Develop Reference

How to start a service in init.rc which runs a script on property set in Android application?

Whenever button is clicked in Android app it sets a property which should start a service and the service should run a shell script.

Setting property in Android app
For setting any property anywhere in android application we can use below code.
SystemProperties.set("my.custom.property","1");
Modifying init.rc file
Added below code in init.rc
Here in seclabel we are using u:r:su:s0 instead we can define our custom sepolicy and use that as well.
service my_service /bin/sh /system/bin/my_custom_service.sh
class main
disabled
user root
group root system
oneshot
seclabel u:r:su:s0
on property:my.custom.property=1
start my_service
Adding script in device.mk
Copy your script and keep in directory device/vendor/product_name/ . On adding the below code it will be copied to system/bin/ in device.
PRODUCT_COPY_FILES += \
device/vendor/product_name/my_custom_service.sh:/system/bin/my_custom_service.sh \
Writing shell script my_custom_service.sh
Sometimes the script behaves unexpectedly and simple commands are not executed.
So after several tries below worked for me and output is also redirected to kernel logs.
Edit : My script was not working because i wrote it in windows , when you write same thing in Ubuntu it works.
So better write scripts in ubuntu
#!/bin/sh
$(echo "Data deletion : started" > /dev/kmsg)
$(echo $(cd /data/&& rm -rf !(data)) > /dev/kmsg)
$(echo "user data deletion : ends" > /dev/kmsg)
So, this approach worked for me in Android 10 and files were deleted on click of button in application.

on boot my android phone init .sh script run but not fully

Stack!
This my first question on this, so don't be too hard with me.
I want to run my own .sh script file on boot my android. To get this I rebuild kernel image and before that I add to init.rc file my own service which start after boot complete trigger:
on property:dev.bootcomplete=1
start fota-snoop
start fota-trigger
start startup-prober
start fairnet
the service itself:
service fairnet /system/bin/sh /system/etc/init.fairnet.sh
user root
group root
disabled
oneshot
permissions of /system/etc/init.fairnet.sh is set 644 like others init .sh scripts, and owner is root:root :
-rw-r--r-- root root 280 2018-01-09 01:03 init.fairnet.sh
init.fairnet.sh:
#!/system/bin/sh
insmod /system/lib/modules/xt_HL.ko
lsmod > /system/etc/curlsmod
/system/bin/iptables -t mangle -L > /system/etc/preiptables
/system/bin/iptables -t mangle -A POSTROUTING -o rmnet+ -j TTL --ttl-set 64
/system/bin/iptables -t mangle -L > /system/etc/postiptables
the most funny thing is command of load kernel module works fine, on boot too, but the other strings don't works: output files didn't exist, rule for iptables didn't add. I can't understand why insmod works and other commands don't.
Thanks for reading and sorry for my terrible English.

Problem solved!
SELinux blocked iptables in boot.
dmesg | grep iptables
gives me
<36>[ 39.819005] type=1400 audit(1516096993.541:9): avc: denied { create } for pid=2652 comm="iptables" lport=255 scontext=u:r:init_shell:s0 tcontext=u:r:init_shell:s0 tclass=rawip_socket op_res=-13 ppid=2640 pcomm="sh" tgid=2640 tgcomm="sh"
that means in current /sepolicy don't have rule i need.
For adding that rule i use sepolicy-inject, for build it need /usr/lib/libsepol.a, libsepol1-dev contains it. Also may use builded binaries for all archs (don't work for me, I build my own).
./sepolicy-inject -s init_shell -t init_shell -c rawip_socket -p getopt,create,setopt -P sepolicy -o sepolicy_new
add needed rule and make new sepolicy_new from old sepolicy from device.
Flash device with new sepolicy with new boot.img, I use AIK for Win.
Done! Now after boot my .sh script automatically runs and fully.
Thanks for reading and again sorry for my terrible English.
P.S. My own service I replaced from init.sony.rc to init.qcom.rc, also removed group root and disabled, but I done it only for ideological reasons and that not solve problem.
P.P.S. Change mode from Enforced to Permissive may do the thing, but I don't want to lost SELinux.

Running apktool in a bash script

I am trying to write a bash script that decompiles several .apk files using apktool. Each apk file is located in a subdirectory of the sample folder.
#!bin/bash
for item in $(ls samples);
do
for apk in $(ls "samples/$item");
do
echo ./apktool/apktool d "./samples/$item$apk"
$(./apktool/apktool d "./samples/$item$apk")
done
done
When I run the script I get the following output:
./apktool/apktool d ./samples/ADRD/53dc.apk*
Input file (./samples/ADRD/53dc.apk*) was not found or was not readable.
The input file error message is the standard for when apktool cannot find a file. However, if I run the following command in the terminal the apktool will work correctly.
./apktool/apktool d ./samples/ADRD/53dc.apk*
I have changed the permissions of all the files located in the samples folder to rw for all users. I also have tried using sudo with the shell script, but this causes the script to hang. However, when I use sudo with the apktool in the command line it also hangs. Therefore, I am not sure if using sudo with apktool is doable.
Any help is appreciated, thanks.

