Error in creating a process using runtime class - please help

Question

Hi,
I am experimenting with the following piece of code. I tried to run it in one windows machine and it works fine. But i tried to run it in a different windows machine i get error in creating a process. The error is attached below the code. I don't understand why i couldn't create a process with the 'exec' command in the second machine. Can anyone please help?
CODE:
import java.io.*;
class test{
public static void main(String[] args){
try{
Runtime r = Runtime.getRuntime();
     Process p = null;
     p= r.exec("dir");
     BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
     System.out.println(br.readLine());
catch(Exception e){e.printStackTrace();}
ERROR (when run in the dos prompt):
java.io.IOException: CreateProcess: dir error=2
at java.lang.Win32Process.create(Native Method)
at java.lang.Win32Process.<init>(Win32Process.java:63)
at java.lang.Runtime.execInternal(Native Method)
at java.lang.Runtime.exec(Runtime.java:550)
at java.lang.Runtime.exec(Runtime.java:416)
at java.lang.Runtime.exec(Runtime.java:358)
at java.lang.Runtime.exec(Runtime.java:322)
at test.main(test.java:16)
thanks,
Divya

Answer 1

As much as I understand from the readings in the forums, Runtime.exec can only run commands that are in files, not native commands.
Hmm how do I explain that again?
Here:
Assuming a command is an executable program
Under the Windows operating system, many new programmers stumble upon Runtime.exec() when trying to use it for nonexecutable commands like dir and copy. Subsequently, they run into Runtime.exec()'s third pitfall. Listing 4.4 demonstrates exactly that:
Listing 4.4 BadExecWinDir.java
import java.util.*;
import java.io.*;
public class BadExecWinDir
public static void main(String args[])
try
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("dir");
InputStream stdin = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(stdin);
BufferedReader br = new BufferedReader(isr);
String line = null;
System.out.println("<OUTPUT>");
while ( (line = br.readLine()) != null)
System.out.println(line);
System.out.println("</OUTPUT>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);
} catch (Throwable t)
t.printStackTrace();
A run of BadExecWinDir produces:
E:\classes\com\javaworld\jpitfalls\article2>java BadExecWinDir
java.io.IOException: CreateProcess: dir error=2
at java.lang.Win32Process.create(Native Method)
at java.lang.Win32Process.<init>(Unknown Source)
at java.lang.Runtime.execInternal(Native Method)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at BadExecWinDir.main(BadExecWinDir.java:12)
As stated earlier, the error value of 2 means "file not found," which, in this case, means that the executable named dir.exe could not be found. That's because the directory command is part of the Windows command interpreter and not a separate executable. To run the Windows command interpreter, execute either command.com or cmd.exe, depending on the Windows operating system you use. Listing 4.5 runs a copy of the Windows command interpreter and then executes the user-supplied command (e.g., dir).
Taken from:
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html