Why is `sudo cat /tmp/1 > file` wrong?

Question

I do sudo cat /tmp/1 > /etc/udev/rules.d/69-libmtp.rules but I get

bash: /etc/udev/rules.d/69-libmtp.rules: Permission denied

System: Ubuntu 16.04
Linux kernel: 4.6

score 2 · Accepted Answer · edited Apr 13 '17 at 12:36

2

Redirections are set up by the current shell, so sudo has no effect on your ability to write in /etc/udev/rules.d.

The usual trick for this is to use tee:

sudo tee /etc/udev/rules.d/69-libmtp.rules < /tmp/1

As pointed out by infixed though, in this particular case you don't need a redirection:

sudo cp /tmp/1 /etc/udev/rules.d/69-libmtp.rules

edited Apr 13 '17 at 12:36

Community

answered Jun 14 '16 at 19:54

Stephen Kitt

I get the output to STOUT when doing this. Is it the purpose? – Léo Léopold Hertz 준영 Jun 14 '16 at 19:58
Yes, tee outputs to the file given as its parameter, and to standard output. You can redirect the output to /dev/null if you don't want to see it! – Stephen Kitt Jun 14 '16 at 20:07
1

Redirect STDOUT to /dev/null if you do not wish to see the output – fpmurphy Jun 14 '16 at 20:09
"tee" is useful if you want to append to a file; e.g. "tee -a /protected/file" – Stephen Harris Jun 14 '16 at 23:45

1 Answers1