Linux Shell Example (ii)

First, regular expression
A, the basic regular expression

Meta character	Description
.	Match any single character
*	Match any of its preceding characters any time
.*	Any character of any length
[]	Matches any single character within the specified range
[^]	Matches any single character outside the specified range
[: Lower:]	lowercase letters
[: Upper:]	Capital
[: Alpha:]	All letters
[:d Igit:]	Digital
[: Alnum:]	All numbers and letters
[:p UNCT:]	Punctuation
[: Space:]	White space characters
\?	Match its preceding character 1 or 0 times
{M,n}	Matches the preceding character at least m times, up to N times
^	Riveting the beginning of the line, any content after this character must appear at the beginning of the line
$	Rivet line end, any content in front of this character must appear at the end of the row
^$	Represents a blank line
\< or \b	The first of the riveting word, any character after it must appear as the header of the word
\> or \b	A riveting ending, any character in front of which must appear as the tail of a word
()	Group
(AB) *	AB as a whole, can appear any time
(AB). *\1	Refers to the first opening parenthesis and all the contents of the corresponding closing parenthesis
(AB). *\2	Refers to the second opening parenthesis and all the contents of the corresponding closing parenthesis

B. Extend the entire expression

.	match any single character
[]	Matches any single character within the specified range
[^]	Matches any single character outside the specified range
*	Match its preceding characters any time
?	Match its first character 0 or 1 times
+	Match its preceding character at least 1 times, similar to the basic regular expression {1,}
{M,n}	Matches the preceding character at least m times, up to N times
^	Header
$	End of Line
\< or \b	Word Head
\> or \b	Ending

C, examples
CP one copy of/etc/passwd file to/tmp

Linux Shell Example (ii)