Loading... <p style="text-align:justify"> <strong><span style="font-family:宋体;color:#FF0000;font-size:16px">何谓正则表达式</span></strong> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-indent:28px;text-align:justify"> <span style="font-family:'Microsoft YaHei'">正则表达式,又称正规表示法、常规表示法(Regular Expression,在代码中常简写为regex、regexp或RE),是一类字符所书写的模式,其中许多字符不表示其字面意义,而是表达控制或通配等功能。正则表达式使用单个字符串来描述、匹配一系列符合某个句法规则的字符串。在很多文本编辑器里,正则表达式通常被用来检索、替换那些符合某个模式的文本。许多程序设计语言都支持利用正则表达式进行字符串操作。</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-indent:28px;text-align:justify"> <span style="font-family:'Microsoft YaHei'">正则表达式语言由两种基本字符类型组成:原义(正常)文本字符和元字符。元字符使正则表达式具有处理能力。所谓元字符就是指那些在正则表达式中具有特殊意义的专用字符,不表示其字面意义,而用于额外功能性描述。</span> </p> <p style="text-align:justify"> <span style="color:#FF0000;font-size:16px"><strong><span style="font-family:宋体;font-size:16px">正则表达式分类</span></strong></span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-indent:28px;text-align:justify"> <span style="font-family:'Microsoft YaHei'">正则表达式根据元字符的数量及功能不同又分为基本正则表达式(grep)和拓展正则表达式(egrep)。而grep和egrep同属于文本搜索工具,可根据用户指定的文本模式(搜索条件)对目标文件进行逐行搜索,显示能匹配到的行。用法上grep –E等同于egrep,与grep和egrep相似的文本搜索工具还有fgrep,因不支持使用正则表达式,所以不再单独介绍。</span> </p> <p style="text-align:justify"> <strong><span style="font-family:宋体;color:#FF0000;font-size:16px">基本正则表达式(grep)</span></strong> </p> <p style="text-align:justify"> <span style="font-family:'Microsoft YaHei';font-size:14px">语法格式:grep[option]… ‘PATTERN’ FILE…</span> </p> <p style="text-align:justify"> <span style="font-family:'Microsoft YaHei';font-size:14px">基本正则表达式元字符:</span> </p> <p style="text-align:justify"> <strong><span style="font-family:宋体;font-size:14px">1.字符匹配:</span></strong> </p> <pre class="prettyprint lang-bsh"> .:任意单个字符 [ ]:匹配指定范围内的任意单个字符 [0-9]:匹配单个数字 [a-z]:匹配单个小写字母 [A-Z]:匹配单个大写字母 [[:digit:]]:匹配单个数字 [[:lower:]]:匹配单个小写字母 [[:upper:]]:匹配单个大写字母 [[:space:]]:匹配单个空白字符 [[:punct:]]:匹配单个标点符号 [[:alnum:]]:匹配单个字母或数字 [[:alpha:]]:匹配单个字母(不分大小写) [^]:匹配范围外的任意单个字符</pre> <p> <strong><span style="font-family:宋体;font-size:14px">2.次数匹配</span></strong><span style="line-height:1.5;font-family:宋体;font-size:14px">:</span> </p> <p> <span style="font-family:宋体"> </span> </p> <pre class="prettyprint lang-bsh">*:任意次(前面字符出现任意次) \?:0次或1次(前面字符可有可无) \{m\}: m次(前面字符出现m次) \{m,n\}:至少m次,至多n次 \{m,\}:至少m次 \{0,n\}:至多n次 .*:任意长度的任意字符</pre> <p> <strong><span style="font-family:宋体;font-size:14px">3.位置锚定:</span></strong> </p> <pre class="prettyprint lang-bsh">^:行首锚定(写在模式最左侧) $:行尾锚定(写在模式最右侧) ^$:空白行 \<,/b:词首锚定(出现于单词左侧) \>,/b:词尾锚定(出现于单词右侧) (注:不包含特殊字符的连续字符组成的串叫单词)</pre> <p> <strong><span style="font-family:宋体;font-size:14px">4.分组</span></strong> </p> <pre class="prettyprint lang-bsh"> \( \):如\(ab\)* (分组中的模式匹配到的内容,可由正则表达式引擎记忆在内存中,之后可被引用)</pre> <p> <strong><span style="font-family:宋体;font-size:14px">5.引用</span></strong> </p> <pre class="prettyprint lang-bsh">\n:引用前面的第n个左括号以及与之对应的右括号中的模式所匹配到的内容</pre> <p> <strong><span style="font-size:16px;background-color:#FFFFFF;color:#E53333">拓展正则表达式(egrep)</span></strong> </p> <p> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="font-family:宋体"><span style="color:#FF0000"><strong></strong></span><span style="color:#000000;font-family:'Microsoft YaHei'">语法格式:</span></span><span style="font-family:'Microsoft YaHei'">egrep [option] ‘PATTERN’ FILE…</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="font-family:'Microsoft YaHei'">拓展正则表达式元字符:</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span><span style="font-family:宋体, SimSun"><strong>1.字符匹配</strong>:</span></span> </p> <pre class="prettyprint lang-bsh"> .:任意单个字符 [ ]:匹配范围内的任意单个字符 [^]:匹配范围外的任意单个字符</pre> <p> <strong><span style="color:#000000;font-size:14px"><span style="font-family:宋体, SimSun;font-size:14px">2.次数匹配:</span></span></strong> </p> <pre class="prettyprint lang-bsh">*:任意次 ?: 0或1次 +:至少1次 {m}: m次 {m,n}:至少m次,至多n次 {m,}:至少m次 {0,n}:至多n次</pre> <p> <strong><span style="font-size:14px">3.位置锚定:</span></strong> </p> <pre class="prettyprint lang-bsh">^:行首锚定 $:行尾锚定 \<,\b:词首锚定 \>,\b:词尾锚定 ^$,^[[:space:]]*$:空白行</pre> <p> <span style="color:#2C2C2C;font-size:14px;line-height:1.5;font-family:宋体, SimSun"><strong>4.