Linux-grep的使用

Linux-grep的使用

马草原 728 2020-08-13

grep的使用

最近经常需要到Linux上查日志，于是重新学习了一下grep命令，下面做个笔记。
grep是Linux上非常常见的文本搜索工具，如果一个人说他不会用grep，那么他肯定不会Linux。

1. grep-输出匹配的行

案例

cd /usr/share/centos-release
cat EULA
CentOS 7 Linux EULA

CentOS 7 Linux comes with no guarantees or warranties of any sorts, 
either written or implied.

The Distribution is released as GPLv2. Individual packages in the
distribution come with their own licences. A copy of the GPLv2 license
is included with the distribution media.

常见用法如下：

1. 不区分大小写，逐字符匹配。
[root@localhost centos-release]# grep -i linux EULA 
CentOS 7 Linux EULA
CentOS 7 Linux comes with no guarantees or warranties of any sorts,
2. 匹配内容添加行数。
[root@localhost centos-release]# grep -n -i linux EULA 
1:CentOS 7 Linux EULA
3:CentOS 7 Linux comes with no guarantees or warranties of any sorts,
3. 打印匹配内容的前几行，后几行或者前后几行。
  • A After，后几行
  • B before 前几行
  • C context 上下几行
[root@localhost centos-release]# grep -A 2 'Dis' EULA 
The Distribution is released as GPLv2. Individual packages in the
distribution come with their own licences. A copy of the GPLv2 license
is included with the distribution media.
[root@localhost centos-release]# grep -B 2 'Dis' EULA 
either written or implied.

The Distribution is released as GPLv2. Individual packages in the
[root@localhost centos-release]# grep -C 2 'Dis' EULA 
either written or implied.

The Distribution is released as GPLv2. Individual packages in the
distribution come with their own licences. A copy of the GPLv2 license
is included with the distribution media.
4. 使用正则匹配。这个时候可以使用egrep命令
4.1 仅仅匹配以The开头的行
[root@localhost centos-release]# egrep '^The' EULA 
The Distribution is released as GPLv2. Individual packages in the
4.2 精确匹配某个单词。使用-w或者egrep
[root@localhost centos-release]# egrep '\bcome\b' EULA 
distribution come with their own licences. A copy of the GPLv2 license

[root@localhost centos-release]# egrep '\bcomes\b' EULA 
CentOS 7 Linux comes with no guarantees or warranties of any sorts,

[root@localhost centos-release]# grep -w come EULA 
distribution come with their own licences. A copy of the GPLv2 license
4.3 模糊匹配一些字符。.代表任意字符，包括空格。
[root@localhost centos-release]# egrep 'Dis...' EULA 
The Distribution is released as GPLv2. Individual packages in the
4.4 []查询，查询In或on
[root@localhost centos-release]# egrep '[Io]n' EULA 
The Distribution is released as GPLv2. Individual packages in the
distribution come with their own licences. A copy of the GPLv2 license
is included with the distribution media.
5. 重复次数查询，或者量词查询。

正则表达式可能重复几次撇皮
? 前面的字符是可选的和只匹配一次

  • 前面的字符可以匹配0此或者更多次
  • 前面的字符至少匹配一次，可以匹配更多次
    {n} 前面的字符精确匹配 n 此
    {n,}前面的字符匹配n此以上
    {,m}前面的字符至多匹配m次
    ():向后引用，引用：\1, \2, \3
[root@localhost centos-release]# egrep 'e{2}' EULA 
CentOS 7 Linux comes with no guarantees or warranties of any sorts,
6. 或者匹配，匹配条件中任选其一。
[root@localhost centos-release]# egrep '(or|of)' EULA 
CentOS 7 Linux comes with no guarantees or warranties of any sorts, 
either written or implied.
distribution come with their own licences. A copy of the GPLv2 license
7. 递归搜索目录下是否有文件符合自己想要的内容。
cd /usr/local/openresty/nginx/conf/
[root@localhost conf]# grep -n  -r '\$server_protocol' ./ 
./fastcgi.conf:12:fastcgi_param  SERVER_PROTOCOL    $server_protocol;
./fastcgi.conf.default:12:fastcgi_param  SERVER_PROTOCOL    $server_protocol;
./fastcgi_params:11:fastcgi_param  SERVER_PROTOCOL    $server_protocol;
./fastcgi_params.default:11:fastcgi_param  SERVER_PROTOCOL    $server_protocol;
./scgi_params:10:scgi_param  SERVER_PROTOCOL    $server_protocol;
./scgi_params.default:10:scgi_param  SERVER_PROTOCOL    $server_protocol;
./uwsgi_params:10:uwsgi_param  SERVER_PROTOCOL    $server_protocol;
./uwsgi_params.default:10:uwsgi_param  SERVER_PROTOCOL    $server_protocol;

以上就是在使用Linux过程中，常用到的grep命令Demo。

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