[android-developers] Re: on sdcard, File.canRead() = true, File.canWrite() = false
Ah, yes, of course. That critical fact slipped my mind -- thanks Dianne! This is, of course, a major reason why ability to write to the SD card is controlled by an application permission. Even without the limitations of FAT, file ownership is a tenuous concept with removable media. I have scripts to set up EC2 instances, and I have to force user UIDs in each created, so that the filesystems I mount on those instances can be consistent. And that's using the ext3 filesystem. On Aug 9, 3:25 pm, Dianne Hackborn hack...@android.com wrote: You can't change the permissions on stuff in external storage. That uses a FAT filesystem, which doesn't have permissions, so all files there simply immutably use the permissions of the mount point. -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: on sdcard, File.canRead() = true, File.canWrite() = false
Kostya and Mark answered your main question; I'll address your ps. Applications are indeed 'other' in the permissions you list below, but applications do have their own uids, so an Application's directory will be owned by its uid. An application with the right permission I'm guessing is put into the sdcard_rw group, and thus would come in under the group permissions instead. I believe chmod command doesn't take the symbolic arguments -- you'll have to use the numeric arguments like we did back in the 1970's. I'm not sure why you were trying to remove the 'other' permissions on that file, but let's say you did ls -l on it, and the permissions were -rw-r--r--. You'd convert this to the numeric form: 644. Your o-rwx would mean 'turn off all the bits in the last digit', so you'd want chmod 640 ... I'd love to have a document on the command-line commands! You can install the busybox toolkit, and get much improved versions of many commands, such as this. I find a rooted device without busybox to be very disconcerting. Busybox puts a large number of commands in one executable to make it quite small, and then symlinks to it under each command name. It looks at the name to figure which command you're asking for. On Aug 9, 10:59 am, john brown johnbrowngreybe...@gmail.com wrote: P.S. I got a command prompt via c:\Program Files\Android-SDK\tools adb shell # ls -l /sdcard/Android/data/lms rwxr-x system sdcard_rw 63 2010-07-19 15:17 mpReadAbDdx201006.txt rwxr-x system sdcard_rw 45211 2010-07-19 15:17 mpTranAbDdx201006.txt The way I read this is that the owner's rights are ---, group is rwx, others is r-x. I'm just guessing, the application is others? But I cannot get chmod to change the attributes, i.e.: # chmode o-rwx /sdcard/Android/data/lms/mpReadAbDdx201006.txt Bad mode (I get the same file attributes when I copy file to sdcard via DDMS File Explorer.) Where can I find documentation to the Android linux (?) commands? (I mean the command line commands) -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: on sdcard, File.canRead() = true, File.canWrite() = false
SOLVED! THANK YOU Android-Developers group!
Thank you so much for your help. It is wonderful to have someplace to
go for answers.
John Brown
On Aug 9, 11:59 am, john brown johnbrowngreybe...@gmail.com wrote:
Hello,
Documentation source
http://developer.android.com/guide/topics/data/data-storage.html
Every Android-compatible device supports a shared external storage
that you can use to save files. This can be a removable storage media
(such as an SD card) or an internal (non-removable) storage. Files
saved to the external storage are world-readable and can be modified
by the user when they enable USB mass storage to transfer files on a
computer.
PROBLEM: I cannot write to a file on the sdcard.
QUESTION: Is it possible to write to a file on the sdcard?
If YES, what do I need to do to make File.canWrite = true?
I am using Android 2.1 update 1, API level 7, Eclipse, and HVGA skin.
I am running my app / troubleshooting on the Android SDK ADV.
When the AVD is running, I check settings sdcard total 49.21MB,
available 49.07MB.
Environment.getExternalStorageState() yields MEDIA_MOUNTED
getExternalStorageDirectory() to establish the sdcard root directory.
