Linux Practical Set B Solution – Vowels Count & Case Conversion

In this article, we will solve VNSGU TYBCA Semester 5 Linux (UNIX) Practical – Set B using shell scripting.

We will learn how to:

• Count the number of vowels in a string
• Convert a string into uppercase
• Convert a string into lowercase
• Perform the same task using different Linux/UNIX approaches

📌 Practical Question

Write a script to count the number of vowels in the entered string and convert the string into upper case or lower case.

🧠 Concepts Used

This practical covers:

• read
• Variables
• String length
• for loop
• if condition
• case
• tr
• Bash parameter expansion
• String manipulation

✅ Solution 1: Using for Loop

This is one of the best approaches for understanding the logic behind vowel counting.

Shell Script

#!/bin/bash

echo "Enter a string:"
read str

count=0

for ((i=0; i<${#str}; i++))
do
    ch=${str:$i:1}

    case "$ch" in
        a|e|i|o|u|A|E|I|O|U)
            count=$((count + 1))
            ;;
    esac
done

echo "Number of vowels: $count"

echo "Uppercase: ${str^^}"
echo "Lowercase: ${str,,}"

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Example Output

Enter a string:
Hello Linux

Number of vowels: 4
Uppercase: HELLO LINUX
Lowercase: hello linux

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🔍 Understanding the Script

Step 1: Take String Input

read str

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The entered string is stored in the variable str.

Step 2: Initialize Counter

count=0

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Initially, the number of vowels is zero.

Whenever a vowel is found, we increase the counter:

count=$((count + 1))

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Step 3: Find String Length

${#str}

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This gives the number of characters in the string.

For example:

Hello

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has a length of:

5

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Step 4: Get One Character

ch=${str:$i:1}

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This extracts one character from the string.

For example, if:

str = Hello

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then the loop extracts:

H
e
l
l
o

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one by one.

Step 5: Check for Vowels

case "$ch" in
    a|e|i|o|u|A|E|I|O|U)
        count=$((count + 1))
        ;;
esac

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If the character is one of:

a e i o u
A E I O U

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the counter is increased.

Step 6: Convert to Uppercase

${str^^}

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This converts the string into uppercase.

Example:

hello linux

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becomes:

HELLO LINUX

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Step 7: Convert to Lowercase

${str,,}

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This converts the string into lowercase.

Example:

HELLO LINUX

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becomes:

hello linux

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Note: ${str^^} and ${str,,} are Bash parameter-expansion features and are not available in very old shells.

✅ Solution 2: Using tr

Linux provides the tr command for character translation.

We can use it to convert the string into uppercase/lowercase and also count vowels.

Shell Script

#!/bin/bash

echo "Enter a string:"
read str

lower=$(echo "$str" | tr '[:upper:]' '[:lower:]')

count=$(echo "$lower" | tr -cd 'aeiou' | wc -c)

upper=$(echo "$str" | tr '[:lower:]' '[:upper:]')

echo "Number of vowels: $count"
echo "Uppercase: $upper"
echo "Lowercase: $lower"

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Example Output

Enter a string:
Hello Linux

Number of vowels: 4
Uppercase: HELLO LINUX
Lowercase: hello linux

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🔍 How tr Works

Convert to Lowercase

tr '[:upper:]' '[:lower:]'

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Converts uppercase letters into lowercase.

Convert to Uppercase

tr '[:lower:]' '[:upper:]'

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Converts lowercase letters into uppercase.

Remove Everything Except Vowels

tr -cd 'aeiou'

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Here:

• -c → complement
• -d → delete

So characters other than a, e, i, o, u are removed.

For:

Hello Linux

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the result becomes approximately:

eoiu

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Then:

wc -c

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counts the remaining characters.

Therefore:

count=$(echo "$lower" | tr -cd 'aeiou' | wc -c)

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gives the total number of vowels.

✅ Solution 3: Using grep

Another approach is to use grep to identify vowels.

Shell Script

#!/bin/bash

echo "Enter a string:"
read str

count=$(echo "$str" | grep -o -i '[aeiou]' | wc -l)

upper=$(echo "$str" | tr '[:lower:]' '[:upper:]')
lower=$(echo "$str" | tr '[:upper:]' '[:lower:]')

echo "Number of vowels: $count"
echo "Uppercase: $upper"
echo "Lowercase: $lower"

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Example Output

Enter a string:
Welcome to Linux

Number of vowels: 6
Uppercase: WELCOME TO LINUX
Lowercase: welcome to linux

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📊 Comparing the Solutions

Method Vowel Counting Case Conversion Difficulty for + case ✅ Bash ⭐ Easy tr + wc ✅ tr ⭐⭐ grep + wc ✅ tr ⭐⭐

Which solution should you use?

For a practical examination, I recommend the for loop + case solution if you want to demonstrate your shell scripting logic.

If the examiner expects Linux command usage, the tr solution is a very good option.

📝 Quick Revision

Count vowels using loop

case "$ch" in
    a|e|i|o|u|A|E|I|O|U)
        count=$((count + 1))
        ;;
esac

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Uppercase

${str^^}

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Lowercase

${str,,}

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Uppercase using tr

echo "$str" | tr '[:lower:]' '[:upper:]'

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Lowercase using tr

echo "$str" | tr '[:upper:]' '[:lower:]'

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Count vowels using tr

echo "$str" | tr -cd 'aeiou' | wc -c

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🎯 Practical Exam Tips

While writing this program in the practical exam, remember:

1. Initialize the vowel counter with 0.
2. Check both uppercase and lowercase vowels.
3. Use quotes around string variables when passing them to commands.
4. Understand how ${#str} gives the string length.
5. Remember that ${str^^} and ${str,,} are Bash-specific features.
6. If you want a more portable command-based approach, use tr.

📚 Related Linux Practical Sets

This solution is part of the VNSGU TYBCA Sem 5 Linux (UNIX) Practical – OCT/Nov 2025 solution series.

• Set A – Simple Interest & Compound Interest
• Set B – Vowels Count & Case Conversion
• Set C – Palindrome String
• Set D – File Operations & Text Processing
• Set E – Display Lines with Validation
• Set F – Count Files & Directories
• Set G – Recently Modified Files
• Set H – Employee Gross Salary

🐧 Conclusion

The Vowels Count and Case Conversion practical is a useful shell scripting exercise for understanding strings, loops, conditions, Linux commands, and Bash parameter expansion.

Try writing each solution yourself instead of simply copying the code. Understanding the logic will make it much easier to solve similar questions during the practical examination.

Happy Learning & Best of Luck for your Linux Practical! 🐧💻