Function libraries (sourcing scripts) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to source the functions from the file lib.sh.

Bash Scripting

source [1]

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

A./lib.sh

Blib

Cfunctions.sh

Dlib.sh

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add ./ before the script name.

Using just the script name without path.

Using a wrong filename.

To source a script in the current directory, you use source ./filename. This runs the script in the current shell, making its functions available.

2fill in blank

medium

Complete the code to check if the file utils.sh exists before sourcing it.

Bash Scripting

if [ -f [1] ]; then
  source ./utils.sh
fi

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

Autils.sh

B./utils.sh

Cutils

Dfunctions.sh

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for the wrong filename.

Omitting the path and checking a file that may not be found.

Using -d instead of -f.

The -f test checks if a file exists and is a regular file. Using ./utils.sh ensures the correct path is checked.

3fill in blank

hard

Fix the error in the code to source helpers.sh safely.

Bash Scripting

if [ -f helpers.sh ]; then
  [1] ./helpers.sh
fi

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

Ainclude

Bimport

Csource

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using include or import which are not bash commands.

Trying to run the script as a separate process.

In bash, source is the correct command to run a script in the current shell. include and import are not valid bash commands.

4fill in blank

hard

Fill both blanks to source functions.sh only if it exists and is readable.

Bash Scripting

if [ [1] functions.sh -a [2] functions.sh ]; then
  source ./functions.sh
fi

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

A-f

B-r

C-d

D-x

Attempts:

3 left

💡 Hint

Common Mistakes

Using -d which checks for directories.

Using -x which checks for executable permission.

Use -f to check if the file exists and is a regular file, and -r to check if it is readable.

5fill in blank

hard

Fill all three blanks to create a function load_lib that sources a given script if it exists.

Bash Scripting

load_lib() {
  if [ -f [1] ]; then
    source ./[2]
  else
    echo "File [3] not found."
  fi
}

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

A$1

Dlib.sh

Attempts:

3 left

💡 Hint

Common Mistakes

Hardcoding the filename instead of using the argument.

Using different variables for each blank.

The function uses the first argument $1 to check, source, and print the filename dynamically.

Practice

1. What is the main purpose of using function libraries in bash scripting?

easy

A. To reuse functions across multiple scripts without rewriting code

B. To make scripts run faster by compiling them

C. To encrypt scripts for security

D. To automatically update scripts from the internet

Solution

1. Step 1: Understand function libraries

   Function libraries contain reusable functions that can be shared across scripts.

2. Step 2: Identify the benefit

   Reusing functions avoids rewriting code and keeps scripts clean and maintainable.

3. Final Answer:

   To reuse functions across multiple scripts without rewriting code -> Option A

4. Quick Check:

   Function reuse = To reuse functions across multiple scripts without rewriting code [OK]

Hint: Function libraries let you reuse code easily [OK]

Common Mistakes:

• Thinking libraries speed up script execution
• Confusing libraries with encryption tools
• Assuming libraries auto-update scripts

2. Which of the following is the correct syntax to source a script named lib.sh in bash?

easy

A. load lib.sh

B. import lib.sh

C. source lib.sh

D. include lib.sh

Solution

1. Step 1: Recall bash sourcing commands

   Bash uses source or . to load another script.

2. Step 2: Identify correct syntax

   source lib.sh correctly loads the script named lib.sh.

3. Final Answer:

   source lib.sh -> Option C

4. Quick Check:

   source command = source lib.sh [OK]

Hint: Use 'source' or '.' to load scripts in bash [OK]

Common Mistakes:

• Using 'import' which is not a bash command
• Using 'include' or 'load' which are invalid in bash
• Forgetting to specify the script name

3. Given two files:

lib.sh:
function greet() {
  echo "Hello, $1!"
}

main.sh:
source ./lib.sh
greet "Alice"

What will be the output when running bash main.sh?

medium

A. greet: command not found

B. No output

C. Hello, $1!

D. Hello, Alice!

Solution

1. Step 1: Understand sourcing effect

   The source ./lib.sh command loads the greet function into main.sh.

2. Step 2: Analyze function call

   Calling greet "Alice" runs the function, echoing "Hello, Alice!".

3. Final Answer:

   Hello, Alice! -> Option D

4. Quick Check:

   Function loaded and called = Hello, Alice! [OK]

Hint: Sourcing loads functions so they can be called directly [OK]

Common Mistakes:

• Not sourcing the library before calling the function
• Expecting variable $1 to be literal
• Confusing function definition with execution

4. Consider this script snippet:

source lib.sh
greet "Bob"

But running it gives: main.sh: line 2: greet: command not found
What is the most likely cause?

medium

A. lib.sh does not define the greet function

B. The source command is misspelled

C. The greet function is called before sourcing lib.sh

D. lib.sh has wrong file permissions

Solution

1. Step 1: Check function definition in lib.sh

   If greet is not defined in lib.sh, sourcing won't load it.

2. Step 2: Analyze error message

   "command not found" means the function is missing, not a syntax or permission error.

3. Final Answer:

   lib.sh does not define the greet function -> Option A

4. Quick Check:

   Missing function definition = lib.sh does not define the greet function [OK]

Hint: Check if function exists in sourced file first [OK]

Common Mistakes:

• Assuming source command typo without checking
• Ignoring function order in script
• Not verifying file permissions

5. You want to create a reusable library utils.sh with a function timestamp that prints the current date and time. How should you write and use it in your script run.sh to print the timestamp?

hard

A. In utils.sh: timestamp() { date; } and in run.sh: ./utils.sh; timestamp

B. In utils.sh: timestamp() { echo $(date); } and in run.sh: source utils.sh; timestamp

C. In utils.sh: function timestamp { echo date; } and in run.sh: ./utils.sh; timestamp

D. In utils.sh: timestamp() { date; } and in run.sh: bash utils.sh; timestamp

Solution

1. Step 1: Define timestamp function correctly

   Use timestamp() { echo $(date); } to print current date and time.

2. Step 2: Source utils.sh in run.sh and call function

   Use source utils.sh to load the function, then call timestamp.

3. Final Answer:

   In utils.sh: timestamp() { echo $(date); } and in run.sh: source utils.sh; timestamp -> Option B

4. Quick Check:

   Correct function and sourcing = In utils.sh: timestamp() { echo $(date); } and in run.sh: source utils.sh; timestamp [OK]

Hint: Use echo $(date) inside function and source before calling [OK]

Common Mistakes:

• Running utils.sh instead of sourcing it
• Using echo date instead of echo $(date)
• Calling function without sourcing library