runtime.exec() to call unix commands

[rasica sharma]

hi...
i want to call unix commands like 'ls','mkdir' through java & store its result in a text file.
i tried to use runtime.exec() for it...but i dont get the correct output as needed...
If someone knows how to write the code, or even a link....
please....tell me...I need it urgently...

[Yi Meng]

as in jcrontab:

 /**
 *  This file is part of the jcrontab package
 *  Copyright (C) 2001-2003 Israel Olalla
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307, USA
 *
 *  For questions, suggestions:
 *
 *  [e-mail]
 *
 */
package org.jcrontab;
import java.io.InputStream;
import org.jcrontab.log.Log;
/**
 *This class ejecutes a native command
 * @author $Author: iolalla $
 * @version $Revision: 1.16 $
 */
public class NativeExec {
/**
 * main method
 * @param args String[] the params passed from the console
 */
    public static void main(String args[]) {
        if (args.length < 1) {
            System.out.println("java org.jcrontab.NativeExec <cmd>");
            System.exit(1);
        }
        String[] cmd = null;
        
        try {
//with this variable will be done the swithcing
            String osName = System.getProperty("os.name" );
            
    //only will work with Windows NT
            if( osName.equals( "Windows NT" ) ) {
                if (cmd == null) cmd = new String[ args.length + 2];
                cmd[0] = "cmd.exe" ;
                cmd[1] = "/C" ;
                for (int i = 0; i<args.length; i++) 
                    cmd[i+2] = args[i];
            }
    //only will work with Windows 95
            else if( osName.equals( "Windows 95" ) ) {
                if (cmd == null) cmd = new String[args.length + 2];
                cmd[0] = "command.com" ;
                cmd[1] = "/C" ;
                for (int i = 0; i<args.length; i++) 
                    cmd[i+2] = args[i];
            }
    //only will work with Windows 2000
    else if( osName.equals( "Windows 2000" ) ) {
                if (cmd == null) cmd = new String[args.length + 2];
                cmd[0] = "cmd.exe" ;
                cmd[1] = "/C" ;
                
                for (int i = 0; i<args.length; i++) 
                    cmd[i+2] = args[i];
            }
    //only will work with Windows XP
    else if( osName.equals( "Windows XP" ) ) {
                if (cmd == null) cmd = new String[args.length + 2];
                cmd[0] = "cmd.exe" ;
                cmd[1] = "/C" ;
                
                for (int i = 0; i<args.length; i++) 
                    cmd[i+2] = args[i];
            }
    //only will work with Linux
    else if( osName.equals( "Linux" ) ) {
                if (cmd == null) cmd = new String[args.length];
                cmd = args;
            }
    //will work with the rest
            else  {
                if (cmd == null) cmd = new String[args.length];
                cmd = args;
            }
            
            Runtime rt = Runtime.getRuntime();
        // Executes the command
            Process proc = rt.exec(cmd);
            // any error message?
            StreamGobbler errorGobbler = new 
                StreamGobbler(proc.getErrorStream(), "ERROR");            
            
            // any output?
            StreamGobbler outputGobbler = new 
                StreamGobbler(proc.getInputStream(), "OUTPUT");
                
            // kick them off
            errorGobbler.start();
            outputGobbler.start();
                                    
            // any error???
            int exitVal = proc.waitFor();
            System.out.println("ExitValue: " + exitVal);        
        } catch (Throwable t) {
            Log.error(t.toString(), t);
          }
    }
}
 

[Mark Spritzler]

Hi Rasika. Unfortuantely your question isn't about the SCJD exam. I am going to move this thread to the Java-Beginner's forum.
I would really suggest that you avoid using runtime.exec to run OS specific commands. Since Java is write once run anywhere, you are breaking this rule and making it OS specific.
There is the File class that can get a list of files, and do some file stuff, as I am sure other classes already built that are OS independant that you can use to get the results you want.
Mark