分组</strong></span><strong>:</strong> </p> <pre class="prettyprint lang-bsh">( ):分组 |:或 </pre> <p> <strong><span style="font-family:宋体, SimSun;color:#000000">5.引用:</span></strong> </p> <pre class="prettyprint lang-bsh">\n:引用前面的第n个左括号以及与之对应的右括号中的模式所匹配到的内容</pre> <p> <strong><span style="color:#E53333;font-size:16px"><span style="font-family:宋体, SimSun;font-size:16px;color:#E53333">grep及egrep命令选项</span></span></strong> </p> <p style="text-align:justify"> </p> <pre class="prettyprint lang-bsh">-v: 反向选取 -o:仅显示匹配的字串,而非字串所在的行 -i:ignore-case,忽略字符大小写 -A:显示之前两行 -B:显示之后两行 -C:显示上下两行</pre> <p> <strong><span style="color:#FF0000;font-size:16px">牛刀小试</span></strong> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="font-size:12px;font-family:宋体;line-height:13.1875px"> </span><span style="line-height:1.5;color:#00B0F0;font-family:'Microsoft YaHei'">显示/proc/meminfo文件中以大写或小写S开头的行</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-17.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5"> 显示/etc/passwd文件中其默认shell为非/sbin/nologin的用户</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-43.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">显示/etc/passwd文件中其默认shell为/bin/bash的用户中ID号最大的用户</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-5.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">找出/etc/passwd文件中的一位数或两位数</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-92.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">显示/boot/grub/grub.conf中以至少一个空白字符开头的行</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-61.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">显示/etc/rc.d/rc.sysinit文件中,以#开头,后面跟至少一个空白字符,而后又有至少一个非空白字符的行</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:13.1875px"> </span><img src="//cto.wang/usr/uploads/2016/07/20160703163613-43-1.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">找出netstat -tan命令执行结果中以’LISTEN’结尾的行</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-94.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">找出当前系统上其用户名和默认shell相同的用户</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-95.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">显示当前系统上root或scholar用户的默认shell</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <img src="//cto.wang/usr/uploads/2016/07/20160703163613-34.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#337FE5;font-family:'Microsoft YaHei';line-height:1.5">找出/etc/rc.d/init.d/functions文件中某单词后跟一组小括号“()”行</span><span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:13.1875px"> </span><img src="//cto.wang/usr/uploads/2016/07/20160703163613-58.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">使用echo命令输出一个路径,而后使用grep取出其基名</span><span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:13.1875px"> </span><img src="//cto.wang/usr/uploads/2016/07/20160703163613-35.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:1.5">找出ifconfig命令结果中的1-255之间的数字</span><span style="color:#00B0F0;font-family:'Microsoft YaHei';line-height:13.1875px"> </span><img src="//cto.wang/usr/uploads/2016/07/20160703163613-51.jpg" alt="" /> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="font-family:宋体;line-height:13.1875px;color:#00B0F0"><strong><span style="font-size:16px;color:#FF0000">The End</span></strong></span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF;text-align:justify"> <span style="font-family:宋体;line-height:13.1875px;color:#00B0F0"><strong><span style="font-size:16px;color:#FF0000"><br /> </span></strong></span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="font-family:宋体;line-height:13.1875px;color:#00B0F0"> </span><span style="font-family:Microsoft YaHei"> </span><span style="font-family:'Microsoft YaHei'">好了总结到这里,常用的正则表达式用法就整理的差不多了,以上都是个人学习总结,如有错漏,大</span> </p> <p style="color:#2C2C2C;font-family:宋体, 'Arial Narrow', arial, serif;font-size:14px;background-color:#FFFFFF"> <span style="font-family:'Microsoft YaHei'">神勿喷~~~</span></p> 最后修改:2021 年 12 月 10 日 10 : 53 AM © 允许规范转载 赞赏 如果觉得我的文章对你有用,请随意赞赏 赞赏作者 支付宝微信