Using Runtime.exec to execute Java.exe

I am trying to use Runtime.exec to spawn a thread that runs java.exe, but havn't had any luck. I have two versions of code, the first one works (example 1), but I want to eliminate the use of "cmd /c" to keep system independance. The second example (example 2) does not work. Both versions work if invoked from the command line. I'm running Win2000. Any Ideas?
Example 1:
aProcess = aRuntime.exec("cmd /c java.exe
-cp "<MyClassPathHere>" <arg1> <arg2> <arg3> <arg4> <arg5>");
Example 2:
aProcess = aRuntime.exec("java.exe
-cp "MyClassPathHere" <arg1> <arg2> <arg3> <arg4> <arg5>");

I think you mix two concepts: "threads" and "processes". A "thread" is a thread of execution inside the VM, but you want to actually start a new VM in a new process, which is an OS level thing, right?
I've tried Idea 2 also, same result: works if
i specify cmd c/, doesn't if I don't.It should work if java.exe is in your path... are you taking care of the standard streams of your process?

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Using Runtime.exec to execute a C++ executable

Hello,
I would like to know if it possible to execute a C++ executable using Runtime.exec() and wait for it to complete and how do I read back the output file created by the C++ executable into the Java Code?
TIA.
RHP

When I execute the code with Runtime.exec(), and read
from the Process's inputStream I am ablt to view the
cout from the C++ code. But the output file that has
to be created by the C++ code is not created,Then this is maybe an error in the C++ code? Maybe you don't have permissions to create that file where you want to.
where
would the output from the C++ code go to when I use a
ofstream in my C++ code andIf you create the file stream in C++ with an absolute file name then the output goes into that file. If it's a relative file name, then the basis is most likely the current working directory (found in the system property "user.dir" if you used one of Runtime's methods without the File argument, otherwise it's the directory you provide.
How do I read both streams
from the Java Code?You create an FileInputStream and - if you want to read character instead of binary data - on top of that an InputStreamReader. You might add a BufferedReader on top of that if you want to read line by line.
does that answer your questions?
robert

Using Runtime exec() to open java on other directory

HI, I have a little problem and i hope everyone can help me out abit. You see when u use Runtime.exec(), how to you use it so that when the file you want to open is different from your program directory.
For example,
my program is in c:\windows\desktop
but the file i want to open eg. Somthing.class is in c:\my documents\
How do I open it using java and i wish to open the file using the java command. Thank a million

Runtime.getRuntime().exec("cmd /c start /d\"C:\\my documents\" java.exe Somthing");
Can someone explain the /c start /d\"C:\Mydocuments\" java.exe Somthing.
And I try to use ping in RunTime.exec,how do I construct the string?And how do i get the result of the ping?
Thanks

Invoking "java myClass" using Runtime.Exec from a Java Stored Procedure

Hi All,
This is regarding the use of Runtime.getRunTime().exec, from a java programme (a Java Stored Procedure), to invoke another Java Class in command prompt.
I have read many threads here where people have been successuful in invoking OS calls, like any .exe file or batch file etc, from withing Java using the Runtime object.
Even i have tried a sample java programme from where i can invoke notepad.exe.
But i want to invoke another command prompt and run a java class, basically in this format:
{"cmd.exe","java myClass"}.
When i run my java programme (in command prompt), it doesnt invoke another command prompt...it just stays hanging.
When i run the java programme from my IDE, VisualCafe, it does open up a command prompt, but doesnt get the second command "java myCLass".
Infact on the title of the command prompt (the blue frame), shows the path of the java.exe of the Visual Cafe.
and anyway, it doesnt run my java class, that i have specified inside the programme.
Even if i try to run a JAR file, it still doesnt do anything.
(the JAR file other wise runs fine when i manually invoke it from the command prompt).
Well, my question is, actually i want to do this from a Java Stored Procedure inside oracle 8.1.7.
My feeling is, since the Java Stored Procedure wont be running from the command prompt (i will be actually invoking it through a Oracle trigger), it may be able to invoke the command prompt and run the java class i want. and that java class has to run with the SUn's Java, not Oracle JAva.
Does any one have any idea about it?
Has anyone ever invoked a java class or JAR file in command prompt from another Java Programme?
YOur help will be highly appreciated.
(P:S- Right now, my database is being upgraded, so i havent actually been able to create a Java Stored procedure and test it. But i have tested from a normal java programme running in command prompt and also from Visual Cafe).
Thanks in advance.
-- Subhasree.

