向东博客 专注WEB应用 构架之美 --- 构架之美，在于尽态极妍 | 应用之美，在于药到病除|赢在IT，Playin' with IT,Focus on Killer Application,Marketing Meets Technology.

背景：有时你想测试一下传说中的微服务如熔断，服务器的接口超时（尤其是上传姑且叫大文件），这个rpm包应该是有用的。
限速
wondershaper是国外人开发的一款在Linux内核下基于TC工具的对整块网卡的限度工具。

第一种安装方法
首先下载wondershaper的rpm安装包：wondershaper-1.1a-7.noarch.rpm

安装wondershaper：
[root@localhost ~]# rpm -ivh wondershaper-1.1a-7.noarch.rpm


第二种安装方法
由于Centos7第三方库内才有这个软件，先安装第三方库
yum install epel-release -y
yum install wondershaper -y
限速命令：
第一个参数为网卡接口名，后面两个数字分别代表上行和下行的速度（单位Kb）

[root@localhost ~]# wondershaper eth0 5000 500
取消限速：

[root@localhost ~]# wondershaper clear eth0

来自：https://www.shuzhiduo.com/A/LPdo61bg53/

     Alfred是Mac下一个非常强大的工具，网上有许多如何使用的教程，我目前也只是会使用一些基本功能。其中一个我特别喜欢的功能就是直接可以在Alfred里面输入shell命令（默认需要在命令前家>符号，表示是shell命令），然后就会自动打开终端执行。但这里有个问题就是Alfred默认使用Mac自带的Terminal，而大多数在Mac经常使用终端的一般都会使用iTerm2，因为它配合zsh+oh my zsh，真的是非常强大。对于目前最新的iTerm 3.x版本，可以通过如下方法将Alfred内置的Terminal改为iTerm2：

打开Alfred的"Preferences->features->Terminal/shell"，将"Application"选为"custom"，然后将下面的编辑框中的脚本内容替换为下面的
on alfred_script(q)   if application "iTerm2" is running or application "iTerm" is running then     run script "       on run {q}         tell application \":Applications:iTerm.app\"           activate           try             select first window             set onlywindow to true           on error             create window with default profile             select first window             set onlywindow to true           end try           tell the first window             if onlywindow is false then               create tab with default profile             end if             tell current session to write text q           end tell         end tell       end run     " with parameters {q}   else     run script "       on run {q}         tell application \":Applications:iTerm.app\"           activate           try             select first window           on error             create window with default profile             select first window           end try           tell the first window             tell current session to write text q           end tell         end tell       end run     " with parameters {q}   end if end alfred_script

需要注意的是不同的iTerm2版本脚本内容不太一样，该脚本适用于最新的iTerm2版本，即iTerm2 3.0.

实践来自：https://www.cxymm.net/article/qq_29855509/120960802

sudo codesign --force --deep --sign - /Applications/PhotoScapeX.app

修复失败。

https://www.bbsmax.com/A/gAJG2D0zZR/

强制关掉一些进程后，方可使用zsh，发现有一个进程开了太多的进程：
ps -ef|grep UltraSearchSyste|wc -l
    3594
zsh出现 ：fork failed: resource temporarily unavailable，且启动不了程序了。

ps -ef|grep UltraSearchSyste|head -1
    0   105     1   0 四05下午 ??         9:44.65 /var/root/.UltraSearchSystem/UltraSearchSystemDaemon pd

    0 98562   105   0  3:41下午 ??         0:00.00 (UltraSearchSyste)
    0 98569   105   0  9:05下午 ??         0:00.00 (UltraSearchSyste)

开机启动位置，以为它是：
ls ~+/com.UltraSearchSystemDaemon.plist
cat ~+/com.UltraSearchSystemDaemon.plist
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0">   <dict>     <key>Label</key>     <string>com.UltraSearchSystemDaemon</string>     <key>ProgramArguments</key>     <array>       <string>/Library/Application Support/com.UltraSearchSystemDaemon/UltraSearchSystem</string>       <string>r</string>     </array>     <key>RunAtLoad</key>     <true />     <key>StartInterval</key>     <integer>14400</integer>   </dict> </plist>

