Linux Regular expressions

Regular Expressions Reguler expression , REGEXP

Basic REGEXP: base Regular Expression

Extended REGEXP: extending regular Expressions

1.grep [options] mode [files] commands for filtering text using the basic regular expression pattern

-I ignores case

--color plus Color

-V Reverse lookup

-O displays only strings that are matched by the pattern

- e support for extended regular expressions

-A N: shows not only the matches but also the n rows below the line

-B N: Shows not only the matches but also the n rows above the line

-C N: Displays not only matches but also rows above and below the line of n

Pattern rules

. match any single character

[] matches any single character within the specified range

[^] matches any single character outside the specified range

[: Space:]: white space character

[:p Unot:]: punctuation

[: Lower:]: lowercase letters

[: Upper:]: size Letter

[: Alpha:]: uppercase and lowercase letters

[:d igit:]: number

[: Alnum:]: numbers and uppercase and lowercase letters

Two when used [[]]

Number of Matches

*: matches its preceding character any time

\? : matches the preceding character 1 or 0 times

\{m,n\} matches the preceding characters at least m times up to n times

By default in greedy mode, match as many characters as possible

Position lock

^ Rivet Header, must start with its trailing character

$ Rivet Line End

^$ Blank Line

\<: Any character following it must appear as a word header or can be used \b

\>: Any character in front of it must appear as a trailing word or can be used \b

Group

\(\)

\1 referencing the first group

\2 referencing a second group

...

Extending regular Expressions

GREP-E = Egrep to use an extended regular expression

Character Matching:

. usage is the same as the basic regular

[]

[^]

Number of Matches

*:

?:

+: match the characters in front of it at least 1 times

{M,n} The usage is the same as the basic regular, but does not add \

Position Lock: Usage is the same as the basic

^

$

\<

\>

Group:

(): Group

\1 \2 \3 ...

Or

| : OR

Fgrep: Fast Search does not support regular expressions

This article is from the "Mr.zhu-Technology Exchange" blog, please be sure to keep this source http://bjishu.blog.51cto.com/7481301/1699663

Linux Regular expressions