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 body as long as condition is true. It looks like this:

do
  body
while (condition)

Even if condition is false at the start, 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 condition is false to begin with.

Here is an example of a do statement:

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

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

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