其实，它不是，是它，符合位置和pd参数：
/Library/LaunchDaemons/com.UltraSearchSystemP.plist
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0">   <dict>     <key>KeepAlive</key>     <true />     <key>Label</key>     <string>com.UltraSearchSystemP</string>     <key>ProgramArguments</key>     <array>       <string>/var/root/.UltraSearchSystem/UltraSearchSystemDaemon</string>       <string>pd</string>     </array>     <key>RunAtLoad</key>     <true />     <key>StandardErrorPath</key>     <string>/dev/null</string>     <key>StandardOutPath</key>     <string>/dev/null</string>   </dict> </plist>
解决开机启动问题：
sudo rm -rf  ~+/com.UltraSearchSystemP.plist
Password:
来自：

如何删除mac上的ultrasearchapp？
https://www.zhihu.com/question/400059869
再次参考：https://www.makeuseof.com/tag/hidden-launchdaemons-launchagents-mac/
来自：https://www.pcrisk.com/removal-guides/18893-ultrasearchsystem-adware-mac

执行命令：sudo su -
source ~/.zshrc
compinit:503: no such file or directory: /usr/local/share/zsh/site-functions/_brew_cask

出现：compinit:503: no such file or directory: /usr/local/share/zsh/site-functions/_brew_cask
解决办法：
vim /usr/local/share/zsh/site-functions/_brew_cask

#compdef brew-cask #autoload # Zsh Autocompletion script for Homebrew Cask #   https://github.com/homebrew/brew # Authors: #   Patrick Stadler (https://github.com/pstadler) #   Josh McKinney (https://github.com/joshka) # only display the main commands (but enable completing aliases like 'ls') zstyle -T ':completion:*:*:*:brew-cask:*' tag-order && \   zstyle ':completion:*:*:*:brew-cask:*' tag-order 'commands' __brew_all_casks() {   local -a list   local expl   local comp_cachename=brew_casks   if ! _retrieve_cache $comp_cachename; then     list=( $(brew search --cask) )     _store_cache $comp_cachename list   fi   _wanted list expl 'all casks' compadd -a list } __brew_installed_casks() {   local -a list   local expl   list=( $(brew list --cask) )   _wanted list expl 'installed casks' compadd -a list } __brew_cask_commands() {   local -a commands   commands=(     'audit:verifies installability of Casks'     'cat:dump raw source of the given Cask to the standard output'     'create:creates the given Cask and opens it in an editor'     'doctor:checks for configuration issues'     'edit:edits the given Cask'     'fetch:downloads remote application files to local cache'     'home:opens the homepage of the given Cask'     'info:displays information about the given Cask'     'install:installs the given Cask'     'list:with no args, lists installed Casks; given installed Casks, lists staged files'     'outdated:list the outdated installed Casks'     'reinstall:reinstalls the given Cask'     'style:checks Cask style using RuboCop'     'uninstall:uninstalls the given Cask'     'upgrade:upgrade installed Casks with newer versions'     'zap:zaps all files associated with the given Cask'   )   _describe -t commands "brew cask command" commands } __brew_cask_aliases() {   local -a aliases   aliases=(     'dr'     'homepage'     'abv'     'ls'     '-S'     'rm'     'remove'   )   _describe -t commands "brew cask command aliases" aliases } __brew_cask_command() {   local command="$1"   local completion_func="_brew_cask_${command//-/_}"   declare -f "$completion_func" >/dev/null && "$completion_func" && return } _brew_cask_abv() {   _brew_cask_info } _brew_cask_audit() {   __brew_all_casks } _brew_cask_cat() {   __brew_all_casks } _brew_cask_create() {   _arguments '*::token:' } _brew_cask_edit() {   __brew_all_casks } _brew_cask_fetch() {   _arguments : \     '--force:force re-download even if the files are already cached' \     '*::token:__brew_all_casks' } _brew_cask_home() {   __brew_all_casks } _brew_cask_homepage() {   __brew_cask_home } _brew_cask_info() {   __brew_all_casks } _brew_cask_install() {   _arguments : \     '--force:re-install even if the Cask appears to be already present' \     '--skip-cask-deps:skip any Cask dependencies' \     '--require-sha:abort installation if the Cask does not have a checksum defined' \     '*::token:__brew_all_casks' } _brew_cask_list() {   _arguments : \     '-1[format output in a single column]' \     '-l[format as detailed list]' \     '*::token:__brew_installed_casks' } _brew_cask_outdated() {   _arguments : \     '--greedy:also list Casks with auto_updates or version \:latest' \     '*::token:__brew_installed_casks' } _brew_cask_remove() {   _brew_cask_uninstall } _brew_cask_rm() {   _brew_cask_uninstall } _brew_cask_style() {   _arguments : \     '--fix:auto-correct any style errors if possible' \     '*::token:__brew_all_casks' } _brew_cask_uninstall() {   _arguments : \     '--force:uninstall even if the Cask does not appear to be present' \     '*::token:__brew_installed_casks' } _brew_cask_upgrade() {   _arguments : \     '--force:upgrade even if Cask is not present, and --force the install' \     '--greedy:also upgrade Casks with auto_updates or version \:latest' \     '*::token:__brew_installed_casks' } _brew_cask_zap() {   __brew_all_casks } _brew_cask() {   local curcontext="$curcontext" state state_descr line   typeset -A opt_args   _arguments -C : \     '--verbose:Give additional feedback during installation.' \     '--appdir=-:Target location for Applications. The default value is /Applications:' \     '--colorpickerdir=-:Target location for Color Pickers. The default value is ~/Library/ColorPickers.' \     '--prefpanedir=-:Target location for Preference Panes. The default value is ~/Library/PreferencePanes.' \     '--qlplugindir=-:Target location for QuickLook Plugins. The default value is ~/Library/QuickLook.' \     '--dictionarydir=-:Target location for Dictionaries. The default value is ~/Library/Dictionaries.' \     '--fontdir=-:Target location for Fonts. The default value is ~/Library/Fonts.' \     '--servicedir=-:Target location for Services. The default value is ~/Library/Services.' \     '--input_methoddir=-:Target location for Input Methods. The default value is ~/Library/Input Methods.' \     '--internet_plugindir=-:Target location for Internet Plugins. The default value is ~/Library/Internet Plug-Ins.' \     '--audio_unit_plugindir=-:Target location for Audio Unit Plugins. The default value is ~/Library/Audio/Plug-Ins/Components.' \     '--vst_plugindir=-:Target location for VST Plugins. The default value is ~/Library/Audio/Plug-Ins/VST.' \     '--vst3_plugindir=-:Target location for VST3 Plugins. The default value is ~/Library/Audio/Plug-Ins/VST3.' \     '--screen_saverdir=-:Target location for Screen Savers. The default value is ~/Library/Screen Savers.' \     '--no-binaries:Do not link "helper" executables to /usr/local/bin.' \     '--debug:Output debugging information of use to Cask authors and developers.' \     ':command:->command' \     '*::options:->options'   case "$state" in   (command)     _alternative -C 'brew-cask' \       'aliases:alias:__brew_cask_aliases' \       'commands:command:__brew_cask_commands' ;;   (options)     __brew_cask_command "$line[1]" ;;   esac } _brew_cask "$@"

