public static boolean isAvailable() {
  if (Shell.WINDOWS) {
    ShellCommandExecutor shellExecutor = new ShellCommandExecutor(
        new String[] { Shell.WINUTILS, "help" });
    try {
      shellExecutor.execute();
    } catch (IOException e) {
      LOG.error(StringUtils.stringifyException(e));
    } finally {
      String output = shellExecutor.getOutput();
      if (output != null &&
          output.contains("Prints to stdout a list of processes in the task")) {
        return true;
      }
    }
  }
  return false;
}
 

public void run() {
  try {
    Vector<String> args = new Vector<String>();
    if (isSetsidAvailable()) {
      args.add("setsid");
    }
    args.add("bash");
    args.add("-c");
    args.add(" echo $$ > " + pidFile + "; sh " + shellScript + " " + N
        + ";");
    shexec = new ShellCommandExecutor(args.toArray(new String[0]));
    shexec.execute();
  } catch (ExitCodeException ee) {
    LOG.info("Shell Command exit with a non-zero exit code. This is"
        + " expected as we are killing the subprocesses of the"
        + " task intentionally. " + ee);
  } catch (IOException ioe) {
    LOG.info("Error executing shell command " + ioe);
  } finally {
    LOG.info("Exit code: " + shexec.getExitCode());
  }
}
 

/**
 * Is perl supported on this machine ?
 * @return true if perl is available and is working as expected
 */
public static boolean hasPerlSupport() {
  boolean hasPerl = false;
  ShellCommandExecutor shexec = new ShellCommandExecutor(
    new String[] { "perl", "-e", "print 42" });
  try {
    shexec.execute();
    if (shexec.getOutput().equals("42")) {
      hasPerl = true;
    }
    else {
      LOG.warn("Perl is installed, but isn't behaving as expected.");
    }
  } catch (Exception e) {
    LOG.warn("Could not run perl: " + e);
  }
  return hasPerl;
}
 

/**
 * Change the permissions on a file / directory, recursively, if
 * needed.
 * @param filename name of the file whose permissions are to change
 * @param perm permission string
 * @param recursive true, if permissions should be changed recursively
 * @return the exit code from the command.
 * @throws IOException
 */
public static int chmod(String filename, String perm, boolean recursive)
                          throws IOException {
  String [] cmd = Shell.getSetPermissionCommand(perm, recursive);
  String[] args = new String[cmd.length + 1];
  System.arraycopy(cmd, 0, args, 0, cmd.length);
  args[cmd.length] = new File(filename).getPath();
  ShellCommandExecutor shExec = new ShellCommandExecutor(args);
  try {
    shExec.execute();
  }catch(IOException e) {
    if(LOG.isDebugEnabled()) {
      LOG.debug("Error while changing permission : " + filename 
                +" Exception: " + StringUtils.stringifyException(e));
    }
  }
  return shExec.getExitCode();
}
 

public static boolean isAvailable() {
  if (Shell.WINDOWS) {
    ShellCommandExecutor shellExecutor = new ShellCommandExecutor(
        new String[] { Shell.WINUTILS, "help" });
    try {
      shellExecutor.execute();
    } catch (IOException e) {
      LOG.error(StringUtils.stringifyException(e));
    } finally {
      String output = shellExecutor.getOutput();
      if (output != null &&
          output.contains("Prints to stdout a list of processes in the task")) {
        return true;
      }
    }
  }
  return false;
}
 

public void run() {
  try {
    Vector<String> args = new Vector<String>();
    if (isSetsidAvailable()) {
      args.add("setsid");
    }
    args.add("bash");
    args.add("-c");
    args.add(" echo $$ > " + pidFile + "; sh " + shellScript + " " + N
        + ";");
    shexec = new ShellCommandExecutor(args.toArray(new String[0]));
    shexec.execute();
  } catch (ExitCodeException ee) {
    LOG.info("Shell Command exit with a non-zero exit code. This is"
        + " expected as we are killing the subprocesses of the"
        + " task intentionally. " + ee);
  } catch (IOException ioe) {
    LOG.info("Error executing shell command " + ioe);
  } finally {
    LOG.info("Exit code: " + shexec.getExitCode());
  }
}
 

