Linux--Shell programming

Linux--Shell programming one, regular expression 1, regular expression PK wildcard

　　　　

　　　　

2.Basic Regular Expressions1),*The previous character matches 0 or more times

~ grep "A *" Test_rule.txt # matches all content, including blank lines

~ grep "aa*" Test_rule.txt # matches a string that contains at least two consecutive a

~ grep "aaa*" Test_rule.txt # matches a string with a minimum of two consecutive a

~ grep "aaaa*" Test_rule.txt # matches a string with a minimum of four consecutive a

2),.Match any character except line break

~ grep "s.. D "Test_rule.txt #" s.. D "matches a word that must have two characters between the two letters S and D

~ grep "S.*d" Test_rule.txt # match has any character between S and D letters

~ grep ". *" Test_rule.txt # matches all content

3),^Match beginning

~ grep "^m" Test_rule.txt # matches lines beginning with uppercase "M"

4),$Match end of Line

~ grep "n$" Test_rule.txt # matches lines ending in lowercase "n"

~ grep-n "^$" Test_rule.txt # matches blank lines

5),[]Matches any one of the characters set in brackets, matching only one character

~ grep "S[ao]id" Test_rule.txt # matches S and I in the letter, but not a, but

~ grep "[0-9]" Test_rule.txt # matches any number

~ grep "[A-z]" Test_rule.txt # matches a line that starts with a lowercase letter

6),[^]Match any character except the character in brackets

~ grep "^[^a-z]" Test_rule.txt # matches lines that start with no lowercase letters

　　　　　~ grep "^[^a-za-z]" Test_rule.txt # matches lines that don't start with letters

7),\Escape character

~ grep "\.$" Test_rule.txt # Match use ". "End of Line

8),\{n\}Indicates that the preceding character appears exactly n times

~ grep "A\{3\}" Test_rule.txt # matches a character string that appears three consecutive times

~ grep "[0-9]\{3\}" Test_rule.txt # matches a string containing three consecutive digits

9),\{n,\} indicates that the preceding character appears not less than n times

~ grep "^[0-9]\{3,\}[a-z]" Test_rule.txt # matches a line that starts with a minimum of three consecutive digits

10), \{n,m\} matches the characters preceding it at least n times, with a maximum of M times

~ grep "Sa\{1,3\}i" Test_rule.txt # match between letter S and letter I have at least one a, up to three A

Second, character interception command 1, cut 1), field Processing command 2), cut [options] file name

[Options]

-F Line Number: Extract the first few columns

-D delimiter: Split columns by specified delimiter

3), Example:

　　　　　　

　　　　　　

　　　　　　

　　　4) Example limitations (cannot match spaces)

　　　　　　

2, PRINTFF 1), usage

　print ' Output type output format ' output content

　　　　　　　　

　　　　　　　　

2), Practice

　　　　　　

　　　　　　

　　　　　　

　　　　　　

3) and the relationship to awk (printf uses nothing more than a dick, mostly with awk)

Print:print will automatically add a newline character after each input (Linux defaults to no Print command).

printf: is the standard format Output command, and does not manually add line breaks, if you need to wrap, you need to manually add line break

Example

　　　　　　　　

　　　　　　　　

3, awk 1), use:awk ' condition 1 {action 1} condition 2 {action 2} ... '

Condition: general use of relationship expressions as criteria

x>=10 greater than or equal to

X > 10 determine if the variable x is greater than 10

x<=10 less than or equal to

Action

Formatted output

Process Control Statements

2), BEGIN, END, FS built-in variables, relational operators

　　　　　　

　　　　　　

　　　　　　

　　　　　　

　　　　　　

4. Sed

1), Introduction:

SED is a lightweight flow editor that is almost included on all UNIX platforms, including Linux.

SED is primarily used to select, replace, delete, and add commands to the data.

2), Usage:

Sed "Options" "Actions" file name

"Options"

N

E

I

"Actions"

A \:

C \:

i \:

Three, character processing command 1, sort 2, WC four, condition judgment five, flow control 1, if 2, Case 3, for 4, while and until

Linux--Shell programming