来自：https://blog.csdn.net/shentian885/article/details/115902464

ps只能看到部分：
root      3195  2205  0 Jun19 ?        00:00:13 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/0a8be205faf5aa1500e55e83e36a3027c626ae

cat查看：
#cat /proc/3195/cmdline
containerd-shim-namespacemoby-workdir/var/lib/containerd/io.containerd.runtime.v1.linux/moby/0a8be205faf5aa1500e55e83e36a3027c626aea234747a51c949ffb1a9f95c83-address/run/containerd/containerd.sock-containerd-binary/usr/bin/containerd-runtime-root/var/run/docker/runtime-runc-systemd-cgroup



二、执行程序的软链接：
#ls -lart /proc/3195/exe
lrwxrwxrwx 1 root root 0 Jun 25 10:06 /proc/3195/exe -> /usr/bin/containerd-shim



三、环境变量：
#cat /proc/3195/environ
LANG=en_US.UTF-8PATH=/opt/containerd/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/binLD_LIBRARY_PATH=:/opt/containerd/libGOMAXPROCS=2



四、对应的fd编号：
#ls /proc/3195/fd
0  1  10  11  12  13  14  15  16  17  18  19  2  20  3  4  5  6  7  8  9

mac下面sudo su - 后出现：
sudo su
Password:
[Oh My Zsh] Would you like to update? [Y/n]: y
Updating Oh My Zsh
error: 不能变基式拉取：您有未暂存的变更。
error: 请提交或贮藏它们。
There was an error updating. Try again later?

