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<h1 id="see-the-log-from-systemd-service-journalctl">See the log from systemd service: <code>journalctl</code></h1>
<h2 id="common-usage">Common usage</h2>
<p><code>journalctl -u UnitName --since today</code></p>
<p>Use right arrow key to scroll right. Or press <code>-S</code> and Enter in <code>less</code> to toggle word wrap.</p>
<p>Also see <a target="_blank" rel="noopener" href="https://www.digitalocean.com/community/tutorials/how-to-use-journalctl-to-view-and-manipulate-systemd-logs">DigitalOcean's website</a> for more usages.</p>
<h2 id="show-colorful-output">Show colorful output:</h2>
<p>If the original daemon output is already colorized, but the colors are being lost when using journalctl, the <code>--output cat</code> option will restore them. See the manual for more details.</p>
<blockquote>
<p>-o, --output= Controls the formatting of the journal entries that are shown. Takes one of the following options:</p>
</blockquote>
<blockquote>
<p>cat generates a very terse output, only showing the actual message of each journal entry with no metadata, not even a timestamp.</p>
</blockquote>
<h2 id="continuously-print-new-logs">Continuously print new logs</h2>
<p><code>journalctl --follow --no-tail</code> is used when you want all previous lines (better than -n 100000 or arbitrary big line count)</p>
<h2 id="restrict-the-output-to-latest-run">Restrict the output to latest run:</h2>
<p><a target="_blank" rel="noopener" href="https://serverfault.com/questions/768901/is-there-a-way-to-make-journalctl-show-logs-from-the-last-time-foo-service-ran">TL;DR</a>: Use the one liner:</p>
<ul>
<li>System level: <figure class="highlight sh"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">journalctl _SYSTEMD_INVOCATION_ID=`systemctl show -p InvocationID --value service_name.service`</span><br></pre></td></tr></table></figure></li>
<li>User level: <figure class="highlight sh"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">journalctl _SYSTEMD_INVOCATION_ID=`systemctl show -p InvocationID --value service_name.service --user`</span><br></pre></td></tr></table></figure></li>
</ul>
<h1 id="pythonconda-in-systemd-service">Python(conda) in systemd service</h1>
<p>Create a systemd Service File: Create a .service file (e.g., my_server.service) in a location of your choice (usually <code>/etc/systemd/system/</code> for system-level services or <code>~/.config/systemd/user/</code> for user-level services). Open the file for editing.</p>
<p>Define the Service:</p>
<ol type="1">
<li>Add the following content to your .service file: <figure class="highlight toml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="section">[Unit]</span></span><br><span class="line"><span class="attr">Description</span>=My Python Server</span><br><span class="line"></span><br><span class="line"><span class="section">[Service]</span></span><br><span class="line"><span class="attr">Type</span>=simple</span><br><span class="line"><span class="attr">ExecStart</span>=/path/to/conda/envs/env_name/bin/python python_file.py</span><br><span class="line"><span class="attr">WorkingDirectory</span>=/path/to/working/directory</span><br><span class="line"></span><br><span class="line"><span class="section">[Install]</span></span><br><span class="line"><span class="attr">WantedBy</span>=default.target</span><br></pre></td></tr></table></figure></li>
<li>Replace <code>/path/to/conda/envs/env_name</code> with the actual path to your Conda environment. Adjust the WorkingDirectory to the directory where your startup.py resides.</li>
</ol>
<p>Enable and Start the Service:</p>
<ul>
<li><p>If you’re running this as a user-level service, use: <figure class="highlight sh"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">systemctl --user <span class="built_in">enable</span> my_server.service</span><br><span class="line">systemctl --user start my_server.service</span><br></pre></td></tr></table></figure></p></li>
<li><p>For system-level services, use: <figure class="highlight sh"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">sudo systemctl <span class="built_in">enable</span> my_server.service</span><br><span class="line">sudo systemctl start my_server.service</span><br></pre></td></tr></table></figure></p></li>
