Bash脚本：使用su -c运行后台进程时出现奇怪的问题

Question

I have a very strange problem, in my terminal, if I load my binary this way:

adb shell "su -c '
chmod 666 /dev/graphics/fb0
&& export CLASSPATH=/data/local/device.jar
&& export LD_LIBRARY_PATH=/data/local
&& exec app_process /system/bin com.device.client.Main /data/local/device.conf'"

Then the binary loads fine but it is foreground process, and adb shell doesn't return until I kill the program, obviously.

Now here is the weird thing, if I want to app_process as a background process and add & at the end:

&& exec app_process /system/bin com.device.client.Main /data/local/device.conf &'"

It looks like it terminates immediately. I tried adding a sleep:

adb shell "su -c '
chmod 666 /dev/graphics/fb0
&& export CLASSPATH=/data/local/device.jar
&& export LD_LIBRARY_PATH=/data/local
&& exec app_process /system/bin com.device.client.Main /data/local/device.conf & && sleep 50'"

The program runs for 50 seconds, but after that, adb shell returns to the command line and the program is terminated. (my program has a while (true) loop waiting for a socket connection, so it will never terminate).

No error is getting generated or anything. During the 50 seconds of sleep, if I do adb shell and ps, I see "app_process", but after 50, it is not there anymore, and my command line is back to receiving input on my computer.

I am really not sure what is going on. It looks like running as a background process makes "su" return to adb's shell, the shell quits, and the program terminates. If this is the case, how could I please fix it?

Thank you very much.

Answer 1

The usual answer for problems like this is to use nohup(1) and redirect stdin, stdout, and stderr to avoid leaving any descriptors open to the terminal. Try this:

exec nohup app_process /system/bin com.device.client.Main\
/data/local/device.conf >/tmp/out 2>/tmp/err </dev/null &