Is there an equivalent to tee that doesn’t output to stdout?

Question

Currently using the following and would like to remove the > /dev/null part.

cat << "EOF" | sudo tee /etc/pf.conf > /dev/null
EOF

For reference, the following throws an error.

zsh: permission denied: /etc/pf.anchors/local.test

sudo cat << "EOF" > /etc/pf.anchors/local.test
echo "Hello world"
EOF

@anubhava Writing to this file requires root privileges so `> /etc/pf.conf` doesn’t work. — sunknudsen, Mar 04 '20 at 18:57
@anubhava That’s what I tried first. It threw a permission error. See https://stackoverflow.com/a/2954835/4579271 — sunknudsen, Mar 04 '20 at 19:05
@anubhava Please see updated question. Thanks for helping out. — sunknudsen, Mar 04 '20 at 19:14
None as far as I'm concerned. Run the whole command in a root shell (i.e after running `sudo -s`, or `sudo bash -c 'your script here'`) — oguz ismail, Mar 04 '20 at 19:18
@anubhava, `sudo cat` has no advantage there since opening `/etc/pf.conf` is done by the shell before either `sudo` or `cat` is started, so it doesn't benefit from any privileges escalation. — Charles Duffy, Mar 04 '20 at 19:25
I don't see why you'd want to avoid using `tee`. Redirecting its standard output isn't that onerous. — chepner, Mar 05 '20 at 00:45
Also, useless use of `cat`: `sudo tee /etcpf.conf > /dev/null < — chepner, Mar 05 '20 at 00:46

KamilCuk · Answer 1 · 2020-03-04T19:30:04.637

1

You can start a new shell with root rights and redirect inside it:

sudo sh -c 'cat > "$1"' -- /etc/pf.conf

or shorter:

sudo sh -c 'cat > "$0"' /etc/pf.conf
sudo sh -c 'cat>"$0"' /etc/pf.conf

Use awk with redirection:

sudo awk -vf=/etc/pf.conf '{print > f}'

edited Mar 04 '20 at 19:30

answered Mar 04 '20 at 19:20

KamilCuk

Thanks for suggesting an answer. Can you please include the heredoc in your example? I don’t understand... – sunknudsen Mar 04 '20 at 19:21
What do you mean? You mean why does it fail with permission denied when you just do `sudo cat > file`? – KamilCuk Mar 04 '20 at 19:21
I am trying to write a one-liner that outputs the content of an elaborate (simplified in the question) heredoc to `/etc/pf.conf` using sudo. – sunknudsen Mar 04 '20 at 19:25
Just `sudo tee /etc/pf.conf >/dev/null < – KamilCuk Mar 04 '20 at 19:26
@sunknudsen, ...*why* do you object to the `>/dev/null`? – Charles Duffy Mar 04 '20 at 19:26
@CharlesDuffy I don’t, just curious to know if there is a cleaner way to write this line. I tend to learn a lot from you guys. Often there are much more elegant ways of writing this stuff that what I can come up with. – sunknudsen Mar 04 '20 at 19:29
3

Then I think the consensus is to stick to `tee >/dev/null`. – KamilCuk Mar 04 '20 at 19:30

1 Answers1