Android: unable to read a file using bufferedReader whereas cat command run in adb shell works fine

Question

I am trying to read a system file using bufferedReader in Android API=23 but it gives the following error: open failed: EACCES (Permission denied).

The file is read only. On the other hand, 'cat' command run in adb shell just works fine.

Also, File.exists() returns true for my file whereas File.canRead() returns false. Is it something related to the administrative/root access? Does adb shell give you root access to system?

P.S.:I have granted Read/Write permissions to the app (as per API 23)

Possible duplicate of [Android marshmallow request permission?](https://stackoverflow.com/questions/33666071/android-marshmallow-request-permission) — Nayan Srivastava, May 26 '17 at 05:23
No. I have taken that into account. I can read other files with ease!! — PseudoCoder, May 26 '17 at 05:25
You should use Manifest.permission.READ_EXTERNAL_STORAGE for requestPermissions in API = 23 — Jarachanthan Ratnakumar, May 26 '17 at 05:25
For API 23+ you need to request the read/write permissions even if they are already in your manifest. — Avinash Roy, May 26 '17 at 05:26
@AvinashRoy I have included the in my manifest just before the application tag! — PseudoCoder, May 26 '17 at 05:27

score 0 · Answer 1 · answered May 26 '17 at 05:27

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Android added new permission model for Android 6.0 (Marshmallow).

http://www.captechconsulting.com/blogs/runtime-permissions-best-practices-and-how-to-gracefully-handle-permission-removal

So you have to check Runtime Permission :

What Are Runtime Permissions?

With Android 6.0 Marshmallow, Google introduced a new permission model that allows users to better understand why an application may be requesting specific permissions. Rather than the user blindly accepting all permissions at install time, the user is now prompted to accept permissions as they become necessary during application use.

When to Implement the New Model?

it doesn’t require full support until you choose to target version 23 in your application. If you are targeting version 22 or below, your application will request all permissions at install time just as it would on any device running an OS below Marshmallow.

This information is taken from here :

Please check How to implement from this link :

http://www.captechconsulting.com/blogs/runtime-permissions-best-practices-and-how-to-gracefully-handle-permission-removal

answered May 26 '17 at 05:27

Avinash Roy

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I have added runtime permission check and have granted the read/write permissions during runtime. That is not the issue. It is specifically this file. – PseudoCoder May 26 '17 at 05:29
I checked the permissions for this file (using adb shell) and got "read only". Adb shell command -cat works fine for this file. Is it because of root access granted during the adb shell? – PseudoCoder May 26 '17 at 05:31
where is that file located?? – Avinash Roy May 26 '17 at 05:33
Are you running on a emulator or a physical device? Does the /sdcard path exist? – Avinash Roy May 26 '17 at 05:34
The file is a system file. And i am running it on a physical device. – PseudoCoder May 26 '17 at 05:35
my device is not rooted. Could that be the issue for reading the file? – PseudoCoder May 26 '17 at 05:36
I guess not an issue – Avinash Roy May 26 '17 at 05:36
You cannot access that app's files on internal storage. Your permissions are for external storage. – Avinash Roy May 26 '17 at 05:38
It is not the problem. you can still read a file in internal storage. – Quang Nguyen May 26 '17 at 05:50
@Avinash Yeah that may be an issue. I will check on that. But for some reason other system files are readable with these permissions. – PseudoCoder May 26 '17 at 05:52

score 0 · Answer 2 · answered May 26 '17 at 05:40

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If your file exists but can not read, please make sure the followings:
- Permission. Because you can read other files as you said, it may not a problem.
- It is not folder. check it by file.isDirectory().
- Check your file path. For example, it should not start like that: file:/... or /home/storage//th (when you mistakenly append with two dashes).

answered May 26 '17 at 05:40

Quang Nguyen

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it is not a folder. Since cat FILEPATH returns me the desired output. – PseudoCoder May 26 '17 at 05:47
Another common issue as I mentioned above is your file path. – Quang Nguyen May 26 '17 at 05:49
Check them by log two properties: - file.isDirectory() - file.getAbsolutePath() – Quang Nguyen May 26 '17 at 05:51
Output of log properties: isDirectory: false; getAbsolutePath: *returns correct path*; exists(): true; canRead(): false. Thought the permissions for the file is readonly!! – PseudoCoder May 26 '17 at 06:21
Please check the final condition. - file path, and update your question with your codes. – Quang Nguyen May 26 '17 at 06:23

score 0 · Accepted Answer · answered Aug 19 '17 at 14:11

I guess the problem was very much unique to my case. The file was a system file and my app was not given the Permission to read it. It was rectified after I signed my app as a system app.

Probable other solution might be if the app will have root permissions to read such file.

Thanks everyone for your suggestions and answers!!

Android: unable to read a file using bufferedReader whereas cat command run in adb shell works fine

3 Answers3