; else exit 0 for root user.

3. Final Answer:

   if [ "$UID" -ne 0 ]; then exit 10; else exit 0; fi -> Option D

4. Quick Check:

   UID 0 means root; non-zero means not root [OK]

Hint: Use UID 0 to check root, not USER string [OK]

Common Mistakes:

• Comparing USER string instead of UID
• Reversing the exit codes
• Using == instead of -eq for numbers