Windows system root

[Charles Hasegawa]

Is there a way to get the %systemroot% property?
We can assume that the user has given us/java permission to access the file system etc.

I've tried :

Process p = Runtime.getRuntime().exec("cmd");

and then getting the input and output streams and to push commands to, with no luck.

[Joe Ess]

That should work. I will bet you are not putting a line separator on the end of the command. Remember, line separators are not platform independent, and the UNIX one ('\n') does not work on Windows (which expects "\n\r").
Don't hard code the line separator. Either use System.getProperties() to get it or use a PrintWriter or BufferedWriter which provide methods to place a line separator in the stream.
Don't forget to flush the stream after the line separator.

[Stefan Wagner]

well - using "cmd" the system-indepence is already lost.

But what is the %systemroot% property?
The filesystem-root?

[Roshan Lal]

Originally posted by Charles Hasegawa:
Is there a way to get the %systemroot% property?
We can assume that the user has given us/java permission to access the file system etc.

I've tried :

Process p = Runtime.getRuntime().exec("cmd");

and then getting the input and output streams and to push commands to, with no luck.

try {
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("cmd /k echo %systemroot%");
InputStream is = p.getInputStream();
byte[] b = new byte[100];
is.read(b);
String s = new String(b);
System.out.println(s.trim());

} catch (Exception e) {
e.printStackTrace();
}

I just tried the above code and it worked for me.

[Jean-Francois Briere]

You can get any environment variable value from any Windows OS flavor with this utily class:

import java.util.*;
import java.io.*;
 
public class Win32Util {
    public static String getEnv(String envName) throws Exception {
        return theOneInstance.doGetEnv(envName);
    }
    
    private static final String SET_CMD;
    static {
        String osName = System.getProperty("os.name");
        if ((osName.indexOf("NT") != -1) || (osName.indexOf("200") != -1) || (osName.indexOf("XP") != -1))
            SET_CMD = "cmd /c set";
        else // Windows 9x/ME
            SET_CMD = "command /c set";
    }
    private static Win32Util theOneInstance = new Win32Util();
    
    private Win32Util() {
    }
    
    private String doGetEnv(String envName) throws Exception {
        Process p = Runtime.getRuntime().exec(SET_CMD);
        StreamPumper outPump = new StreamPumper(p.getInputStream());
        StreamPumper errPump = new StreamPumper(p.getErrorStream());
        
        outPump.start();
        errPump.start();
        p.waitFor();
        outPump.join();
        errPump.join();
        
        return parseLines(envName, outPump.getLineList());
    }
    
    private String parseLines(String envName, List lineList) {
        for (Iterator iterator = lineList.iterator(); iterator.hasNext(); ) {
            String line = (String)iterator.next();
            String[] elmArray = line.split("=");
            
            if (elmArray[0].equalsIgnoreCase(envName))
                return elmArray[1];
        }
        
        return null;
    }
    
    private class StreamPumper extends Thread {
        private InputStream is;
        private List lineList = new ArrayList();
        
        StreamPumper(InputStream is) {
            this.is = is;
        }
        
        public void run() {
            try {
                BufferedReader br = new BufferedReader(new InputStreamReader(is, "ISO-8859-1"));
                String line;
                
                while ((line = br.readLine()) != null)
                    lineList.add(line);
            }
            catch (Exception e) {
            }
        }
        
        List getLineList() {
            return lineList;
        }
    }
}

And here is an example on how to use it (very simple indeed):

public class GetEnvTest {
    public static void main(String[] args) throws Exception {
        System.out.println("SystemRoot is: " + Win32Util.getEnv("SystemRoot"));
        System.out.println("SystemDrive is: " + Win32Util.getEnv("SystemDrive"));
        System.out.println("TEMP is: " + Win32Util.getEnv("TEMP"));
    }
}

[Charles Hasegawa]

Thanks everyone, lots of good help.

Originally posted by Stefan Wagner:
well - using "cmd" the system-indepence is already lost.
But what is the %systemroot% property?
The filesystem-root?

We weren't trying for system independence with this - we know the client will be on a Win OS but it could be 98, 2k, XP, etc. This all came about because we have to download a dll to run a signature pad, and so we need to know the client's system32 directory location (which can be in the "windows" folder or "winnt" folder and can be on any drive, etc).

On WinOS, open a command prompt and tyep "ECHO %systemroot%" and you should get something like "c:\windows" (or whatever).

[Petr Blahos]

May I humbly suggest that you don't do it through exec ("..cmd...")
but that you use JNI to call SHGetFolderPath()? If I understand
correctly you already use JNI for the DLL, therefore it's no sweat.
I also believe it is, well, slightly cleaner than calling cmd.

Best regards,
Petr

[Stefan Wagner]

well - I don't have a windows to type in 'echo %systemroot%', but I got a hint:
If you're allowed to use java-1.5,

System.getenv ("systemroot");

should work. But probably you're not allowed.