</ul>
<h2 id="activate-a-conda-env-in-systemd-service">Activate a conda env in systemd service</h2>
<p>https://github.com/mmaz/systemd-conda</p>
<h1 id="shell-script">Shell script</h1>
<p>Accessing Individual Arguments: To access specific arguments, use the following variables:</p>
<ul>
<li><code>$0</code>: The script name itself.</li>
<li><code>$1</code>, <code>$2</code>, <code>$3</code>, …: The first, second, third, and subsequent arguments.</li>
<li><code>$#</code>: The total number of arguments.</li>
<li><code>$@</code>: All arguments as a list.</li>
<li><code>$$</code>: The process ID of the script.</li>
<li><code>$?</code>: The exit code of the last executed command.</li>
</ul>
<p>Example Script: <figure class="highlight sh"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#!/bin/sh</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"Script Name: <span class="variable">$0</span>"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"First Parameter: <span class="variable">$1</span>"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"Second Parameter: <span class="variable">$2</span>"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"All Arguments: <span class="variable">$@</span>"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"Total Number of Parameters: <span class="variable">$#</span>"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"Process ID: $$"</span></span><br><span class="line"><span class="built_in">echo</span> <span class="string">"Exit Code: $?"</span></span><br></pre></td></tr></table></figure></p>
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<h1 id="appdata目录详解"><code>%AppData%</code>目录详解</h1>
<p><code>%UserProfile%\AppData</code><a target="_blank" rel="noopener" href="https://www.howtogeek.com/278562/what-is-the-programdata-folder-in-windows/">通常存放用户相关的数据</a>，其下包含3个文件夹</p>
<ol type="1">
<li><code>Roaming</code>，由环境变量<code>%AppData%</code>表示其路径。是许多软件存放（通常与用户相关的）数据的路径。如名中<code>Roaming</code>所暗示的一样，该文件夹内的内容可通过网络同步到不同电脑，前提是在同一域中登入同一账户。<a target="_blank" rel="noopener" href="https://web.archive.org/web/20120621131135/http://technet.microsoft.com:80/en-us/library/cc766489(v=ws.10).aspx">该特性在<code>Windows Vista</code>中被详细介绍。</a></li>
<li><code>Local</code>，由环境变量<code>%LocalAppData%</code>表示其路径。与<code>Roaming</code>文件夹相似，但不会进行同步。</li>
<li><code>LocalLow</code>，此文件夹通常较为少用，与<code>Local</code>文件夹相似，但<a target="_blank" rel="noopener" href="https://superuser.com/questions/21458/why-are-there-directories-called-local-locallow-and-roaming-under-users-user">具备更低的集成度</a>。</li>
</ol>
<h2 id="常见的软件安装位置">常见的软件安装位置</h2>
<p><code>%LocalAppData%\Programs</code>是用来存放单用户安装程序的目录。<code>%LocalAppData%\Programs</code>与<code>%LocalAppData%\ProgramData</code>两者不会出现在<code>%AppData%</code>中。</p>
<p>例如vs code的安装路径就在<code>%LocalAppData%\Programs</code>。Vs code官网对单用户安装与系统级别的安装也进行了<a target="_blank" rel="noopener" href="https://code.visualstudio.com/docs/setup/windows">说明</a>。</p>
<blockquote>
<p>By default, VS Code is installed under <br> <code>C:\Users\{Username}\AppData\Local\Programs\Microsoft VS Code</code>.</p>
</blockquote>
<p>事实上，许多软件会滥用<code>%AppData%</code>目录。例如百度云安装的目录就在<code>%AppData%</code>中，但一般而言，该目录应当存放软件使用过程中产生的数据，而不是软件本身。</p>
<p>目前，Windows 10下软件安装的位置仍然很多样，但比较常见的安装位置通常分布在<code>%ProgramFile%</code>, <code>%ProgramFiles%\WindowsApps</code>以及<code>%LocalAppData%\Programs</code>下。安装在前两者的应用通常是系统层级的，而后者多为用户独有应用，其中<code>WindowsApps</code>通常为微软商店下载的应用位置，<a target="_blank" rel="noopener" href="https://blog.csdn.net/WPwalter/article/details/79394709?spm=1001.2014.3001.5506">即便具备管理员权限也通常不能访问</a>。</p>
<h2 id="常见的软件数据存放位置">常见的软件数据存放位置</h2>
<p>如前所述，<code>%AppData%</code>与<code>%LocalAppData%</code>中通常存放用户相关的软件数据。在两者下，常见的文件夹有Microsoft与Google等。例如微软Edge浏览器的用户数据通常存放在<code>%LocalAppData%\Microsoft\Edge</code>中。此外，由微软发布的非应用级的软件也有可能存放在Microsoft文件夹下。例如，vs code中的<code>C/C++</code>拓展的缓存目录就存放于此。</p>
<h1 id="userprofile目录"><code>%UserProfile%</code>目录</h1>