Hello Hari,
Thanks for your quick reply.
Can you please elaborate a little more on exactly how you did? may be just copy an dpaste taht part of teh code here?
Thanks a lot in advance.
--Subhasree

Problem of executing a process under Linux using Runtime.exec

Hi, All
I am having a problem of executing a process under Linux and looking for help.
I have a simple C program, which just opens a listening port, accept connection request and receive data. What I did is:
1. I create a script to start this C program
2. I write a simple java application using Runtime.exec to execute this script
I can see this C program is started, and it is doing what it supposed to do, opening a listening port, accepting connection request from client and receiving data from client. But if I stop the Java application, then this C program will die when any incoming data or connection request happens. There is nothing wrong with the C program and the script, because if I manually execute this script, everying works fine.
I am using jre1.4.2_07 and running under Linux fedora 3.0.
Then I tried similar thing under Windows XP with service pack2, evrything works OK, the C program doesn't die at all.

Mind reading is not an exact science but I bet that you are not processing either the process stdout or the stderr stream properly. Have you read http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html ?

About use exec to call java.exe!

when i use the exec to call java.exe to run a class,
a dos command window will be showed! The window appear until the java program completed~
i always use "javac filename.java"
,"java filename"
or "cmd.exe \c java filename"
any method can run the class file but the dos command windows wont show?
and also any method in cmd can do the same thing as Linux background process "&". Because when running a class, the cmd is locked until the java program completed.
Thx~

Use javaw if you dont want the dos prompt window.
Use start if you dont want to block the current dos window. e.g.
Start java my.class
Start will start another native thread to run java.exe
hope it helps.

Using runtime.exec,process streams

Hi all,
I am using runtime.exec to execute a batch file(rmdir /s/q directoryname) which deletes all the files in a certain directory(including subdirectories). However, some of the files are not deleted since they are being used by other processes.
I have closed all file references but still the batch file says they are being used by other processes. The File.canWrite() method however, returns true for all the files. I have also tried to delete the files using file.delete but it does not work.
So I have 2 questions.
1. Can I forcibly delete these files some other way.
2. If i call a batch file to delete the files and it fails on some files, the command window displays "cannot delete files". How can I write out thse messages into a text file which i can use as a log file.Do I have to use Process.getInputstream()/Process.getInputstream() ? If so, how?
Thanks for your help.
Vinny

I tried the following before but the string i get is always empty, but i can see there are messages in the command window. Please let me now if i am doing something wrong.
try{
Process p = rt.exec("cmd.exe /c start deletefiles.bat");
InputStream ins = p.getInputStream();
byte[] bytearray = new byte[1024];
int bytecount;
String dos_string="";
BufferedInputStream bis = new BufferedInputStream(ins);
while ((bytecount = bis.read(bytearray, 0, 1024)) > -1) {
String str = new String(bytearray,0,bytecount);
dos_string += str;
System.out.println("dos string is" +dos_string);
catch (Exception e) {
System.out.println("Error: " + e);

Executing bat file without using Runtime.exec()??

Hi all
From my java App ,I am running a bat file. This is what I did:
When I press 'execute' button inside my App, it runs a bat file through Runtime.exec() method. Since exec() runs it through cmd.exe, get a DOS window when I press Execute button. If I manually runs my app from command promt , I dont get it. But I have to create a short cut of my main class in the desktop. This is happening when I run my app from desktop icon.
Now I want to eleminate DOS popup everytime I press execute button. Would anyone pls give an idea how to run bat file without using Runtime.exec()? Any suggestion will be helpful.
Thanks

jscell
Thanks for taking time to answer to my problem .
Here is what my problem: I create a shortcut of my main class in the desktop. Through this shortcut ,I run my java App. My App has a execute button, When I press this button , It run another bat file through Runtime.exec() method, and show some result in the result PAnel. NOw what happen , I get a DOS command window , everytime I press execute button. , Which is very annoying . But If I run my App thorugh command promt by executing: "java myApp", then I dont get this DOS popup. But I have to create a shortcut in the desktop, so other can use it conveniently.
NOw I am not sure why I am getting this DOS window in the middle of my Application. IS it for using Runtime.exec() method? or for running bat file through my application? Can anyone pls tell me? I am kind of new to java, and I am learning lot of stuff from this forum .
Would u pls suggest me about how to eleminate this DOS popup when I press execute button.
Regrds

Where to put files in using runtime.exec(run.exe)?

