Function libraries (sourcing scripts) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output when sourcing a script with a function?

Consider two bash scripts:

lib.sh:

greet() {
  echo "Hello, $1!"
}

main.sh:

#!/bin/bash
source ./lib.sh
greet "Alice"

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

Bash Scripting

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

main.sh:
#!/bin/bash
source ./lib.sh
greet "Alice"

A Hello, Alice!

B greet: command not found

C Hello, $1!

D No output

💡 Hint

Sourcing a script runs its code in the current shell, making functions available.

The source command loads the function greet into the current shell. Calling greet with argument "Alice" prints "Hello, Alice!".

📝 Syntax

intermediate

Identify the correct syntax to source a script in bash

Which of the following lines correctly sources a script named utils.sh in bash?

A include utils.sh

B . utils.sh

C source utils.sh

D import utils.sh

💡 Hint

In bash, sourcing can be done with 'source' or a dot.

Both 'source utils.sh' and '. utils.sh' are valid to source a script. 'include' and 'import' are not bash commands.

🔧 Debug

advanced

Why does the function not get recognized after sourcing?

You have a script functions.sh with:

say_hello() {
  echo "Hi!"
}

You run another script:

#!/bin/bash
source ./functions.sh
say_hello

But you get:

./main.sh: line 3: say_hello: command not found

What is the most likely cause?

A functions.sh has Windows line endings causing sourcing to fail

B say_hello function is private and cannot be sourced

C source command is misspelled

D say_hello is not defined because functions.sh is empty

💡 Hint

Check the file format of the sourced script.

If functions.sh has Windows CRLF line endings, sourcing can fail silently causing functions to be undefined.

🚀 Application

advanced

How to use a function library with parameters in bash

You want to create a reusable bash function library mathlib.sh with a function add that adds two numbers and prints the result. Then you want to use it in calc.sh. Which code in calc.sh correctly uses the function to add 5 and 7?

Bash Scripting

mathlib.sh:
add() {
  echo $(($1 + $2))
}

calc.sh:
#!/bin/bash
# Fill in the missing line here
add 5 7

A run mathlib.sh

B import mathlib.sh

C . mathlib.sh &

D source ./mathlib.sh

💡 Hint

Use the command that loads functions into the current shell.

'source ./mathlib.sh' loads the add function so it can be called with arguments.

🧠 Conceptual

expert

What happens to variables when sourcing a script in bash?

If you source a script vars.sh that sets MYVAR="Hello", what is the value of MYVAR in your current shell after sourcing?

Bash Scripting

vars.sh:
MYVAR="Hello"

main.sh:
#!/bin/bash
source ./vars.sh
echo "$MYVAR"

A Empty string

B Hello

C MYVAR

D Error: MYVAR not defined

💡 Hint

Sourcing runs the script in the current shell environment.

Variables set in a sourced script become part of the current shell environment and are accessible after sourcing.