How to Append to a File as Sudo?
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...
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?
9 Answers
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
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"
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)
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
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
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
This is very simple and puts sudo first, as it is common.
sudo sed -i '$a something' /etc/config_file
$a means to append at the end of the file.
This won't work you are trying to redirect (using >>) the output of sudo. What you really want to do is redirect the output of echo. I suggest you simply use your favorite editor and add that line manually to /etc/profile. This has the additional benefit that you can check whether /etc/profile already sets JAVA_HOME.
Use ex-way:
sudo ex +'$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.
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