Linux regular expressions-Basic Regular Expressions (based on grep)

Linux regular expressions-Basic Regular Expressions (based on grep)

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep. (Note: to make the following case clearer, run this command before doing the following case)

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. a $ indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4 .. represents and can only represent any one character

5. \\. it only indicates the vertex itself. escape characters, so that characters with special identities can be removed from the vest,

6. * repeat 0 or multiple first characters

7. * match all characters. ^. * Starts with any letter and ends with any letter. * $

^. * According to the previous single character, we know that ^. * matches content starting with any number of strings.

8. [abc] match any character in the character set [a-z].

9. [^ abc] match content that does not contain any character after ^

[^ A-z] does not contain lowercase letters

[^ 0-9] does not contain numbers

10. a \ {n, m \} repeats n to m times, the previous repeating character. If you use egrep, you can remove the diagonal line.

\ {N, \} should be repeated at least n times, with the previous repeated characters. If you use egrep, you can remove the diagonal line.

\ {N \} repeats n times, the previous character is repeated. If you use egrep, you can remove the diagonal line.

\ {, M} \ repeat a maximum of m times-it is best not to use it.

[Root @ nginx_back ~] # Grep ". *" test. log = matches 0 or more, so there are empty rows.

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "." test. log = match any character, at least one, so there is no blank line.

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep-v "^ $" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep-vn "^ $" test. log

1: linux regular expression:

2: in short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

3: Notes for using regular expressions:

. Linux regular expressions are generally processed in the unit of action.

. Alias grep = 'grep -- color = auto'. The lecture is based on grep.

. Pay attention to the character set, LC_ALL = C

7: linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

10: a. Basic Regular Expression (based on grep)

11: 1. ^ a indicates searching for content starting with

12: 2. $ a indicates searching for content ending with

13: 3. ^ $ indicates empty rows, not Spaces

14: 4.

[Root @ nginx_back ~] # Grep-v n "^ $" test. log

Grep: ^ $: No file or directory

Test. log: in short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Note:

Test. log: 2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

Test. log: 3. Note the character set LC_ALL = C.

Test. log:

Test. log:

Test. log: a. Basic Regular Expression (based on grep)

Test. log: 1. ^ a indicates that the content starting with a is searched.

Test. log: 2. $ a indicates that the content ending with a is searched.

Test. log: 3. ^ $ indicates empty rows, not Spaces

Test. log: 4.

[Root @ nginx_back ~] # Grep-v-n "^ $" test. log

1: linux regular expression:

2: in short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

3: Notes for using regular expressions:

. Linux regular expressions are generally processed in the unit of action.

. Alias grep = 'grep -- color = auto'. The lecture is based on grep.

. Pay attention to the character set, LC_ALL = C

7: linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

10: a. Basic Regular Expression (based on grep)

11: 1. ^ a indicates searching for content starting with

12: 2. $ a indicates searching for content ending with

13: 3. ^ $ indicates empty rows, not Spaces

14: 4.

[Root @ nginx_back ~] # Grep "$" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "C $" test. log

3. Note the character set LC_ALL = C.

[Root @ nginx_back ~] # Grep "." test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "\." test. log

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "rep" test. log

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

[Root @ nginx_back ~] # Grep "grep" test. log

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

[Root @ nginx_back ~] # Grep ". $" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "\. $" test. log

4.

[Root @ nginx_back ~] # Grep "\. * $" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

[Root @ nginx_back ~] # Grep ". *" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "." test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep ". $" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep ". * $" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "\. *" test. log

Linux regular expression:

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

Notes for using regular expressions:

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "grep" test. log

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

A. Basic Regular Expression (based on grep)

[Root @ nginx_back ~] # Grep "\." test. log

In short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

1. linux regular expressions are generally processed in the unit of action.

2. alias grep = 'grep -- color = auto'. The lecture is based on grep.

3. Note the character set LC_ALL = C.

1. ^ a indicates searching for content starting with

2. $ a indicates searching for content ending with

3. ^ $ indicates empty rows, not Spaces

4.

[Root @ nginx_back ~] # Grep "C $" test. log

3. Note the character set LC_ALL = C.

[Root @ nginx_back ~] # Grep-v-n "^ $" test. log

1: linux regular expression:

2: in short, regular expressions are a set of rules and methods defined to process a large number of strings. For example, suppose @ represents 123456 ,! Represents abcde. the system administrator can quickly filter, replace, or output the desired characters by defining these special symbols.

3: Notes for using regular expressions:

. Linux regular expressions are generally processed in the unit of action.

. Alias grep = 'grep -- color = auto'. The lecture is based on grep.

. Pay attention to the character set, LC_ALL = C

7: linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep.

10: a. Basic Regular Expression (based on grep)

11: 1. ^ a indicates searching for content starting with

12: 2. $ a indicates searching for content ending with

13: 3. ^ $ indicates empty rows, not Spaces

14: 4.

