Shulou(Shulou.com)06/01 Report--

Awk is a line processor: compared to the advantages of screen processing, there is no memory overflow or slow processing when dealing with large files, and is usually used to format text information.

Awk process: each row is processed in turn, and then output

Awk command form:

Awk [- F |-f |-v] 'BEGIN {} / / {command1; command2} END {}' file

[- F |-f |-v] large parameter,-F specifies delimiter,-f calls script,-v defines variable var=value

'' reference code block

BEGIN initialization code block, initializing the code before processing each line, mainly referencing global variables and setting the FS delimiter

/ / match the code block, which can be a string or a regular expression

{} command code block containing one or more commands

Multiple commands are separated by semicolons

END ending code block, a code block that executes after each line is processed, mainly for final calculation or output ending summary information

Special points:

$0 represents the entire current line

$1 first field of each line

NF field quantity variable

NR record number per line, multi-file record increment

FNR is similar to NR, except that multi-file records are not incremented, and each file starts at 1

\ t Tab character

\ nLine feed character

Define delimiters when FS BEGIN

The record delimiter entered by RS, which defaults to the newline character (that is, text is entered on one line)

~ match, which is not an exact comparison compared with =

! ~ mismatch, imprecise comparison

= = equal to, must be all equal, accurate comparison

! = not equal to exact comparison

& & Logic and

| | Logic or

+ 1 or more when matching

/ [0-9] [0-9] + / two or more digits

/ [0-9] [0-9] * / one or more numbers

FILENAME file name

OFS output field delimiter, which is also a space by default, and can be changed to tabs, etc.

The record delimiter of the ORS output, which defaults to the newline character, that is, the processing result is also output to the screen one by one.

-F'[: # /] 'defines three delimiters

Print & $0

Print is the main command for awk to print specified content.

Awk'{print}'/ etc/passwd = = awk'{print $0}'/ etc/passwd

Awk'{print ""}'/ etc/passwd / / does not output the contents of passwd, but outputs the same number of blank lines, which further explains that awk processes text one line at a time.

Awk'{print "a"}'/ etc/passwd / / outputs the same number of a lines with only one letter a

Awk-F ":"'{print $1}'/ etc/passwd

Awk-F:'{print $1; print $2}'/ etc/passwd / / output the first two fields of each line, line by line, to further understand how to process text one line at a time

Awk-F:'{print $1 OFS= 6} 'OFS= "\ t" / etc/passwd / / output field 1, 3, 6, with tabs as delimiters

-f specify the script file

Awk-f script.awk file

BEGIN {

FS= ":"

}

{print $1} / / the effect is the same as awk-F ":"'{print $1}', except that the delimiter is specified in the code itself using FS

Awk 'BEGIN {Xerox 0} / ^ $/ {Xerox 1} END {print "I find", X, "blank lines."}' test

I find 4 blank lines.

Ls-l | awk 'BEGIN {sum=0}! / ^ d / {sum+=$5} END {print "total size is", sum}' / / calculate the file size

Total size is 17487

-F specifies the delimiter

1 means that after the delimiter is specified, the first field, the third field of $3, and\ t is the tab character.

One or more consecutive spaces or tabs are treated as a delimiter, that is, multiple spaces are treated as a space

Awk-F ":"'{print $1}'/ etc/passwd

Awk-F ":'{print $1 $3}'/ etc/passwd / / $1 is connected to the output of $3 without separation

Awk-F ":" {print $1 < 3}'/ etc/passwd / / an extra comma is added, and $1 and $3 are separated by a space

Awk-F ":"'{print $1 "" $3}'/ etc/passwd / / manually add a space separation between $1 and $3

Awk-F ":"'{print "Username:" $1 "\ t\ t Uid:" $3}'/ etc/passwd / / Custom output

Awk-F:'{print NF}'/ etc/passwd / / shows how many fields there are in each line

Awk-F:'{print $NF}'/ etc/passwd / / print out the value of the NF field of each line

Awk-F: 'NF==4 {print}' / etc/passwd / / displays rows with only four fields

Awk-F:'NF > 2 {print $0}'/ etc/passwd / / displays rows with more than 2 fields per row

Awk'{print NR,$0}'/ etc/passwd / / output the line number of each line

Awk-F:'{print NR,NF,$NF, "\ t", $0}'/ etc/passwd / / print line number, number of fields, last field value, tab, each line

Awk-F: 'NR==5 {print}' / etc/passwd / / shows line 5

Awk-F: 'NR==5 | | NR==6 {print}' / etc/passwd / / shows lines 5 and 6

Route-n | awk 'NRemote1 {print}'/ / does not display the first line

/ / match the code block

/ / Pure character matching! / / Pure character mismatch ~ / / Field values match! ~ / / Field values do not match ~ / A1 | a2 / Field values match A1 or a2

Awk'/ mysql/' / etc/passwd

Awk'/ mysql/ {print}'/ etc/passwd

Awk'/ mysql/ {print $0}'/ etc/passwd / / three instructions have the same result

Awk'! / mysql/ {print $0}'/ etc/passwd / / output lines that do not match mysql

Awk'/ mysql | mail/ {print}'/ etc/passwd

Awk'! / mysql | mail/ {print}'/ etc/passwd

Awk-F:'/ mail/,/mysql/ {print}'/ etc/passwd / / interval matching

Awk'/ [2] [7] [7] * / {print $0}'/ etc/passwd / / matches lines that start with 27 numbers, such as 27, 277, 2777.

