A *conditional expression* is a special kind of expression with
three operands. It allows you to use one expression's value to select
one of two other expressions.

The conditional expression is the same as in the C language:

selector?if-true-exp:if-false-exp

There are three subexpressions. The first, `selector`, is always
computed first. If it is "true" (not zero and not null) then
`if-true-exp` is computed next and its value becomes the value of
the whole expression. Otherwise, `if-false-exp` is computed next
and its value becomes the value of the whole expression.

For example, this expression produces the absolute value of `x`

:

x > 0 ? x : -x

Each time the conditional expression is computed, exactly one of
`if-true-exp` and `if-false-exp` is computed; the other is ignored.
This is important when the expressions contain side effects. For example,
this conditional expression examines element `i`

of either array
`a`

or array `b`

, and increments `i`

.

x == y ? a[i++] : b[i++]

This is guaranteed to increment `i`

exactly once, because each time
only one of the two increment expressions is executed,
and the other is not.
See section Arrays in `awk`

,
for more information about arrays.

As a minor `gawk`

extension,
you can continue a statement that uses ``?:'` simply
by putting a newline after either character.
However, you cannot put a newline in front
of either character without using backslash continuation
(see section `awk`

Statements Versus Lines).

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