How to append to a file as sudo?

Question

I want to do:

echo "something" >> /etc/config_file

But, since only the root user has write permission to this file, I can't do that. But the following also doesn't work.

sudo echo "something" >> /etc/config_file

Is there a way to append to a file in that situation without having to first open it with a sudo'd editor and then appending the new content by hand?

I am using Ubuntu 9.04 and am able to use sudo for every command I've needed to so far. Spawning a sub-shell worked. — Matt Norris, Oct 13 '09 at 14:57
Strongly related: [Redirecting stdout to a file you don't have write permission on](http://unix.stackexchange.com/q/1416/23408) (on Unix & Linux). Weakly related: [`ls` with directory path shows files, but `ls` with file pattern does not?](http://superuser.com/q/893761/150988) — Scott - Слава Україні, Aug 28 '15 at 12:47

score 458 · Accepted Answer · edited Aug 01 '19 at 23:57

458

Use tee -a (or tee --append) with sudo

tee - read from standard input and write to standard output and files
[...]
   -a, --append
      append to the given FILEs, do not overwrite
[...]

So your command becomes

echo "something" | sudo tee -a /etc/config_file

The advantages of tee over executing Bash with administrative permissions are

You do not execute Bash with administrative permissions
Only the 'write to file' part runs with advanced permissions
Quoting of a complex command is much easier

edited Aug 01 '19 at 23:57

Boris Verkhovskiy

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answered May 01 '10 at 06:25

akira

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2

On OS X tee only seems to have an -a flag. – Lri Jun 20 '12 at 14:48
Debian 8 `tee` has the `-a` append flag. – clay Mar 13 '17 at 18:46
17

Use `echo "output" | sudo tee -a file > /dev/null` if you want to skip console output. – Moshe Bixenshpaner Sep 22 '17 at 01:16
Works well for WSL as well. – kayleeFrye_onDeck Dec 08 '17 at 00:18
What if `"something"` is some _secret_ value, that you don't want to be outputted to the terminal and potential be saved in logs etc.? – quapka Aug 11 '20 at 14:45
It would be nice if sudo itself had such a feature to avoid having to use `tee` and having to redirect standard output to `/dev/null`. Something like `echo "something" | sudo --out /etc/config_file`. – Piotr Dobrogost Sep 04 '21 at 09:24

score 59 · Answer 2 · answered May 01 '10 at 05:54

59

The redirection is executed in the current shell. In order to do the redirection with elevated privileges, you must run the shell itself with elevated privileges:

sudo bash -c "somecommand >> somefile"

answered May 01 '10 at 05:54

Ignacio Vazquez-Abrams

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Doug Harris · Answer 3 · 2009-10-13T14:28:39.397

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Have sudo spawn a sub-shell:

sudo sh -c "echo 'JAVA_HOME=/usr/lib/jvm/java-6-sun' >> /etc/profile"

In this example, sudo runs "sh" with the rest as arguments.

(this is shown as an example in the sudo man page)

edited Oct 13 '09 at 14:28

answered Oct 13 '09 at 14:23

Doug Harris

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The reason is that it's your shell (running as you) that does the redirection, not sudo. Since you don't have permission to write to the file, you get the Permission denied error. What this answer does is to start a new shell that is running as root, and therefore is able to write to the file. – Randy Orrison Oct 13 '09 at 14:48
This is not the right answer. This is a right answer. Akira's got a better one, for the logic provided in that answer. – TOOGAM Jun 16 '16 at 17:42

score 11 · Answer 4 · answered Jun 16 '16 at 16:16

11

I usually use shell HERE document with sudo tee -a. Something along the lines of:

sudo tee -a /etc/profile.d/java.sh << 'EOF'
# configures JAVA
JAVA_HOME=/usr/lib/jvm/java-8-oracle
export JAVA_HOME
export PATH=$PATH:$JAVA_HOME/bin
EOF

answered Jun 16 '16 at 16:16

Nicholas Sushkin

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score 6 · Answer 5 · answered Apr 18 '14 at 18:03

6

In my opinion, the best in this case is dd:

sudo dd of=/etc/profile <<< END
JAVA_HOME=/usr/lib/jvm/java-6-sun
END

answered Apr 18 '14 at 18:03

user316693

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Be careful. This command would overwrite /etc/profile. You should add "conv=notrunc oflag=append" arguments to achieve the desired behavior. – likebike Oct 03 '21 at 11:51

score 3 · Answer 6 · edited Nov 23 '09 at 10:36

3

There may be a problem with the sudo here and the redirecting. Use a texteditor of your choice instead to add the line.

sudo nano /etc/profile

Or, you could try su instead

su
echo ‘JAVA_HOME=/usr/lib/jvm/java-6-sun’ >> /etc/profile
exit

edited Nov 23 '09 at 10:36

BinaryMisfit

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answered Oct 13 '09 at 14:10

Bobby

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Unfortunately, this produced the same result. – Matt Norris Oct 13 '09 at 14:57
1

`su -c 'echo "JAVA_HOME=/usr/lib/jvm/java-6-sun" >> /etc/profile'` should work. since there's nothing the shell can mistakenly expand in the arg to echo, single-quote the overall command. – quack quixote Oct 13 '09 at 15:55
That's fantastic. Now do this as part of a script. – Ernie Dunbar May 09 '18 at 16:02

score 2 · Answer 7 · answered Jan 12 '20 at 00:00

2

This is very simple and puts sudo first, as it is common.

sudo sed -i '$a something' /etc/config_file

$a means to append at the end of the file.

answered Jan 12 '20 at 00:00

antonio

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score 0 · Answer 8 · answered Oct 13 '09 at 14:36

This won't work you are trying to redirect (using >>) the output of sudo. What you really want to do is redirect the output of echo. I suggest you simply use your favorite editor and add that line manually to /etc/profile. This has the additional benefit that you can check whether /etc/profile already sets JAVA_HOME.

score 0 · Answer 9 · answered May 24 '15 at 22:22

Use ex-way:

sudo ex +'$put =\"FOO\"' -cwq /etc/profile

and replace FOO with your variable to append.

In some systems (such as OS X), the /etc/profile file has 444 permissions, so if you still getting permission denied, check and correct the permission first:

sudo chmod 644 /etc/profile

then try again.

How to append to a file as sudo?

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