Why conditionals branch script logic in Bash Scripting - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a file exists.

Bash Scripting

if [ -e [1] ]; then
  echo "File exists"
fi

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

Afilename

B-f

C/tmp

Dmyfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the test option like -f instead of the file name.

Leaving the blank empty.

The test command [ -e myfile.txt ] checks if the file named 'myfile.txt' exists.

2fill in blank

medium

Complete the code to print "Yes" if variable x equals 10.

Bash Scripting

x=10
if [ [1] -eq 10 ]; then
  echo "Yes"
fi

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

A$x

B10

C==

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using x without $ which compares string 'x' not the variable value.

Using == which is not for numeric comparison in test.

Use $x to get the value of variable x inside the test brackets.

3fill in blank

hard

Fix the error in the conditional to check if a directory exists.

Bash Scripting

DIR="/home/user"
if [ [1] "$DIR" ]; then
  echo "Directory exists"
fi

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

A-x

B-e

C-d

D-f

Attempts:

3 left

💡 Hint

Common Mistakes

Using -f which checks for regular files, not directories.

Using -e which checks for any file type but not specifically directory.

Use -d to check if the path is a directory.

4fill in blank

hard

Fill both blanks to check if variable num is greater than 5 and print a message.

Bash Scripting

num=7
if [ [1] [2] 5 ]; then
  echo "Greater than five"
fi

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

A$num

B-gt

C-lt

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable name without $.

Using -lt which means less than.

Use $num to get the variable value and -gt to check if greater than 5.

5fill in blank

hard

Fill both blanks to create a conditional that checks if a string is empty.

Bash Scripting

str=""
if [ [1] [2] ]; then
  echo "String is empty"
fi

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

A-z

B$str

C""

D-n

Attempts:

3 left

💡 Hint

Common Mistakes

Using -n which checks for non-empty string.

Using str without the leading $.

Use -z $str to test if the string length is zero.

Practice

1. What is the main purpose of using if statements in a bash script?

easy

A. To make decisions and run different commands based on conditions

B. To repeat commands multiple times

C. To define functions

D. To declare variables

Solution

1. Step 1: Understand the role of if in scripts

   if statements check conditions and decide which commands to run next.

2. Step 2: Compare with other options

   Repeating commands is done by loops, functions define reusable code, and variables store data, so these are not the main purpose of if.

3. Final Answer:

   To make decisions and run different commands based on conditions -> Option A

4. Quick Check:

   Conditionals branch logic = A [OK]

Hint: If it chooses what to do next, it's an if statement [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if defines functions
• Mixing variable declaration with conditionals

2. Which of the following is the correct syntax to start an if statement in bash?

easy

A. if condition {}

B. if (condition) {

C. if condition then

D. if [ condition ]; then

Solution

1. Step 1: Recall bash if syntax

   Bash requires square brackets around the condition and a semicolon before then.

2. Step 2: Check other options for syntax errors

   Options A, B, and C use incorrect syntax styles not valid in bash.

3. Final Answer:

   if [ condition ]; then -> Option D

4. Quick Check:

   Bash if syntax = D [OK]

Hint: Remember: if [ condition ]; then is bash style [OK]

Common Mistakes:

• Omitting semicolon before then
• Using parentheses instead of brackets
• Missing brackets around condition

3. What will be the output of this script?

#!/bin/bash
num=5
if [ $num -gt 10 ]; then
  echo "Greater than 10"
elif [ $num -eq 5 ]; then
  echo "Equals 5"
else
  echo "Less than 5"
fi

medium

A. Equals 5

B. Greater than 10

C. Less than 5

D. No output

Solution

1. Step 1: Check the value of num

   The variable num is set to 5.

2. Step 2: Evaluate the conditions in order

   First condition checks if 5 > 10 (false), second checks if 5 == 5 (true), so it prints "Equals 5".

3. Final Answer:

   Equals 5 -> Option A

4. Quick Check:

   num=5 matches elif condition = A [OK]

Hint: Check conditions top to bottom; first true runs [OK]

Common Mistakes:

• Assuming first condition is true
• Ignoring elif branch
• Confusing numeric comparison operators

4. Identify the error in this bash conditional snippet:

if [ $value = 10 ]; then
  echo "Value is 10"
fi

medium

A. Missing semicolon before then

B. Using single equals for numeric comparison

C. Brackets should be double [[ ]]

D. No error, script runs fine

Solution

1. Step 1: Understand comparison operators in bash

   For numeric comparison inside [ ], use -eq instead of =.

2. Step 2: Check the snippet

   The snippet uses = which is for string comparison, so numeric comparison is incorrect here.

3. Final Answer:

   Using single equals for numeric comparison -> Option B

4. Quick Check:

   Numeric compare needs -eq not = [OK]

Hint: Use -eq for numbers, = for strings in [ ] [OK]

Common Mistakes:

• Confusing string and numeric operators
• Thinking = works for numbers
• Ignoring bash operator rules

5. You want a script to print "Positive", "Zero", or "Negative" based on a variable num. Which conditional structure correctly branches all cases?

hard

A. if [ $num -ge 0 ]; then echo "Positive"; else echo "Negative"; fi

B. if [ $num = 0 ]; then echo "Zero"; else echo "Non-zero"; fi

C. if [ $num -gt 0 ]; then echo "Positive"; elif [ $num -eq 0 ]; then echo "Zero"; else echo "Negative"; fi

D. if [ $num -lt 0 ]; then echo "Negative"; elif [ $num -gt 0 ]; then echo "Positive"; fi

Solution

1. Step 1: Identify all required cases

   We need to handle positive (>0), zero (=0), and negative (<0) values.

2. Step 2: Check each option for coverage

   if [ $num -gt 0 ]; then echo "Positive"; elif [ $num -eq 0 ]; then echo "Zero"; else echo "Negative"; fi covers all three cases with if, elif, else branches. Others miss zero or one case.

3. Final Answer:

   if [ $num -gt 0 ]; then echo "Positive"; elif [ $num -eq 0 ]; then echo "Zero"; else echo "Negative"; fi -> Option C

4. Quick Check:

   All cases covered with if-elif-else = B [OK]

Hint: Use if-elif-else to cover all conditions [OK]

Common Mistakes:

• Missing zero case
• Using wrong comparison operators
• Not using else for last case