@Override 
public void init() throws IOException {        
  // Send command to executor which will just start up, 
  // verify configuration/permissions and exit
  List<String> command = new ArrayList<String>(
      Arrays.asList(containerExecutorExe,
          "--checksetup"));
  String[] commandArray = command.toArray(new String[command.size()]);
  ShellCommandExecutor shExec = new ShellCommandExecutor(commandArray);
  if (LOG.isDebugEnabled()) {
    LOG.debug("checkLinuxExecutorSetup: " + Arrays.toString(commandArray));
  }
  try {
    shExec.execute();
  } catch (ExitCodeException e) {
    int exitCode = shExec.getExitCode();
    LOG.warn("Exit code from container executor initialization is : "
        + exitCode, e);
    logOutput(shExec.getOutput());
    throw new IOException("Linux container executor not configured properly"
        + " (error=" + exitCode + ")", e);
  }
 
  resourcesHandler.init(this);
}
 

public void mountCgroups(List<String> cgroupKVs, String hierarchy)
       throws IOException {
  List<String> command = new ArrayList<String>(
          Arrays.asList(containerExecutorExe, "--mount-cgroups", hierarchy));
  command.addAll(cgroupKVs);
  
  String[] commandArray = command.toArray(new String[command.size()]);
  ShellCommandExecutor shExec = new ShellCommandExecutor(commandArray);

  if (LOG.isDebugEnabled()) {
      LOG.debug("mountCgroups: " + Arrays.toString(commandArray));
  }

  try {
      shExec.execute();
  } catch (IOException e) {
      int ret_code = shExec.getExitCode();
      LOG.warn("Exception in LinuxContainerExecutor mountCgroups ", e);
      logOutput(shExec.getOutput());
      throw new IOException("Problem mounting cgroups " + cgroupKVs + 
        "; exit code = " + ret_code + " and output: " + shExec.getOutput(), e);
  }
}
 

/**
 * Is perl supported on this machine ?
 * @return true if perl is available and is working as expected
 */
public static boolean hasPerlSupport() {
  boolean hasPerl = false;
  ShellCommandExecutor shexec = new ShellCommandExecutor(
    new String[] { "perl", "-e", "print 42" });
  try {
    shexec.execute();
    if (shexec.getOutput().equals("42")) {
      hasPerl = true;
    }
    else {
      LOG.warn("Perl is installed, but isn't behaving as expected.");
    }
  } catch (Exception e) {
    LOG.warn("Could not run perl: " + e);
  }
  return hasPerl;
}
 

/**
 * Change the permissions on a file / directory, recursively, if
 * needed.
 * @param filename name of the file whose permissions are to change
 * @param perm permission string
 * @param recursive true, if permissions should be changed recursively
 * @return the exit code from the command.
 * @throws IOException
 */
public static int chmod(String filename, String perm, boolean recursive)
                          throws IOException {
  String [] cmd = Shell.getSetPermissionCommand(perm, recursive);
  String[] args = new String[cmd.length + 1];
  System.arraycopy(cmd, 0, args, 0, cmd.length);
  args[cmd.length] = new File(filename).getPath();
  ShellCommandExecutor shExec = new ShellCommandExecutor(args);
  try {
    shExec.execute();
  }catch(IOException e) {
    if(LOG.isDebugEnabled()) {
      LOG.debug("Error while changing permission : " + filename 
                +" Exception: " + StringUtils.stringifyException(e));
    }
  }
  return shExec.getExitCode();
}
 

/**
 * Change the permissions on a file / directory, recursively, if
 * needed.
 * @param filename name of the file whose permissions are to change
 * @param perm permission string
 * @param recursive true, if permissions should be changed recursively
 * @return the exit code from the command.
 * @throws IOException exception on chmod
 */
public static int chmod(String filename, String perm, boolean recursive)
    throws IOException {
  String [] cmd = Shell.getSetPermissionCommand(perm, recursive);
  String[] args = new String[cmd.length + 1];
  System.arraycopy(cmd, 0, args, 0, cmd.length);
  args[cmd.length] = new File(filename).getPath();
  ShellCommandExecutor shExec = new ShellCommandExecutor(args);
  try {
    shExec.execute();
  }catch(IOException e) {
    if(LOG.isDebugEnabled()) {
      LOG.debug("Error while changing permission : {} Exception: {}", filename, StringUtils.stringifyException(e));
    }
  }
  return shExec.getExitCode();
}
 

/**
 * Helper method that runs a LinuxTaskController command
 * 
 * @param taskCommand
 * @param user
 * @param cmdArgs
 * @param env
 * @throws IOException
 */
private void runCommand(TaskCommands taskCommand, String user,
    List<String> cmdArgs, File workDir, Map<String, String> env)
    throws IOException {

