Linux Common command-grep and regular expressions

Regular expression: REGular expression,regexp

Metacharacters

.: Matches any single character

Touch a file

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M01/7F/B4/wKiom1cpn1fzagelAAAHYouJBOw881.png "title=" QQ picture 20160504150537.png "alt=" Wkiom1cpn1fzagelaaahyoujbow881.png "/>

Use grep on the Test.txt file to query ' a ' separately

650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M02/7F/B2/wKioL1cpoJaSJGQSAAAL_Z3uj5Q079.png "title=" QQ picture 20160504150726.png "alt=" Wkiol1cpojasjgqsaaal_z3uj5q079.png "/>

Use '. '

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/7F/B2/wKioL1cppvXjn2VTAAAQwQZpIio148.png "title=" QQ picture 20160504153501.png "alt=" Wkiol1cppvxjn2vtaaaqwqzpiio148.png "/>

End With ' A ', any one of the preceding characters, beginning with ' A ', followed by any character.

[]: matches any single character within the specified range

[^]: matches any single character outside the specified range

650) this.width=650; "src=" Http://s1.51cto.com/wyfs02/M00/7F/B2/wKioL1cpqOWA0KUgAAAfQg2D39E572.png "title=" QQ picture 20160504154312.png "alt=" Wkiol1cpqowa0kugaaafqg2d39e572.png "/>

Character Set:

Pure numerals [[:d igit:]] or [0-9]

lowercase letters [[: Lower:]] or [A-z]

uppercase [[: Upper:]] or [A-z]

Uppercase and lowercase letters [[: Alpha:]] or [a-za-z]

Number plus letter [[: Alnum:]] or [0-9a-za-z]

blank character [[: Space:]]

Non-whitespace characters [^[:space:]]

punctuation [[:p UNCT:]]

Number of matches (greedy mode-to match as many as possible):

*: Matches any of its preceding characters any time

\?: Match its preceding character 1 or 0 times

\{m\}: Matches the preceding character m times (exact match)

\{m,n\}: Matches the preceding character at least m times, up to N times

Location anchoring:

^: Anchor the beginning of the line, any content after this character must appear at the beginning of the line

$: Anchor line end, any content in front of the second character must appear at the end of the row

^$: Blank Line

\< or \b: Anchor word, any character following it must appear as the first word

\> or \b: anchors the ending, any character preceding it must appear as the tail of the word

Group:

\ (\): Subsequent references

\1: Refers to the first opening parenthesis and all the contents of the corresponding closing parenthesis

\2: Refers to the second opening parenthesis and all the contents of the corresponding closing parenthesis

This article is from the "rime" blog, please be sure to keep this source http://kinrey.blog.51cto.com/10492082/1770029

Linux Common command-grep and regular expressions