Writing to files (echo, printf) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the content of the file after running this script?

Consider the following bash script that writes to a file named output.txt. What will be the content of output.txt after running it?

Bash Scripting

echo "Hello World" > output.txt
printf "Line1\nLine2\n" >> output.txt

A Hello World\nLine1\nLine2

B Hello World\nLine1 Line2

C Hello World

D Line1\nLine2

💡 Hint

Remember that > overwrites the file and >> appends to it.

The first command writes "Hello World" and overwrites any existing content. The second command appends two lines: "Line1" and "Line2". So the file contains three lines in total.

💻 Command Output

intermediate

What does this command write to the file?

What will be the exact content of data.txt after running this command?

Bash Scripting

printf "%s\n" "apple" "banana" "cherry" > data.txt

A apple\nbanana\ncherry

B apple\nbanana\ncherry\n

C apple\nbanana cherry

D apple banana cherry

💡 Hint

Each %s\n prints the string followed by a newline.

The printf command prints each string followed by a newline, so the file ends with a newline after "cherry".

📝 Syntax

advanced

Which option correctly appends a line with a variable to a file?

You want to append the text "User: alice" to a file named log.txt, where the username is stored in a variable user. Which command is correct?

Bash Scripting

user=alice

A printf 'User: $user\n' >> log.txt

B echo 'User: $user' >> log.txt

C printf "User: $user\n" > log.txt

D echo "User: $user" >> log.txt

💡 Hint

Think about how single and double quotes handle variables.

Double quotes allow variable expansion, so $user becomes 'alice'. Single quotes do not expand variables, so $user is written literally. Also, >> appends, > overwrites.

🔧 Debug

advanced

Why does this script not write the expected content to the file?

This script is intended to write "Count: 5" to count.txt. Why does it fail?

Bash Scripting

count=5
echo 'Count: $count' > count.txt

A Because single quotes prevent variable expansion, so $count is written literally.

B Because echo does not support variables.

C Because the file count.txt is read-only.

D Because the > operator only works with printf.

💡 Hint

Check how quotes affect variables inside echo.

Single quotes prevent the shell from expanding variables, so the literal string 'Count: $count' is written instead of 'Count: 5'.

🚀 Application

expert

How to write a multi-line formatted report to a file using printf?

You want to create a report file report.txt with the following content exactly (including newlines):

Report Summary:
- Total: 10
- Passed: 8
- Failed: 2
End of Report

Which command correctly writes this using a single printf command?

A echo -e "Report Summary:\n- Total: 10\n- Passed: 8\n- Failed: 2\nEnd of Report" > report.txt

B printf 'Report Summary:\n- Total: 10\n- Passed: 8\n- Failed: 2\nEnd of Report\n' > report.txt

C printf "Report Summary:\n- Total: %d\n- Passed: %d\n- Failed: %d\nEnd of Report\n" 10 8 2 > report.txt

D

printf "Report Summary:
- Total: 10
- Passed: 8
- Failed: 2
End of Report" > report.txt

💡 Hint

Use printf format specifiers and escape sequences carefully.

Option C uses printf with format specifiers %d and newline escapes \n correctly, writing the exact formatted report with variables.

Practice

1. Which command in bash writes the text Hello World to a file named greeting.txt and adds a newline automatically?

easy

A. echo "Hello World" > greeting.txt

B. printf "Hello World" > greeting.txt

C. echo -n "Hello World" > greeting.txt

D. printf "Hello World\n" > greeting.txt

Solution

1. Step 1: Understand echo behavior

   The echo command prints text and adds a newline by default.

2. Step 2: Compare with printf

   printf requires explicit newline characters to add a newline.

3. Final Answer:

   echo "Hello World" > greeting.txt -> Option A

4. Quick Check:

   echo adds newline automatically = A [OK]

Hint: Use echo for quick writes with newline [OK]

Common Mistakes:

• Using printf without \n misses newline
• Using echo -n suppresses newline
• Confusing > and >> operators

2. Which of the following is the correct syntax to append the line Log entry to a file log.txt using printf?

easy

A. printf "Log entry" >> log.txt

B. printf -n "Log entry" >> log.txt

C. printf "Log entry\n" >> log.txt

D. printf -e "Log entry" >> log.txt

Solution

1. Step 1: Understand printf newline requirement

   printf does not add newline automatically; you must include \n explicitly.

