博客
关于我
Linux利用grep配合正则表达式显示非空注释行内容
阅读量:390 次
发布时间:2019-03-05

本文共 3106 字,大约阅读时间需要 10 分钟。

  • 显示 /etc/inittab 文件中以 ‘#’ 号后跟着一个或多个空白字符开头并且之后是任意个非空白字符的行
  • 查看/etc/inittab的内容
[04:16:42 rooter@C8-3-55 ~]#cat /etc/inittab# inittab is no longer used.## ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.## Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target## systemd uses 'targets' instead of runlevels. By default, there are two main targets:## multi-user.target: analogous to runlevel 3# graphical.target: analogous to runlevel 5## To view current default target, run:# systemctl get-default## To set a default target, run:# systemctl set-default TARGET.target
  • 显示#开头的注释行
[04:17:54 rooter@C8-3-55 ~]#cat /etc/inittab | grep ^## inittab is no longer used.## ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.## Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target## systemd uses 'targets' instead of runlevels. By default, there are two main targets:## multi-user.target: analogous to runlevel 3# graphical.target: analogous to runlevel 5## To view current default target, run:# systemctl get-default## To set a default target, run:# systemctl set-default TARGET.target
  • 敲错了啥都不显示
    没有加-E不支持正则表达式
[04:19:33 rooter@C8-3-55 ~]#cat /etc/inittab | grep ^#[[:blank:]]+[04:20:28 rooter@C8-3-55 ~]#cat /etc/inittab | grep '^#[[:blank:]]+'
  • 显示#开头,其后是一个或多个空格的行
[04:20:38 rooter@C8-3-55 ~]#cat /etc/inittab | grep -E '^#[[:blank:]]+'# inittab is no longer used.# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target# systemd uses 'targets' instead of runlevels. By default, there are two main targets:# multi-user.target: analogous to runlevel 3# graphical.target: analogous to runlevel 5# To view current default target, run:# systemctl get-default# To set a default target, run:# systemctl set-default TARGET.target
  • 显示#开头之后是1个或多个空格,之后是非空格的行
[04:21:06 rooter@C8-3-55 ~]#cat /etc/inittab | grep -E '^#[[:blank:]]+[^[:blank:]]+'# inittab is no longer used.# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target# systemd uses 'targets' instead of runlevels. By default, there are two main targets:# multi-user.target: analogous to runlevel 3# graphical.target: analogous to runlevel 5# To view current default target, run:# systemctl get-default# To set a default target, run:# systemctl set-default TARGET.target
  • 显示#开头,之后是一个或多个空格,然后是非空格及任意字符的行
[04:21:56 rooter@C8-3-55 ~]#cat /etc/inittab | grep -E '^#[[:blank:]]+[^[:blank:]]+.*'# inittab is no longer used.# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target# systemd uses 'targets' instead of runlevels. By default, there are two main targets:# multi-user.target: analogous to runlevel 3# graphical.target: analogous to runlevel 5# To view current default target, run:# systemctl get-default# To set a default target, run:# systemctl set-default TARGET.target

问题:

  • #号开头之后紧跟着1个以上空格的及任意字符的行,为啥把#后跟空行也过滤掉了?
    空行被过滤掉了

回答:

  • 看起来像#空行,但人家直接#$就结束了!
  • 所以用一个以上blank就把看起来像空行的过滤掉了
    假空行

转载地址:http://eqkzz.baihongyu.com/

你可能感兴趣的文章
Mysql 知识回顾总结-索引
查看>>
Mysql 笔记
查看>>
MySQL 精选 60 道面试题(含答案)
查看>>
mysql 索引
查看>>
MySQL 索引失效的 15 种场景!
查看>>
MySQL 索引深入解析及优化策略
查看>>
MySQL 索引的面试题总结
查看>>
mysql 索引类型以及创建
查看>>
MySQL 索引连环问题,你能答对几个?
查看>>
Mysql 索引问题集锦
查看>>
Mysql 纵表转换为横表
查看>>
mysql 编译安装 window篇
查看>>
mysql 网络目录_联机目录数据库
查看>>
MySQL 聚簇索引&&二级索引&&辅助索引
查看>>
Mysql 脏页 脏读 脏数据
查看>>
mysql 自增id和UUID做主键性能分析,及最优方案
查看>>
Mysql 自定义函数
查看>>
mysql 行转列 列转行
查看>>
Mysql 表分区
查看>>
mysql 表的操作
查看>>