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<!DOCTYPE html><html lang="en" data-theme="light"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width,initial-scale=1"><title>huzixiaoshu - welcome</title><meta name="author" content="huzixiaoshu"><meta name="copyright" content="huzixiaoshu"><meta name="format-detection" content="telephone=no"><meta name="theme-color" content="#ffffff"><meta name="description" content="hello world">
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})(window)</script><meta name="generator" content="Hexo 5.4.0"></head><body><div id="sidebar"><div id="menu-mask"></div><div id="sidebar-menus"><div class="author-avatar"><img class="avatar-img" src="/img/655.jpg" onerror="onerror=null;src='/img/friend_404.gif'" alt="avatar"/></div><div class="site-data"><div class="data-item is-center"><div class="data-item-link"><a href="/archives/"><div class="headline">Articles</div><div class="length-num">23</div></a></div></div></div><hr/><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> Home</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> Archives</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> Tags</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> Categories</span></a></div><div class="menus_item"><a class="site-page" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> List</span><i class="fas fa-chevron-down expand"></i></a><ul class="menus_item_child"><li><a class="site-page child" href="/music/"><i class="fa-fw fas fa-music"></i><span> Music</span></a></li><li><a class="site-page child" href="/movies/"><i class="fa-fw fas fa-video"></i><span> Movie</span></a></li></ul></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fas fa-link"></i><span> Link</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> About</span></a></div></div></div></div><div class="page" id="body-wrap"><header class="full_page" id="page-header" style="background-image: url('/img/655.jpg')"><nav id="nav"><span id="blog_name"><a id="site-name" href="/">huzixiaoshu</a></span><div id="menus"><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> Home</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> Archives</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> Tags</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> Categories</span></a></div><div class="menus_item"><a class="site-page" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> List</span><i class="fas fa-chevron-down expand"></i></a><ul class="menus_item_child"><li><a class="site-page child" href="/music/"><i class="fa-fw fas fa-music"></i><span> Music</span></a></li><li><a class="site-page child" href="/movies/"><i class="fa-fw fas fa-video"></i><span> Movie</span></a></li></ul></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fas fa-link"></i><span> Link</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> About</span></a></div></div><div id="toggle-menu"><a class="site-page"><i class="fas fa-bars fa-fw"></i></a></div></div></nav><div id="site-info"><h1 id="site-title">huzixiaoshu</h1><div id="site_social_icons"><a class="social-icon" href="https://github.com/huzixiaoshu" target="_blank" title="Github"><i class="fab fa-github"></i></a></div></div><div id="scroll-down"><i class="fas fa-angle-down scroll-down-effects"></i></div></header><main class="layout" id="content-inner"><div class="recent-posts" id="recent-posts"><div class="recent-post-item"><div class="post_cover left_radius"><a href="/2021/05/05/TCP%E5%AD%A6%E4%B9%A0/" title="TCP学习"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="TCP学习"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/05/05/TCP%E5%AD%A6%E4%B9%A0/" title="TCP学习">TCP学习</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-05-04T17:23:57.186Z" title="Created 2021-05-05 01:23:57">2021-05-05</time></span></div><div class="content">TCP学习
