The Linux Report Generator tool awk

The Linux Report Generator tool awk

awk: Displayed after formatting based on input information

1.1. awk Basic Usage

awk [Options] ' script ' File1,file2,....

or awk [options] PATTERN [ACTION] ' file1,file2 ....

Example: awk ' {print '} ' test.txt

Options

-F: defining delimiters

Example awk-f: delimiter with a colon

1.2. awk built-in variables

(1) Record variables

FS: Set default split Word descriptor example awk-f: Colon as delimiter

RS: Set default line break

OFS: Set Default Output delimiter

ORS: Set default output line delimiter

(2) Data variables

The number of records (rows) processed by the Nr:awk command, if there are multiple files, the total number of records

The record (row) that the Fnr:awk is processing is the total number of records (rows) currently processed in this file

NF: The number of fields in the current record (row)

ARGV: Array, save the command line itself this string

Parameters of the Argc:awk command

The name of the file processed by the Filename:awk command

ENVIRON: An associative array of current shell environment variables and their values

1.3, the use of print format

Print ITEM1,ITEM2,...

Each item is separated by commas, and the output is separated by a space

1.4. printf

Unlike print, printf needs to specify the format

Use format: printf format,item1,item2 ...

The format indicator is preceded by%, followed by a character

%c: ASCII code for displaying characters

%d,%i: Decimal integer

%f: Show floating-point numbers

%s: Display string

Percent: show% itself

Format modifiers

N: Display width

-: Align Left

+: Display numeric symbols

Example: awk-f: ' {PRINTF '%-15s '%i\n,$1,$3} '/etc/passwd

1.5. Awk's operator

(1) Arithmetic operators

-X: Negative value

+x: Convert to Numeric

(2) Assignment operator

=

+=

%=

(3) Comparison operators

= =: Equal

! =: Unequal

(4) Logical relationship between expressions

&&

||

1.6. awk mode pattern

Use format: awk ' pattern{action} ' file1 file2

Common pattern types

1 Regular expressions,/pattern/

2 expressions, where ~ and!~ indicate matching and mismatches

3 Specifies the match range, formatted as PATTERN1,PATTERN2, from match pattern1 start to match to Pattern2 end

4 Begin/end: Special mode, run only once or before the end of the awk command execution

5 empty (Null mode): matches any row

The Common Acton

An expression

Control statements for and so on

if (condition) (then ...) Else{[...]}

while (condition) {Statement 1, statement 2 ...}

do{Statement 1, Statement 2 ....} while (condition)

for (condition) {Statement 1, statement 2 ...}

switch (expression) {case-value or regular-expression: statement 1...default: statement 1 ...}

Compound statement

Input and OUTPUT statements

Break and continue are often used in loops or case statements

Next: End the processing of the bank's text in advance and proceed to the next line

Example: Display a user whose ID is odd

Awk-f: ' {if ($3%2==0) next;print $1,$3} '/etc/passwd

1.7. Using Arrays in awk

array[array subscript or index]

Netstat-ant | awk '/^tcp/{++s[$NF]} END {for (a in S) print A, s[a]} '

Each occurrence of a row that is matched to the/^tcp/pattern, the array s[$NF] adds 1,nf to the last field of the row that is currently matched to,

This is the index of the elements of the array s with its value;

1.8. Awk built-in functions

Split: Split function

How to use Split (String,a,pattern): Splits a string by pattern and stores it as a[1],a[2]

Length ([string])

Returns the number of characters in string strings;

SUBSTR (String, start [, length])

Takes a substring of string, starting with start, taking length; start counting from 1;

System (Command)

Executes the system command and returns the result to the awk command

Systime ()

Fetch System Current Time

ToLower (String)

Convert all letters in a string to lowercase

ToUpper (s)

Convert all letters in s to uppercase

XI. user-defined functions

The custom function uses the function keyword. The format is as follows:

function f_name ([variable]) defining custom functions

{

Statements

}

F_name: Using a custom function

The function can also return a value using the return statement in the form "return value".

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The Linux Report Generator tool awk