Develop Reference

how to hide files in android (new proposed method)

is it possible to hide files in android by transfering/moving them to a location or sector (like in root folders or something) of which other apps don't have access to (via adb or termux or something)?.
I have mentioned adb and termux because i've seen performing actions like uninstalling system apps from device. and if possible, i don't want to root my device.
One humble request: i don't know the ABC's of app building/compiling, maximum i can do is execute commands in adb/termux. so if you paste any code, please also mention what to do with it.
i have tried:
putting dot at starting of the name of the files is too older method and everyone knows about it. encryption and decryption is too much time consuming process. And i don't have that much important data, i just want to hide it from direct access so that most of the people can't find it by normal methods.
Thank you very much

Android Native - how to intercept or filter logcat

I'm compiling in debug mode a certain .so in the Android-Native layer which by default outputs to the default logging file.
However, I do not want this data to be saved to the logs in the first place because it will overwhelm the logging file; I plan on streaming it off of the device.
POSSIBLE SOLUTIONS
Modify the .so code to output the debug info to NOT the logging file.
Definitely the most straightforward way but I'd prefer not to do this since this'll require modification of the .so. I agree this should be trivial modification but I have a requirement to modify the .so as little as possible.
Is there a way to create an alias for a file, pipe all writes to it through my app (like tee) and selectively allow writes to the real file?
Is there a built-in logcat filtering tool that can do this filtering for me with some regexs?

First of all, the first solution is indeed the trivial and the better one - since it remains in the code unlike the logcat filtering that might get deleted.
If the requirement is to modify the .so as little as possible, there is no real problem - you modify the code using #ifdef for debug only, so the code changes for debug mode, but the generated .so for release does not change. This will give you a very good control - but in case you have a lot of 'special' debug code, it will make your code a little ugly...
Edit:
If you want to write to you own log, you can run logcat using Runtime class, with your own parameters - look here: Using GREP command to filter logcat in Android.
Regarding the logcat filtering - you can use regex in the filtering in Android Studio. You have a 'regex' check box next to the input box. See here for more details: How to exclude certain messages by TAG name using Android adb logcat?

pull only new files (photos) from Android adb to linux os

I've been pulling photos from my android device to my linux OS like this:
$ adb pull <what-to-pull> <where-to-place>
In the future I would prefer to pull only the ones I don't alreay have.
What's the best way to do this?
Maybe I could put all the photos I've downloaded to the same folder and skip the ones with names that already exist in the folder I'm pulling from? How to do that?
Is that even the best way? Does an easier way to do this exist?
If so... how?
I'm on arch linux by the way, in case the distribution effects your suggested answer.

adb shell find "/sdcard/DCIM" -iname "*.jpg" | tr -d '\015' | while read line; do adb pull $line; done;
^that works well enough.
From here.

The adb-sync tool worked for me: https://github.com/google/adb-sync
Note that I had to make several changes to the source code to get it working for my use-case (invalid paths for Windows causing crash, Python version mismatch apparently, etc -- for details, see issues I commented in), but it ended up being the only way I was able to retrieve my files from a corrupted data partition.
(The adb pull of the whole directory would crash on various files, and I didn't want to manually have to delete each one then restart the whole transfer. With adb-sync [+my modifications] it would just fail that one file then continue.)
Regarding your question of having it only transfer new files, I believe adb-sync does that automatically if a file hasn't been changed. If you don't want it to re-transfer an existent file ever (ie. even if the file has been updated), I think that's what the flag mentioned here is for: https://github.com/google/adb-sync/issues/22

Changing some system file values in Android failing

I am trying to change some sys values but I don't seem to be having much success.
In my case I am trying to change values of files in the folder
"/sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0"
e.g. the file bInterfaceClass which currently has value 09
My tries:
(In shell, as root)
chmod 777 bInterfaceClass
echo 07 >> bInterfaceClass
I didn't receive an error but when looking up the value
cat bInterfaceClass
It is still 09
Now looking up this file in Root Explorer, I can see that the last modification date of the file has changed, so my guess: something resets the value of such a sys file as soon as it changes. Can anyone shine some more light on this issue? How can I change the value?
Many thanks!

