Java's Runtime.exec() method

When you shell out to java's Runtime.exec() method, are the process name and arguments the same for the child process that is spawned.
We see duplicated processes about the time when our logs tell us this command was run. However, we cannot seem to reproduce this. Has anyone else seen anyone this before?

That's what I though too. But check this out . . .
Our code looks as follows:
private Runtime rt;
private Process p;
rt = Rutime.getRuntime();
p = rt.exec(command);
This exec() call creates a new process, which is a child of the java process that runs this command. The final process looks like the "command" string that is passed to the exec() method call. In our case, the command is a call to the /usr/bin/mail utility to send out faxes and emails.
We ran a very tight loop executing the rt.exec() call over and over. What we found was that for a minor fraction of a second, the newly created process looks just like the original process including the same arguments. However, the PID's indicated that one process was the child of the other. This is why it looked like we had 2 of the same processes. WILD!
Thanks guys!

Similar Messages

The Runtime.exec methods doesn't work well on Solaris ???

I have two threads and I set the different running time.
I use Runtime.exec to a run the command and use Process to get the process.
It works properly in the windows2000 platform.
However, when I transfer the platform to Solaris...and run the program...
Two threads always at the same time....It is very wired....I always debug
for 2 days....
(at first I run "vmstat 1 2" command, later I change to "ls","rmdir"....etc,
all of them don't work.....
If I close the Runtime.exec..........Everything works well......)
And I study the API. I found this message...
The Runtime.exec methods may not work well for special processes on certain
native platforms, such as native windowing processes, daemon processes,
Win16/DOS processes on Win32, or shell scripts. The created subprocess does
not have its own terminal or console.
Could someone share her/his experience.....:(
And if any other way I can run command inside java code instead of
Runtime.exec.....???
Please reply my mail to [email protected] I do appreciate your kindly &
great help!!!!!!!!
This is my code.......
import java.io.*;
import java.lang.*;
import java.util.*;
* <p>ServerThread1</p>
* <p>??�X???��?�D???�X???, "Vmstat 1 2".</p>
class ServerThread1 extends Thread{
private ServerAgent Sa;
public ServerThread1 (String Name, ServerAgent Sa){
super(Name);
this.Sa = Sa; file://Assign ServerAgent reference Sa
public void run(){
while(true){
try{
Thread.sleep(5000);
catch (Exception e){
System.out.println("ServerThread1 fails");
System.out.println("Thread1 is running.");
try {
Runtime rt1 = Runtime.getRuntime();
Process proc1 = rt1.exec("mkdir"); ------>If I close
rt1.exec , two threads works seperately...........:(
catch (Exception e) {
System.out.println("Thread1 Error");
class ServerThread2 extends Thread{
private ServerAgent Sa;
public ServerThread2 (String Name, ServerAgent Sa){
super(Name);
this.Sa = Sa;
public void run(){
while(true){
try{
Thread.sleep(15000);
catch (Exception e){
System.out.println("ServerThread2 fails");
System.out.println("Thread2 is running.");
try {
Runtime rt2 = Runtime.getRuntime();
Process proc2 = rt2.exec("vmstat 1 2"); ----->If I don't run
the rt2.exe, two threads work seperately....
catch (Exception e) {
System.out.println("Thread2 Error");
public class ServerAgent{
private Vector v1 = new Vector();
private Vector v2 = new Vector();
private Hashtable currentData = new Hashtable();
private static String startUpSwap = null;
private static String startUpMem = null;
public static void main(String[] arg) {
ServerAgent s = new ServerAgent();
ServerThread1 st1 = new ServerThread1("Thread1",s);
ServerThread2 st2 = new ServerThread2("Thread2",s);
st1.start();
st2.start();

