Function definition in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a simple Bash function call

What is the output of this Bash script?

Bash Scripting

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

A Hello, World!

B greet World

C Hello, $1!

D World

💡 Hint

Look at how the function uses the first argument $1 inside echo.

The function greet takes the first argument and prints it with Hello. Calling greet World passes 'World' as $1, so output is 'Hello, World!'.

💻 Command Output

intermediate

Return value from a Bash function

What is the output of this Bash script?

Bash Scripting

add() {
  echo $(( $1 + $2 ))
}
result=$(add 3 4)
echo $result

A 34

B add 3 4

C 3 4

D 7

💡 Hint

The function echoes the sum of two numbers, which is captured in result.

The add function calculates the sum of $1 and $2 and echoes it. The output is captured in 'result' and then printed, so the output is 7.

📝 Syntax

advanced

Identify the syntax error in this Bash function

Which option contains the correct syntax for defining a Bash function?

A greet() { echo "Hi" }

B greet() echo "Hi"

C function greet() { echo "Hi" }

D function greet { echo "Hi" }

💡 Hint

A Bash function needs parentheses and braces properly placed.

Options A and C use correct syntax: function name with parentheses followed by braces enclosing the commands. Option D is also valid in Bash but less common.

🔧 Debug

advanced

Why does this Bash function not print the expected output?

Given this script, what is the reason it prints nothing? myfunc() { local msg="Hello" } myfunc echo $msg

A The variable msg is local to the function and not visible outside.

B The function myfunc is never called.

C The echo command is inside the function but not executed.

D The variable msg is misspelled.

💡 Hint

Think about variable scope inside and outside functions.

The variable msg is declared local inside the function, so it does not exist outside. The echo command outside prints an empty value.

🚀 Application

expert

Function to check if a file exists and is readable

Which function definition correctly checks if a file exists and is readable, then prints 'File OK' or 'File missing or unreadable'?

A

check_file() {
  if [[ -r "$1" ]]; then
    echo "File OK"
  else
    echo "File missing or unreadable"
  fi
}

B

check_file() {
  if test -r "$1"; then
    echo "File OK"
  else
    echo "File missing or unreadable"
  fi
}

C

check_file() {
  if [ -f "$1" -a -r "$1" ]; then
    echo "File OK"
  else
    echo "File missing or unreadable"
  fi
}

D

check_file() {
  if [ -e "$1" ] && [ -r "$1" ]; then
    echo "File OK"
  else
    echo "File missing or unreadable"
  fi
}

💡 Hint

Check both if the file exists and is readable using test operators.

Option C uses [ -f "$1" -a -r "$1" ] which checks if the file exists and is a regular file and readable. This is the most precise check.

Practice

1. What is the correct way to define a function named greet in bash?

easy

A. greet() { echo "Hello"; }

B. function greet[] { echo "Hello"; }

C. def greet() { echo "Hello"; }

D. function greet() echo "Hello"

Solution

1. Step 1: Understand bash function syntax

   Bash functions are defined using either name() { commands; } or function name { commands; }.

2. Step 2: Check each option

   greet() { echo "Hello"; } uses the correct syntax with parentheses and braces. Options B, C, and D have syntax errors or use wrong keywords.

3. Final Answer:

   greet() { echo "Hello"; } -> Option A

4. Quick Check:

   Function syntax = greet() { ... } [OK]

Hint: Use parentheses and braces to define bash functions [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Using Python 'def' keyword
• Omitting braces around commands

2. Which of the following is a valid function definition syntax in bash?

easy

A. function myFunc() { echo "Hi"; }

B. myFunc[] { echo "Hi"; }

C. function myFunc[] echo "Hi"

D. myFunc() echo "Hi"

Solution

1. Step 1: Recall valid bash function syntax

   Bash allows defining functions as function name() { commands; } or name() { commands; }.

2. Step 2: Evaluate options

   function myFunc() { echo "Hi"; } matches valid syntax. Options A and C use square brackets incorrectly. myFunc() echo "Hi" misses braces around commands.

3. Final Answer:

   function myFunc() { echo "Hi"; } -> Option A

4. Quick Check:

   Valid syntax includes 'function name() { ... }' [OK]

Hint: Remember to use braces {} to group commands in functions [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Omitting braces after function name
• Missing parentheses after function name

3. What will be the output of this bash script?

say_hello() {
  echo "Hello, $1!"
}
say_hello Alice

medium

A. Error: function not found

B. Hello, Alice!

C. say_hello Alice

D. Hello, $1!

Solution

1. Step 1: Understand function call with argument

   The function say_hello takes one argument and prints it using $1.

2. Step 2: Substitute argument and print

   Calling say_hello Alice replaces $1 with "Alice", so output is "Hello, Alice!".

3. Final Answer:

   Hello, Alice! -> Option B

4. Quick Check:

   Function argument $1 = Alice [OK]

Hint: Use $1 to access first argument inside bash functions [OK]

Common Mistakes:

• Printing literal $1 instead of its value
• Forgetting to call the function
• Syntax errors in function definition

4. Identify the error in this bash function definition:

function greet {
  echo "Hi"
}

medium

A. Missing parentheses after function name

B. Missing braces around commands

C. Missing semicolon after echo

D. No error; parentheses are optional with 'function' keyword

Solution

1. Step 1: Check function syntax with 'function' keyword

   Bash allows function name() { commands; } or function name { commands; }. Parentheses after the name are optional.

2. Step 2: Identify if there's an error

   The code function greet { echo "Hi"; } is valid syntax.

3. Final Answer:

   No error; parentheses are optional with 'function' keyword -> Option D

4. Quick Check:

   function name { ... } [OK]

Hint: Parentheses () are optional with 'function name' [OK]

Common Mistakes:

• Omitting parentheses after function name
• Confusing braces and parentheses
• Assuming semicolon needed after echo

5. You want to create a bash function sum that takes two numbers and prints their sum. Which function definition correctly does this?

hard

A. function sum { echo $1 + $2; }

B. sum() { echo $1 + $2; }

C. sum() { echo $(($1 + $2)); }

D. sum() { echo $1 $2; }

Solution

1. Step 1: Understand arithmetic in bash functions

   To add numbers, use arithmetic expansion $(()) inside echo.

2. Step 2: Evaluate each option

   sum() { echo $(($1 + $2)); } correctly sums $1 and $2 using $(($1 + $2)). Options A and B print strings with plus sign, not sum. sum() { echo $1 $2; } prints numbers without adding.

3. Final Answer:

   sum() { echo $(($1 + $2)); } -> Option C

4. Quick Check:

   Use $(()) for arithmetic in bash functions [OK]

Hint: Use $(()) to perform math inside bash functions [OK]

Common Mistakes:

• Printing variables without arithmetic expansion
• Omitting parentheses for function definition
• Using 'function' without parentheses