sudo cat << EOF > 文件不起作用，sudo su 起作用

Question

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 ?

Answer 1

Output redirection (eg, >) 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'

Answer 2

Another option is tee.

cat << EOF | sudo tee -a /etc/yum.repos.d/some-name.repo
...
EOF

Answer 3

As a variation to @Yuriy Nazarov's answer, only the piped output needs to be elevated thru sudo . The piped input can stay un-elevated:

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

This means a much smaller portion of the command needs to be quoted and sent thru to sudo .

Answer 4

As others have pointed out the shell redirection is done by the current shell not by cat. sudo only changes the permission of the program that is executed not of the shell doing the redirect. My solution to this is to avoid the redirect:

sudo dd of=/etc/yum.repos.d/some-name.repo << EOF

Answer 5

if you are using ' inside the text then you may use:

$ sudo bash -c "cat > /etc/postfix/mysql-virtual_forwardings.cf << EOF
user = mail_admin
password = password
dbname = mail
query = SELECT destination FROM forwardings WHERE source='%s'
hosts = 127.0.0.1
EOF
"

this is tested on google cloud's virtual server centos 7.0