Develop Reference

Getting cpu and memory usage for a period of time

I have some old shell scripts that needs to be executed on an android device but the command to fetch the total cpu, memory and swap usage is top. More specific it is:
top -m 1 -d 1.0 -n $duration
Now I have been looking to find a replacement for this and I found out that I can use dumpsys. The problem what I have is that I want to give a timeout like this:
dumpsys -t 20 cpuinfo
I checked this site: https://developer.android.com/studio/command-line/dumpsys.html but didn't find out why this doesn't work. Even when I try the help I get the same error
dumpsys --help
Can't find the service: --help
Does someone know what is going on? My current android version is 6.0.1 if this is important.
Thanks in advance!

It is true that dumpsys --help does not work. I think there is a mistake in their document. However, below works:
# adb shell dumpsys input
# adb shell dumpsys -l

Add permission on your manifest "android.permission.DUMP".or
There's another (hacky) way to access dumpsys without rooting your device - through adb shell.
This will require allowing USB debugging, and finding the port of the adb service.
Enable USB debugging on your device. This option is found under Settings -> Developer Options.
Connect your device to a PC, and run the following command from the PC's shell/command line: adb tcpip 12345. Then, from your devices shell, issue the command adb connect localhost:12345 from your application. You can now disconnect the device from USB. Alternatively, you can scan the ports on your device one by one without USB connection, using adb connect localhost: and find the port adb service is listening to.
Authorize USB debugging from the pop up confirmation dialog, if prompted. Check the "always" checkbox to do not require this step again.
Now, when you have access to the adb service, use adb shell dumpsys ... from your application code to get whatever service dump you need.

adb shell command to find the device RAM

I am trying to find device RAM (512 MB or 1GB) using adb shell commands.
Following commands giving more details about the free,used & total memory. But how to find the device overall RAM?
adb shell "cat /proc/meminfo"
adb shell dumpsys meminfo
adb shell procrank

So it looks to me that MemTotal is probably the field you are looking for:
MemTotal — Total amount of physical RAM, in kilobytes.
While it is not the strictly Android, another Linux flavour CentOS provides the following page regarding /proc/meminfo. It seems that Red Hat, and other variants also describe it similarily.
Is there something that is making you suspect that this is not the physical RAM? On my device the value reported for MemTotal matches what I expect.

People who post answers often forget that Windows users don't have access to grep, cat, etc. Add shell to the beginning of your pipe.
.\adb.exe -s whichever-device shell "cat /proc/meminfo | grep MemTotal"
This is assuming you're connected to multiple devices. If you're only connected to one, you can remove -s whichever-device (usually the ip if you're connected by wifi or the device number from the device list if connected by wire.).

Detecting if emulator has started completely

I want to check if all the emulators has booted successfully. I have tried with this command adb shell getprop sys.boot_completed this works if i am running one emulator. But if i have more than one emulator this command returns error as following: error: more than one device/emulator.How to solve this?

You should specify the device serial number on the adb command line to let it know which one you want to interact with.
Something like
adb -s emulator-5554 shell ...
Also, if you are doing it from the command line, multiple times and you are starting to be annoyed by that, you can try https://gist.github.com/dtmilano/4537110 which allows you to select the device
$ adb shell
1) 02783201431feeee device 3) emulator-5554
2) 3832380FA5F30000 device 4) emulator-5556
Select the device to use, <Q> to quit: 1
$

How do I stop the monkey madness?

I'm using the monkey tool to run a test of my Android application. For example, I might do a run like the following:
adb shell monkey -p com.myapp -v 10000
However, if I change my mind and need to cancel the test, there doesn't seem to be a way to do so that doesn't involve waiting multiple minutes for the damned monkey to finish most or all of its run.
Killing the adb shell process on my mac doesn't solve the problem. Killing the com.myapp process on my phone using ddms doesn't work. Unplugging my phone doesn't work.
How do I cancel the monkey madness?

