When should I see 'no device' output when running 'adb devices'?

Question

The adb documentation says that when you issue the adb devices command, you get back the state for each device: https://developer.android.com/studio/command-line/adb.html#devicestatus

The connection state of the device can be one of the following: offline, device, no device

When I run adb devices without any device connected to my machine, I get this empty result:

$adb devices

List of devices attached

My question is, under what circumstances can I see the no device state when issuing the adb devices command? Since if there are no devices, I simply get an empty output, but no no device output. The documentation is not clear to me at this part.

Edit:
I am asking this question, because one can also get for example 'unauthorized' state, even though the documentation says nothing about it. So I was curious about this so-called 'no device' state, whether it is a real state, etc.

I don't understand the reason why you want "no devices" to be seen when an empty message conveys the same meaning — OneCricketeer, Mar 15 '17 at 08:40
Yes, when there is no device attached, we get empty result. Don't get confused. — Mehmood Memon, Mar 15 '17 at 08:40
@cricket_007 I ask this, because one can also get 'unauthorized' state, even though the documentation says nothing about it. So I was curious about this so-called 'no device' state. — pjozsef, Mar 15 '17 at 08:50
To the unauthorized state? I have seen it in my terminal. But here's a SO question also: http://stackoverflow.com/questions/23081263/adb-android-device-unauthorized — pjozsef, Mar 15 '17 at 08:54

score 2 · Accepted Answer · answered Mar 15 '17 at 09:02

Not sure if this helps, but one can inspect enough of the adb code in a Hex or Text editor to see hard-coded strings.

There are only a handful of instances of no devices, but nothing that says "no device"

Also highlighted unauthorized, which does seem like a conditional when kick_func_ != null

emulators found�no devices/emulators foundno devices foundmore than one device�more than one emulator�more than one device/emulator�device unauthorized.
�ADB_VENDOR_KEYS�This adb server's $ADB_VENDOR_KEYS is �not set�Try 'adb kill-server' if that seems wrong.
�Otherwise check for a confirmation dialog on your device.�device offline�success�Check failed: kick_func_ != nullptr�offline�unauthorized�

When should I see 'no device' output when running 'adb devices'?

1 Answers1