THIS IS HACKERY, you have been warned! :)
Instructions here are not generally found on the Internet, but can be great for testing interfaces and capabilities without significantly changing system code. THESE CAN BE USED TO ADDRESS ANYTHING WHICH IS BEING OVERWRITTEN without warning or cause. Using these, you can sometimes see based off of using dmesg ps and logcatwhat exactly is causing you so many problems, while testing a solution.
The is likely in the Kernel with things like this getting written over, maybe a system service or script internally. A quality perm fix would be in the /drivers folder of the kernel. I can only assume this is on a Beagle or Panda Board, maybe a Moto device. If it is Beagle or Panda, this will be easier (yay Linaro, AOSP support, big community!).
If this is something that does not need to Hold USB open, but merely have the desired number present you can try below:
Open up your boot.img and open he Root Disk/Ramdisk and finally one of your init..rc files. You can use this tool: https://github.com/dsixda/Android-Kitchen - requires Linux and a few packages, great tool!
If you are lucky, this will appear as part of the init.rc files (which you can check in-system) or in the /system/etc folder as one of the class main or core scripts.
You can declare the value you want if you look for it in the:
on init
Section of the init.platform.rc and look where
/sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0
is initialized,
then in the .rc file
chmod 777 /sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0/bInterfaceClass
write /sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0/bInterfaceClass 07
Then if doing that and initializing it as such does not hold by that alone, open the normal init.rc and add
on nonencrypted
write /sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0/bInterfaceClass 07
and also
on property:vold.decrypt=trigger_shutdown_framework
write /sys/devices/platform/omap/musb-omap2430/musb-hdrc/usb1/1-0:1.0/bInterfaceClass 07
as those two properties or functions will cover you at the end of the inits to set that property again (you already gave it 777 privilages earlier as part of the on init)
If you want something you can play with without flashing new Boot.img files:
Declare your script in the system/bin as a service in the init.platform.rc (don't worry most every .rc file is linked and includes each other) using:
service usbchanger /system/bin/sh /system/bin/usbchanger.sh
class late_start
user root
disabled
Then in the normal init.rc
on nonencrypted
start usbchanger
on property:vold.decrypt=trigger_shutdown_framework
start usbchanger
Your script will then become a constantly running service (you can do the same with a binary). This is totally a desired trait when doing debugging and testing new features/fixes because you can change the values and running commands while the system is open and does not require you to re-flash after every change. However, for production you should not have this going. Its bad code to do that generally when really, it should be in the kernel or core.

Cooking Android

Can someone consider and evaluate my approach to customization of Froyo? I'm a beginner.
I've download the sources from Android website and i've successfull recompiled and run it on my (study) device.
Let's consider a trivial customization: on Settings activity the last choice is something like 'Info about the phone' but... my device is not a phone so i want to replace this string.
Once moved to [my froyo]/packages/apps/Settings/res/values i've edited the 'string.xml' file with the right value. At this point my problems begin...
Considering that i've the Java compiler, how can i recompile only the (i.e.) Settings apk and not the entire operating system (my solution has been to recompile the whole operating system)???
Once obtained the NEW Settings.apk, how can i upload it to my device substituting the previous (system) one? I've tryed 'adb install' with all the options but it fails; i've tryed 'adb unistall' on the previous (system) one but it fails as well. (my solution was to upload again the whole operation system).
In conclusion, how can i change a string from 'phone' in 'squirrel' without spending an hour? I want only to customize a little bit the system applications. I'd like to edit the source, try it on device and only once that all the customizations have been done recompile the operating system.

Okay lets start with the first question. To recompile a specific package you can just type
make <PackageName>
in your case it should be make Settings.
Then after the new package was compiled you will find it in the build directory.
copy the apk directly to the /system/app folder in your device and delete the /data/dalvik-cache/ entry for it and reboot the device, the new package should be loaded.
For making the /system partition writable you need to type
adb remount
But note that some Packages may have dependencies which might be needed for your customization. Something like the framework_res.apk