42 lines
1.1 KiB
Markdown
42 lines
1.1 KiB
Markdown
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### 部分概念
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- 元字符：在正则表达式中具有特殊意义的字符，如星号(*)、问号(?)和点(.)
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- 前导字符：位于元字符前边的第一个字符
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### 其他常用元字符
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```
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me@me-EQ59:~/shell_demo$ cat hello_grep.txt
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hello world
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hello hello
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me@me-EQ59:~/shell_demo$ grep '\<hel' hello_grep.txt
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hello world
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hello hello
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me@me-EQ59:~/shell_demo$ grep 'lo\>' hello_grep.txt
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hello world
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hello hello
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me@me-EQ59:~/shell_demo$
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```
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```
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me@me-EQ59:~/shell_demo$ grep '\d' hello_grep.txt
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hello world
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me@me-EQ59:~/shell_demo$ grep -P '\d' hello_grep.txt
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10.1.1.1
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me@me-EQ59:~/shell_demo$ cat hello_grep.txt
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hello world
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hello hello
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10.1.1.1
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me@me-EQ59:~/shell_demo$
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```
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### 扩展正则
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- grep 使用需要加参数 `-E` 或者使用 egrep
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- sed 使用需要加参数 `-r`
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### 第二类正则
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