I copied the files to the sdcard with adb push source destination
I am able to successfully read other files in that directory.
psudo code:
// __
File fFile = new File(pathFile);
if (fFile.exists()){ ... // returns true
if (fFile.canRead()){ ... // returns true
if (fFile.canWrite()){ ... // returns false
try{
FileWriter Fw = new FileWriter(fFile, true);
BufferedWriter Bw = new BufferedWriter(Fw);
PrintWriter outPw = new PrintWriter(Bw, true);
outPw.println(strRec);
outPw.close();
}
catch(IOException ex){
System.out.println(IO Error - + ex.toString());
System.exit(0);
}
//
System.out shows:
IO Error - java.io.FileNotFoundException
but we know the file is there from the preceding checks:
if (fFile.exists()){ ... // returns true
if (fFile.canRead()){ ... // returns true
What do I need to do to make the file writable?
Or
I want to write to the file. What am I doing wrong?
Thanks, John Brown
P.S.
I got a command prompt via c:\Program Files\Android-SDK\tools adb
shell
# ls -l /sdcard/Android/data/lms
rwxr-x system sdcard_rw 63 2010-07-19 15:17
mpReadAbDdx201006.txt
rwxr-x system sdcard_rw 45211 2010-07-19 15:17
mpTranAbDdx201006.txt
The way I read this is that the owner's rights are ---, group is rwx,
others is r-x. I'm just guessing, the application is others?
But I cannot get chmod to change the attributes, i.e.:
# chmode o-rwx /sdcard/Android/data/lms/mpReadAbDdx201006.txt
Bad mode
(I get the same file attributes when I copy file to sdcard via DDMS
File Explorer.)
Where can I find documentation to the Android linux (?) commands? (I
mean the command line commands)
--
You received this message because you are subscribed to the Google
Groups Android Developers group.
To post to this group, send email to android-developers@googlegroups.com
To unsubscribe from this group, send email to
android-developers+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en
Re: [android-developers] Re: on sdcard, File.canRead() = true, File.canWrite() = false
You can't change the permissions on stuff in external storage. That uses a FAT filesystem, which doesn't have permissions, so all files there simply immutably use the permissions of the mount point. On Mon, Aug 9, 2010 at 11:46 AM, Bob Kerns r...@acm.org wrote: Kostya and Mark answered your main question; I'll address your ps. Applications are indeed 'other' in the permissions you list below, but applications do have their own uids, so an Application's directory will be owned by its uid. An application with the right permission I'm guessing is put into the sdcard_rw group, and thus would come in under the group permissions instead. I believe chmod command doesn't take the symbolic arguments -- you'll have to use the numeric arguments like we did back in the 1970's. I'm not sure why you were trying to remove the 'other' permissions on that file, but let's say you did ls -l on it, and the permissions were -rw-r--r--. You'd convert this to the numeric form: 644. Your o-rwx would mean 'turn off all the bits in the last digit', so you'd want chmod 640 ... I'd love to have a document on the command-line commands! You can install the busybox toolkit, and get much improved versions of many commands, such as this. I find a rooted device without busybox to be very disconcerting. Busybox puts a large number of commands in one executable to make it quite small, and then symlinks to it under each command name. It looks at the name to figure which command you're asking for. On Aug 9, 10:59 am, john brown johnbrowngreybe...@gmail.com wrote: P.S. I got a command prompt via c:\Program Files\Android-SDK\tools adb shell # ls -l /sdcard/Android/data/lms rwxr-x systemsdcard_rw63 2010-07-19 15:17 mpReadAbDdx201006.txt rwxr-x systemsdcard_rw 45211 2010-07-19 15:17 mpTranAbDdx201006.txt The way I read this is that the owner's rights are ---, group is rwx, others is r-x. I'm just guessing, the application is others? But I cannot get chmod to change the attributes, i.e.: # chmode o-rwx /sdcard/Android/data/lms/mpReadAbDdx201006.txt Bad mode (I get the same file attributes when I copy file to sdcard via DDMS File Explorer.) Where can I find documentation to the Android linux (?) commands? (I mean the command line commands) -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.comandroid-developers%2bunsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
