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 ?

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JVM spawning mysterious child process of itself using Runtime.exec()

Hello, I'm not sure if this is how this is supposed to work but I have a java application that monitors legacy c programs and after a period of time (its intermittent), I'll see a duplicate jvm process running the same classpath, classname as a child of the java application monitor. This behaviour can be reproduced with the following simple class running on either solaris 9 or 10 using 1.6.0_03-b05:
public class Monitor {
Process procss;
public Monitor() {
try {
Runtime runtime = Runtime.getRuntime();
for (int i = 0; i < 10000; i++) {
System.out.println("execing command ls -l.");
procss = runtime.exec("ls -l");
procss.waitFor();
catch (Exception e) {
e.printStackTrace();
public static void main(String[] args) {
new Monitor();
Using java -classpath ./ Monitor to run it. While this is running, at intermittent times doing a ps -ef you will see a duplicate jvm running whose parent process is the one that was started on the command line. Ie:
UID PID PPID etc
user 17434 10706 .... java -classpath ./ Monitor (the one I put running)
user 27771 17434 .....java -classpath ./ Monitor (intermittently started)
in another window I'll run the following shell script that will output the processes when a duplicate java process gets started as they don't seem to run very long (on my production system they will occasionally get hung up until I manually kill them):
#!/usr/bin/ksh
while ((1 == 1))
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VAL=`cat /tmp/test.out | wc -l`
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echo "Duplicate java process started"
cat /tmp/test.out
fi
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This is true for Solaris and Linux. Sun's implementation does a fork. A lot of people who have very large memory java applications wish there was a way to create a process from Java that doesn't involve copying the parent process. As far as I know your stuck.
A workaround: Use jms, rmi, sockets, or files to communicate with a low memory footprint java application whose sole purpose is to spawn child processes.

Problem with executing shell script on linux through java code.

i am facing problem to kill jboss process on linux that is my application requirement. for that i created one shell script that will get all the process for jboss instance and kill them when i am running that script from command prompt on linux its working perfectly.
The command i am using ---
/opt/RW9/jboss/v4.0.5.GA/bin/restartjboss.sh.
but when i am running through java code its not working.
the java code i am using is:-
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Edited by: akm198110 on Sep 2, 2008 9:24 AM

I got the problem after long struggle ,after doing proper path i am able to execute the shell script..

Trying to execute shell process in Linux

Hi. I'm trying to execute a simple command in the form of 'bash -c "ls ~root ~"' from within java. I've tried using both the java.lang.Runtime.exec() methods and the java.lang.ProcessBuilder class but both produce the same error message (which I get from the OutputStream of the Process):
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It seems that when I have a 'bash -c "ls <arguments>" as the command from within java, bash believes that the entire argument in double quotes ("ls <arguments>") is the command. It doesn't seem to "see" the spaces.
Would anyone know what I might do in this case? Below is my code:
import java.util.ArrayList;
import java.io.*;
public class ShellCommand {
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I have just used Runtime.exec() on        final String[] command = {"bash","-c", "ls ~root ~" };As expected, the stderr stream produces
ls: /root: Permission denied
and stdout produces a directory listing of ~ (my home directory).
You should read the man page for bash -c and read http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html to see how to handle stdout and stderr.

Running java process in a while loop using Runtime.exec() hangs on solaris

I'm writting a multithreaded application in which I'll be starting multiple instances of "AppStartThread" class (given below). If I start only one instance of "AppStartThread", it is working fine. But if I start more than one instance of "AppStartThread", one of the threads hangs after some time (occasionaly). But other threads are working fine.
I have the following questions:
1. Is there any problem with starting a Thread inside another thread?. Here I'm executing the process in a while loop.
2. Other thing i noticed is the Thread is hanging after completing the process ("java ExecuteProcess"). But the P.waitFor() is not coming out.
3. Is it bcoz of the same problem as given in Bug ID : 4098442 ?.
4. Also java 1.2.2 documentation says:
"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. "
I'm running this on sun Solaris/java 1.2.2 standard edition. If any of you have experienced the same problem please help me out.
Will the same problem can happen on java 1.2.2 enterprise edition.?
class AppStartThread implements Runnable
public void run()
while(true)
try
Process P=Runtime.getRuntime().exec("java ExecuteProcess");
P.waitFor();
System.out.println("after executing application.");
P.destroy();
P = null;
System.gc();
catch(java.io.IOException io)
System.out.println("Could not execute application - IOException " + io);
catch(java.lang.InterruptedException ip)
System.out.println("Could not execute application - InterruptedException" + ip);
catch (Exception e)
System.out.println("Could not execute application -" + e.getMessage());

