awk assignment operator

Once a variable is given a value, it can be referenced with the variable name. The following expression represents the addition of the value of the variable x and 1 and assigns the result to the variable y:

Y=X+ 1

That is, the value of x plus 1 is computed and the result is assigned to the variable Y. Statement

Print Y

Prints the value of Y. If the following series of statements will appear in the script:

X=1
Y=X+1
Print Y

Then the value of Y is 2.

We can reduce these 3 statements to two:

X= 1
Print X+1

assignment operator

operator

definition
++	variable plus 1
--	variable minus 1
+=	Assign the result of the addition to the variable
-=	Assigns the result of the subtraction to the variable
*=	Assigns the result of the multiply to the variable
/+	Assign the result of the addition to the variable
%=	Assign the result of the modulo to the variable
^=	Assigns the result of the exponentiation to the variable
**=	Assigns the result of the exponentiation to the variable

The following example is used to calculate a directory of empty rows in a file.
#统计空行数

/^$/{Print X+=1}

Although there is no initial value assigned to variable x here. But it has a value of 0 until the first empty row is encountered. The expression x+=1 evaluates and increments the value of X by 1 each time a blank row is encountered. The print statement prints the value returned by the expression. Because we execute the PRINT statement when we encounter every empty row, we get a continuous value for the number of empty rows.

Expressions can be expressed in different forms and somewhat more concise. The expression x+=1 than the equivalent expression: x=x+1 is more concise. But neither of these two are as concise as the following expression:

++X

"+ +" is the increment operator ("--" is the decrement operator). An expression increases by 1 for each time the value of the variable is evaluated. The increment and decrement operators can appear on either side of the operand, where different results can be computed.
++x increment the value of x (prefix) before returning the result

X + + increments the value of x. (suffix) after returning the result

Reference: http://www.linuxawk.com/communication/480.html

awk assignment operator