Basic use of awk

Awk command format:

Awk [Options] 'awk-script' input-file...

Options:

-F: Specifies the field separator domain separator.

-F: Specifies the awk-script file name.

Awk-Script: Specifies the awk command

Input-file: Specifies the awk input file

Structure of awk-script:

It consists of three parts: Begin, body, and end.

Begin format:

Begin {awk-commands}

Used to print the header

Initialize variable

The begin keyword must be capitalized.

Optional begin keywords

Body format:

/Pattern/{action}

Execute once for each line of input-File

End format:

End {awk-commands}

Print the end of a table

The end keyword must be capitalized.

The end keyword is optional.

Print command: print is equivalent to print $0, and $0 represents all records.

# cat employee.txt101,Johnny Doe,CEO102,Jason Smith,IT Manager103,Raj Reddy,Sysadmin104,Anand Ram,Developer105,Jane Miller,Sales Manager# awk -F, ‘{print}‘ employee.txt101,Johnny Doe,CEO102,Jason Smith,IT Manager103,Raj Reddy,Sysadmin104,Anand Ram,Developer105,Jane Miller,Sales Manager# awk -F, ‘{print $0}‘ employee.txt101,Johnny Doe,CEO102,Jason Smith,IT Manager103,Raj Reddy,Sysadmin104,Anand Ram,Developer105,Jane Miller,Sales Manager

Print command: The position parameter $1 $2... $ n represents the 1st columns and 2nd columns of a record, respectively. column N

# awk -F, ‘{print $1,$2}‘ employee.txt 101 Johnny Doe102 Jason Smith103 Raj Reddy104 Anand Ram105 Jane Miller

 

Built-in variables of awk:

FS: input field separator

OFS: output field separator

RS: Input record separator input record Separator

ORS: Output record separator output record Separator

Nr: number of records Record Number

Filename: current file name input file name

FNR: file "number of records" indicates the number of records for the file.

NF: number of field fields

FS:

# awk ‘BEGIN { FS=","; print "UserID\tTitle\n------------" } { print $1,$3 } END { print "------------" }‘ employee.txt  UserID  Title------------101 CEO102 IT Manager103 Sysadmin104 Developer105 Sales Manager------------

OFS:

# awk ‘BEGIN { FS=","; OFS=":";print "UserID\tTitle\n------------" } { print $1,$3 } END { print "------------" }‘ employee.txt    UserID  Title------------101:CEO102:IT Manager103:Sysadmin104:Developer105:Sales Manager------------

RS:

# cat employee-one-line.txt                                           101,Johnny Doe:102,Jason Smith:103,Raj Reddy:104,Anand Ram:105,Jane Miller# awk ‘BEGIN{RS=":"}{print $1}‘ employee-one-line.txt        101,Johnny102,Jason103,Raj104,Anand105,Jane# awk ‘BEGIN{FS=",";RS=":"}{print $1}‘ employee-one-line.txt          101102103104105

ORS:

# cat employee-one-line.txt                                           101,Johnny Doe:102,Jason Smith:103,Raj Reddy:104,Anand Ram:105,Jane Miller# awk ‘BEGIN{FS=",";RS=":"}{print $1,$2}‘ employee-one-line.txt       101 Johnny Doe102 Jason Smith103 Raj Reddy104 Anand Ram105 Jane Miller# awk ‘BEGIN{FS=",";RS=":";ORS="\n----\n"}{print $1,$2}‘ employee-one-line.txt 101 Johnny Doe----102 Jason Smith----103 Raj Reddy----104 Anand Ram----105 Jane Miller----

 

Nr:

# awk ‘BEGIN {FS=",";print "-----------"}{print "Record",NR,"is",$1,$2,$3}‘ employee.txt        -----------Record 1 is 101 Johnny Doe CEORecord 2 is 102 Jason Smith IT ManagerRecord 3 is 103 Raj Reddy SysadminRecord 4 is 104 Anand Ram DeveloperRecord 5 is 105 Jane Miller Sales Manager

Filename:

# awk ‘BEGIN {FS=",";print "-----------"}{print FILENAME,"Record",NR,"is",$1,$2,$3}‘ employee.txt -----------employee.txt Record 1 is 101 Johnny Doe CEOemployee.txt Record 2 is 102 Jason Smith IT Manageremployee.txt Record 3 is 103 Raj Reddy Sysadminemployee.txt Record 4 is 104 Anand Ram Developeremployee.txt Record 5 is 105 Jane Miller Sales Manager

 

FNR:

# awk ‘BEGIN {FS=",";print "-----------"}{print FILENAME,"Record",NR,"is",$1,$2,$3}‘ employee.txt items.txt -----------employee.txt Record 1 is 101 Johnny Doe CEOemployee.txt Record 2 is 102 Jason Smith IT Manageremployee.txt Record 3 is 103 Raj Reddy Sysadminemployee.txt Record 4 is 104 Anand Ram Developeremployee.txt Record 5 is 105 Jane Miller Sales Manageritems.txt Record 6 is 101 HD Camcorder Videoitems.txt Record 7 is 102 Refrigerator Applicanceitems.txt Record 8 is 103 MP3 Player Audioitems.txt Record 9 is 104 Tennis Racket Sportsitems.txt Record 10 is 105 Laser Printer Office# awk ‘BEGIN {FS=",";print "-----------"}{print FILENAME,"Record",FNR,"is",$1,$2,$3}‘ employee.txt items.txt -----------employee.txt Record 1 is 101 Johnny Doe CEOemployee.txt Record 2 is 102 Jason Smith IT Manageremployee.txt Record 3 is 103 Raj Reddy Sysadminemployee.txt Record 4 is 104 Anand Ram Developeremployee.txt Record 5 is 105 Jane Miller Sales Manageritems.txt Record 1 is 101 HD Camcorder Videoitems.txt Record 2 is 102 Refrigerator Applicanceitems.txt Record 3 is 103 MP3 Player Audioitems.txt Record 4 is 104 Tennis Racket Sportsitems.txt Record 5 is 105 Laser Printer Office

NF: In the output result, the first column is the file name, the second column is the record number, and the third column is the number of fields for each record.

# awk -F, ‘{print FILENAME,NR,NF}‘ employee.txt employee.txt 1 3employee.txt 2 3employee.txt 3 3employee.txt 4 3employee.txt 5 3

 

Awk variables and operators:

Unary operator:

+: Returns the current number.

-: Negative number.

++: Auto-Increment

--: Auto-Subtraction

+:

# cat employee-sal.txt 101,Johnny Doe,CEO,10000102,Jason Smith,IT Manager,5000103,Raj Reddy,Sysadmin,4500104,Anand Ram,Developer,4500105,Jane Miller,Sales Manager,3000# awk ‘BEGIN{FS=","}{print +$4}‘ employee-sal.txt 100005000450045003000

 

-:

# awk ‘BEGIN{FS=","}{print -$4}‘ employee-sal.txt  -10000-5000-4500-4500-3000

++: Pre auto-increment, auto-increment first, and then print the variable

# awk ‘BEGIN{FS=","}{print ++$4}‘ employee-sal.txt  100015001450145013001

 

--: Pre auto-subtraction, First Auto-subtraction, and then printing the variable

# awk ‘BEGIN{FS=","}{print --$4}‘ employee-sal.txt   99994999449944992999

 

++: Post auto-increment: print the variables first, and then add

# awk ‘BEGIN{FS=","}{print $4++}‘ employee-sal.txt      100005000450045003000# awk ‘BEGIN{FS=","}{$4++;print $4++}‘ employee-sal.txt 100015001450145013001

--: Post auto-subtraction. Print the variables first and then auto-subtraction.

# awk ‘BEGIN{FS=","}{print $4--}‘ employee-sal.txt   100005000450045003000# awk ‘BEGIN{FS=","}{$4--;print $4--}‘ employee-sal.txt 99994999449944992999

 

Mathematical operations:

+: Add

-: Minus

*: Multiplication

/:

%: Modulo

# cat arit.awk BEGIN{ FS=","; OFS=","; item_discount=0;}{ item_discount=$4*20/100; print $1,$2,$3,$4-item_discount,$5-1} # cat items.txt 101,HD Camcorder,Video,210,10102,Refrigerator,Applicance,850,2103,MP3 Player,Audio,270,15104,Tennis Racket,Sports,190,20105,Laser Printer,Office,475,5# awk -f arit.awk items.txt  101,HD Camcorder,Video,168,9102,Refrigerator,Applicance,680,1103,MP3 Player,Audio,216,14104,Tennis Racket,Sports,152,19105,Laser Printer,Office,380,4

Character operation:

# cat string.awk BEGIN { FS=","; OFS=","; string1="Hello"; string2="World"; numberstring="100"; string3=string1" "string2; print "Concatenate string is: " string3; numberstring+=1; print "String to number: " numberstring; }# awk -f string.awk items.txt Concatenate string is: Hello WorldString to number: 101

Assignment operation:

=: Value assignment

+ =: A + = 1 is equivalent to a = a + 1

-=: A-= 1 equivalent to a = A-1

* =: A * = 2 is equivalent to a = A * 2

/=: A/= 2 is equivalent to a = A/2

% =: A % = 2 is equivalent to a = A % 2

# cat total.awk BEGIN { total1=total2=total3=total4=total5=10; total1+= 5; print total1; total2-= 5; print total2; total3*= 5; print total3; total4/= 5; print total4; total5%= 5; print total5;} # awk -f total.awk 155502

Comparison:

>:

>=:

<:

<=:

=:

! =:

&&:

|:

# cat items.txt 101,HD Camcorder,Video,210,10102,Refrigerator,Applicance,850,2103,MP3 Player,Audio,270,15104,Tennis Racket,Sports,190,20105,Laser Printer,Office,475,5# awk -F, ‘$5 <=5‘ items.txt 102,Refrigerator,Applicance,850,2105,Laser Printer,Office,475,5

 

# awk -F, ‘$4 < 200‘ items.txt    104,Tennis Racket,Sports,190,20

# awk -F, ‘$4 == 475 && $5 == 5‘ items.txt  105,Laser Printer,Office,475,5

 

# awk -F, ‘$4 == 475 || $5 == 15‘ items.txt   103,MP3 Player,Audio,270,15105,Laser Printer,Office,475,5

# awk -F, ‘$3 != "Video"‘ items.txt  102,Refrigerator,Applicance,850,2103,MP3 Player,Audio,270,15104,Tennis Racket,Sports,190,20105,Laser Printer,Office,475,5

Regular Expression operation:

~ : Match

!~ : Mismatch

# awk -F, ‘$3 ~ "ce"‘ items.txt 102,Refrigerator,Applicance,850,2105,Laser Printer,Office,475,5# awk -F, ‘$3 !~ "ce"‘ items.txt101,HD Camcorder,Video,210,10103,MP3 Player,Audio,270,15104,Tennis Racket,Sports,190,20

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Basic use of awk