Why sudo cat gives a Permission denied but sudo vim works fine?

Question

I am trying to automate the addition of a repository source in my arch\'s pacman.conf file but using the echo command in my shell script. However, it fails like th

Answer 1

http://www.innovationsts.com/blog/?p=2758

As the instructions are not that clear above I am using the instructions from that blog post. With examples so it is easier to see what you need to do.

$ sudo cat /root/example.txt | gzip > /root/example.gz
-bash: /root/example.gz: Permission denied

Notice that it’s the second command (the gzip command) in the pipeline that causes the error. That’s where our technique of using bash with the -c option comes in.

$ sudo bash -c 'cat /root/example.txt | gzip > /root/example.gz'
$ sudo ls /root/example.gz
/root/example.gz

We can see form the ls command’s output that the compressed file creation succeeded.

The second method is similar to the first in that we’re passing a command string to bash, but we’re doing it in a pipeline via sudo.

$ sudo rm /root/example.gz
$ echo "cat /root/example.txt | gzip > /root/example.gz" | sudo bash
$ sudo ls /root/example.gz
/root/example.gz