如何使用sed替换文本文件中声明的变量值

Question

I would like to edit the /etc/environment file to change the MY_VARIABLE from VALUE_01 to VALUE_02 .

Here is the context of the /etc/environment file:

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"
JAVA_HOME="/usr/java/jdk8/jdk1.8.0_92-1"
MY_VARIABLE=VALUE_01

Ideally I would like to use sed command to edit it, for example (please note it is not working command):

sed -e 'MY_VARIABLE=VALUE_02' -i /etc/environment

How can I achieve it?

Answer 1

sed -- 's/MY_VARIABLE=.*/MY_VARIABLE=VALUE_02/' /etc/environment

Once you check it works, add the -i option:

sed -i -- 's/MY_VARIABLE=.*/MY_VARIABLE=VALUE_02/' /etc/environment

You will probably need root access.

Answer 2

Instead of trying to use sed -i and hoping your version of sed implements that option and working out if it takes a mandatory argument or not (I have a feeling you're not using GNU sed like the linux tag suggests you should be), just use ed to edit files in scripts.

ed -s /etc/environment <<EOF
/^MY_VARIABLE=/c
MY_VARIABLE=VALUE_02
.
w
EOF

c hanges the first line starting with MY_VARIABLE= to the given new text, and w rites the file back to disk.