  ShellCommandExecutor shExec =
      buildTaskControllerExecutor(taskCommand, user, cmdArgs, workDir, env);
  try {
    shExec.execute();
  } catch (Exception e) {
    LOG.warn("Exit code from " + taskCommand.toString() + " is : "
        + shExec.getExitCode());
    LOG.warn("Exception thrown by " + taskCommand.toString() + " : "
        + StringUtils.stringifyException(e));
    LOG.info("Output from LinuxTaskController's " + taskCommand.toString()
        + " follows:");
    logOutput(shExec.getOutput());
    throw new IOException(e);
  }
  if (LOG.isDebugEnabled()) {
    LOG.info("Output from LinuxTaskController's " + taskCommand.toString()
        + " follows:");
    logOutput(shExec.getOutput());
  }
}
 

/**
 * Convenience method used to sending appropriate Kill signal to the task 
 * VM
 * @param context
 * @param command
 * @throws IOException
 */
private void finishTask(TaskControllerContext context,
    TaskCommands command) throws IOException{
  if(context.task == null) {
    LOG.info("Context task null not killing the JVM");
    return;
  }
  ShellCommandExecutor shExec = buildTaskControllerExecutor(
      command, context.env.conf.getUser(), 
      buildKillTaskCommandArgs(context), context.env.workDir,
      context.env.env);
  try {
    shExec.execute();
  } catch (Exception e) {
    LOG.warn("Output from task-contoller is : " + shExec.getOutput());
    throw new IOException(e);
  }
}
 

@Override
void terminateTask(TaskControllerContext context) {
  ShellCommandExecutor shexec = context.shExec;
  if (shexec != null) {
    Process process = shexec.getProcess();
    if (Shell.WINDOWS) {
      // Currently we don't use setsid on WINDOWS. 
      //So kill the process alone.
      if (process != null) {
        process.destroy();
      }
    }
    else { // In addition to the task JVM, kill its subprocesses also.
      String pid = context.pid;
      if (pid != null) {
        if(ProcessTree.isSetsidAvailable) {
          ProcessTree.terminateProcessGroup(pid);
        }else {
          ProcessTree.terminateProcess(pid);
        }
      }
    }
  }
}
 

@Override
void killTask(TaskControllerContext context) {
  ShellCommandExecutor shexec = context.shExec;
  if (shexec != null) {
    if (Shell.WINDOWS) {
      //We don't do send kill process signal in case of windows as 
      //already we have done a process.destroy() in termintateTaskJVM()
      return;
    }
    String pid = context.pid;
    if (pid != null) {
      if(ProcessTree.isSetsidAvailable) {
        ProcessTree.killProcessGroup(pid);
      }else {
        ProcessTree.killProcess(pid);
      }
    }
  }
}
 

public void testShellCommandTimeout() throws Throwable {
  String rootDir = new File(System.getProperty(
      "test.build.data", "/tmp")).getAbsolutePath();
  File shellFile = new File(rootDir, "timeout.sh");
  String timeoutCommand = "sleep 4; echo \"hello\"";
  PrintWriter writer = new PrintWriter(new FileOutputStream(shellFile));
  writer.println(timeoutCommand);
  writer.close();
  shellFile.setExecutable(true);
  Shell.ShellCommandExecutor shexc 
  = new Shell.ShellCommandExecutor(new String[]{shellFile.getAbsolutePath()},
                                    null, null, 100);
  try {
    shexc.execute();
  } catch (Exception e) {
    //When timing out exception is thrown.
  }
  shellFile.delete();
  assertTrue("Script didnt not timeout" , shexc.isTimedOut());
}
 

public void run() {
  try {
    Vector<String> args = new Vector<String>();
    if(ProcessTree.isSetsidAvailable) {
      args.add("setsid");
    }
    args.add("bash");
    args.add("-c");
    args.add(" echo $$ > " + pidFile + "; sh " +
                      shellScript + " " + N + ";") ;
    shexec = new ShellCommandExecutor(args.toArray(new String[0]));
    shexec.execute();
  } catch (ExitCodeException ee) {
    LOG.info("Shell Command exit with a non-zero exit code. This is" +
             " expected as we are killing the subprocesses of the" +
             " task intentionally. " + ee);
  } catch (IOException ioe) {
    LOG.info("Error executing shell command " + ioe);
  } finally {
    LOG.info("Exit code: " + shexec.getExitCode());
  }
}
 