协议上限分析：
以太网：1500
IP:65536
数据包上限是为了防止数据丢了重发速度快
TCP: 不是不会丢包，是丢了可以重传
netstat -apn | grep 6666
端口复用12int opt=1;setSockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));</div></div></div><div class="recent-post-item"><div class="post_cover right_radius"><a href="/2021/05/05/%E5%A4%9A%E8%B7%AFIO%E8%BD%AC%E6%8E%A5/" title="多路IO转接"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="多路IO转接"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/05/05/%E5%A4%9A%E8%B7%AFIO%E8%BD%AC%E6%8E%A5/" title="多路IO转接">多路IO转接</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-05-04T17:23:43.538Z" title="Created 2021-05-05 01:23:43">2021-05-05</time></span></div><div class="content">多路I/O转接服务器
多路I/O转接服务器也叫做多任务I/O服务器。该类服务器实现的主旨思想是，不再由应用程序自己监视客户端连接，取而代之由内核替应用程序监视文件。select
文件描述上限–1024： 同时监听的文件描述符1024个
for循环才能判断具体是哪一个，效率低
监听集合和满足的集合是一个，所有需要保存一下。poll
1024 突破
监听、返回集合 分离
搜索范围小epoll
是否在线
心跳包
乒乓包
探测分节
</div></div></div><div class="recent-post-item"><div class="post_cover left_radius"><a href="/2021/05/05/shell/" title="shell"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="shell"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/05/05/shell/" title="shell">shell</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-05-04T17:23:23.579Z" title="Created 2021-05-05 01:23:23">2021-05-05</time></span></div><div class="content">shell编程
#！ 指定解释器 例如：#!/bin/bash
# 注释
运行：
chmod a+x sample.sh + ./sample.sh
/bin/bash sample.sh
/bin/sh sample.sh
. sample.sh
source sample.sh内建命令和小括号
man bash-builtins 查看man手册
( shell 命令 ) 不会改变工作目录
; 多个命令可用相隔使用变量按照惯例，shell变量通常由字母加下划线，由任意长度的字母、数字、下划线组成。有两种类型的shell变量
环境变量环境变量可用父进程传给子进程，因此shell 进程的环境变量可用从当前进程传给fork出来的子进程，用printenv命令可以显示当前shell进程的环境变量
本地变量只存在于当前shell进程，用set命令可以显示当前shell进程中定义的所有变量（包括本地变量和环境变量）和函数
可以用export导出，使其为环境变量
用unset命令可以删除已定义的环境变量或本地变量
alias取别名文件名代换（Globbing）这些用于匹配的字 ...</div></div></div><div class="recent-post-item"><div class="post_cover right_radius"><a href="/2021/04/23/%E6%97%B6%E9%97%B4_%E5%8E%9F%E5%AD%90%E6%93%8D%E4%BD%9C_%E5%BC%82%E5%B8%B8/" title="时间_原子操作_异常"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="时间_原子操作_异常"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/23/%E6%97%B6%E9%97%B4_%E5%8E%9F%E5%AD%90%E6%93%8D%E4%BD%9C_%E5%BC%82%E5%B8%B8/" title="时间_原子操作_异常">时间_原子操作_异常</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-22T17:14:01.302Z" title="Created 2021-04-23 01:14:01">2021-04-23</time></span></div><div class="content">基础
值语义： 可以拷贝的，拷贝之后，与原对象脱离关系
对象语义，要么是不能拷贝的，要么可以拷贝，拷贝之后与原对象仍然存在一定的关系，比如共享底层资源（要实现自己的拷贝构造函数）
继承了两个类，copyable，or nocopyable。nocopyable只需要让其拷贝构造函数和赋值构造函数定义为=delete即可(c++11特性)或者将其定义为private。其默认构造函数和析构函数需要定义为protectd，使得只能为子类使用，但是子类不具有复制行为。123456789class noncopyable {public: noncopyable(const noncopyable&) = delete; void operator=(const noncopyable&) = delete;protected: noncopyable() = default; ~noncopyable() = default;};
muduo::copyable 空基类，标识类，值类型Timestamp
