Lengthy sleep command not working in script

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                          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 ###

1. @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.

2. Tried @mirabilos's daemonise suggestion with the same result: backs up data only after boot.

3. Tried nohup:

        nohup /system/bin/sh -T- -c '...' >/dev/null 2>&1 &

    Same result.

                        

Asked by andronoid (41 rep)

Feb 17, 2019, 03:01 PM
Last activity: May 5, 2020, 11:33 AM

Lengthy sleep command not working in script

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