You can kill the monkey process just doing this:
$ adb shell ps | awk '/com\.android\.commands\.monkey/ { system("adb shell kill " $2) }'

[Nitpick] You're confusing monkeyrunner with monkey.
The monkeyrunner tool is not related to the UI/Application Exerciser
Monkey, also known as the monkey tool. The monkey tool runs in an adb
shell directly on the device or emulator and generates pseudo-random
streams of user and system events. In comparison, the monkeyrunner
tool controls devices and emulators from a workstation by sending
specific commands and events from an API.
[/Nitpick]
On my Android 2.2 device when I start monkey, I see a process started in DDMS by the name "?" (just a question mark). When I killed that process, the monkey madness stopped.

adb shell
ps | grep monkey
kill process_id

adb shell kill $(adb shell pgrep monkey)
kudo to #deadfish

For what it's worth, I use Android Studio 3.1.4 on a Mac in 2018 and I had to alter the accepted answer like so:
./adb shell ps | awk '/com\.android\.commands\.monkey/ { system("./adb shell kill " $2) }'
Hope that help prevent some hair-pulling and pencil snapping out there!
Also... when it comes to the monkey, always be sure to pin your app!!! Otherwise you might accidentally send all your selfies to a random email in China like I did. ¯\_(ツ)_/¯

Kill the monkey by shell will cause a small problem, the IActivityController in ActivityTaskManagerService will not be set to null, which it should. And the ActivityManager.isUserAMonkey() still return true.
If monkey stop automatically, it will reset the Controller properly：
Monkey.java{
private int run(String[] args) {
...
try {
mAm.setActivityController(null, true);
mNetworkMonitor.unregister(mAm);
}
...
}
}

How I can simulate "tail" command for file on the Android file system?

I have file on SD-CARD and my app using it as log file.
Is it possible through the adb to watch file with all changes in real time?
Like with tail -f /sdcard/myfile.log command.

This seems to work great for me:
adb shell "while true; do cat; sleep 1; done < /sdcard/myfile.log"

You can install busybox and then:
adb shell
tail -f /path/of/your/file
But remember that you should have root access to install busybox. If you are using the emulator check this one:
How to get root access on Android emulator?

You can do this with logcat. You can add a view that will only show log entries from your app and it will be continuously updated.

There is a great app for this: Terminal IDE. It contains many linux commands, and it does not need root access. You can install it from GooglePlay. Is is free of charge (and open source, GPLv2).
One of its best features is that it can be used through telnet. Start it on your phone, and type telnetd command. It will start a telnet daemon, which listens on port 8080 by default.
After that you can connect it from your PC, with the following command: (use cygwin on windows)
telnet 192.168.1.8 8080
You should use your phone's IP address instead of the above one. After a successful connection you will have an arbitrary sized terminal on your PC, which is capable to run tail -f command on your phone. And many others, such as bash and all of its builtin commands.

Building upon Jesse's answer, to do similar with a file within an app's private storage area:
adb shell "while true; do run-as com.yourdomain.yourapp cat /data/data/com.yourdomain.yourapp/app_flutter/yourfile.txt; sleep 5; done" | egrep -o 'sometext.{0,50}'
(This example is for a flutter app on Android, but is similar minus the app_flutter directory.)
do run-as changes the user under which the command is run to the application. By default adb shell user shouldn't have access to any files under an application's private storage area.
| egrep -o 'sometext.{0,50}' the cat command sends the file contents to STDOUT. egrep is taking the contents & searching for -o (only) sometext + 50 characters" using regex (hence egrep instead of grep).
Last Line Only
Replace cat with tail -n 1.
Add --line-buffered to egrep
adb shell "while true; do run-as com.yourdomain.yourapp tail -n 1 /data/data/com.yourdomain.yourapp/app_flutter/yourfile.txt; sleep 5; done" | egrep --line-buffered -o 'sometext.{0,50}'