I try to use the following program in EJB to call my EXE program in the J2EE server:
runtime.exec("c:\\j2ee\\public\\exe\\run.exe temp.txt");
In the execution of mill_turn.exe, it will open several files for read and write.
So where to put the file temp.txt and other files the run.exe need to read?
Looks like the J2EE server can not find them?
Thanks!

I got it in Java SE1.4.
File dir=new File("c:\\j2ee\\public_html\\Mill_turn\\exe\\");
Process proc = rt.exec(cmd,null,dir);Use above codes, I really got the right output from my external program for the first time. But , after that, the output keeps same when I change the filename in the following code:
cmd="c:\\..\\run.exe temp.prt"
to
cmd="c:\\..\\run.exe Abc1.prt" , which must have different output.
The codes for calling external program are implemented in the SessionBean of J2EE.

How to capture output of java files using Runtime.exec

Hi guys,
I'm trying to capture output of java files using Runtime.exec but I don't know how. I keep receiving error message "java.lang.NoClassDefFoundError:" but I don't know how to :(
import java.io.*;
public class CmdExec {
public CmdExec() {
public static void main(String argv[]){
     try {
     String line;
     Runtime rt = Runtime.getRuntime();
     String[] cmd = new String[2];
     cmd[0] = "javac";
     cmd[1] = "I:\\My Documents\\My file\\CSM\\CSM00\\SmartQ\\src\\E.java";
     Process proc = rt.exec(cmd);
     cmd = new String[2];
     cmd[0] = "javac";
     cmd[1] = "I:\\My Documents\\My file\\CSM\\CSM00\\SmartQ\\src\\E";
     proc = rt.exec(cmd);
     //BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
     BufferedReader input = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
     while ((line = input.readLine()) != null) {
        System.out.println(line);
     input.close();
    catch (Exception err) {
     err.printStackTrace();
public class E {
    public static void main(String[] args) {
        System.out.println("hello world!!!!");
}Please help :)

Javapedia: Classpath
How Classes are Found
Setting the class path (Windows)
Setting the class path (Solaris/Linux)
Understanding the Java ClassLoader
java -cp .;<any other directories or jars> YourClassNameYou get a NoClassDefFoundError message because the JVM (Java Virtual Machine) can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.
javac -classpath .;<any additional jar files or directories> YourClassName.javaYou get a "cannot resolve symbol" message because the compiler can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.

Can we run a java application using Runtime.exec()?

Can we run a java application using Runtime.exec()?
If yes what should i use "java" or "javaw", and which way?
r.exec("java","xyz.class");

The best way to run the java application would be to dynamiically load it within the same JVM. Look thru the class "ClassLoader" and the "Class", "Method" etc...clases.
The problem with exec is that it starts another JVM and moreover you dont have the interface where you can throw the Output directly.(indirectly it can be done by openong InputStreams bala blah............). I found this convenient. I am attaching part of my code for easy refernce.
HIH
ClassLoader cl = null;
Class c = null;
Class cArr[] ;
Method md = null;
Object mArr[];
cl = ClassLoader.getSystemClassLoader();
try{
     c = cl.loadClass(progName.substring(0,progName.indexOf(".class")) );
} catch(ClassNotFoundException e) {
System.out.println(e);
     cArr = new Class[1] ;
     try{
     cArr[0] = Class.forName("java.lang.Object");
     } catch(ClassNotFoundException e) {
     System.out.println(e);
     mArr = new Object[1];
     try{
     md = c.getMethod("processPkt", cArr);
     } catch(NoSuchMethodException e) {
     System.out.println(e);
     } catch(SecurityException e) {
     System.out.println(e);
try {
processedPkt = md.invoke( null, mArr) ;
} catch(IllegalAccessException e) {
          System.out.println(e);
} catch(IllegalArgumentException e) {
          System.out.println(e);
}catch(InvocationTargetException e) {
          System.out.println(e);
}catch(NullPointerException e) {
          System.out.println(e);
}catch(ExceptionInInitializerError e) {
          System.out.println(e);
}

