How to execute arbitrary command under `bash -c`

Question

What is a procedure to decorate an arbitrary bash command to execute it in a subshell? I cannot change the command, I have to decorate it on the outside.

the best I can think of is

>bash -c '<command>'

works on these:

>bash -c 'echo'
>bash -c 'echo foobar'
>bash -c 'echo \"'

but what about the commands such as

echo \'

and especially

echo \'\"

The decoration has to be always the same for all commands. It has to always work.

Answer 1

You say "subshell" - you can get one of those by just putting parentheses around the command:

x=outer
(x=inner; echo "x=$x"; exit)
echo "x=$x"

produces this:

x=inner
x=outer