Android Runtime.getRuntime().exec() 使用方法

Android 可以通过Runtime.getRuntime().exec()方法来执行命令或者创建进程。

1. Runtime.getRuntime().exec共有六个重载方法：

public Process exec(String command)

在单独的进程中执行指定的字符串命令。
public Process exec(String [] cmdArray)

在单独的进程中执行指定命令和变量

public Process exec(String command, String [] envp)

在指定环境的独立进程中执行指定命令和变量
public Process exec(String [] cmdArray, String [] envp)

在指定环境的独立进程中执行指定的命令和变量
public Process exec(String command,String[] envp,File dir)

在有指定环境和工作目录的独立进程中执行指定的字符串命令
public Process exec(String[] cmdarray,String[] envp,File dir)

在指定环境和工作目录的独立进程中执行指定的命令和变量

我们先来比较exec(String command)与exec(String[] cmdArray)的区别，其实他们是等价的，最终都会调用：

exec(String[] cmdarray,String[] envp,File dir)，我们看看方法exec(String cmdarray,String[] envp,File dir) throws IOException的实现代码：

public Process exec(String command, String[] envp, File dir) throws IOException {
    if (command.length() == 0) throw new IllegalArgumentException("Empty command");
    StringTokenizer st = new StringTokenizer(command);
    String[] cmdarray = new String[st.countTokens()];
    for (int i = 0; st.hasMoreTokens(); i++) {
        cmdarray[i] = st.nextToken();
    }
    return exec(cmdarray, envp, dir);
}

从上面的代码，我们可以看出最终调用的代码都是：exec(String[] cmdArray,String envp,File dir)。exec(String command)相当于exec(command,null,null)，exec(String[] cmdArray)相当于exec(cmdArray,null,null)。

2. 参数说明：

cmdarray– 包含所调用命令及其参数的数组

envp– 字符串数组，其中每个元素的环境变量的设置格式为 name=value，如果子进程应该继承当前进程的环境，或该参数为 null

dir– 子进程的工作目录；如果子进程应该继承当前进程的工作目录，则该参数为 null

3. 关于返回结果类型：Process，它有几个方法：

(1).destroy()：杀掉子进程

(2).exitValue()：返回子进程的出口值，值0表示正常终止

(3).getErrorStream()：获取子进程的错误流

(4).getInputStream()：获取子进程的输入流

(5).getOutputStream()：获取子进程的输出流

(6).waitFor()：导致当前线程等待，如有必要，一直要等到由该Process对象表示的进程已经终止。如果已终止该子进程，此方法立即返回。如果没有终止该子进程，调用的线程将被阻塞，直到退出子进程，根据惯例, 0表示正常终止

4. 如何获取command 最终执行的结果？

(1) 执行command命令，将命令行输出重定向到一个文件，再读取文件判断执行结果。

比如命令：javap -l xxx > output.txt , 调用exec(String[] cmdArray)如下：

Process p = Runtime.getRuntime().exec(new String[]{"/bin/sh","-c", "javap -l xxx > output.txt"});

(2) 也可以通过InputStream/OutputStream, 获取命令执行的结果。

下面例子是先利用“su”提权，然后执行command，完整代码：

    private static boolean exeCommand(String command) {
        boolean ret = false;
        try {
            VirtualTerminal vt;
            vt = new VirtualTerminal("su");
            VTCommandResult r = vt.runCommand(command);
            ret = r.success();
            vt.shutdown();
        } catch (Exception e) {
            e.printStackTrace();
        }

        return ret;
    }

VirtualTerminal.java

package com.test.mytest;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;

import android.util.Log;

public class VirtualTerminal {

    private static final String TAG = "VirtualTerminal";

    private final Object mReadLock = new Object();
    private final Object mWriteLock = new Object();
    private Process mProcess = null;

    private DataOutputStream mOutputStream;
    private ByteArrayOutputStream mInputBuffer = new ByteArrayOutputStream();
    private ByteArrayOutputStream mErrBuffer = new ByteArrayOutputStream();
    private InputReaderThread mInputReaderThread;
    private InputReaderThread mErrReaderThread;

    public VirtualTerminal(String shell) throws IOException, InterruptedException {
        
        mProcess = Runtime.getRuntime().exec(shell);
        
        mOutputStream = new DataOutputStream(mProcess.getOutputStream());

        mInputReaderThread = new InputReaderThread(mProcess.getInputStream(), mInputBuffer);
        mErrReaderThread = new InputReaderThread(mProcess.getErrorStream(), mErrBuffer);
        Thread.sleep(50);
        mInputReaderThread.start();
        mErrReaderThread.start();
    }

    public VTCommandResult runCommand(String command) throws Exception {
        synchronized (mWriteLock) {
            mInputBuffer.reset();
            mErrBuffer.reset();
        }

