top命令是怎么实现的

1370672326

好奇top命令是怎么实现的，看代码看不太懂。

自己尝试写了个小程序，去读/proc下的文件获取所有进程信息，挺占cpu和内存。

top刷新频率1s，刷新频率很高了，但占很少资源，它的进程信息难道不是从/proc下的进程相关文件里读取的，还是有什么优化技巧？

1370672326

坐等大神来解答啊

1370672326

求大神解答，不要沉了啊

pddnet

top命令应该有开发者的文档的吧，查查看

1370672326

pddnet 發表於 2016-5-24 15:59
top命令应该有开发者的文档的吧，查查看

源码里没有找到，不知道还能去哪找

pddnet

1370672326 發表於 2016-5-25 12:27
源码里没有找到，不知道还能去哪找

/*
* Copyright (c) 2008, The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*  * Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
*  * Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in
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*    distribution.
*  * Neither the name of Google, Inc. nor the names of its contributors
*    may be used to endorse or promote products derived from this
*    software without specific prior written permission.
*
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/  
  
#include <ctype.h>  
#include <dirent.h>  
#include <grp.h>  
#include <pwd.h>  
#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <sys/types.h>  
#include <unistd.h>  
  

skyseawing

等大神解答

1370672326

pddnet 發表於 2016-5-25 18:35
/*
* Copyright (c) 2008, The Android Open Source Project
* All rights reserved.

没看懂想表达什么

1370672326

elitebook 發表於 2016-7-9 15:40
http://blog.csdn.net/earbao/article/details/43453111
通过读/proc目录的文件

这个实现性能和top命令差太多，进程越多，占用cpu飙升

alan3

top估计是直接读取内核进程链等参数的，你直接通过文件系统去读写，那一定慢了