If I close the Runtime.exec..........Everything works
well......)You don't empty the output of the command, that blocks the process.
A citation from
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
Why Runtime.exec() hangs
The JDK's Javadoc documentation provides the answer to this question:
Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, and even deadlock.
Try out something like this:
String s;
try {
   Process myProcess =
   Runtime.getRuntime().exec("ls -l"));
   DataInputStream in = new DataInputStream(
          new BufferedInputStream(myProcess.getInputStream()));
    while ((s = in.readLine()) != null) {
        out.println(s);
catch (IOException e) {
    out.println("Error: " + e);
}Another source of trouble under Unix is not having the correct permission for that user that executes the Java VM, which will be the permissions for the spawned subprocess. But this probably not the case, as you see something after exit.
Regards,
Marc

Java.lang.Runtime.exec problem in ubuntu 9.10

Hi:
I tried to run some command in the java code , for example "grass64 -text /home/data/location", this command works well in the terminal, however when I call it in the java code I got some excepetions.
My code is :
public class Grass {
     public static String grassBatJob="GRASS_BATCH_JOB";
     public void run(String cmd,String jobPath) {
          //set the environments variables
          Map<String, String> env=new HashMap<String, String>();
          env.put(grassBatJob, jobPath);
          String gisDataBase="/home/kk/grass/GrassDataBase";
          String location="spearfish60";
          String mapset="PERMANENT";
          cmd=cmd+" "+gisDataBase+"/"+location+"/"+mapset;
          CommandLine line=new CommandLine(cmd);
          //the real cmd should be >>grass64 -text /home/kk/grass/GrassDataBase/spearfish60/PERMANENT
          System.out.println("start line=="+line.toString());
          DefaultExecutor de=new DefaultExecutor();
          try {
               int index=de.execute(line,env);
               System.out.println(index);
          } catch (ExecuteException e) {
               e.printStackTrace();
          } catch (IOException e) {
               e.printStackTrace();
     public static void main(String[] args) {
          String jobPath=Grass.class.getResource("grass.sh").getFile();
          new Grass().run("grass64 -text", jobPath);
The real cmd I want to execute is "grass64 -text /home/kk/grass/GrassDataBase/spearfish60/PERMANENT" with the envrionment variable "GRASS_BATCH_JOB=jobPath",it works well in the ternimal ,however in my application I got the exception"
java.io.IOException: Cannot run program "grass64 -text /home/kk/grass/GrassDataBase/spearfish60/PERMANENT": java.io.IOException: error=2, No such file or directory
     at java.lang.ProcessBuilder.start(ProcessBuilder.java:459)
     at java.lang.Runtime.exec(Runtime.java:593)
     at org.apache.commons.exec.launcher.Java13CommandLauncher.exec(Java13CommandLauncher.java:58)
     at org.apache.commons.exec.DefaultExecutor.launch(DefaultExecutor.java:246)
     at org.apache.commons.exec.DefaultExecutor.executeInternal(DefaultExecutor.java:302)
     at org.apache.commons.exec.DefaultExecutor.execute(DefaultExecutor.java:149)
     at org.kingxip.Grass.run(Grass.java:27)
     at org.kingxip.Grass.main(Grass.java:38)
Caused by: java.io.IOException: java.io.IOException: error=2, No such file or directory
     at java.lang.UNIXProcess.<init>(UNIXProcess.java:148)
     at java.lang.ProcessImpl.start(ProcessImpl.java:65)
     at java.lang.ProcessBuilder.start(ProcessBuilder.java:452)
     ... 7 more
I wonder why?