        // $? 表示最后运行的命令的结束代码（返回值）
        mOutputStream.writeBytes(command + "\necho :RET=$?\n");
        mOutputStream.flush();
        
        while (true) {
            synchronized (mReadLock) {
                boolean doWait = false;
                synchronized (mWriteLock) {
                    byte[] inpbyte = mInputBuffer.toByteArray();
                    String inp = new String(inpbyte);
                    doWait = !inp.contains(":RET=");
                }
                if (doWait) {
                    mReadLock.wait();
                }
            }

            synchronized (mWriteLock) {
                byte[] inpbyte = mInputBuffer.toByteArray();
                byte[] errbyte = mErrBuffer.toByteArray();
                String inp = new String(inpbyte);
                String err = new String(errbyte);

                //Please keep log statement or else it will dead loop
                if (inp.contains(":RET=")) {
                    if (inp.contains(":RET=EOF") || err.contains(":RET=EOF")) {
                        Log.w(TAG, "exec:[eof]" + inp);
                    }
                    
                    if (inp.contains(":RET=0")) {
                        Log.w(TAG, "exec:[ok]" + inp);
                        return new VTCommandResult(0, inp, err);
                    } else {
                        Log.w(TAG, "exec:[err]" + inp);
                        return new VTCommandResult(1, inp, err);
                    }
                }
            }
        }
    }

    public void shutdown() {
        mInputReaderThread.interrupt();
        mErrReaderThread.interrupt();
        mProcess.destroy();
    }

    /**
     * A thread class helps to read/write data
     */
    public class InputReaderThread extends Thread {
        private InputStream mInputStream;
        private ByteArrayOutputStream mByteArrayOutputStream;

        public InputReaderThread(InputStream in, ByteArrayOutputStream out) {
            mInputStream = in;
            mByteArrayOutputStream = out;
        }

        @Override
        public void run() {
            if (mInputStream != null) {
                try {
                    byte[] buffer = new byte[1024];
                    while (true) {
                        int read = mInputStream.read(buffer);
                        if (read < 0) {
                            synchronized(mWriteLock) {
                                String eof = ":RET=EOF";
                                mByteArrayOutputStream.write(eof.getBytes());
                            }
                            synchronized (mReadLock) {
                                mReadLock.notifyAll();
                            }

                            break;
                        } else if (read > 0) {
                            synchronized(mWriteLock) {
                                mByteArrayOutputStream.write(buffer, 0, read);
                            }
                            synchronized (mReadLock) {
                                mReadLock.notifyAll();
                            }
                        }
                    }
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }
    }

    /**
     * A result wrapper for exec()
     */
    public class VTCommandResult {
        public final String mStdout;
        public final String mStderr;
        public final Integer mExitValue;

        VTCommandResult(Integer exit_value_in, String stdout_in, String stderr_in) {
            mExitValue = exit_value_in;
            mStdout = stdout_in;
            mStderr = stderr_in;
        }

        VTCommandResult(Integer exit_value_in) {
            this(exit_value_in, null, null);
        }

        public boolean success() {
            return mExitValue != null && mExitValue == 0;
        }
    }
}

5. 如何用Worker thread 实现 exec() 的等待超时机制？

  /**
     * 运行一个外部命令，返回状态, 可以设置超时时间
     * @param command
     * @param timeout, in milliseconds
     * @return
     */
    private int execCommand(final String[] commandArray, final long timeout) {
        Worker worker = null;
        try {
            worker = new Worker(commandArray);
            worker.start();
            worker.join(timeout);
        } catch (Throwable t) {
            t.printStackTrace();
        } finally {
            if (worker.exit != Integer.MAX_VALUE) {
                return worker.exit;
            } else {
                worker.interrupt();
            }  
        }
        return ErrorCodeDefine.DOROOT_FAIL;
    }

    /**
     * 用Worker thread 可以实现超时机制
     */
    private static class Worker extends Thread {
        private final String[] commandArray;
        private int exit = Integer.MAX_VALUE;

        private Worker(String[] commandArray) {
            this.commandArray = commandArray;
        }

        public void run() {
            Process process = null;
            try {
                process = Runtime.getRuntime().exec(commandArray);
                if (process != null) {
                    exit = process.waitFor();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Throwable t) {
                t.printStackTrace();
            } finally {
                if (process != null) {
                    killProcess(process);
                }
            }
        }
    }

    /**
     * 通过Android底层实现进程关闭
     */
    private static void killProcess(Process process) {
        int pid = getProcessId(process.toString());
        if (pid != 0) {
            try {
                closeAllStream(process);
                android.os.Process.killProcess(pid);
            } catch (Exception e) {
                try {
                    process.destroy();
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }
    }

    /**
     * 获取当前进程的ID
     */
    private static int getProcessId(String str) {
        try {
            int i = str.indexOf("=") + 1;
            int j = str.indexOf("]");
            String cStr = str.substring(i, j).trim();
            return Integer.parseInt(cStr);
        } catch (Exception e) {
            return 0;
        }
    }

    /**
     * 关闭进程的所有流
     *
     * @param process
     */
    public static void closeAllStream(Process process) {
        try {
            InputStream in = process.getInputStream();
            if (in != null)
                in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            InputStream in = process.getErrorStream();
            if (in != null)
                in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            OutputStream out = process.getOutputStream();
            if (out != null)
                out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

原文链接：https://blog.csdn.net/wangbaochu/article/details/44941045

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