public List<TaskTrackerLoadInfo> releaseTrackers(int numTrackers)
        throws IOException {
  List<TaskTrackerLoadInfo> releasedTrackers =
          new ArrayList<TaskTrackerLoadInfo>();
  TaskTrackerLoadInfoIterator iterator = new WastedTimeTTLIIterator();
  iterator.setTrackers(trackers);
  while (releasedTrackers.size() < numTrackers && iterator.hasNext()) {
    TaskTrackerLoadInfo tracker = iterator.next();
    String host = tracker.getTaskTrackerHost();
    if (trackers.contains(host)) {
      continue;
    }
    ShellCommandExecutor removeHostCommand = new ShellCommandExecutor(
            new String[]{"ssh", hostName,
              "cd " + hadoopHome + " && " + "bin/hadoop " +
              TTMover.class.getCanonicalName() + " -remove " + host});
    try {
      removeHostCommand.execute();
      releasedTrackers.add(tracker);
    } catch (IOException ex) {
      DynamicCloudsDaemon.LOG.error("Error removing tracker " +
              tracker.getTaskTrackerName(), ex);
    }
  }
  return releasedTrackers;
}
 

public List<TaskTrackerLoadInfo> addTrackers(List<TaskTrackerLoadInfo> trackers) {
  List<TaskTrackerLoadInfo> trackersAdded = new ArrayList<TaskTrackerLoadInfo>();
  for (TaskTrackerLoadInfo tracker : trackers) {
    String host = tracker.getTaskTrackerHost();
    ShellCommandExecutor addHostCommand = 
        new ShellCommandExecutor(
        new String[]{"ssh", hostName,
        "cd " + hadoopHome + " && " + "bin/hadoop " +
        TTMover.class.getCanonicalName() +
        " -add " + host});
    try {
      addHostCommand.execute();
      trackersAdded.add(tracker);
    } catch (IOException ex) {
      DynamicCloudsDaemon.LOG.error("Error adding tracker " + tracker.getTaskTrackerName(), ex);
    }
  }
  return trackersAdded;
}
 

/**
 * Change the permissions on a file / directory, recursively, if
 * needed.
 * @param filename name of the file whose permissions are to change
 * @param perm permission string
 * @param recursive true, if permissions should be changed recursively
 * @return the exit code from the command.
 * @throws IOException
 * @throws InterruptedException
 */
public static int chmod(String filename, String perm, boolean recursive)
                          throws IOException, InterruptedException {
  StringBuffer cmdBuf = new StringBuffer();
  cmdBuf.append("chmod ");
  if (recursive) {
    cmdBuf.append("-R ");
  }
  cmdBuf.append(perm).append(" ");
  cmdBuf.append(filename);
  String[] shellCmd = {"bash", "-c" ,cmdBuf.toString()};
  ShellCommandExecutor shExec = new ShellCommandExecutor(shellCmd);
  try {
    shExec.execute();
  }catch(IOException e) {
    if(Log.isDebugEnabled()) {
      Log.debug("Error while changing permission : " + filename 
          +" Exception: " + StringUtils.stringifyException(e));
    }
  }
  return shExec.getExitCode();
}
 

/**
 * Sends kill signal to process, forcefully terminating the process.
 * 
 * @param pid process id
 */
public static void killProcess(String pid) {

  //If process tree is not alive then return immediately.
  if(!ProcessTree.isAlive(pid)) {
    return;
  }
  String[] args = { "kill", "-9", pid };
  ShellCommandExecutor shexec = new ShellCommandExecutor(args);
  try {
    shexec.execute();
  } catch (IOException e) {
    LOG.warn("Error sending SIGKILL to process "+ pid + " ."+ 
        StringUtils.stringifyException(e));
  } finally {
    LOG.info("Killing process " + pid + " with SIGKILL. Exit code "
        + shexec.getExitCode());
  }
}
 

/**
 * Sends kill signal to all process belonging to same process group,
 * forcefully terminating the process group.
 * 
 * @param pgrpId process group id
 */
public static void killProcessGroup(String pgrpId) {

  //If process tree is not alive then return immediately.
  if(!ProcessTree.isProcessGroupAlive(pgrpId)) {
    return;
  }

