tee for splitting output in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to save the output of ls command to a file files.txt while still showing it on the screen.

Linux CLI

ls | [1] files.txt

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

Acat

Bgrep

Ctee

Dawk

Attempts:

3 left

💡 Hint

Common Mistakes

Using cat which only reads files.

Using grep or awk which filter or process text but don't split output.

The tee command splits the output so it goes both to the file and the screen.

2fill in blank

medium

Complete the code to append the output of date command to log.txt while still showing it on the screen.

Linux CLI

date | [1] -a log.txt

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

Atee

Bcat

Chead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Using cat which does not write output to files.

Using head or tail which only show parts of input.

The -a option with tee appends output to the file instead of overwriting it.

3fill in blank

hard

Fix the error in the code to save output of echo Hello to greeting.txt and still show it on screen.

Linux CLI

echo Hello | [1] greeting.txt

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

Acat

Btee

Cecho

Dls

Attempts:

3 left

💡 Hint

Common Mistakes

Using cat which reads files but does not write output here.

Using echo or ls which do not split output.

Only tee can split output to file and screen. Others do not work here.

4fill in blank

hard

Fill both blanks to save output of ps aux to processes.txt and append output to all_processes.txt while showing on screen.

Linux CLI

ps aux | [1] processes.txt | [2] -a all_processes.txt

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

Atee

Bcat

Dgrep

Attempts:

3 left

💡 Hint

Common Mistakes

Using cat which does not split output.

Using grep which filters but does not write to files.

The first tee writes to processes.txt. The second tee -a appends to all_processes.txt.

5fill in blank

hard

Fill all three blanks to save output of find . -type f to files.txt, append to all_files.txt, and filter lines containing .txt.

Linux CLI

find . -type f | [1] files.txt | [2] -a all_files.txt | [3] '.txt'

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

Atee

Cgrep

Dcat

Attempts:

3 left

💡 Hint

Common Mistakes

Using cat which does not write output to files.

Using grep before tee which changes output flow.

First two blanks use tee to write and append files. Last blank uses grep to filter lines.

Practice

1. What does the tee command do in Linux?

easy

A. It splits the output of a command to both the screen and a file simultaneously.

B. It merges multiple files into one.

C. It deletes files after displaying their content.

D. It changes file permissions.

Solution

1. Step 1: Understand the purpose of tee

   The tee command takes the output of a command and sends it to both the terminal (screen) and a file at the same time.

2. Step 2: Compare options with this behavior

   Only It splits the output of a command to both the screen and a file simultaneously. describes this behavior correctly. Other options describe unrelated actions.

3. Final Answer:

   It splits the output of a command to both the screen and a file simultaneously. -> Option A

4. Quick Check:

   tee splits output = A [OK]

Hint: Remember: tee shows output and saves it simultaneously [OK]

Common Mistakes:

• Thinking tee merges files
• Confusing tee with file deletion
• Assuming tee changes permissions

2. Which of the following is the correct syntax to use tee to save output to a file named log.txt?

easy

A. tee command > log.txt

B. command tee > log.txt

C. command | tee log.txt

D. command > tee log.txt

Solution

1. Step 1: Recall the pipe usage with tee

   The output of a command is piped using | into tee to save it to a file.

2. Step 2: Check each option's syntax

   Only command | tee log.txt uses the correct pipe syntax: command | tee log.txt. Others misuse redirection or order.

3. Final Answer:

   command | tee log.txt -> Option C

4. Quick Check:

   Pipe output to tee = D [OK]

Hint: Use pipe (|) before tee to split output [OK]

Common Mistakes:

• Using > before tee instead of pipe
• Placing tee before command
• Confusing redirection with tee syntax

3. What will be the output on the screen and in the file output.txt after running this command?

echo "Hello World" | tee output.txt

medium

A. Screen: Hello WorldFile output.txt: Hello World

B. Screen: (empty)File output.txt: Hello World

C. Screen: Hello WorldFile output.txt: (empty)

D. Screen: (empty)File output.txt: (empty)

Solution

1. Step 1: Understand echo piped to tee

   The echo command outputs "Hello World" which is piped to tee. Tee writes it to the file and also outputs it to the screen.

2. Step 2: Determine output locations

   Both the screen and the file output.txt will contain "Hello World".

3. Final Answer:

   Screen: Hello World; File output.txt: Hello World -> Option A

4. Quick Check:

   tee duplicates output to screen and file = B [OK]

Hint: tee shows output on screen and saves to file simultaneously [OK]

Common Mistakes:

• Assuming tee only writes to file
• Thinking tee suppresses screen output
• Confusing echo output with tee behavior

4. You want to append output to log.txt instead of overwriting it. Which command fixes the error in this script?

ls -l | tee log.txt

medium

A. ls -l > tee -a log.txt

B. ls -l | tee > log.txt

C. tee -a ls -l log.txt

D. ls -l | tee -a log.txt

Solution

1. Step 1: Identify the need to append output

   The default tee overwrites files. To append, use the -a option.

2. Step 2: Check correct syntax for appending

   ls -l | tee -a log.txt correctly uses tee -a log.txt with pipe from ls -l. Others misuse redirection or order.

3. Final Answer:

   ls -l | tee -a log.txt -> Option D

4. Quick Check:

   Use -a with tee to append = C [OK]

Hint: Add -a option to tee to append instead of overwrite [OK]

Common Mistakes:

• Using > redirection with tee incorrectly
• Placing tee before command
• Forgetting the -a option for append

5. You want to run a script that outputs system info and save it to sysinfo.log while still seeing it live on screen. You also want to keep adding to the log without erasing old data. Which command achieves this?

hard

A. uname -a | tee sysinfo.log

B. uname -a | tee -a sysinfo.log

C. tee -a sysinfo.log | uname -a

D. uname -a > tee -a sysinfo.log

Solution

1. Step 1: Understand the requirement to append and show output

   The command must show output on screen and append to the file without overwriting.

2. Step 2: Identify correct tee usage

   uname -a | tee -a sysinfo.log uses tee -a sysinfo.log with pipe from uname -a, which appends and shows output live.

3. Step 3: Eliminate incorrect options

   uname -a | tee sysinfo.log overwrites file. Options C and D misuse command order and redirection.

4. Final Answer:

   uname -a | tee -a sysinfo.log -> Option B

5. Quick Check:

   Pipe output to tee -a to append and show = A [OK]

Hint: Use pipe and tee -a to append and display output live [OK]

Common Mistakes:

• Forgetting -a causes overwrite
• Placing tee before command
• Using > redirection incorrectly with tee