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Editorial Team
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Asked: 2026-05-13T13:02:59+00:00

I found out that you can use something like this to create a file:

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I found out that you can use something like this to create a file:

FileOutputStream  fs = openFileOutput("/test.in", MODE_WORLD_WRITEABLE);
String s = "[Head]\r\n";
s += "Type=2";
byte[] buffer = s.getBytes();
fs.write(buffer);
fs.close();

When running the above code I get an IllegalArgumentException stating:

java.lang.IllegalArgumentException:
File /test.in contains a path
separator

and I’m guessing the “/” is not appreciated. I wanted the “/” since I need to write the file to the root directory of the device, as stated in the API in trying to follow:

A request is a textfile (UNICODE) with
the file extension “.in”. The
application reads and parses the .in
file when it’s placed in root
directory on the mobile device.

Question is: how do I place a file in the root-directory? I have been looking around for an answer, but haven’t found one yet.

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1 Answer

  1. Editorial Team

    Context.openFileOutput is meant to be used for creating files private to your application. they go in your app’s private data directory. you supply a name, not a path: “name The name of the file to open; can not contain path separators”.

    http://developer.android.com/reference/android/content/Context.html#openFileOutput(java.lang.String, int)

    as for your question, you can’t write to / unless you’re root:

    my-linux-box$ adb shell ls -l -d /
    drwxr-xr-x root root 2010-01-16 07:42
    $

    i don’t know what your API is that expects you to write to the root directory, but i’m guessing it’s not an Android API and you’re reading the wrong documentation 😉

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