Thanks for all of your reply, and now I can run the command, however I met some problems when I tried to get the result of the exec.
The core codes are shown below:
String cmd="g.version";
String[] exe={"bash","-c",cmd};
Process p1=Runtime.getRuntime.exec(exe,env); // the env has been set
GrassThread outThread=new GrassThread("out", p1.getInputStream());
outThread.start();
GrassThread errorThread=new GrassThread("error", p1.getErrorStream());
errorThread.start();
int exitVal = p1.waitFor();
String resu=outThread.sb.toString();
System.out.println("==========the output start========");
System.out.println(resu);
System.out.println("==========the output end========");
System.out.println("ExitValue: " + exitVal); //------------------> line one
public class GrassThread extends Thread{
     public StringBuffer sb=new StringBuffer();
     public GrassThread(String type,InputStream is) {
          this.type=type;
          this.is=is;
     public void run() {
          try {
               InputStreamReader isr = new InputStreamReader(is);
               BufferedReader br = new BufferedReader(isr);
               String line = null;
               while ((line = br.readLine()) != null) {
                    System.out.println(type + ">" + line);
                    sb.append(line).append("\r"); // ----------------------------> line two
}I define a StringBuffer in the GrassThread to save the output (see the code where I marked by "line two"), and when the process complete, I check the StringBuffer to get the output (see code where I marked by "line one"), however the output in the console of the IDE are :
----------- output in the console of the IDE start -------------
==========the output start========
==========the output end========
ExitValue: 0
out>GRASS 6.4.0RC5 (2009)
----------output in the console of the IDE end--------------------
I can not understand, in the code "line one", I first get the output using "System.out.println(resu);",then I print the exitvalue,but why the order of the output in the console is not what I expected?
Another question, the code above assume the output can be got from the Process's getInputStream, however sometimes the output maybe come from the Process's getErrorStream, so how to handle it?
Edited by: apachemaven on 2010-3-5 ??5:38

Spawn a java process using runtime.exec() method

Hi,
This is my first post in this forum. I have a small problem. I am trying to spawn a java process using Runtime.getRuntime().exec() method in Solaris. However, there is no result in this check the follwoing program.
/* Program Starts here */
import java.io.*;
public class Test {
public static void main(String args[]) {
String cmd[] = {"java", "-version"};
Runtime runtime = Runtime.getRuntime();
try{
Process proc = runtime.exec(cmd);
}catch(Exception ioException){
ioException.printStackTrace();
/* Program ends here */
There is neither any exception nor any result.
The result I am expecting is it should print the following:
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
Please help me out in this regard
Thanks in advance
Chotu.

Yes your right. It is proc.getInputStream() or proc.getErrorStream(). That is what I get for trying to use my memory instead of looking it up. Though hopefully the OP would have seen the return type of the other methods and figured it out.

How to disable Runtime.exec method ?

i want to disable some method in java like Runtime.getRuntime().exec() and Runtime.getRuntime().totalMemory()
can i implement it by change java.policy file ,and how to do it?

You can use Set Menu Item Info with items from a runtime menu file. You don't need to insert items programmatically to use Set Menu Item Info. Use the Current VI's Menubar function to get the menubar refnum, then call Set Menu Item Info along with three inputs:
1. The menubar refnum.
2. The item tag for the item to be disabled or enabled. You may need to go back to the menu editor to get the tag, which may or may not be the same as the displayed item name.
3. A boolean wired to enabled.
I referred you to the examples just to see one part of the diagram.

Runtim exec() method not working.....giving Exception

whts the code to use exec() method. i m using it as follows and also catching exception.
Runtime r=Runtime.getRuntime();
Process p=r.exec("java A");
code is giving IOException at runtime with error=2.

Here is an example I used when I first needed to test the runtime.exec
import java.util.*;
import java.lang.*;
import java.io.*;
public class TestRuntime {
    public static void main(String args[])
        try
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("java A");
            InputStream stderr = proc.getErrorStream();
            InputStreamReader isr = new InputStreamReader(stderr);
            BufferedReader br = new BufferedReader(isr);
            String line = null;
            System.out.println("<ERROR>");
            while ( (line = br.readLine()) != null)
                System.out.println(line);
            System.out.println("</ERROR>");
            int exitVal = proc.waitFor();
            System.out.println("Process exitValue: " + exitVal);
        } catch (Throwable t)
            t.printStackTrace();
}Are you waiting for the process to end before exiting your program?

