run() does not return null on failure about libsuperuser HOT 5 CLOSED

There is no reliable way to know if access was denied or the command returned no output, without echo-ing something yourself first.

from libsuperuser.

The docs at http://su.chainfire.eu/ say otherwise.

The SH variants are used for a non-root shell, where the SU variants are used for a root shell. These calls return a List containing the output of the shell commands. If there was no output, the list is empty, but not null. The result is only null in case an error occured - including the user not granting your app su access. These are blocking calls.

Please update them, if the call really does never return 'null'.

What is the best practice to check for a permission error, then?
Something like Shell.SU.run("echo foo > bar && echo 0")?

from libsuperuser.

If read the few lines of code, you'll see it does indeed sometimes return null. Specifically, when an error has occurred.

On some su binaries it does generate null, on others it does not.

Using Shell.SU.available() to check root is generally considered a good idea. Or indeed, you can echo something first. But you still need to check for null either way.

from libsuperuser.

The issue with Shell.SU.available() is that this is effectively the same as executing a custom command and checking its output. Thus, there are 2 calls with possibly 2 requests to the user (if he does not use 'always allow') and even if there are not 2 popups, it will be twice as slow, resulting in a ~700ms response instead of a ~350ms response during my tests on my Nexus 5x.

Thus, I now just run my custom command and check if it has worked afterwards without making an additional SU call.

It should definitely be added to the docs that it is not guaranteed to return null on errors that are caused by denied su access.

from libsuperuser.

If you want to use a single shell for all of this, use Shell.Builder / Shell.Interactive, that's what it's for.

I'll adjust that doc, though, it is incomplete.

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