Awk-F:'$1~/mail/ {print $1}'/ etc/passwd / / $1 is displayed only if the specified content is matched.

Awk-F:'{if ($1~/mail/) print $1}'/ etc/passwd / / same as above

Awk-F:'$1 mismatch mail / {print $1}'/ etc/passwd / /

Awk-F:'$1 print print mail | mysql/ {mail $1}'/ etc/passwd

IF statement

Must be used in {}, and the comparison is expanded with ()

Awk-F:'{if ($1~/mail/) print $1}'/ etc/passwd / / abbreviation

Awk-F:'{if ($1~/mail/) {print $1}}'/ etc/passwd / / write all

Awk-F:'{if ($1~/mail/) {print $1} else {print $2}}'/ etc/passwd / / if...else...

Conditional expression

= =! > > =

Awk-F ":"'$1percent = "mysql" {print $3}'/ etc/passwd

Awk-F ":"'{if ($1mm = "mysql") print $3}'/ etc/passwd / / same as above

Awk-F ":" $1percent = "mysql" {print $3}'/ etc/passwd / / is not equal to

Awk-F ":" $3 > 1000 {print $3}'/ etc/passwd / / greater than

Awk-F ":" $3 > = 100 {print $3}'/ etc/passwd / greater than or equal to

Awk-F ":" $38 {print}'/ etc/passwd / / Logic matches mail with $1, and $3 > 8

Awk-F:'{if ($1~/mail/ & & $3 > 8) print}'/ etc/passwd

Awk-F:'$1~/mail/ | | $3 > 1000 {print}'/ etc/passwd / / logical or

Awk-F:'{if ($1~/mail/ | | $3 > 1000) print}'/ etc/passwd

Numerical operation

Awk-F:'$3 > 100' / etc/passwd

Awk-F:'$3 > 100 | | $3

200'/ etc/passwd

Awk-F:'/ mysql | mail/ {print $3 million 10}'/ etc/passwd / / the third field plus 10 printing

Awk-F:'/ mysql/ {print $3murf 4}'/ etc/passwd / / subtraction

Awk-F:'/ mysql/ {print $3 times 4}'/ etc/passwd / / multiply

Awk'/ MemFree/ {print $2amp 1024}'/ proc/meminfo / / Division

Awk'/ MemFree/ {print int ($2y1024)}'/ proc/meminfo / / rounding

Output delimiter OFS

Awk'$6 ~ / FIN/ | | NR==1 {print NR,$4,$5,$6} 'OFS= "\ t" netstat.txt

Awk'$6 ~ / WAIT/ | | NR==1 {print NR,$4,$5,$6} 'OFS= "\ t" netstat.txt

/ / output field 6 matches the line of WAIT, where the line number of each line is output, and the field is split with tabs.

Output the processing results to a file

① outputs route-n directly in the command code block | awk 'NRRDB1 {print > ". / fs"}'

② uses redirection to output route-n | awk 'NRZ output 1 {print}' >. / fs

Formatted output

Netstat-anp | awk'{printf "%-8s%-8s%-10s\ n", $1meme 2 meme 3}'

Printf representation format output

% format output delimiter

-8 is 8 characters in length

S represents the type of string

Print the first three fields of each line, specifying the first field output string type (length 8) and the second field output string type (length 8)

The third field outputs the string type (length 10)

Netstat-anp | awk'$6 seconds = "LISTEN" | | NR==1 {printf "%-10s%-10s%-10s\ n", $1 for 2meme 3}'

Netstat-anp | awk'$6 seconds = "LISTEN" | | NR==1 {printf "%-3s%-10s%-10s%-10s\ n", NR,$1,$2,$3}'

IF statement

Awk-F:'{if ($3 > 100) print "large"; else print "small"}'/ etc/passwd

Small

Small

Small

Large

Small

Small

Awk-F: 'BEGIN {Amusement Bour0} {if ($3 > 100) {Aguilar; print "large"} else {print A, "small"}} END {print A, "\ t", B}' / etc/passwd

/ / ID is greater than 100m A plus 1, otherwise B plus 1

Awk-F:'{if ($3100? "yes": "no")}'/ etc/passwd

Awk-F:'{print ($3 > 100? $3 ":\ tyes": $3 ":\ tno")}'/ etc/passwd

While statement

Awk-F: 'BEGIN {iTun1} {while (I

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.