Bash – sudo cat << EOF > File doesn’t work, sudo su does

bashshellsudo

I tried the following on the command prompt in bash:

sudo cat << EOF > /etc/yum.repos.d/some-name.repo
#Content
#....
#...
EOF

It complained :

-bash: /etc/yum.repos.d/some-name.repo: Permission denied

Then I did sudo su and tried the exact same thing except the sudo before cat, and it worked without any problem. What am I missing in the above ?

Best Answer

Output redirection (e.g., >) is performed by bash, not by cat, while running with your UID. To run with root's UID use sudo:

sudo bash -c 'cat << EOF > /etc/yum.repos.d/some-name.repo
line1
line2
line3
EOF'

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Use tee --append or tee -a.

echo 'deb blah ... blah' | sudo tee -a /etc/apt/sources.list

Make sure to avoid quotes inside quotes.

To avoid printing data back to the console, redirect the output to /dev/null.

echo 'deb blah ... blah' | sudo tee -a /etc/apt/sources.list > /dev/null

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The test command ([ here) has a "not" logical operator which is the exclamation point (similar to many other languages). Try this:

if [ ! -f /tmp/foo.txt ]; then
    echo "File not found!"
fi

Best Answer

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