Shell Script-Regular expression

character class (Character Class): The above example x and y, which represent one character in the pattern , but the range of values is a class of words

Any one of them.

Quantity Qualifier (quantifier): each part of a mail address can have one or more x character , IP each part of the address

can have 1-3 a y character

(Anchor) : Describes the positional relationships between the various character classes and ordinary characters, such as e-mail addresses that are divided into three

section , @ and . separate ,ip address four parts with . separate

description. In order to represent positional relationships , the concept of positional qualifiers is required , as described below.

specify some special syntax to represent character classes, quantifier and positional relationships , then use these special syntax and ordinary characters

together represents a pattern , that's the regular expression . (Regular Expression) .

Note the regular expression parameter with encloses the , shell

it has a special meaning . ( e.g. \), It is only possible to enclose these characters in single quotes to ensure that they are passed intact . grep command , and not

will be Shell explain it out.

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The above introduction is grepof the regular expressionExtendedSpecification, BasicThe specification also has these grammars, just characters ? +{}| () should be

interpreted as normal character ,to indicate the above special meaning, you need to add \escaped. If you usegrepand not Egrep,and does not add- e

Parameters , you should follow Basic specification to write regular expressions. (Be sure to pay attention to!!!!! )

Convenient here is to rename the command here

Alias grep= ' Grep-e--colour '

Example:

[[email protected] grep]$ echo ' @ @abc ' |grep ' [@asd].ab '

@ @abc

[[email protected] grep]$ echo ' @ @abc ' |grep ' [. Asd].ab '

[[email protected] grep]$ echo ' [email protected] ' |grep ' [. Asd].ab '

[Email protected]

There are no special meanings for all the characters in this []. But outside it's a match for any one of them.

Match e-mail:

Original:

[[email protected] grep]$ cat file

[Email protected]

Dksaljdkl-sdasdas.com

[Email protected]

[Email protected]@454654

[Email protected]#@.com

[Email protected] grep]$ grep-e ' [A-za-z0-9_.-][email protected][a-za-z0-9_.-]+\. [a-za-z0-9_.-]+ ' File[email protected][email protected][email protected]@454654

More precise and ^$ limit the beginning line end

[Email protected] grep]$ grep-e ' ^[a-za-z0-9_.-][email protected][a-za-z0-9_.-]+\. [a-za-z0-9_.-]+$ ' File[email protected][email protected]

egrep Equivalent to means grep basic and

Extended two types of specifications , the difference between them is explained in the next section. There is also the fgrep command , equivalent to grep-f, which indicates that only

searching for fixed strings without searching for regular expression patterns , The following arguments are not interpreted by the syntax of the regular expression.

Matching IP

File content

192.168.11.2

192.168.1sas1.2

19as2.121.11.2

192.1sa28.11.2

192.16as1.11.2

192.111.1s1.2

192.1.1.8.12.2

192.168.2sa1.2

192.1.68.12.1

[[email protected] grep]$ grep ' [0-9]{1,3}\. [0-9] {1,3}\. [0-9] {1,3}\. [0-9] {1,3} ' file192.168.11.219as2.121.11.2192.1.1.8.12.2 #grep is looking for a row that contains a pattern because it contains a pattern 192.1.1.8 so this line is also found 192.1.68.12 .1

Another way:

[[email protected] grep]$ grep ' ([0-9]{1,3}\.) {3} [0-9] {1,3} ' file192.168.11.219as2.121.11.2192.1.1.8.12.2 192.1.68.12.1

A more precise approach:

[[email protected] grep]$ grep ' ^ ([0-9]{1,3}\.) {3} [0-9] {1,3}$ ' file192.168.11.2

This article is from the "City Hunter" blog, please be sure to keep this source http://alick.blog.51cto.com/10786574/1841252

Shell Script-Regular expression