Custom exit codes (exit N) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the exit code of this script?

Consider this bash script:

#!/bin/bash
exit 42

What will be the exit code when this script finishes?

Bash Scripting

#!/bin/bash
exit 42

A 42

B 0

C 1

D 255

💡 Hint

The exit command returns the number you give it as the exit code.

The script uses 'exit 42', so the exit code is 42.

💻 Command Output

intermediate

What is the exit code after this command?

You run this command in bash:

exit 300

What will be the actual exit code returned?

Bash Scripting

exit 300

A 44

B 300

C 255

D 0

💡 Hint

Exit codes are limited to 0-255 and wrap around using modulo 256.

300 modulo 256 is 44, so the exit code is 44.

🔧 Debug

advanced

Why does this script always exit with code 0?

Look at this script:

#!/bin/bash
false
exit 0

Why does it always exit with code 0 even though 'false' failed?

Bash Scripting

#!/bin/bash
false
exit 0

A Because the shell ignores exit codes from commands.

B Because 'false' actually returns 0.

C Because exit codes are always 0 unless an error is caught.

D Because the script explicitly exits with 0, ignoring previous commands.

💡 Hint

The last exit command sets the script's exit code.

The script runs 'false' which returns 1, but then runs 'exit 0' which sets the exit code to 0.

🧠 Conceptual

advanced

What is the valid range for exit codes in bash?

Which of these is the correct range for exit codes in bash scripts?

A -128 to 127

B 0 to 1024

C 0 to 255

D Any integer value

💡 Hint

Exit codes are stored in a single byte.

Exit codes are 8-bit unsigned integers, so valid values are 0 to 255.

🚀 Application

expert

What is the exit code of this script?

Consider this bash script:

#!/bin/bash
if false; then
  exit 1
else
  exit 256
fi

What exit code will the script return when run?

Bash Scripting

#!/bin/bash
if false; then
  exit 1
else
  exit 256
fi

A 1

B 0

C 256

D 9

💡 Hint

256 modulo 256 is 0.

The 'if false' condition fails, so the else branch runs 'exit 256'. 256 modulo 256 is 0, so exit code is 0.

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