[Root @ nginx_back ~] # Grep "^ linux" test. log

Linux regular expression:

Linux regular expression. It is mainly the regular expression of the three muskeys of awk, sed, and grep (egrep. ,

[Root @ nginx_back ~] # Cat test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep "c *" test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep-o "c *" test. log

C

C

Ccc

C

C

C

C

C

Ccc

C

C

C

C

[Root @ nginx_back ~] # Grep-o ". *" test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Alias grep = 'grep -- color = auto'

[Root @ nginx_back ~] # Grep "c *" test. log [aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep-o "c *" test. log

C

C

Ccc

C

C

C

C

C

Ccc

C

C

C

C

[Root @ nginx_back ~] # Grep-o ". *" test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep "[abc]" test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep "[a-z]" test. log

[Aaa]

Cfg1 = aaa

Xxxx = bbb

Cfg2 = ccc

Cfg3 = ddd

[Bbb]

Cfg1 = eee

Yyyy = fff

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

[Ccc]

Cfg1 = jjj

Zzzz = kkk

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Grep "[0-9]" test. log

Cfg1 = aaa

Cfg2 = ccc

Cfg3 = ddd

Cfg1 = eee

Cfg2 = ggg

Cfg3 = hhh

Cfg4 = iii

Cfg1 = jjj

Cfg2 = lll

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Vi test. log

[Aaa]

Cfg1 = aaa

. Xxxx = bbb

Cfg2 = ccc

. Cfg3 = ddd

[Bbb]

Cfg1 = eee

. Yyyy = fff/

Cfg2 = ggg

Cfg3 = hhh

C. fg4 = iii/

[Ccc]

Cf. g1 = jjj

Zzzz = kkk/

Limit .2 = lll.

"Test. log" 17L, 154C written

[Root @ nginx_back ~] # Grep "[\.,/]" test. log

. Xxxx = bbb

. Cfg3 = ddd

. Yyyy = fff/

C. fg4 = iii/

Cf. g1 = jjj

Zzzz = kkk/

Limit .2 = lll.

[Root @ nginx_back ~] # Grep "[^ abc]" test. log

[Aaa]

Cfg1 = aaa

. Xxxx = bbb

Cfg2 = ccc

. Cfg3 = ddd

[Bbb]

Cfg1 = eee

. Yyyy = fff/

Cfg2 = ggg

Cfg3 = hhh

C. fg4 = iii/

[Ccc]

Cf. g1 = jjj

Zzzz = kkk/

Limit .2 = lll.

Cfg2 = mmm

Cfg2 = nnn

[Root @ nginx_back ~] # Vi test. log

[Aaa]

Cfg1 = aaa00000

0. xxxx = bbb

Cfg2 = ccc

. 00cfg3 = ddd

[Bbb] 0000

Cfg1 = eee

. Yy00yy = fff/

Cfg2 = ggg

Cfg3 = hhh00000

C. fg400 = iii/

[Ccc]

Cf. g1 = jjj

Zzzz = kk000000000k/

Limit .2 = lll.

Cfg2 = mmm

Cfg2 = nnn

"Test. log" 17L, 184C written

[Root @ nginx_back ~] # Grep "0 \ {1, 3 \}" test. log

Cfg1 = aaa00000

0. xxxx = bbb

. 00cfg3 = ddd

[Bbb] 0000

. Yy00yy = fff/

Cfg3 = hhh00000

C. fg400 = iii/

Zzzz = kk000000000k/

[Root @ nginx_back ~] # Grep "0 \ {1, \}" test. log

Cfg1 = aaa00000

0. xxxx = bbb

. 00cfg3 = ddd

[Bbb] 0000

. Yy00yy = fff/

Cfg3 = hhh00000

C. fg400 = iii/

Zzzz = kk000000000k/

[Root @ nginx_back ~] # Grep "0 \ {2 \}" test. log

Cfg1 = aaa00000

. 00cfg3 = ddd

[Bbb] 0000

. Yy00yy = fff/

Cfg3 = hhh00000

C. fg400 = iii/

Zzzz = kk000000000k/

[Root @ nginx_back ~] # Egrep "0 {1, 3}" test. log

Cfg1 = aaa00000

0. xxxx = bbb

. 00cfg3 = ddd

[Bbb] 0000

. Yy00yy = fff/

Cfg3 = hhh00000

C. fg400 = iii/

Zzzz = kk000000000k/

Common grep parameters:

-A: searches for data in binary files as text files.

-C: calculates the number of times a 'search string' is found.

-O: displays only the content that matches the regexp (used to count the number of times in the text)

-I: Case sensitivity is ignored, so the case sensitivity is the same.

-N: displays the row number at the beginning of the row.

-V: reverse selection, that is, the row without the 'search string' content is displayed.

-E: Extended grep, that is, egrep

-- Color = auto: highlight matching keywords in a specific color

# <-Tip:-I-v is a common Parameter

-A: After indicates that data in n rows After matching strings is displayed.

-B: before indicates that the data of the first n rows matching the string is displayed.

The online environment example cases will be sorted in the future: