Shell_ 02_ Text three swordsman

cut

cut command ： Operate on data in fields

Command format ：cut Options File path

Options	meaning
-d	Specify the delimiter of the data
-f	Specify the field display
-c N	Appoint N The characters are 1 Display units

1）-d and -f Options together make sense （ Only the delimiter of the specified data , Data can be segmented ）

2）-c The value followed by the option “-” There are different meanings in different places

Such as ： Show PATH The fifth path in the variable path

Such as ： Display in different character units test1.txt The contents of the document

sed

sed command ： Replace data in behavioral units 、 Delete 、 newly added 、 Selection and other functions

Command format ：sed Options ‘ operation ’ File path

1） Options are optional , But the operation must have ;

2）sed Command more than two operations , Need to add -e Options ;

3） The operation must be enclosed in two single quotation marks , And between multiple operations “;” Separate ;

Options	meaning
-n	Only output is sed Processed lines
-e	In the command prompt interface sed operation
-f	take sed Write to a file
-r	Use extended regular expression syntax （ The default is the basic regular expression syntax ）
-i	Directly modify the contents of the document （ The default is to only read the file and output it to the terminal ）

operation	meaning
s	Replace / Delete string （ Usually used with regular expressions ）
y	Replace character
i	（ Last line ） Insert
a	（ The next line ） Insert
c	Replacement row
d	Delete row
p	Print （ Usually cooperate -n Options together make sense ）

Replace string

s operation ： Replace the string specified in the data flow

1） Format ：s/ Original string / New string / identification

2） Signs are divided into （p and w It can be used for other operations ）：

identification	explain
g	All occurrences of the original string in the data stream are replaced
p	Print out the line where the string is operated
w File path	Write the result of the operation to the specified file
The number N	Specify the number of... That the string successfully matches in this line N Time , To replace

3） By default, only the first string that is successfully matched is replaced ;

4） If the new string is empty , Then you can delete the original string ;

Such as ： Replace the specified string

Such as ： Only print out by sed Command replacement line

Such as ： adopt s Operation deletes the specified string

y operation ： Replace a single character in the data stream

1） Format ：y/ Original character / New character /

2） The number of original characters should be consistent with the number of new characters ;

3） By default, it works on all strings in the data flow （ The range cannot be specified by addressing ）

Such as ： Replace specified characters

Addressing

Row addressing （Line Addressing）： Appoint sed The scope of the operation of the command line

1）sed The operation of the command works on all data lines by default ;

2） Row addressing is divided into ： Digital addressing 、 Text addressing

（1） Digital addressing

1）sed By default, the row number is assigned from the first row of data 1（ Including the empty line ）;

2） Digital addressing is divided into ： That's ok 、 Row interval

3） Digital addressing format ：‘ Values and operations ’

// When specifying a row interval , Use between multiple values “,” Separate （ The interval contains the value itself ）

Such as ： Through digital addressing , Replace specified data

（2） Text addressing

1） Select the line containing the specified string ;

2） Text addressing format ：‘/ character string / operation ’

Such as ： Through text addressing , Replace specified data

（3） When multiple operations are performed under the same address , Operations need to be specified by branches

// It can also be written on the same line , However, you need to specify addressing multiple times and use “;” Separation operation

Such as ： In the specified row , Replace multiple data at the same time

Delete

d operation ： Delete the specified row in the data flow

1） Format ： Match format d

2） If no string is specified , Then the string of all lines is deleted by default ;

3） Use two text addressing , It can realize the opening and closing of the deletion function ;

// Enable the deletion function when matching to the first text addressing , Close when the second one is matched

Such as ： Delete specified row

Such as ： Addressing through two texts , Realize the opening and closing of the deletion function

Insert

i operation ： Insert a row of data into the previous row of the specified row in the data flow

1） Format ： Addressing i\ insert data

2）i Operation must be coordinated with addressing , And row interval addressing cannot be used ;

// If addressing is not specified , By default, the specified data is inserted in the previous row of all rows

3）a Operation and i Same operation （ The difference lies in ： Insert ）;

Such as ： Read data6 In the file data stream , The first 3 Insert the specified data in the previous row of the row

Replacement row

c operation ： The new row replaces the specified row in the data flow

1） Format ： Addressing c\ New line

2）c Operation must be coordinated with addressing （ If row interval addressing , Then the interval is replaced by a new line ）;

// If addressing is not specified , Replace all rows in the data flow by default

Such as ： The new line replaces the specified line

gawk

gawk Program ：Unix in awk programmatic GNU edition , It has the following functions

1） Variables can be defined to store data ;

2） Use arithmetic and string operators to process data ;

3） Use structured programming concepts to add processing logic to data processing ;

4） By extracting the data elements in the data file , Format it and output ;

gawk command ： The fields in each row are used to replace the data 、 Delete 、 newly added 、 Selection and other functions

Command format ：gawk Options ‘ key word 1{ operation 1} key word 2{ operation 2}’ File path

Options	meaning
-F character	Specifies the separator for the field
-f File path	Specify storage gwak Files for operation
-v Variable name = value	Define variables and variable values
-mf	Specify the maximum number of processing fields in the data flow

1）gawk Unit by behavior , Take the field as the processing unit ;

2）gwak The built-in variables for each field in are ：

Variable name	explain
$0	Represents the whole row of data
$1	On behalf of the 1 A field
$2	On behalf of the 2 A field
$N	On behalf of the N A field

3）gawk Other built-in variables

Variable name	meaning
NF	The total number of fields per row
NR	gawk What line of data is being processed
FS	Input field separator （ Default is space ）
RS	Enter the delimiter of the data row
OFS	Separator for output field
ORS	Separator of output data row

// Built in variables in gawk When used inside , There is no need to add variable symbols before “$”

4）gawk in 3 Key words ：BEGIN（ The first to perform ）、pattern、END（ Finally, execute ）

// When specifying split characters , Need to use BEGIN key word , otherwise gawk When the split character has not been replaced , Other operations have already been processed

// The default is omitted pattern key word （ Use less ）

Such as ： Format output

// When there are multiple commands in an operation , Need to use “;” Separate

Such as ： Store by calling gwak Files for operation , Output /etc/passwd The user name of the file and UID

Such as ： Inquire about /etc/passwd In the file UID Less than 10 Users of , And pass awk Format output

//gawk Operation selection can be realized by logical operation , And awk and gawk Universal

Such as ： adopt gawk Format output

1） To write 3.sh Script files

2） call 3.sh Script files