Replace a string in a file with contents copied from another file

Question

I have figured out and tried replacing strings with the help of gsed -i command like this:

gsed -i 's/sdkUniqueKey=""/sdkUniqueKey="123"/g' AppConstants.txt

Now I want to do the same operation on another string in my file but as my question states, I need to copy the contents from a different file first and then replace a string, something like:

gsed -i 's/sdkPrivateKey=""/sdkPrivateKey="contentsCopiedFromAnotherFile"/g' AppConstants.txt

One more thing, the contents (to be copied), have next line and white space in it, which I would like to remove before copying. Also it has backslash and forward slashes, hope they don't create any issues while replacing the content). Here is what I am trying to copy:

-----BEGIN PRIVATE KEY-----
MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQDNGillPEfz8d7W
0fyJejF9AYeo8OowcdOcxrpzs4IiXCwPEP1MOHAaOwGTdMwSAeQjw9WOYpE1q+DU
I+Zhh4DVUR8dIdYQtXe+oK/QfhVQMJ3AjTKRvhUmFciGwxXlnLBIkN/ePplNdq9Z
Y5DrSR0lE8X2dD+ZRAkQRpsY8TE48b9f443sbsU4sMvNaxd2XTxe2TLYRvB00w6Q
3lqZiKLzttINBCPoCjhJwBdhcF/LHsCmYhfElPqJxH27BTGBOnbICdmazdnChXQg
3hhsbJmnNDe17Spw0lY
-----END PRIVATE KEY-----

I am able to copy the contents of a file into a variable as well:

contents ="`cat fileToBeRead`"

All I need is to remove white spaces and new lines from this string and use this "contents" variable in my gsed command

Answer 1

If I have properly understood your question, the following should do the trick:

#!/bin/bash

fileToBeRead="key.txt" #Whatever

var=$(tr -d '[:blank:]\n' < $fileToBeRead)
sed -i "s#sdkPrivateKey=\"\"#sdkUniqueKey=\"$var\"#g" AppConstants.txt

Since the key contains backslashes/slashes you should use a different separator for sed (e.g. #) or the sentence will be misparsed.

EDIT:

KEY="$var" perl -pi -e 's/sdkPrivateKey=""/sdkUniqueKey="$ENV{KEY}"/g' AppConstants.txt

perl can be used instead of sed in order to avoid sed's separator issues. Check out @DennisWilliamson's comment below.