static_assert 在 ...</div></div></div><div class="recent-post-item"><div class="post_cover left_radius"><a href="/2021/04/23/%E7%BD%91%E7%BB%9C%E5%9F%BA%E7%A1%80/" title="网络基础"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="网络基础"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/23/%E7%BD%91%E7%BB%9C%E5%9F%BA%E7%A1%80/" title="网络基础">网络基础</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-22T17:13:03.412Z" title="Created 2021-04-23 01:13:03">2021-04-23</time></span></div><div class="content">网络基础协议典型协议
传输层：TCP/UDP 协议
应用层： HTTP协议、FTP协议
网络层： IP协议、ICMP协议、IGMP协议
网络接口层：ARP协议、RARP协议
TCP传输控制协议是一种面向连接、可靠的、基于字节流的传输层通信协议
UDP用户数据报协议是OSI参考模型中一种无连接的传输层协议，提供面向事务的简单不可靠信息传送服务
HTTP超文本传输协议是互联网上应用最为广泛的一种网络协议
FTP文本传输协议
IP协议是因特网互联协议
ICMP协议是Internet控制报文协议，它是TCP/IP协议族的一个子协议，用于在IP主机、路由器之间传递控制信息
IGMP协议是Internet组管理协议是因特网协议家族中的一个组播协议。该协议运行在主机和组播路由器之间。
ARP协议是正向地址解析协议，通过已知的IP，寻找对应的主机MAC地址
RARP是反向地址转换协议，通过MAC地址确定IP地址网络设计模式
C/S （客户端、服务器）
优点：
协议选用灵活
缓存数据
缺点：
对用户的安全构成威胁
开发工作量较大，调试困难
B/S (浏览器、服务器)
优点 ...</div></div></div><div class="recent-post-item"><div class="post_cover right_radius"><a href="/2021/04/20/%E7%BA%BF%E7%A8%8B%E7%9A%84%E5%90%8C%E6%AD%A5/" title="线程的同步"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="线程的同步"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/20/%E7%BA%BF%E7%A8%8B%E7%9A%84%E5%90%8C%E6%AD%A5/" title="线程的同步">线程的同步</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-20T13:51:27.440Z" title="Created 2021-04-20 21:51:27">2021-04-20</time></span></div><div class="content">同步概念
同步即协同步调，按预定的先后次序运行。
线程同步，指一个线程发出某一功能调用时，在没有得到结果之前，该调用不返回，同时其它线程为保证数据一致性，不能调用该功能。
锁是建议锁，不具备强制性。
多个控制流，共同操作一个共享资源的时候需要同步。
数据混乱的原因
资源共享（独享资源则不会）
调度随机（意味着数据访问会出现竞争）
线程间缺乏必要的同步机制
前两点不能改变，欲提高效率，传递数据，资源必须共享，只要共享资源，就一定会出现竞争。只要存在竞争关系，数据就很容易出现混乱。所以只能从第三个着手解决，使多个线程在访问共享资源的时候，出现互斥。互斥量mutexpthread_mutex_init 函数
初始化一个互斥锁（互斥量）–> 初值可以看作1
restrict关键字： 只用于限制指针，告诉编译器，所有修改该指针指向内存中内容的操作，只能通过本指针完成。不能通过除本指针以外的其它变量或指针修改。
互斥量属性。是一个传入参数，通常传NULL，选用默认属性（线程间共享）
静态初始化：如果互斥锁mutex是静态分配的（定义在全局，或加了static关键字修饰），可以 ...</div></div></div><div class="recent-post-item"><div class="post_cover left_radius"><a href="/2021/04/19/%E7%BA%BF%E7%A8%8B/" title="线程"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="线程"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/19/%E7%BA%BF%E7%A8%8B/" title="线程">线程</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-19T13:43:26.744Z" title="Created 2021-04-19 21:43:26">2021-04-19</time></span></div><div class="content">线程概念
LWP:light weight process 轻量级进程，本质是仍是进程
进程： 独立地址空间，拥有PCB
线程: 也有PCB，但没有独立的地址空间（共享）
区别： 在于是否共享地址空间。 独居（进程）;合居(线程)。
Linux下：
线程：最小的执行单位
进程：最小分配资源单位，可以看成只有一个线程的进程。
linux下内核线程实现原理
轻量级进程，也有PCB，创建线程使用的底层函数和进程一样，都是clone
从内核里看进程和线程一样，都有各自不同的PCB，但是PCB中指向内存资源的三级页表是相同的
进程可以蜕变成线程
线程可以看作寄存器和栈的集合
在linux下，线程最小的执行单位，进程是最小的资源分配单位
查看LWP号: ps -Lf pid 查看指定线程的lwp号线程共享资源
文件描述符
每种信号的处理方式
当前工作目录
用户ID和组ID
内存地址空间（.text/.data/.bss/heap/共享库）线程非共享资源
线程id
处理器现场和栈指针（内核栈）
独立的栈空间（用户空间栈）
errno变量
信号屏蔽字
调度优先级线程优 ...</div></div></div><div class="recent-post-item"><div class="post_cover right_radius"><a href="/2021/04/18/%E4%BF%A1%E5%8F%B72/" title="信号2"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="信号2"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/18/%E4%BF%A1%E5%8F%B72/" title="信号2">信号2</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-18T04:08:48.751Z" title="Created 2021-04-18 12:08:48">2021-04-18</time></span></div><div class="content">竞态条件（时序竞争）pause函数
调用该函数可以造成进程主动挂起，等待信号唤醒。调用该系统调用的进程将处于阻塞状态（主动放弃cpu）直到有信号递达将其唤醒
int pause (void) 返回值：-1 并设置errno为EINTR
如果信号的默认处理动作是终止进程，则进程终止，pause函数没有机会返回。
如果信号的默认处理动作是忽略，进程继续处于挂起状态，pause函数不返回。
如果信号的处理动作是捕捉，则调用完信号处理函数之后，pause函数返回-1， errno设置为EINTR,表示“被信号中断”，
pause收到的信号不能被屏蔽，如果被屏蔽，那么pause就不能被唤醒。解决时序问题
sigsuspend : 原子操作，不可再分的操作总结  竞态条件，跟系统负载有很紧密的关系，体现出信号的不可靠性。系统负载越严重，信号不可靠性越强。提早预见，主动规避。全局变量的异步尽量避免使用全局变量。类似于多线程中的多个线程对同一个变量进行操作，很容易造成异常。
不可/可重入函数
一个函数在调用执行期间（尚未调用结束），由于某种时序又被重复调用，称之为“ ...</div></div></div><div class="recent-post-item"><div class="post_cover left_radius"><a href="/2021/04/18/%E5%AE%88%E6%8A%A4%E8%BF%9B%E7%A8%8B/" title="守护进程"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="守护进程"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/18/%E5%AE%88%E6%8A%A4%E8%BF%9B%E7%A8%8B/" title="守护进程">守护进程</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-18T04:08:41.259Z" title="Created 2021-04-18 12:08:41">2021-04-18</time></span></div><div class="content">终端
输入输出的总称叫做终端。
terminal 是虚拟终端
简单来说，一个Linux系统启动，大致流程：
init --> fork --> exec --> getty --> 用户输入账号 --> login --> 输入密码 --> exec -- >bash
线路规程 ：line disciline 用来过滤键盘输入的内容
ttyname 函数： 由文件描述符查出对应的文件名进程组概念和特性
进程组，也称为作业。
当父进程，创建子进程的时候，默认子进程与父进程属于同一进程组。进程组ID==第一个进程ID(组长进程)。所以，组长进程标识：其进程组ID==其进程ID。
组长进程可以创建一个进程组，创建该进程组中的进程，然后终止，只要进程中有一个进程存在，进程组就存在，与组长进程是否终止无关。
进程组生存期：进程组创建到最后一个进程离开（终止或转移到另外一个进程组）。
一个进程可以为自己或子进程设置进程组IDgetpgrp函数
获取当前进程的进程组IDgetpgid函数
获取指定进程的进程组IDsetpgid函数
改变进程默 ...</div></div></div><div class="recent-post-item"><div class="post_cover right_radius"><a href="/2021/04/16/%E4%BF%A1%E5%8F%B7/" title="信号"> <img class="post_bg" src="/linear-gradient(20deg,%20#0062be,%20#925696,%20#cc426e,%20#fb0347)" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="信号"></a></div><div class="recent-post-info"><a class="article-title" href="/2021/04/16/%E4%BF%A1%E5%8F%B7/" title="信号">信号</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="far fa-calendar-alt"></i><span class="article-meta-label">Created</span><time datetime="2021-04-16T11:06:59.941Z" title="Created 2021-04-16 19:06:59">2021-04-16</time></span></div><div class="content">信号的概念
三个特征：
简单
不能携带大量信息
满足某个特定条件才发送
信号的特质： 由于信号是通过软件方法实现，其实现手段导致信号有很强的延时性，但是该时间是相对于CPU而言。与信号相关的时间和状态
产生信号
按键产生 如：
ctrl+c : 2)SIGINT(终止/中断) ‘INT’–interrupt
ctrl+z : 20)SIGSTP（暂停/停止） ‘T’ –Terminal终端
ctrl+\ : 3)SIGQUIT(退出)
系统调用产生，如:kill\raise\abort
软件条件产生，如：定时器 alarm
硬件异常产生，如：
非法访问内存（段错误） 11)SIGSEGV(段错误)
除（0）（浮点数例外） 8)SIGFPE(浮点数例外) ‘F’-float
内存对齐出错（总线错误） 7) SIGBUS
命令产生，如：kill命令
递达： 递送应且到达进程
未决：产生和递达之间的状态，主要由于阻塞（屏蔽）导致该状态
信号的处理方式：
执行默认动作
忽略（丢弃）
捕捉（调用户处理函数）信号4要素
信号四要素：
编号
名称
事件
默 ...</div></div></div><nav id="pagination"><div class="pagination"><span class="page-number current">1</span><a class="page-number" href="/page/2/#content-inner">2</a><a class="page-number" href="/page/3/#content-inner">3</a><a class="extend next" rel="next" href="/page/2/#content-inner"><i class="fas fa-chevron-right fa-fw"></i></a></div></nav></div><div class="aside-content" id="aside-content"><div class="card-widget card-info"><div class="card-info-avatar is-center"><img class="avatar-img" src="/img/655.jpg" onerror="this.onerror=null;this.src='/img/friend_404.gif'" alt="avatar"/><div class="author-info__name">huzixiaoshu</div><div class="author-info__description">hello world</div></div><div class="card-info-data"><div class="card-info-data-item is-center"><a href="/archives/"><div class="headline">Articles</div><div class="length-num">23</div></a></div></div><a class="button--animated" id="card-info-btn" target="_blank" rel="noopener" href="https://github.com/huzixiaoshu"><i 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