Problem about running script in init.rc

[yf...@mobvoi.com]

For some reasons I need to run a script whenever system property is changed, so I write code like this in init.rc:

on property:persist.sys.proptest=*

    start mytest

service mytest /system/bin/sh /system/etc/mytest.sh ${persist.sys.proptest}

    class main

    user system

    oneshot

    group system

    disabled

but it didn't work, my script get the "${persist.sys.proptest}" string instead of the value of the persist.sys.proptest. I check all the *.rc file and find out that access ${persist.sys.proptest} in service statement seems not working, so I changed code like this:

on property:persist.sys.proptest=*

    /system/bin/sh /system/etc/mytest.sh ${persist.sys.proptest}

this time my script didn't get called at all. But when I checked init.fugu.rc, this code seems works:

on property:init.post_fs_data.bootreason=*

    # Create dump dir and collect dumps. (use the same location as in init.rc)

    mkdir /data/dontpanic 0750 root log

    copy /proc/emmc_ipanic_console /data/dontpanic/ipanic_console

    chown root log /data/dontpanic/ipanic_console

    chmod 0640 /data/dontpanic/ipanic_console

    copy /proc/emmc_ipanic_threads /data/dontpanic/ipanic_threads

    chown root log /data/dontpanic/ipanic_threads

    chmod 0640 /data/dontpanic/ipanic_threads

    copy /proc/emmc_ipanic_gbuffer /data/dontpanic/ipanic_gbuffer

    chown root log /data/dontpanic/ipanic_gbuffer

    chmod 0640 /data/dontpanic/ipanic_gbuffer

    # Clear panic partition

    write /proc/emmc_ipanic_header 1

so what's wrong with my code? Is the mkdir/chown/copy not the real shell command at all? If then, how could I pass the value of persist.sys.proptest to my script?

[Chih-Wei Huang]

The problem is init.rc is not a shell script.
Each command in init.rc must be an init built-in command.
Apparently /system/bin/sh is not.

Use 'exec' to run an external command, like

  exec -- /system/bin/sh ...

Whether if${persist.sys.proptest} is expanded is another problem.

It depends on each built-in command.
You need to read init's code to understand what would be expanded.
In this case, exec won't expand its arguments.

But since you're writing a script, why bother with it?
Just use 'getprop' to read the property in your script.

yf...@mobvoi.com於 2017年1月4日星期三 UTC+8下午1時04分02秒寫道：

[Yafei Liu]

Thanks for replying, as you say the ${persist.sys.proptest} indeed not a problem, but the exec seems save my life.

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