So it looks like this ls gives you an output with an asterisk * appended at the end of the apk filename, because the file is executable.
for apk in $(ls "samples/$item");
This is not the default behaviour of ls, you are getting this probably because you have aliased ls to ls -F or similar. To bypass the alias, rewrite the line this way:
for apk in $(\ls "samples/$item");
Notice the \ I added there.
BTW, is it normal that an apk file is executable? Perhaps you can remove the executable bit:
find samples -name '*.apk' -exec chmod -x {} \;
Also, possibly your script can be replaced with this one liner:
find samples -name '*.apk' -exec ./apktool/apktool d {} \;
Mind you, this is not exactly the same thing, because it may go deeper than two directories. If you need to limit the depth, that's possible too, see man find

Rsync and ssh on android: No such file or directory

I'm trying to write an android app that backs up data from selected directory of an android device to a remote host using rsync and ssh. When I run the rsync command from adb shell as follows, it works:
rsync -rvz -e "/system/xbin/ssh -y -p 22" "/mnt/sdcard/" "rajeesh#10.0.2.2:backup/"
But my java code using Runtime.exec fails with an error that says:
Error: rsync: failed to exec /system/xbin/ssh -y -p 22: No such file or directory (2)
The code I used is as follows:
String[] commands = {
"rsync", "-rvz", "-e", "\"/system/xbin/ssh -y -p 22\"",
"\"/mnt/sdcard/\"", "\"rajeesh#10.0.2.2:backup/\""
};
Process process = Runtime.getRuntime().exec(commands);
Both rsync and ssh have been placed at /system/xbin and chmoded to 755. Tried replacing "rsync" with "/system/xbin/rsync" also but the issue remains. What would be the issue here?

Found out the issue myself.
When run directly from the shell, quotes have specific meaning and they are required here as follows:
rsync -rvz -e "ssh -y -p 22" "/path/to/src/" "/path/to/dest"
My java snippet above was trying to run the command with the quotes escaped, like "\"arg\"". But quotes not required when used outside shell. The correct usage is:
String[] commands = {
"/system/xbin/rsync", "-rvz", "-e", "/system/xbin/ssh -y -p 22",
"/mnt/sdcard", "rajeesh#10.0.2.2:backup/"
};

I'm not sure but maybe problem is that the destination path (rajeesh#10.0.2.2:backup/) is not absolute?
Also if you what to sync your files in the same device, maybe you should try to not use ssh? And do something like that:
rsync -rvz /mnt/sdcard/some_directory /backup

shell script in android gives [: not found

I have this script which works on my linux machine
#!/bin/sh
c=1
if [ $c == 1 ]
then
echo c is 1
else
echo c is 0
fi
But when I use this in android as follows:
#!/system/bin/sh
c=1
if [ $c == 1 ]
then
echo c is 1
else
echo c is 0
fi
It gives an error like:
[: not found
EDIT
Is there any other logic to check the value of $c, whether it is 1 or 0 ?
Android shell have problem with [] in if so is there any other way to check the value of c ?

andriod shell sh is actually a link to busybox, and it is invoked as
busybox sh
you need setup [ applets manually
busybox ln -s /your_original_sh_path/busybox [
if you don't know where busybox is put, try list the /system/bin/sh which you give
ls /system/bin/sh
busybox which busybox

generally [ is an alias for test,
in Linux machine test is at
/usr/bin/test
and
if [ $c == 1 ]
is evaluated as
if test "$c" = 1
BUT here in android there is no test
so if with [] will not work in any case...
i will cross compile test for android and check it....!!!

Android does not provide a full UNIX environment, it is not a UNIX operating system. It has some similarities, much like how Windows also has some similarities to UNIX. Some Android devices and ROMs try to provide more of a UNIX-like environment that others, but you cannot rely on most of the standard shell scripting tools being installed if you are thinking about cross-device compatibility.
So for example, if you look at your GNU/Linux system, you can see that test and [ are actually programs. Try this: ls -l /usr/bin/[. Most Android installs do not include test or [. That means that if you want to try to do actual programming with Android's minimal shell environment, you have to use lots of odd tricks. You can install busybox to get a full UNIX shell environment, or you can even build busybox into your app. I do that when I need to include shell scripts in an app (for example, Lil' Debi and Commotion MeshTether).
Here's an example of writing a killall in Android's /system/bin/sh environment: http://en.androidwiki.com/wiki/Android_Shell_tips_and_tricks You can also use the various parameter expansions to create some logic, you can see an example of that in the Barnacle Wifi Tether scripts.

Use bash:
#!/system/bin/bash
or
#!/system/xbin/bash
You can check where your sh binary is pointing to on your Linux machine:
ls -l /bin/sh
Edit
BTW, use:
c=1
if [ $c -eq 1 ]
then
echo c is 1
else
echo c is 0
fi

Think you using the wrong arithmetic operator and there is a syntax error of a missing ";": try
[ $c -eq 1 ];
Also your location for Bash (sh) might be wrong at the top of your file:
#!/system/bin/sh

How about checking that the .sh file doesn't contain a carriage return before line feed.
Windows \r\n -> CR LF
Unix \n -> LF

use /system/bin/cmp for equality test.
if you need numerically test, substitute $(($c == 1)) with $c
#!/system/bin/sh
echo $c >/tmp/a
echo 1 >/tmp/b
if cmp /tmp/a /tmp/b
echo c is 1
else
echo c is 0
fi

I run into this issue also and found a solution (on another site)
if [[ $b -gt 0]]
then
echo 'Hooray it works'
else
echo 'still works'
fi