Shulou(Shulou.com)06/02 Report--

Awk report generator, formatted text output

Common option

Awk-F: "delimiter" indicates the field delimiter used when entering

-v: variable assignment

Basic usage

Basic format: awk [options] 'program' file...

Program:pattern {action statements;..}

Pattern and action

The    pattern part determines when the action statement triggers and triggers the event

     BEGIN,END

   action statements processes the data and indicates it in {}

     print, printf

Separators, fields, and records

When the awk executes, the field (domain) separated by a delimiter is marked $1 ~ 2. Domain ID. $0 is all fields. Note: the meaning of the variable $symbol is different from that in shell.

Each line of the    file is called a record

If action is omitted from   , the operation of print $0 will be performed by default.

Example:

Take out the domain name of the third column

Take partition utilization

Take partition utilization and remove%

Take out df partition utilization directly in one step

Take the first and third columns of the / etc/passwd file

Operation

Awk variable

Variables: built-in and custom variabl

FS

Enter a field delimiter, which defaults to a blank character

Awk-v FS=':''{print $1m FS journal 3}'/ etc/passwd

Awk-F:'{print $1, 3, 7}'/ etc/passwd

Example:

RS

Enter the record delimiter to specify the newline character when entering

Awk-v RS='''{print}'/ etc/passwd

ORS

Output record delimiter, using the specified symbol instead of the newline character

Awk-v RS=''- v ORS='###''{print $0}'/ etc/passwd

Example

Use colons as delimiters, take the first character, and break the line by default

Use the equal sign as the delimiter and do not wrap

NF

Number of field

When awk-FRV'{print NF}'/ etc/fstab references a variable, the variable does not need to be preceded by $

Awk-FRV'{print $(NF-1)}'/ etc/passwd

Example:

The last but one.

-1 the penultimate one

Take out the penultimate one.

Sort

NR

Record number

Awk'{print NR}'/ etc/fstab

Awk END'{print NR}'/ etc/fstab

Example

$0 prints all characters and adds numbers

Use colons as delimiters to print out the contents of the file, followed by a number

FNR

Count and record number of each file respectively

Awk'{print FNR}'/ etc/fstab / etc/inittab

FILENAME: current file name

   awk'{print FILENAME}'/ etc/fstab

ARGC

Number of command line arguments

Awk'{print ARGC}'/ etc/fstab / etc/inittab

Awk 'BEGIN {print ARGC}' / etc/fstab / etc/inittab

ARGV

Array, which holds the parameters given by the command line

Awk 'BEGIN {print ARGV [0]}' / etc/fstab / etc/inittab

Awk 'BEGIN {print ARGV [1]}' / etc/fstab / etc/inittab

Practice

Custom variable union operation

Assign and take out the value of USER

Assign to take out the values of USER and UID

Use variables before you use them, otherwise the following will occur

Printf command formatted output: printf "FORMAT", item1, item2,...

(1) FORMAT must be specified

(2) the line wrapping will not occur automatically, and the newline control character needs to be given explicitly,\ n

(3) format characters need to be specified for each subsequent item in FORMAT

Format characters: one-to-one correspondence with item

% c: ASCII code that displays characters

% d,% I: show decimal integers

% e,% E: display scientific counting values

% f: displayed as a floating point number

% g,% G: display values in scientific counting or floating point form

% s: display string

% u: unsigned integer

%%: show% itself

Modifier

# [. #] the first number controls the width of the display; the second # indicates the precision after the decimal point,% 3.1f

Left alignment (default right alignment)%-15s display numeric value plus or minus sign% + d example

Formatted output

Add n to line break

Take out partition utilization and separate 15 placeholders with colons

You can build tables.

Operator arithmetic operator

X% y, x ^ y, x% y

-x: convert to negative number

+ x: convert strings to numeric values

String operator

Unsigned operators, string concatenation

Assignment operator:

=, +, -, *, /,%, ^, +,--

What's the difference between the following two sentences?

Awk 'BEGIN {iMagntinct print + + iMagneI}'

Awk 'BEGIN {iS0th print iTunes I}'

Comparison operator:

=,!, >, >, y?var=x:var=y

     return var

  }

   BEGIN {axiom 3 / b / s / b)}

   awk-f fun.awk

Call shell command system command space in awk is a string concatenator in awk. If you need to use a space in system, variables in awk can be separated by spaces, or all variables except those in awk can be referenced by "".

   awk 'BEGIN {system ("hostname")}'

The    awk 'BEGIN {score=100; system ("echo your score is" score)}' awk script writes the awk program as a script, calling or executing the example directly:

Cat f1.awk

   {if ($3 > = 1000) print $1

Awk-F:-f f1.awk / etc/passwd

.

Cat f2.awk

   #! / bin/awk-f

   # this is an awk script

   {if ($3 > = 1000) print $1

Chmod + x f2.awk

F2.awk-F: / etc/passwd passes the parameter format to the awk script:

Awkfile var=value var2=value2... Inputfile

Note:

Not available during BEGIN. Variables are not available until the first line of input is complete. You can pass the-v argument to let awk get the value of the variable before executing BEGIN. Each specified variable on the command line requires a-v argument

Example:

Cat test.awk

#! / bin/awk-f

{if ($3 > = min & & $3)

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