When does Process end?

[Nepomuk]

Hi!
I'm having a problem - I'm calling an external Process with

Process p = Runtime.getRuntime().exec("cmd /c ...");
 

(of course, without the dots but with a command instead) and have to wait for that Process to be completed before progressing. However, if I try waiting with:

p.waitFor();

or like this:

boolean finished = false;
while(!finished)
{
    try
    {
        p.exitValue();
        finished = true;
    }
    catch(IllegalThreadStateException itse){}
}
 

it goes into an infinite loop or something. Can anyone at least give me a hint? I'm feeling totally lost right now...

Greetings,
Nepomuk

[r035198x]

Hi!
I'm having a problem - I'm calling an external Process with

Process p = Runtime.getRuntime().exec("cmd /c ...");
 

(of course, without the dots but with a command instead) and have to wait for that Process to be completed before progressing. However, if I try waiting with:

p.waitFor();

or like this:

boolean finished = false;
while(!finished)
{
    try
    {
        p.exitValue();
        finished = true;
    }
    catch(IllegalThreadStateException itse){}
}
 

it goes into an infinite loop or something. Can anyone at least give me a hint? I'm feeling totally lost right now...

Greetings,
Nepomuk

Read this javaworld article on Runtime.exec pitfalls.

[Nepomuk]

Read this javaworld article on Runtime.exec pitfalls.

Thanks for the reply, that article is very interesting, but somehow it won't work nevertheless. My code looks like this now:

try
{            
    Runtime rt = Runtime.getRuntime();
    Process proc = rt.exec("cmd /c ...");
    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();
}
 

I basically copied the code from that article and changed the command that it should call. But it still hangs.

Just in case it's of any importance, the program I'm calling is gunzip and the command works fine without that construct. With the construct, it gets stuck while unpacking after 20KB (of the 9.47MB that it should be).

Any other ideas?

Greetings,
Nepomuk

*EDIT:* I found, that as soon as I exit my program manually, the extracted file is complete (so it jumps from 20KB to 9.47MB).

[r035198x]

Thanks for the reply, that article is very interesting, but somehow it won't work nevertheless. My code looks like this now:

try
{            
    Runtime rt = Runtime.getRuntime();
    Process proc = rt.exec("cmd /c ...");
    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();
}
 

I basically copied the code from that article and changed the command that it should call. But it still hangs.

Just in case it's of any importance, the program I'm calling is gunzip and the command works fine without that construct. With the construct, it gets stuck while unpacking after 20KB (of the 9.47MB that it should be).

Any other ideas?

Greetings,
Nepomuk

Sorry but which construct are you talking about?

[Nepomuk]

Sorry but which construct are you talking about?

I mean everything I've added. Sorry for being a bit unclear about that.

Greetings,
Nepomuk

[r035198x]

So you mean the problem is that the process is not exiting or is it that the process ends but there is no output produced when it is successful.

[Nepomuk]

So you mean the problem is that the process is not exiting or is it that the process ends but there is no output produced when it is successful.

I can only guess what happens with it while runtime, but as the result is correct, as soon as I quit my program manually (-> the full 9.47MB are there), it seems to have some temporary data somewhere (in a Buffer maybe?) and it puts it in the place it belongs, when it's closed (or it's damn fast as soon as I attempt to close it).

I just checked and according to the task manager, gunzip runs until I close my program. Am I somehow stopping it from closing?

Greetings,
Nepomuk

[JosAH]

I can only guess what happens with it while runtime, but as the result is correct, as soon as I quit my program manually (-> the full 9.47MB are there), it seems to have some temporary data somewhere (in a Buffer maybe?) and it puts it in the place it belongs, when it's closed (or it's damn fast as soon as I attempt to close it).

I just checked and according to the task manager, gunzip runs until I close my program. Am I somehow stopping it from closing?

Greetings,
Nepomuk

You shouldn't try to capture the process' error output stream *and* wait for the
process to complete in just one thread. Use separate threads for the output
capturing, the completion of the process (use the join() method) and the final
return from the outer method call. A bit of wait/notify etc. will do the job.

kind regards,

Jos

[Nepomuk]

You shouldn't try to capture the process' error output stream *and* wait for the
process to complete in just one thread. Use separate threads for the output
capturing, the completion of the process (use the join() method) and the final
return from the outer method call. A bit of wait/notify etc. will do the job.

kind regards,

Jos

Thanks, that did the trick.

Greetings,
Nepomuk

[oceatoon]

Hi
I seem to have the same pb, would you mind sharing your final working solution.
Thanks in advance

Tibor

[Nepomuk]

Hi
I seem to have the same pb, would you mind sharing your final working solution.
Thanks in advance

Tibor

I'm not able to post the code, as I have no access to it any more (it was for work, but my contract was only for the semester holidays and they are over), but as far as I remember, I basically used 2 new Threads for cleaning the Streams as suggested on this site. (Posted by r035198x in Answer #2.) Look for the StreamGobbler.

Greetings,
Nepomuk

[r035198x]

I'm not able to post the code, as I have no access to it any more (it was for work, but my contract was only for the semester holidays and they are over), but as far as I remember, I basically used 2 new Threads for cleaning the Streams as suggested on this site. (Posted by r035198x in Answer #2.) Look for the StreamGobbler.

Greetings,
Nepomuk

So you're still alive?
I thought you'd gotten kidnapped by terrorists.

[Nepomuk]

So you're still alive?
I thought you'd gotten kidnapped by terrorists.

Na, they looked more like aliens from outa space ;-)
Just been quite busy lately, but ever so often I come and have a look around here. :-D

Greetings,
Nepomuk