Bash return permission denied error when I redirect the output of ls to a file [duplicate]

Question

I'm currently studying shell commands, one of the exercises consists in creating a structure with various directories and subdirectories.

I wrote ls -laR > hello, it was supposed to create a text file named hello. However, I get the following message bash: hello: permission denied, even when I type sudo in the beginning.

The command worked in another Linux distribution. Also, I used a few minutes ago ls -la in the directory where I want to create the file and it gave me this:

drwxr-xr-x 2 root root 4096 Nov 26 10:56 .
drwxr-xr-x 5 root root 4096 Nov 26 10:56 ..

According to the first triad I have writing privileges?

Answer 1

Because root is the owner of the directory where you want to create hello file and users from the same group and other users doesn't have permission to write in that directory, you will get bash: hello: permission denied error when you run ls -laR > hello.

Moreover, you will get exactly the same error when you run the same command using sudo in front of it. This because output redirection (the > operator) is done by the shell, not by ls, so sudo has no effect upon it. sudo has effect only on ls -laR. To prevent this, you have to login as root:

sudo -i

Then you can use redirection:

ls -laR > hello

Otherwise, you can run your bash command in a subshell with root privileges:

sudo bash -c "ls -laR > hello"

Finally, another option, instead to use redirection via the > operator, you can use tee command:

ls -laR | sudo tee hello

You don't have to use in this case sudo for ls command because users from the same group with root and all other users have read and execution permission in that directory.

Answer 2

Either put the hello file in a writable directory like with:

ls -laR > /tmp/hello

or, if you really want to create a file in a directory you don't own, run:

sudo sh -c "ls -laR > hello"