Question

Is it possible with bash to execute a command from shell and if it returns a certain value (or an empty one) execute a command?

if [ "echo test" == "test"]; then
  echo "echo test outputs test on shell"
fi

Answer 1

Yes, you can use backticks or $() syntax:

if [ $(echo test) = "test" ] ; then
  echo "Got it"
fi

You should replace $(echo test) with

"`echo test`"

or

"$(echo test)"

if the output of the command you run can be empty.

And the POSIX “stings are equal” test operator is =.