Replace a text with a variable

Question

How can I do this?

sed -i 's/wiki_host/$host_name/g' /root/bin/sync

It will replace wiki_host with the text $host_name. But I want to replace it with the content of the variable..

I tried it with

sed -i 's/wiki_host/${host_name}/g' /root/bin/sync

It doesn't work either.

Solution

You need to use double quotes:

$ sed -i "s/wiki_host/${host_name}/g" /root/bin/sync

Your single quotes prevent the shell variable from being replaced with its contents.

Comments

[wisbucky]

One important caveat is that the sed delimiter (/ in this case) cannot be part of ${host_name}, otherwise you will get errors.

[Kristjan Adojaan]

In the last case you have to use other delimiters for sed, then it works with replacement value containing slashes as well. For example $ sed -i "s#wiki_host#${host_name}#g" /root/bin/sync