Detailed explanation of linux awk command-PHP开发-php.cn

awk is a line processor: Compared with the advantages of screen processing, there will be no memory overflow or slow processing problems when processing huge files. It is usually used to format text information.

awk processing process: Process each line in turn , and then output the

awk command form:

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

[-F|-f|-v] Large parameters, -F specifies the delimiter, -f calls the script, -v defines the variable var=value

' ' ' ' Quoting the code block

BEGIN initialization code block, before processing each line, initialize the code, mainly referencing the global Variable, set the FS separator

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

{} Command code block, including one or more commands

; Code block, a code block that is executed after each line is processed, mainly performs final calculation or outputs the end summary information

Special points:

$0 Represents the entire current line

$1 The first field of each line

NF Field number variable

NR ‐ ’ ’ s ’ s

’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’

’ newline character When 时FS Begin, define the separators of the separators

RS input, which is default to change the row (that is, the text is input according to one line and line)

~ matching, not accurate compared to == Inexact comparison

== equals, all must be equal, exact comparison

!= not equal, exact comparison

&& Logical AND

|| Logical OR

+ Indicates 1 or more

/ [0-9][0-9]+/ Two or more numbers

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

FILENAME File name

OFS Output field separation character, the default is also a space, which can be changed to a tab character, etc.

ORS The output record separator defaults to a newline character, that is, the processing results are also output to the screen line by line

-F'[:#/]' Define three The delimiter

print & $0

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

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

awk '{ Print "} '/ETC/PASSWD // Do not output Passwd content, but outputs the same number of empty lines, which further explains that AWK is a line of processing text

Awk' {Print" a "} '/etc/etc/ passwd / etc/passwd // Output the first two fields of each line in separate lines to further understand the processing of text line by line

awk -F: '{print $1,$3,$6}' OFS="t" /etc/passwd Output fields 1, 3, 6, with tab characters as delimiters

-f specifies 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 separator is specified in the code itself using FS

awk 'BEGIN{X=0} /^$/{ X+= 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 separator

$1 refers to the first field after specifying the delimiter, $3 the third field, t is the tab character

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

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

awk -F":" '{print $1 $3}' /etc/passwd //$1 and $3 are connected and output without separation

awk -F":" '{print $1,$3}' /etc/passwd // There is an extra comma, $1 and $3 are separated by spaces

awk -F":" " '{print $1 " " $3}' / etc/passwd with ’ s ’ s ’s ’ s out out out out out out out out out‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐/ -F: '{print NF}' /etc/passwd / Print

AWK -F: 'NF == 4 {Print}'/ETC/PASSWD // Display lines with only 4 fields

AWK -F: 'NF & GT; 2 {Print $ 0}'/ETC/PASSWD // Display lines with more than 2 fields per line

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

awk -F: '{print NR,NF,$NF,"t ",$0}' /etc/passwd //Print the line number, field number, last field value, tab character, and content of each line in sequence

awk -F: 'NR==5{print}' /etc/passwd / /Display line 5

awk -F: 'NR==5 || NR==6{print}' /etc/passwd //Display line 5 and line 6

route -n|awk 'NR! = 1 {Print} '// Do not display the first line

// matching code block

// Pure characters match! // Pure characters do not match ~ // field value matching! ~ // Field value does not match matching ~/a1|a2/Field value matches a1 or a2

awk '/mysql/' /etc/passwd

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

awk '/mysql/{print $0} ' /etc/passwd using use with using ‐ ‐ ‐ out out out ’’s ’ ‐ ‐ ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 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 /etc/passwd ~/mail/{print $1}' /etc/passwd //$1 will only be displayed if it matches the specified content

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

awk -F: '$1!~/mail/{print $1}' /etc/passwd //Does not match

awk -F: '$1!~/mail|mysql/{print $1}' /etc/passwd

IF statement

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

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

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

Conditional expression

== != > >=

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

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

awk -F":" '$1!="mysql"{print $3}' /etc/passwd / / Greater than

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

awk -F":" '$3<1{print $3}' /etc/ passwd // Less than

awk -F":" '$3<=1{print $3}' /etc/passwd // Less than or equal to

Logical operator

&& ||

awk -F: ' $1~/mail/ && $3>8 {print }' /etc/passwd //Logical AND, $1 matches mail, 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 operations

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

awk -F: '$3 > ; 100 || $3 < 5' /etc/passwd

awk -F: '$3+$4 > 200' /etc/passwd

awk -F: '/mysql|mail/{print $3+10}' /etc/passwd using 10 use with 10 to be added to ’ ’ /mysql /{print $3 *$4}' /etc/passwd 1024)}' /proc/meminfo // Rounding

Output separator 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 lines matching WAIT, where each line is output Line number, fields 4, 5, 6, and use tabs to separate the fields

Output the processing results to the file

① Directly output in the command code block route -n|awk 'NR!=1{print > "./fs"}'

②Use redirection for output ‐ ‐ ‐ ‐n|‐awk 'NR!=1{print}' ‐ printf "%-8s %-8s %-10sn",$1,$2,$3}'

printf represents format output

% formatted output delimiter

-8 is 8 characters in length

s represents string type

Print the first three fields of each line, specify the first field to output the string type (length is 8), the second field to output the string type (length is 8),

The third field to output the string type ( The length is 10)

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

netstat - anp|awk '$6=="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

large

small

awk -F: 'BEGIN{A=0;B=0} {if($3>100) {A++; print "large"} else {B++; print "small"}} END{print A,"t", B}' /etc/passwd

// Skip if less than 100, otherwise display

awk -F: 'BEGIN{i=1} {if(i

另一种形式

awk -F: '{print ($3>100 ? "yes":"no")}' /etc/passwd

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

while语句

awk -F: 'BEGIN{i=1} {while(i

7 root 1

7 x 2

7 0 3

7 0 4

7 root 5

7 /root 6

数组

netstat -anp|awk 'NR!=1{a[$6]++} END{for (i in a) print i,"t",a[i]}'

netstat -anp|awk 'NR!=1{a[$6]++} END{for (i in a) printf "%-20s %-10s %-5s n", i,"t",a[i]}'

9523 1

9929 1

LISTEN 6

7903 1

3038/cupsd 1

7913 1

10837 1

9833 1

应用1

awk -F: '{print NF}' helloworld.sh //输出文件每行有多少字段

awk -F: '{print $1,$2,$3,$4,$5}' helloworld.sh //输出前5个字段

awk -F: '{print $1,$2,$3,$4,$5}' OFS='t' helloworld.sh //输出前5个字段并使用制表符分隔输出

awk -F: '{print NR,$1,$2,$3,$4,$5}' OFS='t' helloworld.sh //制表符分隔输出前5个字段，并打印行号

应用2

awk -F'[:#]' '{print NF}' helloworld.sh //指定多个分隔符: #，输出每行多少字段

awk -F'[:#]' '{print $1,$2,$3,$4,$5,$6,$7}' OFS='t' helloworld.sh //制表符分隔输出多字段

应用3

awk -F'[:#/]' '{print NF}' helloworld.sh //指定三个分隔符，并输出每行字段数

awk -F'[:#/]' '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12}' helloworld.sh //制表符分隔输出多字段

应用4

计算/home目录下，普通文件的大小，使用KB作为单位

ls -l|awk 'BEGIN{sum=0} !/^d/{sum+=$5} END{print "total size is:",sum/1024,"KB"}'

ls -l|awk 'BEGIN{sum=0} !/^d/{sum+=$5} END{print "total size is:",int(sum/1024),"KB"}' //int是取整的意思

应用5

统计netstat -anp 状态为LISTEN和CONNECT的连接数量分别是多少

netstat -anp|awk '$6~/LISTEN|CONNECTED/{sum[$6]++} END{for (i in sum) printf "%-10s %-6s %-3s n", i," ",sum[i]}'

应用6

统计/home目录下不同用户的普通文件的总数是多少？

ls -l|awk 'NR!=1 && !/^d/{sum[$3]++} END{for (i in sum) printf "%-6s %-5s %-3s n",i," ",sum[i]}'

mysql 199

root 374

统计/home目录下不同用户的普通文件的大小总size是多少？

ls -l|awk 'NR!=1 && !/^d/{sum[$3]+=$5} END{for (i in sum) printf "%-6s %-5s %-3s %-2s n",i," ",sum[i]/1024/1024,"MB"}'

Application 7

Output Score Table

awk 'BEGIN{math=0;eng=0;com=0;printf "Lineno. Name No. Math English Computer Totaln";printf "------ -------------------------------------------------- ---n"}{math+=$3; eng+=$4; com+=$5;printf "%-8s %-7s %-7s %-7s %-9s %-10s %-7s n",NR,$1,$2 ,$3,$4,$5,$3+$4+$5} END{printf "--------------------------------- --------------------------n";printf "%-24s %-7s %-9s %-20s n","Total: ",math,eng,com;printf "%-24s %-7s %-9s %-20s n","Avg:",math/NR,eng/NR,com/NR}' test0

[root @localhost home]# cat test0

Marry 2143 78 84 77

Jack 2321 66 78 45

Tom 2122 48 77 71

Mike 2537 87 97 95

Bob 2415 40 57 62

linux awk命令详解