The proper use of redirection with sudo

We are faced with a problem when trying to redirect with sudo, as the second part of the command is not executed with root privileges.

sudo command > outputfile


<>—-root——<>—user—<>

The solution is to use;


‘sudo tee’ instead of the ‘>’ operator,
‘sudo tee -a’ instead of the ‘>>’ operator.

sudo command | sudo tee outputfile


<>—–root—–<>——-root——<>

The problem can be seen using a simple demonstration:

petur@laptop:/tmp$ sudo date > output
petur@laptop:/tmp$ ls -l
total 4
-rw-r--r-- 1 petur petur 30 2010-07-06 23:14 output

petur.petur is the owner of the output file.

petur@laptop:/tmp$ rm output

petur@laptop:/tmp$ sudo date | sudo tee output

Tue Jul  6 23:15:31 CEST 2010

petur@laptop:/tmp$ ls -l
total 4
-rw-r--r-- 1 root root 30 2010-07-06 23:15 output

root.root is the owner of the output file