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缘由：

在学习Java的过程中不断用文章进行整理总结（常用功能的Java实现），争取早日能较为熟练的使用Java进行开发。

正文：

参考解答：

在Java中执行系统命令可以使用 ProcessBuilder 或者 Runtime.exec 方法。

package com.ixyzero.learn.misc;

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

/**
 * Created by ixyzero on 2018/6/12.
 */
public class TestExecSystemCommand {
    public static void main(String[] args) {
        try {
            String line = null;
            String[] cmd = { "/bin/sh", "-c", "ps aux | grep mysql" }; //要执行的命令
            Process p = Runtime.getRuntime().exec(cmd);
            BufferedReader in =
                    new BufferedReader(new InputStreamReader(p.getInputStream()));
            while ((line = in.readLine()) != null) {
                System.out.println(line);
            }
            in.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }

    }
}

上面这种常规的简单方法可能会hang住JVM。发生这种情况是因为inputStream缓冲区被塞满导致阻塞，直到它被读取；将 waitFor() 方法放在读取 inputStream 之后可以解决这个问题，但前提是errorStream没有被填满。

所以，正确的做法就是——新建2个线程去处理inputStream和errorStream缓冲区，然后再调用 waitFor() 方法。

package com.ixyzero.learn.misc;

import java.io.IOException;
import java.io.InputStream;

/**
 * Created by ixyzero on 2018/6/12.
 */
public class TestExecuteCmd {
    public static void main(String[] args) {
        executeCmd("ls -oa"); // 不支持管道操作符,因为是直接以string的形式传给exec方法的
        System.out.println();

        String[] cmd = { "/bin/sh", "-c", "ps aux | grep mysql" };
        executeCmdArray(cmd);
    }

    private static void executeCmd(String string) {
        try {
            Process aProcess = Runtime.getRuntime().exec(string);

            // These two thread shall stop by themself when the process end
            Thread pipeThread = new Thread(new StreamReader(aProcess.getInputStream()));
            Thread errorThread = new Thread(new StreamReader(aProcess.getErrorStream()));

            pipeThread.start();
            errorThread.start();

            aProcess.waitFor();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException ie) {
            ie.printStackTrace();
        }
    }

    private static void executeCmdArray(String[] cmd) {
        try {
            Process aProcess = Runtime.getRuntime().exec(cmd);

            // These two thread shall stop by themself when the process end
            Thread pipeThread = new Thread(new StreamReader(aProcess.getInputStream()));
            Thread errorThread = new Thread(new StreamReader(aProcess.getErrorStream()));

            pipeThread.start();
            errorThread.start();

            aProcess.waitFor();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException ie) {
            ie.printStackTrace();
        }
    }

}

//Replace the following thread with your intends reader
class StreamReader implements Runnable {

    private InputStream Pipe;

    public StreamReader(InputStream pipe) {
        if(pipe == null) {
            throw new NullPointerException("bad pipe");
        }
        Pipe = pipe;
    }

    public void run() {
        try {
            byte buffer[] = new byte[2048];

            int read = Pipe.read(buffer);
            while(read >= 0) {
                System.out.write(buffer, 0, read);

                read = Pipe.read(buffer);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(Pipe != null) {
                try {
                    Pipe.close();
                } catch (IOException e) {
                }
            }
        }
    }
}

如果希望更灵活的获取执行命令的返回值、输出、错误输出等信息，可以参考一下「Java exec – execute system processes with Java ProcessBuilder and Process」里面的基于 ProcessBuilder 和 新建线程处理inputStream和errorStream缓冲区 的方式实现的类。

参考链接：

• # 基于 ProcessBuilder 和 新建线程处理inputStream和errorStream缓冲区 的方式
  https://alvinalexander.com/java/java-exec-processbuilder-process-1
  https://alvinalexander.com/java/java-exec-processbuilder-process-2
  https://alvinalexander.com/java/java-exec-processbuilder-process-3
  https://alvinalexander.com/java/edu/java-exec/ProcessBuilderExample.java
  https://alvinalexander.com/java/edu/java-exec/SystemCommandExecutor.java
  https://alvinalexander.com/java/edu/java-exec/ThreadedStreamHandler.java
• # 基于 Runtime.exec 和 新建线程处理inputStream和errorStream缓冲区 的方式
  http://rosettacode.org/wiki/Execute_a_system_command#Java
• # 在Java中如何执行带有管道操作符的系统命令（使用string数组）
  https://stackoverflow.com/questions/5928225/how-to-make-pipes-work-with-runtime-exec
• Java程序执行Linux命令
• Java中Runtime.exec的一些事
• Java exec详解 – 调用系统命令以及进程#2类例子都有，且简单易懂
• Java Runtime.exec()的使用
• https://stackoverflow.com/questions/12097095/java-exec-linux-command
• Running system commands in Java applications