Learning record for grep tool under CentOS

One, grep tool quick Find table

grep standard regular correlation meta-character representation and its meaning:

form	Description
.	This is an English point number. matches any single character;
[]	Represents any single character in the specified range;
[^]	Represents any single character outside the specified range;
*	Indicates that the preceding entry is matched 0 or more times;
. *	Any character that matches any length;
\?	Indicates that the match precedes the entry at most once, both 0 or 1 times;
\+	Represents 1 or more occurrences of an entry in front of a match;
\{n\}	Indicates that the match precedes the entry n times, more than n times, less than n times is not feasible;
\{n,\}	Indicates that the match precedes the entry n times or more than n times, which is greater than or equal to n times;
\{,m\}	Indicates that the entry in front of the match is at most m times, less than or equal to M; (GNU extension usage )
\{n,m\}	Indicates that the entry in front of the match is at least N times, at most m times, containing N and M and m greater than or equal to N;
a\| B	Represents part A or part B;
\(...\)	Represents a grouping, which can then be used \num to reference the contents of the grouping, NUM represents the number;
^	The caret is the beginning of the anchor line, which can be understood as a match to an empty string (empty string);
$	The dollar symbol indicates the end of the anchor line, which can be understood as a match to an empty string (empty string);
^$	Represents a matching blank line;
\<	Indicates the first anchor of the word word, which can be understood as an empty string matching to the first word (empty string);
\>	Indicates the word ending anchor, which can be understood as an empty string matched to the ending of the word (empty string);
\b	An anchor that represents the boundary of a word, which can be substituted for \< or \>, which can be understood as an empty string matched to the boundary of a word (empty string);
\b	Represents an empty string that matches a word boundary (empty string);
\w	It is generally understood to be synonymous with [_[:alnum:]], which means matching underscores and alphanumeric characters;
\w	It can be understood as synonymous with [^_[:alnum:]], which means a character that matches an underscore, an alphanumeric character;
[: Alnum:]	Represents an alphanumeric character, using the form [[: Alnum:]], if you want to exclude, you can match the caret [^[:alnum:]];
[: Alpha:]	Represents an alphabetic character, using the form [[: Alpha:]], if you want to exclude, you can match the caret [^[:alpha:]];
[: Cntrl:]	Represents the control character, using the form [[: Cntrl:]] After the article has resolved why the control character, not commonly used. If you want to exclude, [^[:cntrl:]];
[:d Igit:]	Represents a numeric character, using the form [[:d igit:]]. If you want to exclude, [^[:d igit:]];
[: Graph:]	Represents printable and visible characters, followed by annotations. Use form, [[: Graph:]], not commonly used. If you want to exclude, [^[:graph:]];
[: Lower:]	Represents a lowercase alphabetic character, using the form [[: Lower:]], if you want to exclude, [^[:lower:]];
[:p rint:]	Represents printable characters, using the form [[:p rint:]], excluding, [^[:p rint:]];
[:p UNCT:]	Represents the punctuation character, using the form [[:p UNCT:]], excluding, [^[:p UNCT:]]; (except for literal characters [can be interpreted as letters], numbers, control characters, characters other than space characters)
[: Space:]	Space character, use form [[: Space:]], there are spaces, page feeds, line feeds, carriage returns, transverse tabs, vertical tabs; exclude [^[:space:]];
[: Upper:]	Denotes an uppercase character, using the form [[: Upper:]], excluding, [^[:upper:]];
[: Xdigit:]	Represents 16 binary numeric characters, using the form [[: Xdigit:]], excluding, [^[:xdigit:]];
[: Blank:]	Represents a space or transverse tab character, using the form [[: Blank:]], excluding, [^[:blank:]];

grep extends the regular related metacharacters representation and its meaning:

Not to be continued ...

Learning record for grep tool under CentOS