Java.lang.Runtime.exec()

When using the exec method I cannot get it to run the specified application when I try to use the Runtime.execString[] cmdArray)
The application I am running is windump, it runs ok when I specify it in the Runtime.exec(String cmd) method.
I need to use the Runtime.exec(String[] cmdArray) option as I need to specify parameters as part of my project. To be exact I need to tell it to output to a text file.
I can do this when running windump from the command prompt, thus cannot understand whty it wont work when I specify the same option from Runtime.exec(..)
Any ideas how to overcome this?
thanks Conor

This works for me on WindowsNT:
try {
Runtime.getRuntime().exec("cmd.exe /c dir>dirtest.txt");
catch (Exception e) {}
[/code}
Mark

Problem to execute cvs command using Runtime.exec method

Hello,
I want execute this cvs command, with this options:
cvs -d :pserver:[email protected]:/home/cvs/cvsroot rlog -S -d "2007/05/01<now" Project
I tried to execute with Runtime.exec() :
Runtime.exec("cvs -d :pserver:[email protected]:/home/cvs/cvsroot rlog -S -d \"2007/05/01<now\" Project");
But I have an error because the smaller character is interpretate as a redirection, no as a smaller symbol.
How I can do to use this command with Runtime.exec ?
Thanks.
Regards.

Sorry,
I had a typing mistake.
I want say:
Runtime.exec("cvs -d :pserver:[email protected]:/home/cvs/cvsroot rlog -S -d \"2007/05/01<now\" Project");
Regards.

Using Runtime exec() method to run java files and return runtime errors

Hi
I'm writing a java editor and I use
Runtime.getRuntime().exec(command)
to compile the java files. That works fine and I deal with the returned errors using the getErrorStream().
My questions are:
1. Can I use the same technique for returning runtime errors. In any posts I've read the process runs from begining to end, returning the errors after completion. How do I return the errors of the app as they happen interactively?
2. If i cant use the exec and getErrorStream() methods then does anyone know how it is done?
Thanks in advance for any help!

Read this:
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
MOD

Executing a shell script from java using runtime.exec()

Hi I am trying to create a script (test_script) and execute it -- all within one java program...
the code compiles and executes perfectly but nothing happens. This is probably because the script does not get changed to the '777' mode although i am trying to do that ... any suggestions ???
//code
import java.io.*;
import java.util.*;
public class ScriptBuilder
     public ScriptBuilder() {
     public void writeScript() throws java.io.IOException{
     FileWriter writer = new FileWriter(new File("test_script"));
          writer.write("#! /bin/sh\n");
          writer.write("cd prodiags\n");
          writer.write("tar cvf delTask.tar delTask\n");
          writer.write("rm -rf delTask\n");
          writer.flush();
          writer.close();
Runtime rt= Runtime.getRuntime();
String[] cmd = new String[3];
cmd[0] = "ls";
cmd[1] = "chmod 777 test_script";
cmd[2] = "./test_script";
rt.exec(cmd);
     public static void main (String[] args)throws java.io.IOException
     ScriptBuilder sb = new ScriptBuilder();
     sb.writeScript();
}

I don't know exactly but the code written below is working fine try the same with your code .Even with your code instead running the code with
" ./<filename> ",if you execute it with "sh <filename>" command without changing the mode of the file it is executing properly.
import java.io.*;
import java.util.*;
public class ScriptBuilder
public ScriptBuilder()
public void writeScript() throws java.io.IOException
FileWriter writer = new FileWriter(new File("test_script"));
writer.write("#! /bin/sh\n");
writer.write("ll>/home/faiyaz/javaprac/checkll");
writer.flush();
writer.close();
Runtime rt= Runtime.getRuntime();
rt.exec("chmod 777 test_script");
rt.exec("./test_script");
} public static void main (String[] args)throws java.io.IOException
ScriptBuilder sb = new ScriptBuilder();
sb.writeScript();
}

Runtime exec methods

looking at the Runtime API there are two methods listed namely:-
public Process exec(String command)
             throws IOException
    Executes the specified string command in a separate process.and
public Process exec(String[] cmdarray)
             throws IOException
    Executes the specified command and arguments in a separate process.
Question:-
Can the second method listed be used to pass in an array of different commands or not, to be executed one after the other?

I am on window so when I do rt.exec(new String [] {"dir", "c:\\oracle});{code}
I get the following error.
Exception: CreateProcess: dir c:\oracle error=2

Java.lang.Runtime.exec() again

try{
Process registryProcess = null;
Runtime r = Runtime.getRuntime();
String[] cmdArray = {"F:\\windump", ">>new_res.txt"};
registryProcess = r.exec(cmdArray);
}catch(Exception ex){
System.out.println("Exception Caught: " + ex.getMessage());
** Have also tried speicfying the command and the parameters all in the one string like so :
String cmd = "F:\\windump >>F:\\new_res.txt";
registryProcess = r.exec(cmd);

try
String cmd = "cmd /c F:\\windump >> F:\\new_res.txt";
registryProcess = r.exec(cmd);

Problem with Runtime.exec() method

Hi All,
tring _cmd = "cmd /c ";
          cmd =cmd+"sqlldr ";
          cmd = cmd + " userid=" + userId + "/" + passwd + "@"+ tnsEntry;
cmd = cmd + " control=" + controlFilePath;
          cmd = cmd + " log=sql.log skip=1";
          System.out.println(_cmd);
     try{
                         Runtime r = Runtime.getRuntime();
                         Process process = r.exec(_cmd);
                         int exitVal = process.waitFor();
System.out.println("Process exitValue:********** " + exitVal);
               catch(RuntimeException re )
                    System.out.println("Failed to runtime run the process.123.."+re);
I ve used proc.exitValue() to print the value of int value
but i got exception
then i used proc.waitFor() and print the value of int I got value = 4
here it is
Process exitValue:= 4
could u please tell me what does it mean? how to solve if the value is 4?
Thanks in advance

Please don't cross-post, it is extremely rude.
Stick with the [original thread|http://forums.sun.com/thread.jspa?threadID=5329691&tstart=0].

Runtime.exec() batch file problem

Hi folks,
i have a little problem when I want to execute a batch file through java's runtime.exec() method.
the execution of a very simple batchfile works (for example opening notepad or other stuff), but I have problems with the following batch file (although it's still simple):
net use s: \\Dd-nt-fs\Dsmp15_files
set DSCFG=c:\dscfg
set PSPATH=c:\adproof
set ora_path=C:\oracle\ora92
set path=S:\Dsmp_Q4_2004\Bin;%ora_path%\bin;%path%;
set nd_font=S:\Dsmp_Q4_2004\Fonts
set nxPS_FONT_DIR=%ND_FONT%
set PSPATH=c:\adproof
set PSFORMS=S:\Dsmp_Q4_2004\PsForms\Telenor
s:
cd S:\Dsmp_Q4_2004\bin
S:\Dsmp_Q4_2004\Dsmp_Reports\Telenor\adproof.exe DBUSER=a_user DBPSWD=a_pswd DBSTR=dbstr ADINFO=adinfo.lst TASKID=a_taskid
my guess is that there is a problem with the setting of environment variables which correspond to the drive s:
I mannually added the batchfile (line by line) and looked whether it got through to the command which executes the adproof.exe file: for example the below batchfile worked:
set DSCFG=c:\dscfg
set PSPATH=c:\adproof
set ora_path=C:\oracle\ora92
s:
cd S:\Dsmp_Q4_2004\bin
S:\Dsmp_Q4_2004\Dsmp_Reports\Telenor\adproof.exe DBUSER=a_user DBPSWD=a_pswd DBSTR=dbstr ADINFO=adinfo.lst TASKID=a_taskid
Here is the java code: in which i execute the batch file:
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("net use s: \\\\Dd-nt-fs\\DSMP15_FILES");
BufferedReader b = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
while( (line=b.readLine())!=null) {
      System.out.println(line);
int exitVal = proc.waitFor();
System.out.println("Exit Value = " + exitVal);
String[] cmd = new String[1];
cmd[0] = "C:\\Documents and Settings\\tikmi\\My Documents\\mysources\\DSMP Prototype\\print\\hallo3.bat";
// here i declared the needed settings of the environment variable and pass that array to the exec() method
String[] env = new String[8];
env[0] = "DSCFG=c:\\dscfg";
env[1] = "ORA_PATH=C:\\oracle\\ora92";
env[2] = "PSPATH=C:\\Documents and Settings\\tikmi\\My Documents\\mysources\\DSMP Prototype\\print";
env[3] = "ND_FONT=S:\\Dsmp_Q4_2004\\Fonts";
env[4] = "nxPS_FONT_DIR=%ND_FONT%";
env[5] = "PSFORMS=S:\\Dsmp_Q4_2004\\PsForms\\Telenor";
env[6] = "ND_PATH=S:\\Dsmp_Q4_2004\\resource";
env[7] = "PATH=S:\\Dsmp_Q4_2004\\Bin;%ORA_PATH%\\BIN;%ND_PATH%;%PATH%;";
rt = Runtime.getRuntime();
proc = rt.exec(cmd, env);
b = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
while( (line=b.readLine())!=null) {
          System.out.println(line);
exitVal = proc.waitFor();
System.out.println("Exit Value = " + exitVal);Maybe someone else had similar problems or can help me solving that problem.
Any advice would be very appreciated.
regards
mirkolino

