Reading output of a system call

Question

Hi,
It appears that java system call does not return a value in Netware OS.
The same code functions flawlessly on other OS'es, eg. linux and windows.
If the following code is run on a Netware (6.5), the following error is
returned:
External App Returned:
java.io.IOException: Bad file number
Does anyone knows how to receive the values from the system call on Netware?
To reproduce the problem, do the following:
1) save the included source code to netware server's sys:java/classes
with a filename ExecuteExternalApp.java
2) compile it issuing a console command:
javac sys:java/classes/ExecuteExternalApp.java
3) execute the application:
java ExecuteExternalApp volumes
This should successfully launch the system command "volumes" but also
would give an error message:
External App Returned:
java.io.IOException: Bad file number
---- Source code
import java.io.*;
public class ExecuteExternalApp{
public static String executeSystemCommand(String command) throws
Exception {
String ret = "";
try
Process process = Runtime.getRuntime().exec(command);
BufferedReader input = new BufferedReader(new
InputStreamReader(process.getInputStream()));
BufferedReader err = new BufferedReader(new
InputStreamReader(process.getErrorStream()));
//InputStreamReader iar = new
InputStreamReader(process.getInputStream());
StringBuffer sb = new StringBuffer();
String line = "";
//while ((line = input.readLine()) != null)
//testi tuleeko yksi rivi
line = input.readLine();
sb.append(line);
input.close();
ret = sb.toString();
catch (Exception err)
ret = err.toString();
return ret;
public static void main(String[] args) throws Exception {
if (args.length > 0){
String output = executeSystemCommand(args[0]);
System.out.println("External App Returned:");
System.out.println(output);
else
System.out.println("Usage: ExecuteExternalApp <command>");

Answer 1

Guenter wrote:
> Hi Jonne,
> Jonne Viljanen <jonne.viljanen@rmv_this.helsinki.fi> wrote in
> news:y%[email protected]:
>
>> Thank you for your effort. I've been trying to write a simple program
>> that would monitor if any cluster resource would be in comatose and in
>> such case, it would try to online the resource on some other cluster
>> node. For this I'd need to run these system commands and parse their
>> output:
>>
>> - "cluster resources" - to see if any resource is in comatose
>>
>> and
>>
>> - "cluster view" - to determine which nodes are online.
>>
>> Also i'd need to run "cluster offline resource" and "cluster online
>> resource node", but for these command I would not need to get the
>> output.
>>
>> I know that my approach is a bit clumsy, but it's beauty is in its
>> simplicity. Novell's engineer suggested that with a bit more effort one
>> could read the data from ldap or cluster related virtual XML files on
>> the _Admin volume. I think that I should investigate the latter
>> approach, since I'd like to avoid handling the ldap authentication. I
>> appreciate any comments and suggestions. Code examples are also greatly
>> welcomed ;-)
> hmmm, well that sounds to me as if the language doesnt matter at all since
> finally you most likely fire your app from cron to do these tasks frequently
> automatically, right? Therefore I'd suggest you take a look at Perl - it
> seems better suited for these tasks; look at sys:/perl/scripts where you find
> Perl scripts which do already some cluster stuff, and AFAICT these make use
> of the _ADMIN volume.
> Additional info and Perl samples can be found with the VFS NDK IIRC:
> http://developer.novell.com/wiki/ind..._File_Services
>
> greetz, Gnter.
>
Hi Gnter,
Thank you for your excellent help. I started to play with the _ADMIN
-volume today. I was amazed to see how much can be done with it. I got
my little cluster watch application almost working in just 1 hour, but
then spent the rest of the day trying to get it fully functional ;-) I
still cannot figure out what is wrong with my code, so I was wondering
if I could get any help from this newsgroup.
I'm able to read the *.xml files and determine the cluster state and all
the information I need. However I dont seem to be able to write the
command files. I'm trying the following:
public void offlineClusterResource(String resourceName) {
String fileName = "_ADMIN:/Novell/cluster/Resource.cmd";
//String logFile = "sys:java/classes/ClusterWorker.log";
String commandLine = "<virtualIO><datastream
name=\"command\"></virtualIO>"+
"<ncsRequest><offline>" +
"<resource>" + resourceName + "</resource>" +
"</offline></ncsRequest>";
//Log("Turning the cluster resource " + resourceName + "
offline!!!", logFile);
try {
//PrintWriter in autoFlush mode
PrintWriter pw = new PrintWriter(new FileWriter(fileName,
false), false);
pw.println(commandLine);
pw.close();
} catch (IOException e) {
System.out.println("Unable to write " + fileName);
It seems not to write anything to _ADMIN:/Novell/cluster/Resource.cmd.
If I set the file to be eg. SYS:/tmp/Resource.cmd -it writes nicely to
the file.
What am I missing here?
Cheers,
Jonne