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(gawk.info)Do Statement

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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 ten 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.