获取树莓派cpu温度、cpu使用率、内存使用率

树莓派的/proc/文件夹中有各种虚拟文件，可以用来读取系统的各种数据。

下面以读取内存使用率、CPU使用率、CPU温度为例进行演示，用JSP页面实现。代码中的说明部分写明了所要读取的文件和计算方法。

代码片段：

<%@ page language="java" pageEncoding="utf-8" import="java.io.BufferedReader, java.io.FileReader, java.util.*"%>

<%--statebar info start--%>
        <%--
            -function:get memery usage
            -method:(read /proc/meminfo)
            -calculation:
                total memery = MemTotal
                mem free = MemFree + Buffers + Cached
                mem usage = MemTotal - mem free
        --%>
        <%
            FileReader fr_mem_usage=new FileReader("/proc/meminfo");
            BufferedReader br_mem_usage=new BufferedReader(fr_mem_usage);
            String s_mem_total=br_mem_usage.readLine();
            String s_mem_free=br_mem_usage.readLine();
            String s_mem_buffers=br_mem_usage.readLine();
            String s_mem_cached=br_mem_usage.readLine();
            String[] s_mem_total_array = s_mem_total.split("\\s+");
            String[] s_mem_free_array = s_mem_free.split("\\s+");
            String[] s_mem_buffers_array = s_mem_buffers.split("\\s+");
            String[] s_mem_cached_array = s_mem_cached.split("\\s+");
            
            int mem_total = Integer.parseInt(s_mem_total_array[1]);
            int mem_free = Integer.parseInt(s_mem_free_array[1]);
            int mem_buffers = Integer.parseInt(s_mem_buffers_array[1]);
            int mem_cached = Integer.parseInt(s_mem_cached_array[1]);

            int memUsage = 100 - (100 * (mem_free + mem_buffers + mem_cached) / mem_total);

            fr_mem_usage.close();
            br_mem_usage.close();
        %>
        
        <%--
            -function:get cpu usage
            -method:(read /proc/stat)
            -calculation:
                CPU total time=user+nice+system+idle+iowait+irq+softirq
                cpu usage=(idle2-idle1)/(cpu2-cpu1)*100
                OR cpu usage=[(user_2 +sys_2+nice_2) - (user_1 + sys_1+nice_1)]/(total_2 - total_1)*100
        --%>
        <%
            FileReader fr_cpu_usage1=new FileReader("/proc/stat");
            BufferedReader br_cpu_usage1=new BufferedReader(fr_cpu_usage1);
            String s_cpu_usage1=br_cpu_usage1.readLine();
            String[] s_cpu_usage_array1 = s_cpu_usage1.split("\\s+");
            int f_cpu_usage_array1[] = new int[7];
            for(int i=1;i<=7;i++){
                f_cpu_usage_array1[i-1] = Integer.parseInt(s_cpu_usage_array1[i]);
            }
            fr_cpu_usage1.close();
            br_cpu_usage1.close();

            Thread.sleep(100);      
        
            FileReader fr_cpu_usage2=new FileReader("/proc/stat");
            BufferedReader br_cpu_usage2=new BufferedReader(fr_cpu_usage2);
            String s_cpu_usage2=br_cpu_usage2.readLine();
            String[] s_cpu_usage_array2 = s_cpu_usage2.split("\\s+");
            int f_cpu_usage_array2[] = new int[7];
            for(int i=1;i<=7;i++){
                f_cpu_usage_array2[i-1] = Integer.parseInt(s_cpu_usage_array2[i]);
            }
            fr_cpu_usage2.close();
            br_cpu_usage2.close();

            int cputotal1=0,cputotal2=0,idle1=0,idle2=0,cpuUsage=0;
            for(int i=0;i<=6;i++){
                cputotal1 = cputotal1 + f_cpu_usage_array1[i];
            }
            for(int i=0;i<=6;i++){
                cputotal2 = cputotal2 + f_cpu_usage_array2[i];
            }
            idle1 = f_cpu_usage_array1[3];       
            idle2 = f_cpu_usage_array2[3];
            cpuUsage = 100 - (100 * (idle2 - idle1)/(cputotal2 - cputotal1));
        %>
        
        <%--
            -function:get cpu temperature
            -method:(read /sys/class/thermal/thermal_zone0/temp)
            -calculation:
                actual temperature = number_you_read / 1000
        --%>
        <%
            FileReader fr=new FileReader("/sys/class/thermal/thermal_zone0/temp");
            BufferedReader br=new BufferedReader(fr);
            String s=br.readLine();
            int temp = (Integer.parseInt(s))/1000;
            fr.close();
            br.close();
        %>                
<%--statebar info end--%>

结束