最后我的解决办法是：
cd  ~/.oh-my-zsh/

git status
位于分支 master
您的分支与上游分支 'origin/master' 一致。

尚未暂存以备提交的变更：
  （使用 "git add <文件>..." 更新要提交的内容）
  （使用 "git restore <文件>..." 丢弃工作区的改动）
  类型变更： plugins/fedora/fedora.plugin.zsh
  类型变更： plugins/go/go.plugin.zsh
  类型变更： plugins/gradle/_gradle
  类型变更： plugins/gradle/_gradlew
  类型变更： plugins/per-directory-history/per-directory-history.plugin.zsh

git reset --hard origin/master #强制让本地的代码和远端一致
HEAD 现在位于 08da19e3 emacs: revert cab1ac6e682038b2ceca9d16f8c458c0e79149ca (#7765)

git status
位于分支 master
您的分支与上游分支 'origin/master' 一致。

git pull
remote: Enumerating objects: 9644, done.

root@bogon# upgrade_oh_my_zsh
Note: `upgrade_oh_my_zsh` is deprecated. Use `omz update` instead.
Updating Oh My Zsh
From https://github.com/ohmyzsh/ohmyzsh
* branch              master     -> FETCH_HEAD
Current branch master is up to date.
         __                                     __
  ____  / /_     ____ ___  __  __   ____  _____/ /_
/ __ \/ __ \   / __ `__ \/ / / /  /_  / / ___/ __ \
/ /_/ / / / /  / / / / / / /_/ /    / /_(__  ) / / /
\____/_/ /_/  /_/ /_/ /_/\__, /    /___/____/_/ /_/
                        /____/

Oh My Zsh is already at the latest version.
To keep up with the latest news and updates, follow us on Twitter: https://twitter.com/ohmyzsh
Want to get involved in the community? Join our Discord: https://discord.gg/ohmyzsh
Get your Oh My Zsh swag at: https://shop.planetargon.com/collections/oh-my-zsh


参考：https://www.chendalei.com/articles/2018/10/09/1539052284615.html
提示：

Updating Oh My Zsh
error: cannot pull with rebase: You have unstaged changes.
error: please commit or stash them.
There was an error updating. Try again later?

这种情况很可能发生，因为您已经在.oh-my-zsh目录中编辑了一些内容但尚未提交。

导航到该目录（.oh-my-zsh/目录）。
运行git status。 它应该显示已更改的文件列表。
使用git add暂存这些文件
使用git commit -m提交这些更改
你现在应该可以升级了。

可选：在步骤2之后，您可以运行git commit -a -m，它应该暂存所有未暂存的文件并提交这些更改（组合步骤3和4）。
然后通过upgrade_oh_my_zsh命令升级zsh。

参考来源：https://github.com/robbyrussell/oh-my-zsh/issues/1984

解决办法：
下载VCRUNTIME140.dll文件；微软官网：下载地址：https://www.microsoft.com/en-us/download/details.aspx?id=52685

下载真实地址及名称：vc_redist.x64.exe
https://download.microsoft.com/download/0/6/4/064F84EA-D1DB-4EAA-9A5C-CC2F0FF6A638/vc_redist.x64.exe

此次学习来源：https://mp.weixin.qq.com/s/YqZI4XUlsyPpaGIjy0pG3A
#cat p.c
#include <stdio.h> void (*fun)(int a); void function(int value) {   printf("value= %d\r\n",value); } int main(void) { fun = function;//把function赋值给fun fun(520);//fun就等同于function      while(1) { } }

#./p
value= 520

cat pp.c
#include <stdio.h> int res; //void (*fun)(int a); int (*fun)(int a); int function(int value) {   return value; } int main(void) { fun = function;//把function赋值给fun res = fun(520);//fun就等同于function    printf("res = %d",res);   while(1) { } }
#./pp


cat ppp.c
#include <stdio.h> char temp[3]={1,2,3}; char *p; int main(void) {   p=temp;//将数组名赋值给指针变量p，p就指向数组temp的首地址      printf("value0 = %d\r\n",*p);    //p就代表数组的第一个数据的地址   printf("value1 = %d\r\n",*(p+1));//p+1就代表数组的第二个数据的地址   printf("value2 = %d\r\n",*(p+2));//p+2就代表数组的第三个数据的地址      printf("temp[0] = %d\r\n",p[0]);//p[0]等同于temp[0]   printf("temp[1] = %d\r\n",p[1]);//p[1]等同于temp[1]   printf("temp[2] = %d\r\n",p[2]);//p[2]等同于temp[2]   while(1) { } }
#./ppp
value0 = 1
value1 = 2
value2 = 3
temp[0] = 1
temp[1] = 2
temp[2] = 3

以前的学习：
https://jackxiang.com/post/7485/

https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html

真实下载地址：https://download.oracle.com/otn/java/jdk/8u291-b10/d7fc238d0cbf4b0dac67be84580cfb4b/jdk-8u291-macosx-x64.dmg

源码包下载地址：https://download.oracle.com/otn-pub/java/jdk/16.0.1+9/7147401fd7354114ac51ef3e1328291f/jdk-16.0.1_osx-x64_bin.tar.gz?AuthParam=1620358646_aa79aa4a7788c49057533e4b661b7f35
下载前的用户名密码：
https://jackxiang.com/post/6461/
来自：https://zhuanlan.zhihu.com/p/34915988


start.sh
#!/bin/bash JAVA_HOME=/Users/jackXiang/app/jdk-16.0.1.jdk/Contents/Home JAVA=$JAVA_HOME/bin/java $JAVA -jar cntvFtpClientV3.jar -Djava.ext.dirs=$JAVA_HOME/lib

在Centos8环境中配置PHP出现如上报错：
 
原因是没有安装配置oniguruma导致的 
解决方法如下：
1、获取源码，2.并解压

wget https://github.com/kkos/oniguruma/archive/v6.9.4.tar.gz -O oniguruma-6.9.4.tar.gz
tar -zxf oniguruma-6.9.4.tar.gz
cd oniguruma-6.9.4
备用下载： http://down.24kplus.com/linux/oniguruma/oniguruma-6.9.4.tar.gz

3、编译安装

./autogen.sh && ./configure --prefix=/usr
make && make install
如果是Centos7环境中的话：
 解决方法如下：

yum -y install http://mirror.centos.org/centos-7/7.7.1908/cloud/x86_64/openstack-queens/oniguruma-6.7.0-1.el7.x86_64.rpm
yum -y install http://mirror.centos.org/centos-7/7.7.1908/cloud/x86_64/openstack-queens/oniguruma-devel-6.7.0-1.el7.x86_64.rpm
备用下载：

oniguruma：http://down.24kplus.com/linux/oniguruma/oniguruma-6.7.0-1.el7.x86_64.rpm
oniguruma-devel：http://down.24kplus.com/linux/oniguruma/oniguruma-devel-6.7.0-1.el7.x86_64.rpm
————————————————
版权声明：本文为CSDN博主「薄凉小伙」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/Kangshuo2471781030/article/details/107241779

#coding=utf-8 import sys import os import xlrd  # 导入库 for i in range(len(sys.argv)):     print ("sys.argv[%d] = %s" % (i, sys.argv[i]))

python excelsearchKeyList.py k.txt
sys.argv[0] = excelsearchKeyList.py
sys.argv[1] = k.txt

二）判断字符为空：
#coding=utf-8 import sys import os import xlrd  # 导入库 # 打开文件 if len(sys.argv) >= 2:   file = open(sys.argv[1])   # file = open("/Users/jackXiang/pylearning/k.txt") else:   file = open("/Users/jackXiang/pylearning/cctvhyjykeywordslist.txt") for line in file:       line = line.replace('\r','').replace('\n','').replace('\t','')       if line.strip()=='':         print ('line is null')       else:         print(line)

python excelsearchKeyList.py  k.txt
原创视频
line is null
line is null



三）判断是否传入新的参数：
# 打开文件 if len(sys.argv) >= 2:   print(sys.argv[1])   file = open(sys.argv[1]) else:   file = open("/Users/jackXiang/pylearning/cctvhyjykeywordslist.txt") for line in file:       print(line) os._exit(-1) # os._exit(-1) sys.exit()

来自：https://blog.csdn.net/index20001/article/details/74294945#:~:text=Python%E7%A8%8B%E5%BA%8F%E6%9C%89%E4%B8%A4%E7%A7%8D,%E8%A7%A3%E9%87%8A%E5%99%A8%E5%B0%86%E4%BC%9A%E9%80%80%E5%87%BA%E3%80%82

问题：
#ssh -l xiangdong 10.10.0.109 xiangdong@10.10.0.109's password: sudo su - Activate the web console with: systemctl enable --now cockpit.socket Last login: Wed Feb  3 04:50:21 2021 from 10.10.2.1 -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.UTF-8) sudo su - /bin/sh: warning: setlocale: LC_ALL: cannot change locale (zh_CN.UTF-8) /bin/sh: warning: setlocale: LC_ALL: cannot change locale (zh_CN.UTF-8) /bin/sh: warning: setlocale: LC_ALL: cannot change locale (zh_CN.UTF-8) -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.utf8): No such file or directory -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.utf8): No such file or directory -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.utf8): No such file or directory [xiangdong@localhost ~]$ sudo su - -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.utf8): No such file or directory -bash: warning: setlocale: LC_ALL: cannot change locale (zh_CN.utf8): No such file or directory

rpm -qa *langpack*

cat /etc/locale.conf
LC_ALL="zh_CN.utf8"
LC_CTYPE="zh_CN.utf8"
LANG="zh_CN.utf8"

解决办法：
yum install glibc-langpack-zh -y

一、现象


Linux关机或重启时提示A stop job is running for ..


导致关机慢。


二、解决方法


编辑/etc/systemd/system.conf


修改下面两个变量为：


DefaultTimeoutStartSec=10s
DefaultTimeoutStopSec=10s
执行：systemctl daemon-reload



来自：https://blog.csdn.net/penge199761/article/details/79136826

质数定义：只有1和它本身两个约数，除此之外再没有其它约数。

示例1：
#include <stdio.h> #include <stdlib.h> int main() {    int a;    a=5;    if(a%2!=0 && a%3 !=0 && a%4!=0)        printf("质数");    else       printf("合数"); }
make zs
cc     zs.c   -o zs

#./zs
质数

示例2：
#include <stdio.h> #include <stdlib.h> int main() {    int a,count;    a=5;       if(a%2==0)       count++;    if(a%3==0)       count++;    if(a%4==0)       count++;    if(count == 0)        printf("质数");    else       printf("合数"); }

for循环介入：
#cat zs.c #include <stdio.h> #include <stdlib.h> int main() {    int a,count,i;    a=5;    for(i=2;i<=4;i++){       if(a%i==0)         count++;    }      if(count == 0)        printf("质数");    else       printf("合数"); }

引入scanf：
#include <stdio.h> #include <stdlib.h> int main() {    int a,count,i;    scanf("%d",&a);    for(i=2;i<=a-1;i++){       if(a%i==0)         count++;    }      if(count == 0)        printf("质数");    else       printf("合数"); }


#./zs
5
质数
#./zs
6
合数

打印出约数：
#include <stdio.h> #include <stdlib.h> int main() {    int a,count,i;    scanf("%d",&a);    for(i=2;i<=a-1;i++){       if(a%i==0){         count++;         printf("%d ",i);       }    }      if(count == 0)        printf("质数");    else       printf("合数"); }


#./zs
5
质数
#./zs
6
2 3 合数

更快一点，引入break：
#include <stdio.h> #include <stdlib.h> int main() {    int a,count,i;    scanf("%d",&a);    for(i=2;i<=a-1;i++){       if(a%i==0){         count++;         break;       }    }      if(count == 0)        printf("质数");    else       printf("合数"); }


#./zs
6
合数
#./zs
1000
合数



任一大于2的偶数都可以写成两个质数之和，采用部分穷举法，可以从1-100，1-10000啥的，但无法穷举所有：
#include <stdio.h> #include <stdlib.h> int main() {    int n,k,a,b,i,count1,count2;    scanf("%d",&n);//4到n,如：4-n内的偶数都可以写成两个质数之和    for(k=4;k<=n;k=k+2){       for(a=2;a<=k/2;a++){         //判断a是否为质数         count1=0;         for(i=2;i<=a-1;i++){            if(a%i==0){              count1++;              break;            }         }         if(count1==0){ //如果a为质数           b=k-a;           //判断b是否为质数           count2=0;           for(i=2;i<=b-1;i++){              if(b%i==0){                count2++;                break;              }           }           if(count2==0){ //如果b也是质数              printf("%d=%d+%d\n",k,a,b);                        break;           }         }        }    } }

#./zs
100
4=2+2
6=3+3
8=3+5
10=3+7
12=5+7
14=3+11
16=3+13
18=5+13
20=3+17
22=3+19
24=5+19
26=3+23
28=5+23
30=7+23
32=3+29
34=3+31
36=5+31
...

