java 如何监控 ProcessBuilder 运行的外部进程？
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How to monitor external process ran by ProcessBuilder?
提问by ?ukaszBachman
This should be rather simple, but I don't see anything helpful in JavaDocs.
这应该相当简单，但我在JavaDocs中看不到任何有用的东西。
What I need is to run some external process from my Java code and then be able to monitor if this process has been shutdown or not. In other words, I want to be able to reliably determine whether or not my external process was not ended by user.
我需要的是从我的 Java 代码运行一些外部进程，然后能够监视该进程是否已关闭。换句话说，我希望能够可靠地确定我的外部进程是否没有被用户终止。
If no cross platform solution exists, I will accept anything working under Linux.
如果不存在跨平台解决方案，我将接受在 Linux 下运行的任何内容。
My current snippet of code:
我当前的代码片段：
public static void main(String[] args) {
ProcessBuilder pb = new ProcessBuilder("some proces name");
try {
Process p = pb.start();
// p.isRunning(); <- now, that would be helpful :-)
} catch (IOException e) {
e.printStackTrace();
}
}
回答by jtahlborn
Start a new Thread which calls Process.waitFor()and sets a flag when that call returns. then, you can check that flag whenever you want to see if the process has completed.
启动一个新线程，该线程Process.waitFor()在该调用返回时调用并设置一个标志。然后，您可以随时检查该标志以查看该过程是否已完成。
public class ProcMon implements Runnable {
private final Process _proc;
private volatile boolean _complete;
public boolean isComplete() { return _complete; }
public void run() {
_proc.waitFor();
_complete = true;
}
public static ProcMon create(Process proc) {
ProcMon procMon = new ProcMon(proc);
Thread t = new Thread(procMon);
t.start();
return procMon;
}
}
(some boilerplate omitted).
（省略了一些样板文件）。
回答by Gray
I'm not sure I'm understanding the question but one way to do this is to call process.exitValue();. It throws an exception if process has not yet terminated:
我不确定我是否理解这个问题，但一种方法是调用process.exitValue();. 如果进程尚未终止，则抛出异常：
/**
* Returns the exit value for the subprocess.
*
* @return the exit value of the subprocess represented by this
* <code>Process</code> object. by convention, the value
* <code>0</code> indicates normal termination.
* @exception IllegalThreadStateException if the subprocess represented
* by this <code>Process</code> object has not yet terminated.
*/
abstract public int exitValue();
If you don't mind a hack, you can do something like the following if you are working on a ~Unix system which uses the UNIXProcessclass. This does use reflection however:
如果您不介意 hack，并且您正在使用UNIXProcess该类的 ~Unix 系统上工作，则可以执行以下操作。然而，这确实使用了反射：
ProcessBuilder pb = new ProcessBuilder("/bin/sleep", "5");
Process process = pb.start();
// open accessability of the UNIXProcess.hasExited field using reflection
Field field = process.getClass().getDeclaredField("hasExited");
field.setAccessible(true);
// now we can get the field using reflection
while (!(Boolean) field.get(process)) {
...
}
回答by Harrison Telfer
Based on the question's specific code snippet I might be useful to add that since 1.8 the Processclass has an isAlive()method is available
基于问题的特定代码片段，我可能会补充说，自 1.8 以来，Process该类有一个isAlive()可用的方法
Documentation link: https://docs.oracle.com/javase/8/docs/api/java/lang/Process.html
文档链接：https: //docs.oracle.com/javase/8/docs/api/java/lang/Process.html
good luck to anyone reading this!
祝所有阅读本文的人好运！
