How to Redirect Output to a Location You Don’t Have Permission to Write To in Linux

When working on Linux systems, you may come across scenarios where you need to redirect output to a file in a directory where you don’t have write permission. This often leads to the frustrating “Permission denied” error, especially when using sudo to execute commands.

For example, if you try the following command:

sudo ls -hal /root/ > /root/test.out

You’ll likely encounter the error:

-bash: /root/test.out: Permission denied

The issue here is that while the command ls runs as root due to sudo, the redirection (> /root/test.out) is handled by the shell running with your current user’s permissions. As a result, you can’t write to /root/ even though sudo was used for the command itself.

Solutions

Here are several effective ways to work around this problem:

1. Use sudo with Shell Redirection

The simplest way is to run the entire command inside a shell using sudo:

sudo sh -c 'ls -hal /root/ > /root/test.out'

This method tells sudo to run the sh shell, which then handles both the command and its redirection with root permissions.

2. Use tee for Redirection

Another approach is to use the tee command, which can redirect output with elevated privileges:

sudo ls -hal /root/ | sudo tee /root/test.out > /dev/null

Here, tee writes the output to /root/test.out, and the redirection to /dev/null prevents tee from printing the output to the screen. You can append to the file by using tee -a.

3. Using dd Command

A lesser-known but effective solution involves the dd command:

sudo ls -hal /root/ | sudo dd of=/root/test.out

dd is a command-line utility for copying data, and in this case, it copies the output of ls directly into the file.

4. Running Commands in a Subshell

You can also use a subshell to execute commands with sudo:

sudo bash -c "{ ls -hal /root/ > /root/test.out; }"

This approach runs the redirection inside the same command, ensuring that the output is written with elevated permissions.

The key to solving this problem lies in ensuring that both the command and its redirection are executed with root permissions. Whether you choose to use sudo sh -c, tee, dd, or a subshell, each of these methods allows you to write to restricted locations effectively.