背景：有一篇朋友圈说是一个k8s里面Server的Pod销毁上报Zookeeper出现IP地址连接还是原来的，用到了zk的watcher，理论上不应该这样，于是查来查去，其大体意思就是说用了Go的多进程，有一个进程去读取配置了，因为配置还是老的，而用到了Go的多进程，于是文末那代码，我看了下，简单，但不明白，于是顺藤摸瓜学习一下这个rsync的原理。


——————————
#tree  -L 2 .|grep go
├── loop.go
├── pipe.go
├── waitgrouppointer.go
└── wg.go


#cat loop.go
package main

import (
    "fmt"
    //"time"
)

func main(){
    for i := 0; i < 100 ; i++{
        go fmt.Println(i)
    }
    //time.Sleep(time.Second)
}

这个说是运行太快，子进程没输出主进程就退了，啥也不输出。



#cat pipe.go
package main

import (
    "fmt"
    //"time"
)
func main() {
    c := make(chan bool, 100)
    for i := 0; i < 100; i++ {
        go func(i int) {
            fmt.Println(i)
            c <- true
        }(i)
    }

    for i := 0; i < 100; i++ {
        <-c
    }
}

这个说是管道要是上万，会耗尽系统管道资源。


#cat waitgroup.go      
package main

import (
    "fmt"
    "sync"
    //"time"
)
func main() {
    wg := sync.WaitGroup{}
    wg.Add(100)
    for i := 0; i < 100; i++ {
        go func(i int) {
            fmt.Println(i)
            wg.Done()
        }(i)
    }
    wg.Wait()
}


这个说是挺好的，因为它用到了原子加减法，这里好像C语言也有类似的函数，



再就是说它是用来阻塞方进程的，WaitGroup 对象内部有一个计数器，最初从0开始，它有三个方法：Add(), Done(), Wait() 用来控制计数器的数量。Add(n) 把计数器设置为n ，Done() 每次把计数器-1 ，wait() 会阻塞代码的运行，直到计数器地值减为0。

这里首先把wg 计数设置为100， 每个for循环运行完毕都把计数器减一，主函数中使用Wait() 一直阻塞，直到wg为零——也就是所有的100个for循环都运行完毕。相对于使用管道来说，WaitGroup 轻巧了许多。


最后，如果要搞裂成函数，得用引用传入，指针变量：
WaitGroup对象不是一个引用类型
WaitGroup对象不是一个引用类型，在通过函数传值的时候需要使用地址：

#cat waitgrouppointer.go
package main

import (
    "fmt"
    "sync"
    //"time"
)
func main() {
    wg := sync.WaitGroup{}
    wg.Add(100)
    for i := 0; i < 100; i++ {
        go f(i, &wg)
    }
    wg.Wait()
}

// 一定要通过指针传值，不然进程会进入死锁状态
func f(i int, wg *sync.WaitGroup) {
    fmt.Println(i)
    wg.Done()
}


以上来自：https://blog.csdn.net/u013474436/article/details/88749749

溯源来自：https://mp.weixin.qq.com/s/s9G6yDqfeFepbKT6DJASng



#cat wg.go
package main


import (
  "fmt"
  "sync"
)


func main() {
  ok := true
  for i := 0; i <1000; i ++ {
    var arr []int
    wg := sync.WaitGroup{}


    for j := 0; j <2; j ++ {
      wg.Add(1)


      go func() {
        defer wg.Done()
        arr = append(arr, i)
      }()
    }
    wg.Wait()


    if len(arr) < 2 {
      fmt.Printf("error:%d \n", i)
      ok = false
      break
    }
  }


  if ok {
    fmt.Println("ok")
  }
}

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