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查询慢排查
查看>>
MySQL查询报错ERROR:No query specified
查看>>
mysql查询数据库储存数据的占用容量大小
查看>>
MySQL查询数据库所有表名及其注释
查看>>
MySQL查询数据表中数据记录(包括多表查询)
查看>>
MySQL查询结果排序
查看>>
MYSQL查询语句优化
查看>>
mysql查询语句能否让一个字段不显示出来_天天写order by,你知道Mysql底层执行原理吗?
查看>>
MySQL查询语句:揭秘专家秘籍,让你秒变数据库达人!
查看>>
mysql查询超时对PHP执行的影响
查看>>
mysql查询输出到excel文件_如何保存mysql查询输出到excel或.txt文件?
查看>>
mysql查询过程
查看>>
MySQL模拟Oracle序列sequence
查看>>
Mysql模糊查询like效率,以及更高效的写法
查看>>
MySQL死锁套路:一次诡异的批量插入死锁问题分析
查看>>
Mysql死锁问题Deadlock found when trying to get lock;try restarting transaction
查看>>
mysql每个数据库的最大连接数_MySQL数据库最大连接数
查看>>
Mysql流程控制结构,if函数、case结构、if结构、循环结构
查看>>
mysql添加外网访问权限
查看>>
mysql添加用户
查看>>