Awk from entry to earth (7) conditional statements

Just like the actual programming language ,AWK It also provides the execution flow of conditional statement control program . In this chapter, we will introduce AWK How to use conditional statements in .

IF sentence

Conditional statements test conditions, and then select and execute corresponding actions according to the conditions . The following is the syntax of conditional statements ：

if (condition)
    action

Curly braces can also be used to perform a set of operations ：

if (condition)
{
    action-1
    action-1
    .
    .
    action-n
}

The following example determines whether the number is odd or even ：

$ awk 'BEGIN {num = 10; if (num % 2 == 0) printf "%d is even number.\n", num }'

Execute the above command to get the following result ：

10 is even number.

IF - ELSE sentence

if-else Statement allows another set of actions to be performed when the condition is false . The following is if-else The grammar of ：

if (condition)
    action-1
else
    action-2

among , When the condition is true action-1, Execute if condition is false action-2. Here is an example of using this statement to determine whether a number is even ：

$ awk 'BEGIN {num = 11; 
   if (num % 2 == 0) printf "%d is even number.\n", num; 
   else printf "%d is odd number.\n", num 
                    }'

The following results can be obtained by performing the above operation ：

11 is odd number.

if-else-if

We can easily use multiple if-else Sentence construction if-else-if So as to realize the judgment of multiple conditions . Examples are as follows ：

$ awk 'BEGIN {
a=30;
if (a==10)
  print "a = 10";
else if (a == 20)
  print "a = 20";
else if (a == 30)
  print "a = 30";
}'

Execute the above command to get the following result ：

a = 30