user.dir property

[Kresten Krab Thorup]

Here's a question.  

I'm trying to set the property user.dir and thereby effectively cd'ing
to a given directory.  The following piece of code tries do do that, but
fails on JDK1.2.2.  The code does the following

create file "/tmp/foo.bar"
set user.dir = "/tmp"
read "foo.bar"

Obviously, this is only interesting if the original value of "user.dir"
is different from "/tmp".

The question is if this ought to be possible. As I read the javadoc for
java.lang.File, it seems that it should.

Any coments?

--Kresten

----------------------------------------------------------------------
import java.io.*;

public class TestUserDir
{
  public static void main (String[] args)
    throws IOException
  {
    String user_dir = System.getProperty ("user.dir");
    System.out.println ("user.dir = "+user_dir);

    File tmp = File.createTempFile ("foo", "bar");
    System.out.println ("tmpfile  = "+tmp);

    File tmp2 = new File(tmp.getAbsolutePath ());
    System.out.println ("abstmp   = "+tmp2);

    String parent = tmp2.getParent ();
    String file   = tmp2.getName ();

    System.out.println ("parent   = "+parent);
    System.out.println ("file     = "+file);

    try {
      FileOutputStream fo = new FileOutputStream (tmp2);
      fo.write (27);
      fo.close ();
    } finally {
      System.out.println ("wrote one byte to "+tmp2);
    }

    System.setProperty ("user.dir", parent);
    System.out.println ("cd'ed to "+parent);

    try {
      FileInputStream fi = new FileInputStream (file);
      int b = fi.read ();
      if (b == 27)
	{
	  System.out.println ("sucessfully read from "+file);
	}
    } catch (IOException e) {
      System.out.println ("** failed to read "+file);
      throw e;
    }
  }
}



-- 
Kresten Krab Thorup, Director of Research
Eastfork Object Space (EOS), Margrethepladsen 3, 8000  Århus C, Denmark
Tel: +45 8732 8787 / Fax: +45 8732 8788 / Mob: +45 2343 4626