Question

在我的Java代码中，我调用了一个外部程序，我使用以下代码：

int returnCodeC = 0;
String cmnd = "dia -fa -fn res" + file1;
final Process processCC = Runtime.getRuntime().exec(cmnd);
BufferedReader bufC = new BufferedReader(new InputStreamReader(processCC.getInputStream()));
returnCodeC = processCC.waitFor();
    } catch (Exception e1) {e1.printStackTrace();}}

调用外部程序dia的输出应写在名为file1的文件中这一直到今天正常运作。我想问题是，当dia的输出很大时，我没有输出。 BufferReader是否有大小限制？

Answer 1

这更像是一个评论，但是一个波普尔的答案，但我的不良声誉不允许我发表评论。

如果stdout或stderr溢出各自的缓冲区大小，您的进程将阻塞。

在shell中尝试命令，看看会发生什么，并启动线程来读取stdterr和stdout。

编辑：这是我在网上找到的内容，当我不需要stdout和stderr的内容时它适用于我，但只需要运行的命令。我在processCC.waitFor（）之前调用了dropOutput。

private int dropOutput(final Process p) {

    final Thread t = new Thread("drop") {

      @Override
      public void run() {
        _dropOutput(p);
      };
    };

    t.start();
    int ev = 0;
    Timer timer = null;
    try {
      timer = new Timer(true);
      final InterruptTimerTask interrupter = new InterruptTimerTask(Thread.currentThread());
      timer.schedule(interrupter, 2 /*seconds*/* 1000 /*milliseconds per second*/);
      if (p.waitFor() != 0) {
        ev = p.exitValue();

      }
    } catch (final InterruptedException e) {
      //  e.printStackTrace();
    } finally {
      timer.cancel(); // If the process returns within the timeout period, we have to stop the interrupter
                      // so that it does not unexpectedly interrupt some other code later.

      Thread.interrupted(); // We need to clear the interrupt flag on the current thread just in case
                            // interrupter executed after waitFor had already returned but before timer.cancel
                            // took effect.
                            //
                            // Oh, and there's also Sun bug 6420270 to worry about here.
    }
    return ev;
  }

  /**
   * Just a simple TimerTask that interrupts the specified thread when run.
   */
  class InterruptTimerTask extends TimerTask {

    private final Thread thread;

    public InterruptTimerTask(final Thread t) {
      this.thread = t;
    }

    @Override
    public void run() {
      thread.interrupt();
    }

  }

  private void _dropOutput(final Process p) {
    final InputStream istrm = p.getInputStream();
    // final InputStream istrm = p.getErrorStream();
    final InputStreamReader istrmrdr = new InputStreamReader(istrm);
    final BufferedReader buffrdr = new BufferedReader(istrmrdr);

    @SuppressWarnings("unused")
    String data;
    try {
      while ((data = buffrdr.readLine()) != null) {
        // System.out.println(data);
      }
    } catch (final IOException e) {
      // do nothing
    }
  }

Answer 2

现在我认为我更好地理解了这个问题，我建议你使用processBuilder。它允许您对过程输出进行特殊控制。以下链接可能对您有所帮助：ProcessBuilder

proccess接收一个字符串数组作为参数，因此请使用String [] cmd = {"dia", "-fa", "-fn", "res"};

exec的输出没有写入java中的文件

2 个答案: