/dev/null for discarding output in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this command?

Consider the command: echo "Hello World" > /dev/null
What will be printed on the terminal after running it?

Linux CLI

echo "Hello World" > /dev/null

A Hello World

B Error: Permission denied

C No output (empty)

D The string 'Hello World' is saved to a file named /dev/null

💡 Hint

Think about what happens when output is redirected to /dev/null.

Redirecting output to /dev/null sends it to a special place that discards everything. So nothing appears on the terminal.

💻 Command Output

intermediate

What happens when you redirect error output to /dev/null?

Given the command: ls nonexistentfile 2> /dev/null
What will be the output on the terminal?

Linux CLI

ls nonexistentfile 2> /dev/null

A Creates a file named /dev/null with error details

B Displays an error message about nonexistentfile

C Lists all files in the current directory

D No output (empty)

💡 Hint

Remember that 2> redirects error messages.

The error message from ls is sent to /dev/null, which discards it, so nothing appears on the terminal.

📝 Syntax

advanced

Which command correctly discards both standard output and error?

Choose the command that sends both normal output and error messages to /dev/null, so nothing appears on the terminal.

A command &> /dev/null

B command > /dev/null 2> /dev/null

C command 2>&1 > /dev/null

D command 2> /dev/null > /dev/null

💡 Hint

Look for the syntax that redirects both outputs together.

The &> operator redirects both stdout and stderr together in Bash. Option A uses &> correctly.

🔧 Debug

advanced

Why does this command still show output?

You run: grep 'pattern' file.txt > /dev/null
But you still see error messages if the file does not exist. Why?

A Because only standard output is redirected, error output is still shown

B Because /dev/null does not discard output for grep

C Because the command syntax is invalid

D Because the file.txt is empty

💡 Hint

Think about which output streams are redirected.

Redirecting with > /dev/null only sends standard output to /dev/null. Error messages (stderr) still appear on the terminal.

🚀 Application

expert

How to silently run a script ignoring all output and errors?

You want to run myscript.sh so that it produces no output or error messages on the terminal. Which command achieves this?

A ./myscript.sh > /dev/null

B ./myscript.sh > /dev/null 2>&1

C ./myscript.sh 2> /dev/null

D ./myscript.sh &> /dev/null &

💡 Hint

Redirect both stdout and stderr to /dev/null.

Option B redirects stdout to /dev/null and then redirects stderr to where stdout points, effectively discarding both.