Loading... <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px">学习正则表达式之前,看过这复杂的表达式,犹如天书,无比高大上;怀着战战兢兢的心情,开始了学习之旅:</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><strong><span style="font-size: 14px;font-family: Arial, sans-serif;font-weight: normal">一、 </span><span style="font-size: 14px;font-family: Arial, sans-serif;font-weight: normal"> </span><span style="font-size: 14px;font-family: 宋体;font-weight: normal">正则表达式</span><span style="font-size: 14px;font-family: 宋体;font-weight: normal"></span><span style="font-size: 14px;font-family: 宋体;font-weight: normal">:</span>G<span style="font-size: 14px;font-family: Arial, sans-serif;font-weight: normal">lobal search</span> RE<span style="font-size: 14px;font-family: Arial, sans-serif;font-weight: normal">gular expression and </span>P<span style="font-size: 14px;font-family: Arial, sans-serif;font-weight: normal">rint out the line.</span></strong></p> <hr /> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px">我的理解是:通过一大堆符号组成的公式逐行查找文本中匹配的字符串并显示出来</span> </p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 48px"><strong><span style="font-size:14px">分类</span></strong><span style="font-size:14px">:</span></p> <p><span style="font-size: 14px;font-family: Arial, sans-serif"> <strong><span style="font-family: Arial, sans-serif;font-size: 14px">egrep</span></strong><span style="font-family: Arial, sans-serif;font-size: 14px">:</span></span><span style="font-size: 14px">打开对元字符扩展集的支持,实现与</span><span style="font-size: 14px;font-family: Arial, sans-serif"><span style="font-family: Arial, sans-serif;font-size: 14px"> grep -E</span></span><span style="font-size: 14px">相同的功能。</span><span style="font-family: Arial, sans-serif;font-size: 14px"> </span></p> <p><span style="font-size: 14px;font-family: Arial, sans-serif"> <strong> fgrep</strong></span><span style="font-size: 14px">:与</span><span style="font-size: 14px;font-family: Arial, sans-serif">grep</span><span style="font-size: 14px">相似,占用空间比</span><span style="font-size: 14px;font-family: Arial, sans-serif">egrep</span><span style="font-size: 14px">小,速度比</span><span style="font-size: 14px;font-family: Arial, sans-serif">grep</span><span style="font-size: 14px">快,但不识别正则表达式。</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 48px"><span style="font-size:14px"></span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 48px"><span style="font-size:14px">注意:</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 72px">1、 <span style="font-size:14px">只能查找文本</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 72px">2、 <span style="font-size:14px">逐行查找</span></p> <p style="margin: 5px 0px 5px 72px;text-align: left"><strong>二、 <span style="font-size:14px">语法格式</span></strong></p> <hr /> <p style="margin: 5px 0px 5px 72px;text-align: left">grep [option]… 'PATTERN' FILE..</p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 89px">–color=auto <span style="font-size:14px">语法着色,显示匹配的字符</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 89px"><span style="font-size:14px"></span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 89px"><span style="font-size:14px"></span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size:14px"> 命令选项:</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-v: <span style="font-size:14px">反向选取</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-o: <span style="font-size:14px">仅显示匹配的字串,而非字串所在的行</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-i: ignore-case<span style="font-size:14px">,忽略字符大小写</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-E: <span style="font-size:14px">支持使用扩展正则表达式</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-A # <span style="font-size:14px">显示匹配行以及以下</span>#<span style="font-size:14px">行</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-B # <span style="font-size:14px">显示匹配行以及以上</span>#<span style="font-size:14px">行</span></p> <p style="margin: 5px 0"><span style="font-size:14px"> </span>-C # <span style="font-size:14px">显示匹配行以及上下</span>#<span style="font-size:14px">行</span></p> <p style="margin: 5px 0"><strong>三、 <span style="font-size:14px">元字符</span><span style="font-size: 14px">,</span>metacharacter</strong></p> <hr /> <p style="margin: 5px 0"><span style="font-size: 14px">这类的常用字符有:</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-7.png" title="1427784239799636.png" alt="blob.png" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-67.png" title="1427788980130728.png" alt="blob.png" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-87.png" title="1427784280359011.png" alt="blob.png" /><img src="//cto.wang/usr/uploads/2016/07/20160703180140-53.png" title="1427787005493098.png" alt="blob.png" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px;font-family: 微软雅黑, sans-serif"> 举例说明:</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px;font-family: 微软雅黑, sans-serif"> 1、找出/etc/passwd文件中的一位数或两位数</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px;font-family: 微软雅黑, sans-serif"> <img src="//cto.wang/usr/uploads/2016/07/20160703180140-19.png" title="1427785026118790.png" alt="blob.png" /></span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"> <img src="//cto.wang/usr/uploads/2016/07/20160703180140-99.png" title="1427785693352823.png" alt="blob.png" style="font-family: 微软雅黑, sans-serif;font-size: 14px" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size: 14px;font-family: 微软雅黑, sans-serif">2、列出当前系统上其用户名和默认shell相同的用户</span></p> <p>/etc/passwd 下<span style="font-size:14px">的用户格式:</span></p> <p><img src="//cto.wang/usr/uploads/2016/07/20160703180140-90.png" title="1427789735603449.png" alt="blob.png" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size:14px">如上所示,左右字符都一样的予以显示,因此,可以使用分组以及引用功能。</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><span style="font-size:14px"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-44.png" title="1427789396243446.png" alt="blob.png" style="font-size: 14px" /></span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0">3、<span style="font-size:14px;font-family:宋体">使用</span>echo<span style="font-size:14px;font-family:宋体">命令输出一个路径,而后使用</span>grep<span style="font-size:14px;font-family:宋体">取出其基名</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-98.png" title="1427790929851227.png" alt="blob.png" /></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0">4、<span style="font-size:14px;font-family:宋体">找出</span>ifconfig<span style="font-size:14px;font-family:宋体">命令结果中的</span>1-255<span style="font-size:14px;font-family:宋体">之间的数字</span></p> <p style="margin-top:5px;margin-right:0;margin-bottom:5px;margin-left: 0"><img src="//cto.wang/usr/uploads/2016/07/20160703180140-50.png" title="1427791409723546.png" alt="blob.png" /></p> <p><span style="font-size:14px">以上是一些学习小结,后续学习中还会进一步加深</span> <span style="font-size:14px">。</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