<p>该目录通常被称作用户家目录，其路径通常为<code>C:\Users\<username></code>。该目录通常存放一些应用的配置文件相关信息，其大部分配置文件采用类Unix的命名方式，以<code>.</code>作为前缀，尽管Windows并未对该类文件夹或文件赋予默认隐藏属性。一些非常常见的文件夹或文件包括：</p>
<ul>
<li><code>.m2</code>用于存放Maven仓库</li>
<li><code>.p2</code>存放Eclipse插件(Bundle)</li>
<li><code>.ssh</code>存放<code>ssh</code>配置文件相关</li>
<li><code>.vscode</code></li>
<li><code>.android</code></li>
<li>...</li>
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<a href="/2023/10/10/probability_suggestion/" class="post-title-link" itemprop="url">Independence and Suggestion</a>
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<h1 id="independence">Independence</h1>
<p>Page 73, Problem 1.43.</p>
<p>The events <span class="math inline">\(A\)</span> and <span class="math inline">\(B^c\)</span> are independent if <span class="math inline">\(A\)</span> and <span class="math inline">\(B\)</span> are independent. <span class="math display">\[\begin{aligned}
P(B)P(A) + P(A\cap B^c) = P(A) = P(B)P(A) + P(B^c)P(A)
\end{aligned} \]</span> The first equality holds because <span class="math display">\[\begin{aligned} P(A\cap B) + P(A\cap B^c) = P(A) = P(B)P(A) + P(A\cap B^c) \end{aligned}\]</span></p>
<h2 id="transitivity-of-independence-on-sets-complement">Transitivity of Independence on set's complement</h2>
<p>The events <span class="math inline">\(A^c\)</span> and <span class="math inline">\(B^c\)</span> are independent if <span class="math inline">\(A\)</span> and <span class="math inline">\(B\)</span> are independent. Apply the previous result on <span class="math inline">\(A\)</span> and <span class="math inline">\(B\)</span>, then on <span class="math inline">\(B^c\)</span> and <span class="math inline">\(A\)</span>.</p>
<h1 id="suggestion">Suggestion</h1>
<p>Page 69, Problem 1.29.</p>
<p>Let <span class="math inline">\(A\)</span> and <span class="math inline">\(B\)</span> be events with <span class="math inline">\(P(A) > 0\)</span> and <span class="math inline">\(P(B) > 0\)</span>. We say that an event <span class="math inline">\(B\)</span> suggests an event <span class="math inline">\(A\)</span> if <span class="math inline">\(P(A|B) > P(A)\)</span>, and does not suggest event <span class="math inline">\(A\)</span> if <span class="math inline">\(P(A|B) < P(B)\)</span>.</p>
<h2 id="suggestion-is-mutual">Suggestion is mutual</h2>
<p><span class="math display">\[\begin{aligned}
P(A|B) > P(A) \iff P(B|A)> P(B)
\end{aligned} \]</span></p>
<p><span class="math display">\[\begin{aligned}
P(A|B) &> P(A)\\
P(A\cap B)&>P(A)P(B)
\end{aligned}\]</span> Notice the symmetry in the above equivalent formula.</p>
<h2 id="suggestion-is-complementary">Suggestion is complementary</h2>
<p><span class="math display">\[\begin{aligned}
P(A|B) > P(A) \iff P(A|B^c) < P(A)
\label{eq:complement}
\end{aligned}\]</span></p>
<p><span class="math display">\[\begin{aligned}
P(B)P(A) + P(B^c)P(A) = P(A)= P(B)P(A | B) + P(B^c)P(A | B^c)
\end{aligned}\]</span> If <span class="math inline">\(P(A|B) > P(A)\)</span>, to make the above equality holds, <span class="math inline">\(P(A)\)</span> must be less than <span class="math inline">\(P(A|B^c)\)</span>.</p>
<p>Notice <a href="#eq:complement" data-reference-type="ref" data-reference="eq:complement">[eq:complement]</a> could be rewritten as <span class="math display">\[\begin{aligned}
P(A|B) > P(A) > P(A|B^c),
\end{aligned}\]</span> if <span class="math inline">\(A,B\)</span> suggest each other. Thus, the following argument is always true <span class="math display">\[\begin{aligned}
P(A|B) > P(A|B^c) \iff P(A|B) > P(A)
\end{aligned}\]</span></p>
<p>Suggestion is not only complement on the condition, but also on the conditional event, i.e., <span class="math display">\[\begin{aligned}
P(A|B) > P(A) \iff P(A^c|B) < P(A^c)
\end{aligned}\]</span></p>
<p><span class="math display">\[\begin{aligned}
P(A|B) + P(A^c|B) = 1= P(A) + P(A^c)
\end{aligned}\]</span></p>
<p>Double complement suggestion have the same result as the original. In other words, <span class="math display">\[\begin{aligned}
P(A|B) > P(A) \iff P(A^c|B^c) > P(A^c)
\end{aligned}\]</span> This equivalence is trivial by the above arguments.</p>
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