How to save environment variables with newlines into .env file?

Question

I'm probably missing something here but I'm trying to save environment variables with newlines into a .env file. Ideally I want to do this with all available env variables (output of env).

Take this variable:

export MY_VAR="Line 1
Line 2
Line 3"

How do I save this in a .env file that would look like: variables.env

MY_VAR=Line 1\nLine2\nLine3

And how can I do this with all available env variables, like from env? I tried this:

while IFS= read -r -d '' line; do
    line=$(echo -n "$line" | sed '$!s/$/\\n/' | tr -d '\n')
    echo "$line" >> variables.env
done < <(env -0)

But this also doesn't work for \r.

Answer 1

This might be good enough for whatever it is you're trying to do:

$ cat tst.sh
#!/usr/bin/env bash

export MY_VAR="Line 1
Line 2
Line 3"

export MY_VAR2=17

regexp="^[$]?'(.*)'$"
while IFS= read -r -d '' line; do
    printf -v line '%q' "$line"
    # or you could do this if your bash version is 4.4 or newer:
    #    line="${line@Q}"
    if [[ "$line" =~ $regexp ]]; then
        line="${BASH_REMATCH[1]}"
    fi
    printf '%s\n' "$line"
done < <(env -0)

$ ./tst.sh | grep MY_VAR
MY_VAR=Line 1\nLine 2\nLine 3
MY_VAR2=17