Interpretation and application of special characters in Linux

<p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/887/227/171041148555324.jpg" class="lazy" alt="Interpretation and application of special characters in Linux"></p> <p>Interpretation and Application of Special Characters in Linux</p> <p>In the Linux system, special characters are a very important part. They are used in command line operations and script writing. It plays a vital role. Special characters are usually used to control command behavior, file operations, pipe connections, etc. Understanding the meaning and usage of these special characters can improve your work efficiency and scripting abilities. This article will introduce some common special characters and their usage, and give specific code examples. </p> <ol><li>Wildcard character<br>Wildcard character is a special character used to match multiple characters. Commonly used wildcard characters are <code>*</code>, <code>?</code>, <code>[] </code>wait. </li></ol> <ul> <li> <code>*</code>: matches zero or more arbitrary characters; </li> <li> <code>?</code>: matches a single arbitrary character; </li> <li> <code>[]</code>: Matches characters within the specified range. </li> </ul> <p>Example: </p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'># 查找以test开头的文件 ls test* # 查找包含"file"的文件 ls *file* # 删除test开头的所有文件 rm test*</pre><div class="contentsignin">Copy after login</div></div><ol start="2"><li>Redirection symbol<br>Redirection symbol is used to redirect the output of a command to a specified location. Common redirection symbols are <code>></code>, <code>>></code> and <code><</code>. </li></ol><ul><li><code>></code>: Redirect the output of the command to a file, which will overwrite the original content of the file; </li><li><code>>> </code>: Append the output of the command to the end of the file; </li><li><code><</code>: Read input from the file. </li></ul><p>Example: </p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'># 将ls命令的输出重定向到文件list.txt ls > list.txt # 将echo命令的输出追加到文件message.txt echo "Hello, World!" >> message.txt # 从input.txt文件中读取输入 cat < input.txt</pre><div class="contentsignin">Copy after login</div></div><ol start="3"><li>Pipe symbol<br>Pipe symbol<code>|</code> is used to connect two commands, taking the output of the first command as Input for the second command. Through the pipe symbol, multiple commands can be connected in series to achieve complex operations. </li></ol><p>Example: </p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'># 统计当前目录下文件数量 ls | wc -l # 查找包含"error"的日志文件，并输出到error.log grep "error" *.log | tee error.log</pre><div class="contentsignin">Copy after login</div></div><ol start="4"><li>Escape symbol<br>The escape symbol `` is used to cancel the special meaning of special characters and turn special characters into ordinary characters. If you need to use a special character itself in a command, you can escape it with an escape symbol. </li></ol><p>Example: </p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'># 创建名为`file*`的文件 touch file* # 查找含有*字符的文件 ls *</pre><div class="contentsignin">Copy after login</div></div><ol start="5"><li>Special variables<br>In Linux shell scripts, there are also some special variables used to obtain special information, such as <code>$? </code> is used to get the exit status of the previous command, <code>$$</code> is used to get the PID of the current process, etc. </li></ol><p>Example: </p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'># 打印上一个命令的退出状态 echo $? # 打印当前进程的PID echo $$</pre><div class="contentsignin">Copy after login</div></div><p>Summary: Mastering the meaning and usage of special characters in Linux is of great significance for improving work efficiency and writing scripts. Through the introduction and examples of this article, I believe readers can better understand and use special characters and unleash the powerful functions of the Linux system. </p>

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