Question

I am trying to call cleartool from an java application, but cleartool hangs even for a simple “-version” argument. Running cleardiff instead of cleartool works fine, so apparently there is something specific with the cleartool program (which I assume is related to its interactive capabilities).

The following program

import java.io.*;
import java.util.*;

public class ExecTesting extends Thread {

    private List<String> command = new ArrayList<String>();

    public ExecTesting (List<String> command) {
        super();
        this.command = command;
    }

    private void print(String s) {
        System.out.println(s);
    }

    @Override
    public void run() {
        Process process;
        OutputStream stdin;
        InputStream stdout;
        InputStream stderr;
        String line;

        try {
            String commandString = joinList(command, " ");
            print("Executing: " + commandString);

            // runtime.exec has several issues (http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html?page=1)
            // better to use ProcessBuilder (http://java.sun.com/developer/JDCTechTips/2005/tt0727.html#2)
            //process = Runtime.getRuntime().exec(commandString);
            process = new ProcessBuilder(command).start();
            // it fails in both cases though

            stdin  = process.getOutputStream();
            stdout = process.getInputStream();
            stderr = process.getErrorStream();

            BufferedReader bufferedStderr = new BufferedReader(new InputStreamReader(stderr));
            while ((line = bufferedStderr.readLine()) != null) {
                print("stderr: " + line);
            }
            bufferedStderr.close();

            BufferedReader bufferedStdout = new BufferedReader(new InputStreamReader(stdout));
            while ((line = bufferedStdout.readLine()) != null) {
                print("stdout: " + line);
            }
            bufferedStdout.close();

            stdin.close();
            stdout.close();
            stderr.close();

            process.waitFor();
            print("Execution finished, exit code " + process.exitValue());
            process.destroy();
        } catch (IOException e) {
            print("IOException: " +e.getStackTrace());
        } catch (InterruptedException e) {
            print("InterruptedException: " + e.getStackTrace());
        }

    }

    /* assumes a list with at least one element */
    private static String joinList(List<String> list, String glue) {
        Iterator<String> i = list.iterator();
        String ret = i.next();
        while (i.hasNext()) {
            ret += glue + i.next();
        }
        return ret;
    }

    public static void main(String[] args) {
        ArrayList<String> cmd1 = new ArrayList<String>();
        cmd1.add("c:\\Program Files\\Rational\\ClearCase\\bin\\cleardiff.exe");
        cmd1.add("-version");
        ExecTesting et1 = new ExecTesting(cmd1);
        et1.start();

        ArrayList<String> cmd2 = new ArrayList<String>();
        //cmd2.add("c:\\Program Files\\Rational\\ClearCase\\bin\\cleardiff.exe");
        cmd2.add("c:\\Program Files\\Rational\\ClearCase\\bin\\cleartool.exe");
        cmd2.add("-version");
        ExecTesting et2 = new ExecTesting(cmd2);
        et2.start();

        et1 = new ExecTesting(cmd1);
        et1.start();
    }
}

gives the following output

Executing: [c:\Program Files\Rational\ClearCase\bin\cleardiff.exe, -version]
Executing: [c:\Program Files\Rational\ClearCase\bin\cleartool.exe, -version]
Executing: [c:\Program Files\Rational\ClearCase\bin\cleardiff.exe, -version]
stdout: cleardiff                         2003.06.10+ (Tue Jul 13 14:02:05  2004)
Execution finished, exit code 0

hanging on the execution of the cleartool command. If instead cmd2 is changed to cleardiff the output is as expected

Executing: [c:\Program Files\Rational\ClearCase\bin\cleardiff.exe, -version]
Executing: [c:\Program Files\Rational\ClearCase\bin\cleardiff.exe, -version]
Executing: [c:\Program Files\Rational\ClearCase\bin\cleardiff.exe, -version]
stdout: cleardiff                         2003.06.10+ (Tue Jul 13 14:02:05  2004)
Execution finished, exit code 0
stdout: cleardiff                         2003.06.10+ (Tue Jul 13 14:02:05  2004)
Execution finished, exit code 0
stdout: cleardiff                         2003.06.10+ (Tue Jul 13 14:02:05  2004)
Execution finished, exit code 0

Question: Does anyone know why cleartool is hanging and how to fix?

Answer 1

You should consume the stdout and stderr in separate threads, otherwise you will experience blocking behaviour.

I suspect that’s what’s happening in this instance (and that it’s unrelated to cleartool/cleardiff other than they’re outputting stdout/err). See this answer for more information.