Change file permission in application

Question

I try to change file permission in application. Code is below:

Runtime.getRuntime().exec("chmod 777 /sdcard/test.txt");

This code NOT works in my application, but no error log. I also checked the shell tools under /system/bin, find chmod is under /system/bin, but some other info shown that chmod > toolbox. I am not clear about this. My application has used android:sharedUserId="android.uid.system". How to run this code or how to change permission of file? Thanks a lot.

Is your phone rooted? My guess is that such sensitive commands can't be used without being root. — Lennart, Dec 07 '11 at 08:40
I added Runtime.getRuntime().exec("su") before, but it not works. — Queenie Wong, Dec 07 '11 at 08:49

score 2 · Answer 1 · edited Dec 20 '13 at 07:46

2

Runtime rt = Runtime.getRuntime();
Process proc;
try {
    proc = rt.exec(new String[] { "su", "-c", "chmod 777 " + Constants.filename });
    proc.waitFor();
} catch (Exception e){ //DOSTUFFS }

This should do the trick

edited Dec 20 '13 at 07:46

Alexander

2,320
2
25
33

answered Dec 20 '13 at 07:20

Joakim Sandqvist

140
11

score 1 · Answer 2 · answered Dec 07 '11 at 08:46

You've used the path /sdcard/ in your test -- is your SD Card formatted with a filesystem that supports standard Unix permissions? (FAT does not.)

You did not give an explicit path to chmod(1) in your string -- are you certain that chmod(1) is:

available on your device
available with your current PATH environment variable setting?

You can only change the permissions on files you own; are you certain that whatever your application's effective userid is owns the file on the SD card?

Lastly, Android may have additional security restrictions on changing file permissions. I don't know Android well, but perhaps changing file permission bits requires entries in the manifest declaring the operations, perhaps changing file permissions can only be done through provided APIs.

Run command as `$ su` `#chmod 777 /sdcard/test.txt`, permission can be changed. So i think the file path is right. — Queenie Wong, Dec 07 '11 at 08:53
Try changing your string to `"su -c \"chmod 777 /sdcard/test.txt\""` — sarnold, Dec 07 '11 at 08:56

Change file permission in application

2 Answers2

Linked