How to Redirect Output to Privileged Files Using sudo on Ubuntu

Permission denied issue

If the current user lacks write permission for a file, redirecting command output to that file results in a "Permission denied" error. For example, user nick tries to list /root and write the result to /root/test.txt, which he cannot write.

sudo ls -al /root > /root/test.txt

Why the error occurs

The ls command runs with sudo, but the output redirection ( >) is performed by the current shell, which does not have permission to write to /root/test.txt. Hence the operation fails.

Understanding this allows us to apply four different solutions.

1. Run the whole command in a sudo shell

Execute the shell itself with sudo so that both the command and the redirection have elevated privileges.

sudo bash -c 'ls -al /root > /root/test.txt'

2. Write the command into a script and run the script with sudo

Create a script test.sh containing the command, make it executable, and run it with sudo.

#!/bin/bash
ls -al /root > /root/test.txt

chmod +x test.sh
sudo ./test.sh

Alternatively, use a here‑document:

sudo bash <<EOF
ls -al /root > /root/test.txt
EOF

Or pipe the command string to a sudo‑executed bash:

echo 'ls -al /root > /root/test.txt' | sudo bash

3. Use sudo -s to start a root shell

Switch to a root shell with sudo -s, run the command, then exit (Ctrl‑D).

4. Use sudo tee for redirection

The tee command writes its input to a file and optionally to standard output. By piping the output of a sudo command into sudo tee, the write operation gains root privileges.

sudo ls -al /root | sudo tee /root/test.txt > /dev/null

The > /dev/null part suppresses tee's output to the terminal.