Runtime.getRuntime( ).exec( command ); Win vs Unix

[Jonathan Bagshaw]

The following code segment fails in windows, but works under unix:

(note: command = "ls" under unix)

    try {
        // Execute command
        String command = "dir";
        StringBuffer ret=new StringBuffer();
        Process child = Runtime.getRuntime().exec(command);
    
        // Get the input stream and read from it
        InputStream in = child.getInputStream();
        int c;
        while ((c = in.read()) != -1) {
        ret.append((char)c);
        }
        in.close();
        System.out.println(ret.toString());
    } catch (IOException e) {
    e.printStackTrace();
    }

The stack trace is :
C:\CVS_ROOT>java -classpath Carpenter.jar carpenter.Carpenter
java.io.IOException: CreateProcess: dir error=2
at java.lang.ProcessImpl.create(Native Method)
at java.lang.ProcessImpl.<init>(Unknown Source)
at java.lang.ProcessImpl.start(Unknown Source)
at java.lang.ProcessBuilder.start(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at carpenter.Carpenter.main(Carpenter.java:17)

I'm developing under Windows.. Can anyone enlighten me as to how I can use this code in a Windows env?

[Keith Lynn]

In Windows, dir is not a standalone program. It is built into the command shell.

So on Windows you would do something like this.

String[] cmd = {"cmd.exe","/c","dir"};

.

You might also look at ProcessBuilder.

[Jonathan Bagshaw]

<3 Keith.

[Peter Chase]

Presumably, "dir" and "ls" were just example commands picked for prototyping purposes, yes? There's little/no reason to invoke them from Java for any real application, is there?

For "dir", the trick of running it via "cmd" is fine. But most things you would type into a Windows Command Prompt are separate programs and do not need a "cmd". It would be inefficient to use "cmd" for most things.

[Jonathan Bagshaw]

Yes.. dir and ls were simply for prototyping purposes.

[Brian Stinar]

Hello,

I have been looking for places to help me understand the format my String[] cmd must be in for different operating systems. I need to be able to run (primarily) on Windows XP and on Linux. Do you guys know of any good links to help me get a handle on this?

Thanks a lot!!

-Brian J. Stinar-

Originally posted by Keith Lynn:
In Windows, dir is not a standalone program. It is built into the command shell.

So on Windows you would do something like this.

String[] cmd = {"cmd.exe","/c","dir"};

.

You might also look at ProcessBuilder.

[Ulf Dittmer]

Brian, welcome to JavaRanch.

There's an all-time favorite article on the pitfalls of Runtime,exec: http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps_p.html

[Brian Stinar]

Thanks a lot!!

-Brian J. Stinar-