gawk: Do Statement

 
 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 executes 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 the 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, because 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.