Ternary operator and print

Question

What is wrong with below command

awk 'BEGIN {a = 5;b=6; (a==b)? print "a==b" : print "a!=b"}'

Output :

awk: BEGIN {a = 5;b=6; (a==b)? print "a==b" : print "a!=b"}
awk:                           ^ syntax error

Answer 1

Like many other programming languages, awk distinguishes between expressions and statements. By and large, statements are actions that are carried out, while expressions are computations that result in a value.

The ternary operator in awk, like its counterpart in C where it comes from, is itself an expression (not a statement) that expects three other expressions as expr1 ? expr2 : expr3. print is a statement. It cannot be used where an expression is called for, hence the syntax error.

Have you tried awk 'BEGIN {a = 5;b=6; print (a==b)? "a==b" : "a!=b"}' ?

Using a statement where an expression is called for cannot make any sense. Statements don't return values. So when you have condition ? stmt1 : stmt2, what is the value computed by the ternary operator? If condition is false, it should be the value of stmt2 but that's not a value, it's an action.