Member Avatar for uth

I am trying to execute a batch file which in turn executes an exe and writes output to a file, through java. I do not know why but the output file is not always written. Sometimes the program terminates without writing the file and sometimes it does. Any suggestions? Is there anyway i can wait till the execution of the batch file is complete?Will be great if somebody can help!thanks.

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As requested, posted the code that launches a Windows batch from Java and the external output file is only sometimes produced. The problem is almost always environmental or timing-related; the Java process either does not wait for the external work to finish, the file handles are not flushed/closed before the external program reads them, or the batch/exe spawns a background process and exits early. The practical fixes below are concise and testable.

Checklist to apply (in this order)

  • Make sure any Java writers/streams that produced the input file are flushed and closed before launching the batch.
  • Launch the batch with a proper process handle (use ProcessBuilder or Runtime.exec with "cmd /c" on Windows) and set the working directory or use absolute paths so redirection writes where you expect.
  • Consume or redirect the child process stdout/stderr (or use ProcessBuilder.redirectOutput) so the child cannot block on a full buffer.
  • Call waitFor() on the Process and check the exit value to know when the batch has actually finished.
  • If the batch uses cmd "start" or otherwise launches the exe asynchronously, modify the batch to run it synchronously or have the batch wait for the exe to finish — waitFor only waits for the process you started (the shell), not arbitrary grandchildren.

Minimal example pattern (adapt paths)

ProcessBuilder pb = new ProcessBuilder("cmd", "/c", "xsbexec.bat");
pb.directory(new File("C:\\full\\path\\to\\bat\\dir"));
pb.redirectErrorStream(true);
pb.redirectOutput(new File("C:\\full\\path\\to\\xsbex2.out"));
Process p = pb.start();
int rc = p.waitFor(); // blocks until the shell exits

Diagnostics if the problem persists

  • Run the batch manually from the same account/dir and compare timestamps.
  • Log the child's exit code and full stdout/stderr.
  • Temporarily modify the batch to echo debug messages and pause so you can see whether it returns immediately.
    Relevant API reference: ProcessBuilder and Process.waitFor() docs (ProcessBuilder, Process.waitFor).
Member Avatar for sidereal

post the code

Member Avatar for uth

Thanks. The following code is inside a function within a class. Now there is an application called triple used for inferencing. It is an exe but I am not able to invoke it directly. Thats why all the hassle. It consists of two parts.The first part as shown below calls "Commandline" which generates a file. Then when I call the xsbexec.bat, it takes the file thats generated and uses it to generate an output. That i'm redirecting to another file.

String[] args1 = new String[2];

        args1[0] = "copyTriple.triple";
        // "copyTriple.triple";
        args1[1] = "Ignored arguments";
        System.out.println("Calling commandline main");
        Commandline.main(args1);
try {

            Runtime rt = Runtime.getRuntime();
            String[] args2 = { "xsbexec.bat" };
            rt.exec(args2);
            fout1.close();  p1.close();
            boolean success = (new File("copyTriple.triple")).delete();
            if (!success) {
                    System.out.println("copyTriple not deleted");
            }
            System.out.println("done");
            }   
        catch (IOException ioe) {
            System.out.println(ioe);
            }

The following is what the batch file contains:

@echo off

rem adapt paths here

set XSB=C:\XSB\config\x86-pc-windows\bin\xsb
rem end adapt


echo running %1 %2 %3 %4 %5 %6 %7 %8 %9
%XSB% --nobanner --quietload --noprompt -e "['C:\Documents and Settings\Uthru\workspace\Patient records\#out']." >xsbex2.out

echo done.

exit

Thanks a tonne!

post the code

Edited by Member #120589 because: fixed formatting
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