Parameter to shell script using Runtime.exec(string)

Hi all, ( Speciall hi to dheeraj tak )
Briefly : How do i pass an arguement to a non - java executible being called using Runtime.exec.
In detail : i am using Runtime.exec to call a shell script : The code is as follows:
String callAndArgs[] = {"/home/tom/jakarta-tomcat-4.1.24/webapps/dash/script.sh"};
try {
Runtime rt = Runtime.getRuntime();
Process child = rt.exec(callAndArgs);
This works properly & calls the shell script which in turn invokes some other executible (c file).
$HOME/midi/test/build/bin/<C-EXECUTIBLE>
Here i am specifying the name (say hello.exe ) . So far so good.
I want to make this happen dynamiclaly. so i need to pass the name of the executible as a parameter to the script.
To pass a parameter i hav to change the string to :-
String callAndArgs[] = {"/home/tom/jakarta-tomcat-4.1.24/webapps/dash/script.sh <C-EXECUTIBLE HERE>"};
and the script to
$HOME/midi/test/build/bin/$1 --- where $1 refers to argument 1. (C-EXECUTIBLE AGAIN).
This is giving an IO - Execption. Plz help
Code will be very helpful.
Thanx in advance

some 1 plz tell me the difference :-
This is the documentation of Runtime.exec that i found :-
1> exec
public Process exec(String command) throws IOException
Executes the specified string command in a separate process.
The command argument is parsed into tokens and then executed as a command in a separate process. This method has exactly the same effect as exec(command, null).
Parameters:
command - a specified system command
Complete refernce says : Process (String progName) ----- Executes a program specified by programname as a seperate process.
2> exec
public Process exec(String cmdarray[]) throws IOException
Executes the specified command and arguments in a separate process.
The command specified by the tokens in cmdarray is executed as a command in a separate process. This has exactly the same effect as exec(cmdarray, null).
Parameters:
cmdarray - array containing the command to call and its arguments.
Complete reference says : Process exec(String comLineArray[]) ---- Executes the command line specified bythe string in comLineArray as a seperate process.
This means that there is provision 4 command line arguments...
how do u use it then????????????????????????????

How to run db2 command by using Runtime exec

Hello
I am using java. When i am runing db2 command by using Runtime.exec( String cmd, String[] env ). I gave the environment path
DB2CLP=6259901
DB2DRIVER=D:\ibm\db2\java\db2java.zip
DB2HOME=D:\ibm\db2
DB2INSTANCE=DB2
DB2MMTOP=D:\CMBISS
but still I am getting error message
"DB21061E Command line environment not initialized"
after setting the above path in the cmd It is working fine. When i am trying thro java programm i am getting the above error. Can I get answer for this.
bhaski.

Before you can execute DB2 commands you have to open a DB2 CLP. The following code will do so:
import java.io.IOException;
public class Db2 {
     public static void main(String args[]) {
          try {
               Runtime rt = Runtime.getRuntime();
               Process child = rt.exec("db2cmd");
               child.waitFor();
          catch (IOException io) {
               io.printStackTrace();
          catch (InterruptedException e) {
               e.printStackTrace();

Using runtime.exec to zip some files

Hi,
I am using runtime.exec to try to automatically zip a bunch of files on a server. However, it does not seem to be working.
Before I execute the command, I save the zip command in a string. I then print the string to a log file, and then execute the runtime zip command. But nothing happens.
Yet, when I copy the string from the log, and paste it in a terminal, it properly creates the zip files. So, I know I have the correct command string, it just does not seem to be working within the java application. Also, the command string uses fully qualified directories, so it is not a directory issue.
I am using ubuntu linux.
Any ideas?
-Adam

adamSpline wrote:
Hi,
I am using runtime.exec to try to automatically zip a bunch of files on a server. However, it does not seem to be working.
Before I execute the command, I save the zip command in a string. I then print the string to a log file, and then execute the runtime zip command. But nothing happens. Within Runtime.exec() any command does not run in a shell and I bet you use wild cards and/or other commands to be interpreted by a shell which will not be interpreted since there is no shell. And, since you don't mention error messages or the return code, I will also bet you don't process the Process stdout , stderr and the return code properly.
It looks to me like you have fallen for at least two for the traps in [http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html|http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html].
>
Yet, when I copy the string from the log, and paste it in a terminal, it properly creates the zip files. So, I know I have the correct command string, it just does not seem to be working within the java application. Also, the command string uses fully qualified directories, so it is not a directory issue.
I am using ubuntu linux.
Any ideas?I agree with 'masijade' - use the built in Java classes.
>
-Adam

