stdout redirection (>, >>) in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to redirect the output of echo Hello to a file named greeting.txt, overwriting the file if it exists.

Linux CLI

echo Hello [1] greeting.txt

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

A<

B>

C>>

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using >> appends instead of overwriting.

Using < is for input redirection, not output.

Using | pipes output to another command, not a file.

The single greater-than symbol (>) redirects the output to a file, overwriting it if it exists.

2fill in blank

medium

Complete the code to append the output of date to a file named log.txt without deleting existing content.

Linux CLI

date [1] log.txt

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

A>

B|

C<

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using > overwrites the file, losing previous data.

Using < is for input, not output.

Using | sends output to another command.

The double greater-than symbol (>>) appends output to the file, keeping existing content.

3fill in blank

hard

Fix the error in the command to append the output of ls to files.txt.

Linux CLI

ls [1] files.txt

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

A|

B>

C>>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > overwrites the file instead of appending.

Using < is for input redirection.

Using | pipes output to another command.

To add output to the end of a file, use >>. Using > overwrites the file.

4fill in blank

hard

Fill both blanks to redirect the output of echo Test to output.txt and then append date output to the same file.

Linux CLI

echo Test [1] output.txt
date [2] output.txt

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

A>

B>>

C<

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using >> for the first command overwrites nothing, just appends.

Using < is for input, not output.

Using | pipes output, not redirecting to file.

Use > to overwrite the file first, then >> to append to it.

5fill in blank

hard

Fill all three blanks to create a file summary.txt with the output of uname -a, then append the output of whoami, and finally append the current date.

Linux CLI

uname -a [1] summary.txt
whoami [2] summary.txt
date [3] summary.txt

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

A>

B>>

C<

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using > for all commands overwrites the file each time.

Using < is for input, not output.

Using | pipes output instead of redirecting to file.

Use > to create or overwrite the file first, then >> to append outputs.

Practice

1. What does the command echo "Hello" > file.txt do in Linux?

easy

A. It writes "Hello" to file.txt, replacing any existing content.

B. It adds "Hello" to the end of file.txt without removing existing content.

C. It displays "Hello" on the screen without saving to a file.

D. It deletes file.txt if it exists.

Solution

1. Step 1: Understand the > operator

   The > operator redirects output to a file, replacing its content.

2. Step 2: Analyze the command effect

   echo "Hello" outputs "Hello" and > saves it to file.txt, overwriting old content.

3. Final Answer:

   It writes "Hello" to file.txt, replacing any existing content. -> Option A

4. Quick Check:

   > means overwrite file [OK]

Hint: Use > to overwrite file content, >> to append [OK]

Common Mistakes:

• Confusing > with >> and thinking it appends
• Believing output only shows on screen
• Assuming file is deleted

2. Which of the following commands correctly appends the text "Log entry" to a file named log.txt?

easy

A. echo "Log entry" < log.txt

B. echo "Log entry" > log.txt

C. echo "Log entry" >! log.txt

D. echo "Log entry" >> log.txt

Solution

1. Step 1: Identify append operator

   The >> operator appends output to the end of a file without deleting existing content.

2. Step 2: Match command with append operator

   Only echo "Log entry" >> log.txt uses >> correctly to append "Log entry" to log.txt.

3. Final Answer:

   echo "Log entry" >> log.txt -> Option D

4. Quick Check:

   >> means append output [OK]

Hint: Use >> to add text without erasing file [OK]

Common Mistakes:

• Using > which overwrites instead of appending
• Using < which is input redirection, not output
• Using invalid >! operator

3. Given the file content of data.txt is initially empty, what will be the content of data.txt after running these commands in order?

echo "First" > data.txt
echo "Second" >> data.txt
echo "Third" > data.txt

medium

A. Third

B. First\nSecond

C. Second\nThird

D. First\nSecond\nThird

Solution

1. Step 1: Analyze first command

   echo "First" > data.txt writes "First" to data.txt, replacing any content.

2. Step 2: Analyze second command

   echo "Second" >> data.txt appends "Second" after "First".

3. Step 3: Analyze third command

   echo "Third" > data.txt overwrites entire file with "Third" only.

4. Final Answer:

   Third -> Option A

5. Quick Check:

   Last > overwrites file content [OK]

Hint: Last > overwrites file, ignoring previous appends [OK]

Common Mistakes:

• Thinking >> always appends without overwrite
• Assuming all lines remain after last >
• Confusing ">" and ">>" effects

4. You want to append the output of date command to a file named times.log. Which command has an error and why?

A) date >> times.log
B) date > times.log
C) date >>> times.log
D) date >> times.log

medium

A. Correctly appends date output to times.log

B. Overwrites times.log with date output

C. Syntax error due to invalid operator >>>

D. gol.semit ot tuptuo etad sdneppa yltcerroC

Solution

1. Step 1: Check each redirection operator

   A uses >> (append), B uses > (overwrite), C uses >>> (invalid), D uses >> (valid).

2. Step 2: Identify invalid syntax

   Operator >>> is not valid in Linux shell, causing syntax error.

3. Final Answer:

   Syntax error due to invalid operator >>> -> Option C

4. Quick Check:

   >> is invalid operator [OK]

Hint: Only > and >> are valid output redirections [OK]

Common Mistakes:

• Using >>> instead of >>
• Thinking no space after >> is error
• Confusing > and >> effects

5. You have a script that logs errors to error.log. You want to keep all previous errors and add new ones each time the script runs. Which command should you use inside the script to save the error message "Error occurred" to the file without deleting old logs?

hard

A. echo "Error occurred" > error.log

B. echo "Error occurred" >> error.log

C. echo "Error occurred" >! error.log

D. echo "Error occurred" < error.log

Solution

1. Step 1: Understand logging requirement

   We want to keep old logs and add new errors, so appending is needed.

2. Step 2: Choose correct redirection operator

   > overwrites file, >> appends to file. So >> is correct to keep old content.

3. Final Answer:

   echo "Error occurred" >> error.log -> Option B

4. Quick Check:

   Use >> to append logs without deleting [OK]

Hint: Use >> to add logs, never > to avoid losing data [OK]

Common Mistakes:

• Using > which erases old logs
• Using < which is input redirection
• Using invalid >! operator