Sed replace value with variable [duplicate] - bash

Question

This question already has answers here:
sed substitution with Bash variables
(6 answers)
Closed 5 years ago.
I have a variable in a config, which I would like to replace with a value.
ROOT="rROOT"
I would like to replace that with
ROOT="$root"
So with the value of $root (Important are the quotation marks).
So far I have tried it that way
sed -i s/'ROOT=rROOT'/'ROOT="$root"'/g $directory/settings.conf
The result is that
ROOT="$root"
But this is stored in the variable $root (It is always a path)
root: /
How can I replace rROOT with the value of $root?
Sed Version: (GNU sed) 4.2.2

Answer 1

Ok, don't like to ruin my scripts for testing:
cat tageslog.sh | sed "s/alt=185094/alt=\${root}/g"
Use double quotes, but mask the dollar sign, so it doesn't get lost and root interpreted while calling sed.
Use ${root} instead of "$root".
sed "s/ROOT=.rRoot./ROOT=\${root}/g" $directory/settings.conf
if this works, use the -i switch:
sed -i "s/ROOT=.rRoot./ROOT=\${root}/g" $directory/settings.conf

Answer 2

You have different problems:
Testing with echo
I think you tested your command with
echo ROOT="rROOT" | sed s/'ROOT=rROOT'/'ROOT="$root"'/g
The double quotes won't appear in the output of the echo, so you will end up with a command working for ROOT=rROOT.
When the inputfile has qouble quotes, you do not have to insert them.
Testing with the double quotes is possible with
echo 'ROOT="rROOT"' | sed s/'ROOT=rROOT'/'ROOT="$root"'/g
Place the double quotes outside the single quotes;
You can test this with echo:
echo 'Showing "$PWD" in double quotes is "'$PWD'"'
echo 'With additional spaces the last part is " '$PWD' " '
Root vaiable has slashes that will confuse sed.
The root variable is replaced before sed tries to understand the command.
You can use another character, like #, in the sed command:
sed 's#before#after#'
When your input has double quotes:
echo 'ROOT="rROOT"' | sed 's#ROOT="rROOT"#ROOT="'$root'"#g'
# or by remembering strings
echo 'ROOT="rROOT"' | sed -r 's#(ROOT=")rROOT(")#\1'$root'\2#g'
Input without double quotes
echo 'ROOT=rROOT' | sed 's#ROOT=rROOT#ROOT="'$root'"#g'
# or by remembering strings
echo 'ROOT=rROOT' | sed -r 's#(ROOT=)rROOT#\1"'$root'"#g'