2. Step 2: Check append operator

   >> appends to the file without overwriting.

3. Final Answer:

   printf "Log entry\n" >> log.txt -> Option C

4. Quick Check:

   printf needs \n for newline + append with >> = C [OK]

Hint: Always add \n with printf to get a new line [OK]

Common Mistakes:

• Forgetting \n causes no newline
• Using > instead of >> overwrites file
• Using invalid printf flags like -n or -e

3. What will be the content of file.txt after running this script?

echo "Line1" > file.txt
printf "Line2\n" >> file.txt
echo -n "Line3" >> file.txt

medium

A. Line1\nLine2Line3

B. Line1\nLine2\nLine3\n

C. Line1Line2Line3

D. Line1\nLine2\nLine3

Solution

1. Step 1: Analyze echo "Line1" > file.txt

   This writes "Line1" plus newline to file.txt, overwriting existing content.

2. Step 2: Analyze printf "Line2\n" >> file.txt

   This appends "Line2" plus newline to file.txt.

3. Step 3: Analyze echo -n "Line3" >> file.txt

   This appends "Line3" without newline to file.txt.

4. Final Answer:

   Line1\nLine2\nLine3 -> Option D

5. Quick Check:

   echo adds newline, printf adds newline, echo -n no newline = D [OK]

Hint: Remember echo -n skips newline, printf needs explicit \n [OK]

Common Mistakes:

• Assuming echo -n adds newline
• Forgetting printf needs \n
• Confusing overwrite (>) and append (>>)

4. The following script is intended to write two lines to output.txt but only writes one line. What is the error?

echo "First line" > output.txt
printf "Second line" > output.txt

medium

A. printf needs \n to add newline

B. Second command overwrites the file instead of appending

C. echo should use >> to append

D. Missing quotes around Second line

Solution

1. Step 1: Check file redirection operators

   The first command uses > which creates or overwrites output.txt with "First line".

2. Step 2: Check second command redirection

   The second command also uses > which overwrites output.txt, replacing previous content.

3. Step 3: Correct approach

   To keep both lines, second command should use >> to append instead of overwrite.

4. Final Answer:

   Second command overwrites the file instead of appending -> Option B

5. Quick Check:

   Using > twice overwrites file = D [OK]

Hint: Use >> to append, > overwrites file [OK]

Common Mistakes:

• Thinking \n missing causes no second line
• Confusing > and >> operators
• Assuming echo always appends

5. You want to create a file report.txt with exactly two lines:
"Summary:"
"All tests passed"
Which script snippet correctly creates this file with proper newlines and no extra blank lines?

hard

A. printf "Summary:\nAll tests passed\n" > report.txt

B. echo "Summary:" > report.txt && echo "All tests passed" > report.txt

C. echo -n "Summary:\nAll tests passed" > report.txt

D. printf "Summary:" > report.txt && printf "All tests passed" >> report.txt

Solution

1. Step 1: Check echo commands in echo "Summary:" > report.txt && echo "All tests passed" > report.txt

   echo "Summary:" > report.txt && echo "All tests passed" > report.txt uses echo twice with > redirection, so the second command overwrites the first line.

2. Step 2: Check printf commands in printf "Summary:\nAll tests passed\n" > report.txt

   printf "Summary:\nAll tests passed\n" > report.txt uses printf with explicit \n for newlines, creating exactly two lines with no extra blank lines.

3. Step 3: Analyze Options C and D

   echo -n "Summary:\nAll tests passed" > report.txt uses echo -n which suppresses newlines and includes literal \n, so no actual new lines appear. printf "Summary:" > report.txt && printf "All tests passed" >> report.txt uses printf without \n, so lines run together.

4. Final Answer:

   printf "Summary:\nAll tests passed\n" > report.txt -> Option A

5. Quick Check:

   printf with explicit \n creates exact lines = B [OK]

Hint: Use printf with \n for precise multi-line output [OK]

Common Mistakes:

• Using echo -n with \n prints literal \n
• Forgetting \n in printf causes no new lines
• Using > and >> inconsistently