Re: Process.exec() problem

I've tried this now using sdk-1.12 and that is still showing the same  
behaviour.


On Jul 11, 2005, at 1:49 PM, Peter Lovell wrote:

> Hi folks,
> I'm having a problem which I believe to be with exec'ing a process  
> and wonder if someone might be able to help. Sometimes another set  
> of eyeballs is all it takes.
>
> The problem is an intermittent failure which appears to be a  
> deadlock somewhere. The frequency is about two or three times every  
> hundred tries. I've appended the java code below (small extract)  
> and I can't see any specific problem with it - after all it works - 
> most- of the time. Problem is that the call is made to this method  
> and the process then remains asleep. In a few instances, the  
> process list shows a zombie process...
> 31747 pts/49   Z+     0:00 [who] <defunct>
>
> A few items of background - I see this problem on Linux (SuSE 9.1,  
> kernel 2.6.4) and Mac OS X (10.4.1, dual processor G5). There had  
> been a couple of instances on Linux 2.4.20 SuSE 8.2 but that does  
> not seem to be happening now (more testing needed). Testing on Sun  
> Java has never produced a failure, even in days of testing. The  
> sable+classpath version is 1.1.8 but comparison of that code with  
> current doesn't seem to show any substantial difference in this  
> area [I've been trying today to get latest code but sablevm.org  
> site is down, unfortunately]
>
> I'm suspecting a subtle timing issue within classpath as the root  
> cause. All suggestions gratefully accepted.
>
> Thanks.....Peter
>
>
>
>
>    public String[] getConnectedUsers()
>    {
>       int              count = 0;
>       int              status = -1;
>       String           s;
>       Runtime          rt;
>       Process          p;
>       ArrayList        return_data = new ArrayList(32);
>       String[]         cu = new String[0];
>
>       try {
>          rt = java.lang.Runtime.getRuntime();
>          p = rt.exec(("who"));
>          status = p.waitFor();
>          if (status != 0){
>             System.err.println("WARNING:  'who' failed,  
> getConnectedUsers failed");
>             return cu;
>          }
>          InputStream ain = p.getInputStream();
>          if ( ain == null ){
>             System.err.println("WARNING:  'who' missing,  
> getConnectedUsers failed");
>             return cu;
>          }
>          BufferedReader in = new BufferedReader( new  
> InputStreamReader ( ain ) );
>          if ( in == null ) {
>             System.err.print("getConnectedUsers: in is null -  
> command must have failed, status = ");
>             System.err.println(status);
>          } else {
>             while ( (s = in.readLine()) != null) {
>                if ( (s.length() < 1) || (s.substring(0,1).equals 
> ("#")))
>                   continue;    //ignore zero-length line (if any)  
> and the user count line
>                return_data.add(s.substring(0, 9).trim());
>             }
>             cu = (String[])return_data.toArray(new String 
> [return_data.size()]);
>          }
>       }
>       catch (InterruptedException ie) {
>          System.err.println("InterruptedException caught");
>       }
>       catch (IOException ioe) {
>          System.err.println("i/o error");
>       }
>       return cu;
>    }
>
>
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