How to correctly quote `adb shell su -c`

adb shell su -c is a commonly used adb command. Normally you just need to append arguments to the command line like this:

adb shell su -c echo ab

However, things can be tricky if you want to add quotes. For example, to print a b (there are 2 spaces), these won't work:

adb shell su -c echo "a  b"

adb shell su -c "echo \"a  b\""

adb shell su -c "echo 'a  b'"

You have to use these:

adb shell su -c "\"echo \\\"a  b\\\"\""

adb shell "su -c \"echo \\\"a  b\\\"\""

adb shell su -c "\"echo 'a  b'\""

adb shell "su -c \"echo 'a  b'\""

I'd like to know which is the standard way of writing such a command. Standard means it handles quotes correctly and in the most straightforward way.

My current research:

• adb handles command arguments the same way as ssh: Arguments are connected (with space) into a string, and that string is executed.




• su -c expects a single string as the command line, and it doesn't do the concatenation for you.

So I think the most standard way of writing adb shell su -c should be like:

adb shell "su -c \"echo \\\"a  b\\\"\""

However, I'm not very confident about this. Does anyone have concrete reference confirming what I'm doing or showing I'm doing it wrong?