Awk Actions unit is Awk syntax

Awk syntax usage

1. Print and Printf statements

Test data emp.dat

A125 Jenny 100 210
A341 Dan 110 215
P158 Max 130 209
P148 John 125 220
A123 Linda 95 210

1.print statement

BEGIN{
	print "start"
	print "----------------------------"
}

{
	print $0
}

END{
	print "----------------------------"
	print "end"
}

result:

[root@VM-0-6-centos mnt]# awk -f test.awk emp.dat
start
----------------------------
A125 Jenny 100 210
A341 Dan 110 215
P158 Max 130 209
P148 John 125 220
A123 Linda 95 210
----------------------------
end

2.printf statement
formatted output

BEGIN{
	printf("start\n")
	printf("----------------------------\n")
}

{
	# printf("%s\n",$4)
	# printf("%5s\n",$4)
	# printf("%d\n",$4)
	# printf("%5d\n",$4)
	# printf("%f\n",$4)
	printf("%.4f\n",$4)
}

END{
	printf("----------------------------\n")
	printf("end\n")
}

The result is:

[root@VM-0-6-centos mnt]# awk -f test.awk emp.dat
start
----------------------------
210.0000
215.0000
209.0000
220.0000
210.0000
----------------------------
end

2. If statement

1. if statement
   a. Requirements: whether the results are qualified

BEGIN{
	score=79

	if(score>=60){
		print "yes"
	}

	if(score<60){
		print "no"
	}
}

2. if...else statement
   a. Requirement: whether the result is qualified

BEGIN{
	score=59

	if(score>=60){
		print "yes"
	}else{
		print "no"
	}
}

b. Demand: whether the gender is male or female

BEGIN{
	sex="girl"

	if(sex=="boy"){
		print "男"
	}else{
		print "女"
	}
}

3. if...else if...else statement
   a. Requirement: Which grade is the grade of A, B, C, or D, grade D below 60, grade C 60-79, grade B 80-89, grade A above 90

BEGIN{
	score=92

	if(score>=90){
		print "A"
	}else if(score>=80 && score<90){
		print "B"
	}else if(score>=60 && score<80){
		print "C"
	}else{
		print "D"
	}
}

#Optimized code

BEGIN{
	score=92

	if(score>=90){
		print "A"
	}else if(score>=80){
		print "B"
	}else if(score>=60){
		print "C"
	}else{
		print "D"
	}
}

Three. While and Do While statement

1. while statement
   Calculate the cumulative sum of 1-100 numbers
   a. Ordinary

BEGIN{
	num=100
	tot=0

	while(num>0){
		tot+=num
		num--
	}

	print tot
}

b. Optimization

BEGIN{
	num=100

	while(num>0){
		tot+=num--
	}

	print tot
}

2. do while statement
   Press y or n in the system to exit, otherwise it will always execute "Enter y or n"
   a. Normal

BEGIN{
	print "Enter y or n"
	getline data

	while( data !~ /^[yn]$/){
		print "Enter y or n"
		getline data
	}
}

b. Optimization

BEGIN{
	do{
		print "Enter y or n"
		getline data
	} while( data !~ /^[yn]$/)
}

Four. For statement

1. for statement
   #Requirement: Calculate the cumulative sum of 1-100 numbers

BEGIN{
	for(i=1;i<=100;i++){
		tot+=i
	}
	
	print tot
}

2. for in statement
   #Requirement: traverse the array

BEGIN{
	arr[0]="linux"
	arr[1]="php"
	arr[2]="javascript"
	arr[3]="java"
	arr[4]="python"

	for(i in arr){
		print i,arr[i]
	}
}

Five. Continue and Break statements

1. continue statement
   #Requirement: skip even 2 and 4

BEGIN{
	#1,2,3,4,5

	for(i=1;i<=5;i++){
		if(i%2==0){
			continue
		}
		tot+=i
	}

	print tot
}

2. break statement
   #requires to stop the for loop when i is equal to 3

BEGIN{
	#1,2,3,4,5

	for(i=0;i<=5;i++){
		if(i==3){
			break
		}
		tot+=i
	}

	print tot
}

6. Delete statement

#Delete array (array) data method

BEGIN{
	arr[0]="linux"
	arr[1]="php"
	arr[2]="java"

	# delete arr[0]
	delete arr
	print arr[2]
}

Seven. exit statement

#Can stop awk script execution

#First paragraph

BEGIN{
	print 1
	print 2
	exit
	print 3
	print 4
	print 5
}

#Second paragraph

BEGIN{
	for(i=0;i<5;i++){
		if(i==1){
			exit
		}
		print i
	}

	print 2
	print 3
}