Issue using Runtime.exec() in Vista

I've coded a simple method using Runtime.exec() to get the client MAC ID , and it worked alright on XP. Now my client want to switch to vista , and the method is not working. Here's my code
import java.io.*;
import java.util.regex.*;
public class GetMac
     public static String getMacAddress()
          String mac="";
          System.out.println("getMacAddress");
          try {
               RunTimeExecutor re=new RunTimeExecutor("ipconfig /all");
                mac=re.executeAndReturnMac();
                re.destroy();
          } catch (Exception e) {
               e.printStackTrace();
          return mac;
import java.io.IOException;
import java.io.InputStream;
* @author amal
public class RunTimeExecutor
          String cmd;
          Process proc;
           * @param cmd
          public RunTimeExecutor(String cmd)
                    this.cmd=cmd;
           * @return boolean
           * @throws WIException
          public String executeAndReturnMac() throws Exception
               System.out.println("run");
               String mac="";
                    if(cmd==null)
                              throw new Exception("No Commands");
                    try
                          final Runtime rt = Runtime.getRuntime();
                          proc = rt.exec(cmd);
                          final StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream());
                          InputStream iis=proc.getInputStream();
                          final StreamGobbler outputGobbler = new StreamGobbler(iis);
                          errorGobbler.start();
                          outputGobbler.start();
                          int exit=proc.waitFor();
                          System.out.println("exitVAl "+exit);
                          if(exit==0)
                               mac=outputGobbler.MAC;
                          return (exit==0) ? mac :null;
                catch (IOException e)
                          e.printStackTrace();
                catch (InterruptedException e)
                          e.printStackTrace();
                catch(Exception e)
                     e.printStackTrace();
                return null;
          public void destroy()
                    if(proc!=null )
                              proc.destroy();
* @author amal
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
* @author amal
public class StreamGobbler extends Thread
    InputStream is;
    OutputStream os;
    public String MAC;
    StreamGobbler(InputStream is)
        this(is,null);
    StreamGobbler(InputStream is,OutputStream redirectTo)
        this.is = is;
        this.os = redirectTo;
     * @see java.lang.Thread#run()
    public void run()
        try
            PrintWriter pw = null;
            if (os != null)
                pw = new PrintWriter(os);
            InputStreamReader isr = new InputStreamReader(is);
            int c=0;
            BufferedReader br = new BufferedReader(isr);
            String line=null;
System.out.println("Start Reading");
                 while ( (line = br.readLine()) != null)
                      System.out.println(line);
                     if (pw != null)
                         pw.println(line);
                     Pattern p = Pattern.compile(".*Physical Address.*: (.*)");
                        Matcher m = p.matcher(line);
                        if (m.matches())
                             MAC = m.group(1);
                             System.out.println("seting MAC to "+MAC);
                             break;
            if (pw != null)
                pw.flush();
        } catch (Exception e)
            e.printStackTrace();
}The inputStream of the process doesnt get printed at all , the loop condition in StreamGobbler 'while ( (line = br.readLine()) != null)
' is never true.
Also , in random cases i've seen the System.out.println("exitVAl "+exit); line executing before the System.out.println("Start Reading"); line , and i though proc.waitFor() would guarentee otherwise.

thx guys for ur replies . The issue was because of some browser security system ( or so they said . ).However i'm still puzzled about the 'waiting for the stream to finish' part .
paul.miner wrote:
{I think the process is allowed to end with output still in the >>buffers, ..so this would be expected. You should be waiting for >>your .streams to finish, since that's what you really >>care .about. .Also, .you need to add synchronization between your >>threads so you can accurately retrieve "MAC". Also, do not break out >>of the loop when you find what you're looking for, you should >>continue .reading until the end of the stream.Wasn't I suppose to be reading out of the stream to prevent an overflow?Also the break is done there are multiple lines like 'Physical address .....: xxxxxxxxxx ' in the output , and the macid is the first one.About the ProcessBuilder , I'll look into it . Thx for your advice.

Using Runtime.exec to execute Java.exe

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