一、执行ls -l /system/bin/ 查看一下用户和权限。

二、这些权限在哪里修改呢？ 默认编译system/bin/可执行程序赋予权限的地方system\core\libcutils\fs_config.cpp 文件里面的android_files

三、使用实例，只有root和系统app权限才能执行某个命令，如上面的sn_writer命令，只有系统app和root权限才能运行。

 

package com.giada.sn_writer;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;public class MainActivity extends AppCompatActivity {private Button m_Button;private EditText m_EditText;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);m_Button=(Button)findViewById(R.id.button);m_EditText = (EditText) findViewById(R.id.textView);m_Button.setOnClickListener(new Button.OnClickListener() {public void onClick(View v){String str = m_EditText.getText().toString();sn_writer_command("sn_writer write-key "+ str);//  playRunTime("sn_writer write-key "+ str);}});}public static String sn_writer_command(String cmd) {try {//String keyCommand = "setprop " + propName;Runtime runtime = Runtime.getRuntime();Process proc = runtime.exec(cmd);} catch (IOException e) {e.printStackTrace();}return  cmd;}private String playRunTime(String cmd) throws Exception{//  String cmd = "adb version";String ret = null;Process p = Runtime.getRuntime().exec(cmd);InputStream is = p.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(is));String line; while ((line = reader.readLine()) != null){//tv_result.append(line + "");ret = line;}p.waitFor();is.close();reader.close();p.destroy();return ret;}}

四、有价值的参考文章

[RK3288][Android6.0] 调试笔记 --- 修改默认system/bin/下可执行程序权限_KrisFei的博客-CSDN博客_android system/bin 权限