awk 笔记之二正则表达式

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#正则表达式 #character #graph #class #c

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本文介绍了awk中正则表达式的使用方法，包括/ regexp /匹配整行、exp ~ /regexp/在字段中匹配以及exp !~ /regexp/匹配不到的情况。还详细讲解了转义序列、正则操作符如, ^, $, .等，并阐述了字符列表和字符类，如[:alnum:], [:alpha:], [:digit:]等的功能。最后提到了tolower()和toupper()函数用于字符转换。" 109994521,8175762,钢笔书法签名设计技巧与选择指南,"['艺术设计', '书法', '签名', '钢笔文化']

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1. 正则表达式的使用方法

a) / regexp / 在整行中匹配

b) exp ~ /regexp/ 在exp中匹配如: awk ' $1 ~ /J/' aaa.txt

c) exp !~ /regexp/ 在exp没有匹配到

2. Escape Sequence

\nnn

\xhh

3. 正则表达式操作符

\ , ^, $, ., [...], [^...],|, (...), *, +, ?, {n}, {n,}, {n,m},

4. 字符列表

[a-dx-z]

字符类(Character class)

[:alnum:] Alphanumeric characters.
[:alpha:] Alphabetic characters.
[:blank:] Space and TAB characters.
[:cntrl:] Control characters.
[:digit:] Numeric characters.
[:graph:] Characters that are both printable and visible. (A space is printable but not visible, whereas an ‘a’ is both.)
[:lower:] Lowercase alphabetic characters.
[:print:] Printable characters (characters that are not control characters).
[:punct:] Punctuation characters (characters that are not letters, digits, control characters, or space characters).
[:space:] Space characters (such as space, TAB, and formfeed, to name a few).
[:upper:] Uppercase alphabetic characters.
[:xdigit:] Characters that are hexadecimal digits.

5. tolower() , toupper()