I'm writting a multithreaded application in which I'll
be starting multiple instances of "AppStartThread"
class (given below). If I start only one instance of
"AppStartThread", it is working fine. But if I start
more than one instance of "AppStartThread", one of the
threads hangs after some time (occasionaly). But other
threads are working fine.
I have the following questions:
1. Is there any problem with starting a Thread inside
another thread?. Here I'm executing the process in a
while loop.Of course this is OK, as your code is always being run by one thread or another. And no, it doesn't depend on which thread is starting threads.
2. Other thing i noticed is the Thread is hanging
after completing the process ("java ExecuteProcess").
But the P.waitFor() is not coming out.This is a vital clue. Is the process started by the Runtime.exec() actually completing or does the ps command still show that it is running?
3. Is it bcoz of the same problem as given in Bug ID :
4098442 ?.
4. Also java 1.2.2 documentation says:
"Because some native platforms only provide limited
ed 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. "These two are really the same thing (4098442 is not really a bug due to the reasons explained in the doc). If the program that you are exec'ing produces very much output, it is possible that the buffers to stdout and stderr are filling preventing your program from continuing. On Windows platforms, this buffer size is quite small (hundreds of characters) while (if I recall) on Solaris it is somewhat larger. However, I have seent his behavior causing problem on Solaris 8 in my own systems.
I once hit this problem when I was 'sure' that I was emitting no output due to an exception being thrown that I wasn't even aware of - the stack trace was more than enough to fill the output buffer and cause the deadlock.
You have several options. One, you could replace the System.out and System.err with PrintStream's backed up by (ie. on top of) BufferedOutputStream's that have large buffers (multi-K) that in turn are backed up by the original out and err PrintStream's. You would use System.setErr() and System.setOut() very early (static initializer block) in the startup of your class. The problem is that you are still at the mercy of code that may call flush() on these streams. I suppose you could implement your own FilterOutputStream to eat any flush requests...
Another solution if you just don't care about the output is to replace System.out and System.err with PrintStreams that write to /dev/nul. This is really easy and efficient.
The other tried and true approach is to start two threads in the main process each time you start a process. These will simply consume anything that is emitted through the stdout and stderr pipes. These would die when the streams close (i.e. when the process exits). Not pretty, but it works. I'd be worried about the overhead of two additional threads per external process except that processes have such huge overhead (considering you are starting a JVM) that it just won't matter. And it's not like the CPU is going to get hit much.
If you do this frequently in your program you might consider using a worker thread pool (see Doug Lea's Executor class) to avoid creating a lot of fairly short-lived threads. But this is probably over-optimizing.
Chuck

Using runtime.exec,process streams

Hi all,
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So I have 2 questions.
1. Can I forcibly delete these files some other way.
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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");
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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);

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
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where
would the output from the C++ code go to when I use a
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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

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

Hi all
From my java App ,I am running a bat file. This is what I did:
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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.
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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?
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aProcess = aRuntime.exec("cmd /c java.exe
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aProcess = aRuntime.exec("java.exe
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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
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IOException File not found - While using Runtime.exec

Hey All,
I have written a Java application which needs to start up another external application. I have executables for that external application for different platforms (Win32, PPC and Linux). When the Java application is started it detects the OS and starts up the right executable according to the OS. The executable loads up fine on Windows without any problems. But in both Linux and Max OS X I get this exception:
java.io.IOException: java.io.IOException: "/home/vilas/Documents/Project/build/CLISP/linux/lisp.run": not found
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        at java.lang.Runtime.execInternal(Native Method)
        at java.lang.Runtime.exec(Runtime.java:566)
        at java.lang.Runtime.exec(Runtime.java:428)
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        at java.lang.Thread.run(Thread.java:534)lisp.run has all the necessary permissions. If I copy the string (/home/vilas/Documents/Project/build/CLISP/linux/lisp.run) and paste it in a terminal and press enter, the application starts up fine without any problems!! Can you please tell me what could be going wrong?
The following extra information maybe helpfull:
1) I use the exec(String command, String[] envp, File dir) version of exec.
2) The complete format of the command is as follows (one long string):
"/home/vilas/Documents/Project/build/CLISP/linux/lisp.run" -B "/home/vilas/Documents/Project/build/CLISP/linux" -M "/home/vilas/Documents/Project/build/CLISP/linux/lispinit.mem" -i loader.lisp
Thanks in advance for your time and efforts.

I found the problem after extensively searing the forums (looking upto page 4 !! of the results). The problem was that I was using quotes to surround the paths in the command. If you copy and paste it in a terminal it will work fine but it does not work with runtime.exec. I am not sure, but I think the reason is that when a terminal is used, some pre-processing of the commands take place before they are passed onto the OS(shell). But while using runtime.exec, that pre-processing is not peformed and therefore some things will not work.
In order to fix the problem, I use quotes only when the OS is windows. In other cases(OS X, Linux) I escape the spaces i.e. replace " " with "\ ".
PS: The executable is a binary compiled from C code.

Strange problem when a c++ program is triggered by Runtime.exec()

I am working in linux system. I have 2 programs:
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case 1
if I run c++ program AAA directly, everything goes well, gcc call via "system" is successful.
case 2
if I run java program BBB to trigger AAA indirectly, the AAA can be executed, but the system call (gcc call inside AAA) is failed.
so, what is wrong? any hints? what is the solution to make case #2 work? I just want to use BBB to trigger AAA, and the system call should also be successful.
thanks in advance for your help!

"...but the system call (gcc call inside AAA) is failed."
Isn't terribly descriptive, but I'm guessing that it complains it can't find gcc?
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Someone else'll be able to tell you how to get it to work. I'm sure I've seen this sort of problem here several times.

Trying to run external script using Runtime.exec

Hey,
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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.
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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

Running ssh in xterm using Runtime.exec !! URGENT

I am not able to run the following command using Runtime.exec() but if the same command is executed in shell it gets executed.
I am working on solais 8
String toExecStr =
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catch(Exception e){
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Can some body help me solve this ???

How to capture output of java files using Runtime.exec

Hi guys,
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public class E {
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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.

Problem of executing a process under Linux using Runtime.exec

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