7.4.3 The do-while Statement

The do loop is a variation of the while looping statement. The do loop executes the body once and then repeats the body as long as the condition is true. It looks like this:

do
  body
while (condition)

Even if the condition is false at the start, the body is executed at least once (and only once, unless executing body makes condition true). Contrast this with the corresponding while statement:

while (condition)
  body

This statement does not execute body even once if the condition is false to begin with. The following is an example of a do statement:

{
       i = 1
       do {
          print $0
          i++
       } while (i <= 10)
}

This program prints each input record 10 times. However, it isn’t a very realistic example, since in this case an ordinary while would do just as well. This situation reflects actual experience; only occasionally is there a real use for a do statement.