Regular Expression
Regular Expressions
-
POSIX Basic Regular Expression
- grep
-
POSIX Extended Regular Expression
- egrep
- awk
- emacs
GNU Extensions
Shorthand Classes
| shorthand | equivalence |
|---|---|
\w |
[[:alnum:]_] |
\W |
[^[:alnum:]_] |
\s |
[[:space:]] |
\S |
[^[:space:]] |
Word Boundaries
| shorthand | matches |
|---|---|
\b |
position at a word boundary |
\B |
position not at a word boundary |
\< |
position at the start of a word |
\> |
position at the end of a word |
\` (backtick) |
position at the start of subject string |
\' (single quote) |
position at the end of subject string |
Perl Compatiable Regular Expression (PCRE)
grep multiline match
-P: 使用 Perl 正则表达式扩展-z: 让 grep 把输入的行看成是一个多个行的集合，一个整体.*?: 后面的?表示.*按 non-greedy 模式匹配，也就是尽可能少(短)的匹配(?s): 让.匹配任意字符，包括\n(aka. PCRE_DOTALL)