如何使用javas Process.waitFor（）？ [英] How to use javas Process.waitFor()?

问题描述

我正在尝试从Java运行命令行命令，快速的健全性检查让我意识到我遇到麻烦的原因是我无法获得 pr.waitFor（）请致电以下工作。这个程序在不到30秒后结束，并且在foo：之后不打印任何内容。我预计它需要超过30秒并在foo：之后打印一个随机数。我究竟做错了什么？

I am trying to run command line commands from Java and a quick sanity check made me realize that the reason I am having trouble is that I can't get the pr.waitFor() call below to work. This programs ends in less than 30s and prints nothing after "foo:". I expected it to take just over 30 s and print a random number after "foo:". What am I doing wrong?

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Sample {

    public static void main(String[] args) throws Exception {
        Runtime rt = Runtime.getRuntime();
        Process pr = rt.exec("sleep 32; echo $RANDOM");
        pr.waitFor();

        BufferedReader input = new BufferedReader(
                                   new InputStreamReader(pr.getInputStream()));
        String line=null;

        StringBuilder s = new StringBuilder();
        while((line=input.readLine()) != null) {
            System.out.println(s);
            s.append(line);
        }
        System.out.println("foo: " + s.toString());
    }
}

推荐答案

你应该尝试这个：

Process pr = rt.exec(new String[]{ "bash","-c", "sleep 32; echo $RANDOM" });

这将启动一个shell进程，然后在shell中运行你的命令。在命令完成之后，shell才会返回。

This launches a shell process and then within the shell runs your commands. The shell doesn't return till AFTER the commands have completed.

请告诉我这是否适合您。

Let me know if that works for you.

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