finally I got it working now.
for those who are interested in the problem, my code that's now working is the following
Runtime rt = Runtime.getRuntime();
                        Process proc = null;
                        String cmd = "cmd.exe /c c:\\adproof\\hallo3.bat";
                        proc = rt.exec(cmd);
                        InputStream in = proc.getInputStream();
                        BufferedReader br = new BufferedReader ( new InputStreamReader(in));
                        String line;
                        while( (line=br.readLine()) != null) {
                            System.out.println(line);
                        int exit = proc.waitFor();
                        System.out.println();
                        System.out.println("Process exited with: " + exit);the problem was, that i have to handle and read the input stream
thanks for you help
greetings from mirkolino

Running batch files from Java using exec method

Hi,
I want to run a batch file from my Java program like this:
try {
Process proc = Runtime.getRuntime().exec("C:\\Refresh.bat");
catch (Exception e) {
MessageBox.show(e.getMessage());
Refresh.bat file contains two commands.
First one unzips certain zip file.
Second one refreshes a SQL Server database using osql utility.
Problem is that when program is run it executes only the first command and hangs on the second one.
Please help.
TIA
Ravinder

From the FAQ:
2. How do you launch an external program on a Microsoft Windows platform from a program developed on the Java [tm] programming language?
The following will launch notepad in Microsoft Windows NT:
Runtime.getRuntime().exec("cmd /c notepad.exe");
To launch a program in Microsoft Windows 95/98 use:
Runtime.getRuntime().exec("c:\\windows\\notepad.exe");
The Runtime class allows interaction between a program and its environment. The first string command instructs the command line interpretor, cmd to open up the calculator application.
The exec() methods do not use a shell; any arguments must have the full pathname to the shell as well as the command itself.
For example, to run a shell on the UNIX� platform, type:
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("/usr/bin/sh -c date");
To run a batch file under Microsoft Windows 95/98:
Process p = rt.exec("command.com /c c:\\mydir\\myfile.bat");
To run a batch file under Microsoft Windows NT:
Process p = rt.exec("cmd /c c:\\mydir\\myfile.bat");
where 'cmd' and 'command.com' are the command-line interpreters for Microsoft Windows machines.
The Runtime.exec() methods might not work effectively for some processes on certain platforms. Special care should be taken with native windowing, daemon, WIN16/DOS process or some shell scripts.
regards,
jarshe

Java's Runtime.exec() method

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