  String[] args = { "kill", "-9", "-"+pgrpId };
  ShellCommandExecutor shexec = new ShellCommandExecutor(args);
  try {
    shexec.execute();
  } catch (IOException e) {
    LOG.warn("Error sending SIGKILL to process group "+ pgrpId + " ."+ 
        StringUtils.stringifyException(e));
  } finally {
    LOG.info("Killing process group" + pgrpId + " with SIGKILL. Exit code "
        + shexec.getExitCode());
  }
}
 

String getAllProcessInfoFromShell() {
  ShellCommandExecutor shellExecutor = new ShellCommandExecutor(
      new String[] { Shell.WINUTILS, "task", "processList", taskProcessId });
  try {
    shellExecutor.execute();
    return shellExecutor.getOutput();
  } catch (IOException e) {
    LOG.error(StringUtils.stringifyException(e));
  }
  return null;
}
 

String getSystemInfoInfoFromShell() {
  ShellCommandExecutor shellExecutor = new ShellCommandExecutor(
      new String[] { Shell.WINUTILS, "systeminfo" });
  try {
    shellExecutor.execute();
    return shellExecutor.getOutput();
  } catch (IOException e) {
    LOG.error(StringUtils.stringifyException(e));
  }
  return null;
}
 

/**
 * Returns true if the process with the specified pid is alive.
 *
 * @param pid String pid
 * @return boolean true if the process is alive
 */
@VisibleForTesting
public static boolean containerIsAlive(String pid) throws IOException {
  try {
    new ShellCommandExecutor(Shell.getCheckProcessIsAliveCommand(pid))
      .execute();
    // successful execution means process is alive
    return true;
  }
  catch (Shell.ExitCodeException e) {
    // failure (non-zero exit code) means process is not alive
    return false;
  }
}
 

protected CommandExecutor buildCommandExecutor(String wrapperScriptPath, 
    String containerIdStr, String user, Path pidFile, Resource resource,
    File wordDir, Map<String, String> environment)
        throws IOException {
  
  String[] command = getRunCommand(wrapperScriptPath,
      containerIdStr, user, pidFile, this.getConf(), resource);

    LOG.info("launchContainer: " + Arrays.toString(command));
    return new ShellCommandExecutor(
        command,
        wordDir,
        environment); 
}
 

/**
 * Returns true if the process with the specified pid is alive.
 * 
 * @param pid String pid
 * @return boolean true if the process is alive
 */
@VisibleForTesting
public static boolean containerIsAlive(String pid) throws IOException {
  try {
    new ShellCommandExecutor(Shell.getCheckProcessIsAliveCommand(pid))
      .execute();
    // successful execution means process is alive
    return true;
  }
  catch (ExitCodeException e) {
    // failure (non-zero exit code) means process is not alive
    return false;
  }
}
 

private static void unTarUsingTar(File inFile, File untarDir,
    boolean gzipped) throws IOException {
  StringBuffer untarCommand = new StringBuffer();
  if (gzipped) {
    untarCommand.append(" gzip -dc '");
    untarCommand.append(FileUtil.makeShellPath(inFile));
    untarCommand.append("' | (");
  } 
  untarCommand.append("cd '");
  untarCommand.append(FileUtil.makeShellPath(untarDir)); 
  untarCommand.append("' ; ");
  untarCommand.append("tar -xf ");

  if (gzipped) {
    untarCommand.append(" -)");
  } else {
    untarCommand.append(FileUtil.makeShellPath(inFile));
  }
  String[] shellCmd = { "bash", "-c", untarCommand.toString() };
  ShellCommandExecutor shexec = new ShellCommandExecutor(shellCmd);
  shexec.execute();
  int exitcode = shexec.getExitCode();
  if (exitcode != 0) {
    throw new IOException("Error untarring file " + inFile + 
                ". Tar process exited with exit code " + exitcode);
  }
}
 

public NodeHealthMonitorExecutor(String[] args) {
  ArrayList<String> execScript = new ArrayList<String>();
  execScript.add(nodeHealthScript);
  if (args != null) {
    execScript.addAll(Arrays.asList(args));
  }
  shexec = new ShellCommandExecutor(execScript
      .toArray(new String[execScript.size()]), null, null, scriptTimeout);
}
 

String getAllProcessInfoFromShell() {
  ShellCommandExecutor shellExecutor = new ShellCommandExecutor(
      new String[] { Shell.WINUTILS, "task", "processList", taskProcessId });
  try {
    shellExecutor.execute();
    return shellExecutor.getOutput();
  } catch (IOException e) {
    LOG.error(StringUtils.stringifyException(e));
  }
  return null;
}