Develop Reference

Is there any command for installing an app in Genymotion?

Hey guise I want to install an app on several devices in Genymotion by using terminal in ubuntu. Each time I do this:
adb install package.app
It gives me the below error:
error: more than one device/emulator
- waiting for device -
error: more than one device/emulator
I also read about
adb -s udid uninstall package.app
but this is not the solve I want. I don't want to use udid and also I don't know which device has my app from before?
Any suggestions?!

adb help is not extremely clear on what to do:
-d - directs command to the only connected USB device...
-e - directs command to the only running emulator...
-s <serial number> ...
-p <product name or path> ...
The flag you decide to use has to come before the actual adb command:
adb -e install path/to/app.apk

You cannot pass adb commands when there are more than one device connected and running at the same time ; this is a limitation with adb.

Wow finally!
I found this command as my answer:
adb devices | awk 'NR>1{print $1}' | xargs -n1 -I% adb -s % install app.apk
Thanks to sivze

Check if adb device connected condition

How can I check adb device is connected in batch files?
I wrote "adb devices" in the batch file, but I want it as a condition so the app working smoothly and automatically
So if the user is not connected his device print no device and exit the app,
Otherwise resume the app.

Pipe the output to find and analyse the errorlevel:
adb devices -l | find "device product:" >nul
if errorlevel 1 (
echo No connected devices
) else (
echo Found!
..............
)

For user in bash or similar shell environment, try
$ adb get-state 1>/dev/null 2>&1 && echo 'device attached' || echo 'no device attached'

This is the easiest and is most accurate since it'll only find "device" and not other words containing the string such as "devices":
adb devices | findstr "\<device\>"
Take note that findstr works on Windows but not in Unix terminals. So the equivilent would be to use find and grep together. John explains this well in this page Using find and grep to Mimic findstr Command

Open USB Relay - Android

I have KMtronics USB relay which I want to control with my Android device. Is it possible to run the following Linux command:
#!/bin/sh
# sends on signal to the USB relay
echo -e '\xff\x01\x01' > /dev/ttyUSB0
I tried to execute same command with some Shell Executor apps but always either getting Permission Denied or Unable to create file/folder. Even I tried to run it on Rooted device too.

Permission problem could be solved like this:
echo -e '\xff\x01\x01' | sudo dd of=/dev/ttyUSB0

How to use android monkey

I am a little confused on how to actually use monkey, i thought you were supposed to power on your emulator and go into terminal editor and type:
$ adb shell monkey -p insert.my.package.name.here -v 500
since that did not work (error, adb: permission denied)
i tried monkey -p insert.blah.blah -v 500 and this comes up that it has been killed, what am I doing wrong?

It's probably trying to talk to a device over your USB port.
You probably just need to add an -e in there to tell adb to connect to the emulator:
$ adb shell monkey -p insert.my.package.name.here -v 500
(Or -s serialnum if you have more than one emulator running.)
See Directing commands in the ADB docs.

It's well explained here:
https://android.googlesource.com/platform/development/+/master/cmds/monkey/README.NETWORK.txt
it's a tool for testing apps, and the port indicates which porto to connect (binds to localhost) to issue remote commands

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}'