I've written a su.d script to periodically (every 4 hours) back up data from an app using a looped sleep command:
#!/system/bin/sh
(
# Wait for boot to complete
until [ "$(getprop sys.boot_completed)" ]
do
sleep 300
done
while true
do
(
new_dir="/storage/emulated/0/temp/AppData/$(date '+%Y%m%d-%H%M')"
mkdir -p $new_dir
cp /data/data/com.example.app/files/*.json $new_dir
echo "$(date '+%F %T') | app data backup OK!" >> /storage/emulated/0/su.d.log
) &
sleep 14400 # 4 hours
done
) &
In practice, the script backs up the data only after boot—not every 4 hours.
However, if I enter a remote shell via adb and leave it alone, then the data does get backed up every 4 hours.
How can I force the periodic backup without being permanently connected to a PC? (And why isn't it working as expected?)
EDITS
@Irfan Latif's comment gave me the idea of trying a different interpreter (busybox ash -
#!/system/xbin/sh), but the result was the same. I'll try @mirabilos's daemonise suggestion (sh -T- -c '...') next.Tried @mirabilos's daemonise suggestion with the same result: backs up data only after boot.
Tried
nohup:
nohup /system/bin/sh -T- -c '...' >/dev/null 2>&1 &
Same result.