Read CPU frequency using linux command "cat /sys/devices/system/cpu/cpuX/cpufreq/scaling_cur_freq"

This example read files "/sys/devices/system/cpu/cpu[0..]/cpufreq/scaling_cur_freq" with Linux's cat command, to determine running cpu frequency.

In Linux, there will be some file like this, to show the CPUs frequency.
/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
/sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq
...

Run adb command:
$ adb shell ls /sys/devices/system/cpu/

It will show some directory named cpu0, cpu1..., it is the number of cpu in your system.

Run adb command, to show the current frequency of cpu0:
$ adb shell cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

package com.example.androidcpu;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.io.InputStream;
import java.util.regex.Pattern;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {
 
 TextView textAvProc, textNumOfCpu, textMsg;
 Button btnReadCpuFreq;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textAvProc = (TextView)findViewById(R.id.avproc);
        textNumOfCpu = (TextView)findViewById(R.id.numofcpu);
        textMsg = (TextView)findViewById(R.id.msg);
        btnReadCpuFreq = (Button)findViewById(R.id.readfreq);
        
        Runtime runtime = Runtime.getRuntime();
        int availableProcessors = runtime.availableProcessors();
        textAvProc.setText("availableProcessors = " + availableProcessors);

        btnReadCpuFreq.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {
    readCpuFreqNow();
   }});
        
        readCpuFreqNow();
    }
    
    private void readCpuFreqNow(){
     File[] cpuFiles = getCPUs();
        textNumOfCpu.setText("number of cpu: " + cpuFiles.length);
        
        String strFileList = "";
        for(int i=0; i<cpuFiles.length; i++){
         
         String path_scaling_cur_freq = 
          cpuFiles[i].getAbsolutePath()+"/cpufreq/scaling_cur_freq";
         
         String scaling_cur_freq = cmdCat(path_scaling_cur_freq);
         
         strFileList +=
          i + ": " 
          + path_scaling_cur_freq + "\n"
          + scaling_cur_freq
          + "\n";
        }
        
        textMsg.setText(strFileList);
    }

    //run Linux command 
    //$ cat f
    private String cmdCat(String f){

     String[] command = {"cat", f};
     StringBuilder cmdReturn = new StringBuilder();
     
     try {
      ProcessBuilder processBuilder = new ProcessBuilder(command);
      Process process = processBuilder.start();
      
      InputStream inputStream = process.getInputStream();
      int c;
      
      while ((c = inputStream.read()) != -1) {
       cmdReturn.append((char) c); 
      }
         
      return cmdReturn.toString();
      
     } catch (IOException e) {
      e.printStackTrace();
      return "Something Wrong";
     }

    }

    /*
     * Get file list of the pattern
     * /sys/devices/system/cpu/cpu[0..9]
     */
    private File[] getCPUs(){
     
     class CpuFilter implements FileFilter {
            @Override
            public boolean accept(File pathname) {
                if(Pattern.matches("cpu[0-9]+", pathname.getName())) {
                    return true;
                }
                return false;
            }      
        }
     
     File dir = new File("/sys/devices/system/cpu/");
     File[] files = dir.listFiles(new CpuFilter());
     return files;
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidcpu.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />
    
    <TextView
        android:id="@+id/avproc"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <Button
        android:id="@+id/readfreq"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Read CPUs Frequency now"/>
    <TextView
        android:id="@+id/numofcpu"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/msg"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

Related:
- Java SE version on Raspberry Pi and Linux