CMD List [7]

1          Regular Expressions 正则表达式

 

(1)      Pattern could be wildcard or regular expression; most of them are the same usage; but some are different.

(2)      Wildcard can be used in sed, awk, grep, egrep etc.; regular expression can be used in sed, awk, grep -E, egrep etc.

(3)      grep -E, egrep and awk use extend regular expressions, perl even more extended.

 

Option or argument	Function
(x)	Regular expression for grouping.
^	(1) 对行首 e.g. ^the对以the开头行 ^d..x..x..x 对用户、用户组及其他用户组成员有可执行权限的目录
$	对行尾 e.g. ^USER$ 对只包含USER的行 [tty]$ 对表示以 t 或者 y 结尾的行 [^$] 对空行
[xy]  [a-c]	Any single character in the set specified. e.g [Ss]igna[lL]对匹配单词signal、signaL、Signal、SignaL [Ss]igna[lL]\. 对同上，但加一句点 [mayMAY] 对包含mayMAY中任一字母的行 [iI] [nN] 对大写或小写i或n [Dd]evice 对单词device或Device
[^xy]  [^a-c]	Any single character NOT in the set specified. e.g. [^0-9\$] 对非数字或美元标识
.	Any single character. e.g. ^......$ 对包括6个字符的行
x*  [a-c]*	Zero or more occurrences of character x. e.g. [a-z][a-z]* 对至少一个小写字母
x+  expr+	One or more occurrences of character x or regular expression.
x?  expr?	Zero or one occurrences of character x or regular expression.
x|y	Either x or y.
\x	(1) Force to read as letter, not as meaning it has. e.g. \^q对以^q开始行 ^\.[0-9][0-9] 对以一个句点和两个数字开始的行   (2) e.g. [0-9]\{2\}-[0-9]\{2\}-[0-9]\{4\} 对日期格式dd-mm-yyyy
(order)	The operators order is [, ], *, ?, +, concatenation, |

 

Symbol	ed	ex	vi	sed	awk	grep	egrep	Action
.	Y	Y	Y	Y	Y	Y	Y	Match any character.
*	Y	Y	Y	Y	Y	Y	Y	Match zero or more preceding.
^	Y	Y	Y	Y	Y	Y	Y	Match beginning of line.
$	Y	Y	Y	Y	Y	Y	Y	Match end of line.
\	Y	Y	Y	Y	Y	Y	Y	Escape character following.
[ ]	Y	Y	Y	Y	Y	Y	Y	Match one from a set.
\(\)	Y	Y		Y				Store pattern for later replay.
\{\}	Y			Y		Y		Match a range of instances.
\<\>	Y	Y	Y					Match word's beginning or end.
+					Y		Y	Match one or more preceding.
?					Y		Y	Match zero or one preceding.
|					Y		Y	Separate choices to match.
()					Y		Y	Group expressions to match.