How to replace placeholder character or word in variable with value from another variable in Bash?

Question

I\'m trying to write a simple Bash script. I have a simple \"template\" variable:

template = \"my*appserver\"

I then have a function (

Answer 1

There are so many posts available online but the one which worked fine for me is as below.

There are 2 ways to achieve this, if you want to replace a string (my old string is with special character :) with another string in a file, then use this:

sed -i '/oldtext:/c\newtext: Rahul'  ./printName.txt

Secondly, if you want to search for a string and then replace it with your variable, then do this:

#here im concatinating two key + value(myvariable).
firstkey="oldtext: old"

key="newtext: "

value=$(cat ./variableStoredHere.txt)

key+=$value

result for below command will be oldtext: old

echo $firstkey 

result for below command will be will be newtext: Rahul

echo $key 


sed -i "s/$firstkey/$key/g" ./printName.txt