mjhjmtu

How do I use sed to edit the file /etc/heat/heat.conf?

I want to add the new lines under the default section

[DEFAULT]
rabbit_host =controller
rabbit_password =RABBIT_PASS

You can use a /regexp/ address to find the line containing [DEFAULT], and then an append (a) command to add lines under it. Pass -i to sed to have it modify the file in-place (you might want to run without it first to make sure it's doing the right thing; it will output what the changed file will look like without actually changing it):

# sed -i '/^[DEFAULT]$/a rabbit_host =controllernrabbit_password =RABBIT_PASS' /etc/heat/heat.conf

if you have a file /tmp/a with the contnet

hello my friend

You can use sed to replace strings:

sed -i 's/hello/hi/g' /tmp/a

this will result in:

hi my friend

see: man sed

Also you can add lines without sed to a file by using >>:

echo "I like you">>/tmp/a

I am sure the requester has found a solution by now but just in case.

This request is ideal for application crudini
it is available for all the major linux dustibutions
for example the following will add a line to DEFAULT section of /etc/heat/heat.conf

crudini --set /etc/heat/heat.conf DEFAULT mysetting true

The section:

[DEFAULT]
rabbit_host =controller
rabbit_password =RABBIT_PASS
mysetting = true

will update if entry already in conf file.

Old school ed approach

ed -s test <<EOF
/^[DEFAULT]$/
a
rabbit_host =controller
rabbit_password =RABBIT_PASS
.
w
q
EOF