Develop Reference

Command to clear the previous dumpsys info

Question is straight forward and simple. Is it possible to get the dumpsys information after certain point or certain user action. Not from the scratch.

There is no such thing.
Logs belong to the logcat facility. dumpsys is mostly for reporting the current state and some more advanced things. It is true that few of the Android service developers included some limited logging excerpts into their dumpsys output but virtually none of them implemented a way to clear those logs.

I realise this is a bit late but...
As per the documentation:
Connect your mobile device to your computer.
Open a terminal and type the following commands to reset the adb server:
adb kill-server
adb devices
This will list any connected devices (If you don't see any devices listed, make sure your phone is connected, and USB Debugging is turned on, and then kill and restart adb again).
Next you will need to reset battery data gathering. The device is always collecting batterystats and other debugging information in the background. Resetting erases old battery collection data. If you do not reset, the output will be huge.
In terminal use command:
adb shell dumpsys batterystats --reset
Disconnect your device from your computer so that you are only drawing current from the device's battery.
Play with your app and perform actions for which you would like data; for example, disconnect from WiFi and send data to the cloud.
Reconnect your phone and make sure it is recognized:
adb devices
Dump all battery data (This can take a while):
adb shell dumpsys batterystats > [path/]batterystats.txt
The batterystats.txt file is created in the directory you specify using the optional path argument. If you leave out [path/], the file is created in your home directory.
You can find the home directory in Android Studio by going to:
Tools > SDK Manager > Android SDK Location.
Navigate to that filepath then open the subdirectory 'platform-tools' and look for batterystats.txt.

how can I understand if the phones are really rebooted adb

Im trying to reboot the devices and really check that they are really rebooted. I tried to use uptime like this: adb s device id uptime
but didnt work .

For the purpose of checking device's uptime the following command provides data in a format which is much easier to work with:
adb -s <device_id> shell cut -d' ' -f1 /proc/uptime
But checking the device's uptime immediately after reboot is pointless - the device would not be available. So it would make more sense to check the local USB device enumeration instead.

simulate status using adb & telnet

I am trying to understand how to simulate statuses (battery, sensors, etc) using adb and telnet. I am using emulator.
On doing:
adb shell battery
there is no change in simulator status
But on doing:
adb shell dumpsys battery set level 5
I can see change in value.
I therefore would like to ask:
Is there any reason why "adb shell battery " does not work with emulator?
setting value with dumpsys does works, although it is documneted that dumpsys is used for dumping status (and there is no documentation for other usages). and the questions, is whether we can use dumpsys to set other statuses, such as sensors ? if yes - how we can find out how to set other values ?
What is ther purpose of telnet to the device ? Seems that some attributes can be set using telnet and some using the adb utility. Why are these 2 utilities required and not only one ?

How to disable battery charging during ADB connection?

Problem description:
Each time wen I connect USB cable between PC and my mobile phone the battery automatically is charged. I want to use ADB protocol but I don't want to charge my battery during ADB connection. Is it possible to to turn off this charging? And ofcourse how can I do this?
Environment:
Mobile phone with Android os 4 and higher
I need only mention that my referential device working on android 5 so there is no /sys/class/power_supply/battery/force_usb_charging file

BEWARE: adb shell dumpsys battery unplug only MOCKS the battery status. I checked with a current indicator on my usb cable and this does not change the amount of flowing current at all so the battery is still charging.
It only changes what applications think about the state, so for example google play would not start updating if you have configured that it can only update when charging...
Changing the value of a file like /sys/devices/battery.XX/power_supply/battery/hv_charger_set to 0 does really work but its a different file for every device. For example, for my yotaphone 2 with a snapdragon 805 there is a file: /sys/devices/qpnp-charger-14/power_supply/battery/charging_enabled
So you could make a script that you can use in tasker(if you have root):
echo $1 > /sys/devices/qpnp-charger-14/power_supply/battery/charging_enabled
if you write that to an executable file /data/setcharging.sh then you could call the script like /data/setcharging.sh 0 to disable or
/data/setcharging.sh 1 to enable.
This works, I checked with my current metering usb cable, but it does not show that it works in the battery status icon. So you could use a combination of this and adb shell dumpsys battery unplug / reset to make it look better, but the problem is that then apps like tasker don't know whether you have ac power or not, so you can not put triggers for that when you've set it to unplugged...
One more thing, I also tested what it does in recovery (twrp) and during boot. And it turns out that during boot and in recovery, the charging just works. So its not like your device will end up dead if you forget to turn on charging again. You can always charge it in recovery mode and then boot up and change the value again (or change it while in recovery if your recovery gives access to adb).
Lastly, there are apps on the play store that are made exactly for this, but I would recommend getting such a current indicating usb-cable and checking if they really do what they say and are not just mocking.

You can make the system think it is not loading th battery using
adb shell dumpsys battery unplug
Refer to this good article :
https://stanfy.com/blog/android-shell-part-1-mocking-battery-status/

Try this for rooted device:
To enable battery Charging:
adb shell dumpsys battery set ac 1
adb shell dumpsys battery set usb 1
adb shell dumpsys battery set wireless 1
To disable battery Charging:
adb shell dumpsys battery set ac 0
adb shell dumpsys battery set usb 0
adb shell dumpsys battery set wireless 0

Probably it can be done via (root privileges):
/sys/devices/battery.XX/power_supply/battery/hv_charger_set
0 - Disable USB Charging
1 - Enable USB Charging

if android os version is more than 6 use unplug and reset to revert back.
adb shell dumpsys battery unplug
adb shell dumpsys battery reset

Copied from perfetto.dev
On rooted phones the power management IC driver allows to disconnect the USB charging while keeping the USB data link active. This feature is SoC-specific, is undocumented and not exposed through any HAL. For instance on a Pixel 2 this can be achieved running, as root: echo 1 > /sys/devices/soc/800f000.qcom,spmi/spmi-0/spmi0-02/800f000.qcom,spmi:qcom,pmi8998#2:qcom,qpnp-smb2/power_supply/battery/input_suspend. Note that in most devices the kernel USB driver holds a wakelock to keep the USB data link active, so the device will never fully suspend even when turning the screen off.

Detect if ADB server is running on Android?

I am trying to detect if the adb server is running on the Android device for part of an anti-cheating implementation for my free game.
Specifically, I want to stop use of adb shell input tap x,y, since the game is a competitive multiplayer puzzle game.
Things I have tried:
Using battery info I can detect if USB is plugged in. Well, that is also a legit use.
Using Settings.Secure or Settings.Global, I can query ADB_ENABLED, but that always returns 1 if adb is enabled. It DOES NOT take into account adb connected or not!
Querying all system services, but I cannot see anything that looks like an adb service.
At this point, I am out of ideas. Hopefully someone else knows how to do this?

You can check for running adbd process or query init.svc.adbd system property:
$ ps adbd
USER PID PPID VSIZE RSS WCHAN PC NAME
root 14947 1 4596 208 ffffffff 00019358 S /sbin/adbd
$ getprop init.svc.adbd
running
In Android the adb driver is implemented as a function of universal usb driver. You can check the (comma separated) list of currently enabled usb functions to see if it includes "adb":
$ cat /sys/devices/virtual/android_usb/android0/functions
mtp,adb
But you would not be able stop cheating while your app is running completely on the user controlled device.